Weather and meteorology glossary

A

Ablation/
Ablation nivale

Reduction of the water equivalent of a snow cover by melting, evaporation, wind and avalanches.

Absolute humidity/
Humidité absolue

Absolute humidity is the amount of water in the air, measured in grams per cubic meter. As the temperature changes during the day, absolute humidity does not change

Acid Rain/
Pluies acides

A generic term used for precipitation that contains an abnormally high concentration of sulphuric and nitric acid. These acids form in the atmosphere when industrial gas emissions combine with water, and have negative impacts on the environment and human health.

Advection Fog/
Brume d’advection

Fog which forms when a relatively moist and warm air mass moves over a colder water or land surface.

Advisory/
Avis

A type of alert from Environment and Climate Change Canada’s Meteorological Service (MSC), where a certain weather or environmental hazard (for example air quality and tsunami) is either occurring, imminent or is expected to occur.

Aged Ridge/
Vieille crête

Sea-ice terminology that describes a ridge that has undergone considerable weathering. These ridges are like undulations or waves.

Agglomerated Brash/
Sarrasins agglomérés

Canadian sea-ice terminology that is not part of the World Meteorological Organization’s (WMO) terminology. An area of brash ices that is not compacted.

Air Mass/
Masse d'air

An extensive body of the atmosphere with comparable temperature and humidity. It may extend over an area of several million square kilometres and over a depth of several kilometres.

Air temperature/
Température de l'air

Air temperature is how hot or cold the air feels on our skin. Also known as “surface temperature”, we measure it in degrees Celsius on a thermometer that is exposed to the air (but away from direct sunlight).

Alert/
Message pour alerter le public/
Alert

A transmitted signal used to heighten awareness and/or initiate preparation for action. Alerts are issued by Environment and Climate Change Canada’s Meteorological Service (MSC) for weather or environmental hazard events that are either occurring, imminent, or forecast to develop. Alerts are currently issued as special weather statements, advisories, watches and warnings.

Anchor Ice/
Glace de fond

Sea-ice terminology that describes submerged ice attached or anchored to the bottom of the sea, irrespective of the nature of its formation.

Anticyclone/
Anticyclone

A high pressure system with an anticyclonic circulation. It is also called a "high," and is generally associated with fair weather.

Anticyclonic/
Anticyclonique

Rotation that is counter-clockwise in the Southern Hemisphere and clockwise in the Northern Hemisphere. It is the opposite of cyclonic.

Apogee (lunar)/
Apogée (lunaire)

The point in the moon’s orbit that is farthest from the Earth. It is the opposite of perigee.

Arctic Sea Smoke (also called Steam Fog)/
Fumée de mer arctique (aussi appelée « Brouillard d'évaporation »)

A type of fog that forms when an outbreak of cold Arctic air settles over an expanse of open, relatively warmer water.

Arrangement of the Ice/
Disposition des glaces

Sea-ice terminology, that includes the terms:

1. Drift Ice/Pack Ice
2. Ice Cover
3. Concentration
4. Ice Distribution
5. Openings in the Ice
6. Ice Edge
7. Ice Boundary
8. Iceberg Limit 

Atmosphere/
Atmosphère

The mass of air held close to the earth by gravity. The atmosphere is divided into four sections: the troposphere reaches an altitude of about 10 km from the earth's surface; the stratosphere which is at 10 km to 50 km from the earth’s surface; the mesosphere which is at 50 km to 80 km from the earth’s surface; and lastly the thermosphere which is anything beyond 80 km from the earth’s surface.

Atmospheric Pressure/
Pression atmosphérique

The pressure exerted by the weight of air above a given point, sometimes expressed in millibars (mb) or inches of mercury (Hg). The internationally recognized unit for measuring atmospheric pressure is the kilopascal (kPa).

Aurora Borealis/
Aurore boréale

The luminous, radiant emission from the upper atmosphere that appears over middle and high latitudes, and is centered on the earth's magnetic poles. These silent fireworks are often seen on clear winter nights in a variety of shapes and colours, and are referred to as the Northern Lights.

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B

Backing Wind/
Vent lévogyre

A counter-clockwise change in wind direction. For example, from southwest to southeast, through south. It is the opposite of veering wind.

Bare Ice/
Glace vive

Sea-ice terminology that describes ice without snow cover.

Batture Floes/
Floes de batture

Canadian sea-ice terminology that is not a part of the World Meteorological Organization’s (WMO) terminology. It defines large, thick, uneven and discoloured ice floes that form on the upstream side of shoals and islets in rivers, when cold weather precedes or accompanies neap tides. It is composed of ice of different thicknesses formed under pressure during ebb tide, the entire mass freezes together and gradually increasing in size, with each successive tide. As the range increases between the neap and spring tides, large sections of grounded ice break away and drift down river causing the floes.

Beaufort Wind Force Scale/
Échelle de Beaufort

A scale numbered from 0 to 12 used to estimate the force of marine wind, based on the observed effects of the wind on sea state.

Belt/
Ceinture

Sea-ice terminology meaning a large area of pack/drift ice that is longer than it is wide. It can be from 1 km to more than 100 km in width.

Bergy Bit/
Fragment d’iceberg

Sea-ice terminology that describes a piece of glacier ice, generally showing at 1m to less than 5m above sea level; with a length of 5m to less than 15m. They normally have an area of 100-300 sq. m.

Bergy Water/
N/A

Sea-ice terminology that describes an area of freely navigable water, in which ice of land origin is present. Other ice types may be present, although the total concentration of all other ice is less than 1/10.

Beset/
Coincé

Sea-ice terminology meaning a situation in which a vessel is surrounded by ice and unable to move.

Blight/
Baie

Sea-ice terminology that describes an extensive crescent-shaped indentation in the ice edge, formed by either wind or current.

Blizzard/
Blizzard

A severe weather condition characterized by reduced visibility from falling and/or blowing snow and strong winds that may be accompanied by low temperatures.

Blizzard Warning/
Avertissement de blizzard

A warning issued by Environment and Climate Change Canada’s Meteorological Service (MSC) for hazardous weather conditions characterized by high winds, and a widespread reduction in visibility due to falling and/or blowing snow. Blizzard conditions may persist for a period of time on their own or be part of an intense winter storm. In the latter case, a blizzard warning is issued instead of a winter storm or snowfall warning. Blizzard conditions may be accompanied by a severe wind chill making them even more dangerous.

Blocky Iceberg/
Iceberg en bloc

Sea-ice terminology that describes a flat-topped iceberg with steep vertical sides.

Blowing Dust/
Chasse-poussière élevée

Dust, raised by the wind to moderated heights above the ground. The visibility at eye level is reduced.

Blowing Snow/
Poudrerie élevée

Snow lifted from the earth's surface by the wind to a height of 2 metres or more.

Blowing Snow Warning/
Avertissement de poudrerie

A warning issued by Environment and Climate Change Canada’s Meteorological Service (MSC) for wind-driven snow that reduces visibility to near-whiteout conditions. A blowing snow event is less extreme than a blizzard in duration and/or visibility.

Brash Ice/
Sarrasins

Sea-ice terminology that describes the accumulation of floating ice comprised of fragments not more than 2 metres across. It is the result of the wreckage of other forms of ice.

Building Codes/
Codes du bâtiment

Standards and guidelines for construction of buildings to ensure a minimum level of safety for the occupants.

Bummock/
Bummock

Sea-ice terminology that describes a downward projection from the underside of sea ice; the submariner's counterpart of a hummock.

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C

Calving/
Vêlage

Sea-ice terminology that describes the breaking away of a mass of ice from an ice wall, ice front or iceberg.

Cape Verde-type Hurricanes/
Ouragans de type cap-verdien

Cape Verde-type hurricanes are Atlantic basin tropical cyclones that develop into tropical storms fairly close (less then 1000 kilometres) to the Cape Verde Islands, off the west coast of Africa, and then become hurricanes before reaching the Caribbean. Typically, this occurs in August and September.

Chance of Precipitation (COP)/
Probabilité de précipitations (PDP)

The chance that measurable precipitation (0.2 mm of rain or 0.2 cm of snow) will fall on any random point of the forecast region during the forecast period.

Chinook/
Chinook

Chinooks occur when mountain ranges are exposed to strong prevailing crosswinds. Moist air is forced up the mountains bringing both clouds and precipitation to the windward side. The descending air becomes warmer and drier as it is forced down the leeward (sheltered) side of the mountains. The relatively warm, dry, gusty winds that occasionally occur to the leeward side of mountain ranges around the world are known by many names. In Canada and the northern United States, they are referred to as Chinooks. In the southern states, they are known as Santa Ana winds and in parts of Europe, foehn winds.

Cirrus/
Cirrus

White patches of cloud composed of ice crystals, found at altitudes of 6,000 metres or higher. Fine and delicate in appearance, their shape and texture often resemble a mare’s tail.

Climate/
Climat

The prevalent or characteristic weather conditions of a place or region over a period of years.

Close Pack/
Drift/
Banquise serrée

Sea-ice terminology that describes floating ice that has a concentration of 7/10 to 8/10. It is composed mostly of ice floes that are in contact with one another.

Cloud/
Nuage

A visible cluster of water droplets and/or ice particles in the atmosphere.

Cloud-to-cloud Lightning/
Éclair nuage-nuage

A lightning discharge that occurs between areas of the same cloud (intra cloud) or from one cloud to another cloud (inter cloud). Cloud-to-cloud flashes are much more common than cloud to ground flashes (on average there are three to five cloud-to-cloud flashes, for every one cloud-to-ground flash).

Cloud-to-ground Lightning/
Éclair nuage-sol

A lightning discharge that occurs between a cumulonimbus cloud (thunderstorm) and the ground.

Cold Front/
Front froid

A transition zone where a cold air mass advances and replaces a warm air mass.

Compact Ice/
Banquise compacte

Sea-ice terminology that describes floating ice that has a concentration of 10/10, and no water is visible.

Compacted Ice Edge/
Lisière serrée

Sea-ice terminology that describes a clear-cut ice edge that is compacted by wind or current, usually on the windward side of an area of ice.

Compacting/
Tassement

Sea-ice terminology that describes an increase in ice concentration and/or a stress that may result in ice deformation (i.e. the ice becoming warped).

Concentration/
Concentration

Sea-ice terminology, for a ratio (expressed in tenths) which describes the area of the water surface covered by ice, as a fraction of the whole area. Total concentration includes all stages of development that are present. Partial concentration refers to the amount of a particular stage or of a particular form of ice, and represents only a part of the total.

Concentration Boundary/
Ligne de démarcation de concentrations

Sea-ice terminology, describing a line that marks the transition between two areas of floating ice with different concentrations.

Condensation/
Condensation

The physical process through which water vapour becomes a liquid.

Consolidated Ice/
Banquise consolidée

Sea-ice terminology, meaning floating ice in which the concentration is 10/10, and the floes are frozen together.

Consolidated Ridge/
Crête consolidée

Sea-ice terminology, describing a ridge in which the base has frozen together.

Coriolis Force/
Force de Coriolis

Apparent effect of the earth’s rotation to deflect the direction of any object - including the wind - to the right in the northern hemisphere and to the left in the southern hemisphere. The Coriolis Force is responsible for giving a cyclone its spin, and without it, tropical cyclones would not form.

Crack/
Fissure

Sea-ice terminology that describes any fracture of fast ice, consolidated ice or a single floe which may have been followed by separation ranging from a few centimetres to 1 metre.

Criteria Threshold(s)/
Seuil(s)

A set of values associated to weather or environmental factors used to issue an alert.

Cumulo-nimbus Clouds/
Cumulonimbus

Large, dense cloud that frequently has an anvil-shaped top. These clouds produce heavy rain showers, lightning, thunder and sometimes hail or tornadoes. The entire cloud can only be seen from a distance. (See thunderstorm)

Cumulus Clouds/
Cumulus

Bright clouds that appear in fair weather, that have broad, horizontal bases, producing no precipitation and rarely covering more than one-half of the sky.

Cyclone/
Cyclone

A low pressure system with a cyclonic circulation. It is also called a "low," or a "depression," and is generally associated with poor or stormy weather. The point of lowest atmospheric pressure marks the centre of the cyclone.

Cyclonic/
Cyclonique

Rotation that is counter-clockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. It is the opposite of anticyclonic.

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D

Dark Nilas/
Nilas sombre

Sea-ice terminology that describes a nilas of up to 5 cm in thickness, which is very dark in colour.

Deformed Ice/
Glace déformée

Sea-ice terminology. It is a general term for ice that has been squeezed together, and in places, forced upwards and downwards. The subdivisions of deformed ice are known as rafted ice, ridged ice, and hummocked ice.

Dew Point (also known as Dewpoint)/
Point de rosée

The temperature to which air must be cooled in order to become saturated by the water vapour already present in the air.

Difficult Area/
Zone difficile

Sea-ice terminology. A general qualitative expression that indicates that the relative severity of prevailing ice conditions in a particular area are such that navigation will be difficult.

Diffuse Ice Edge/
Lisière lâche

Sea-ice terminology, meaning a poorly defined ice edge that limits an area of dispersed ice, usually on the leeward side of an area of ice.

Diverging/
Divergence

Sea-ice terminology that describes ice fields or floes in an area, that move in opposite directions, reducing ice concentration and/or relieving stresses in the ice.

Domed Iceberg/
Iceberg en dôme

Sea-ice terminology, meaning an iceberg that is smooth and rounded on top.

Downburst/
Rafales descendantes

A strong convective downdraft resulting in an outward burst of often damaging winds at or near the surface. The affected area may be from less than 1 km to more than 100 km in horizontal dimension.

Draft/
Courant d'air

A small, gusty current associated with the abrupt vertical movement of air.

Dried Ice/
Glace asséchée

Sea-ice terminology that describes an ice surface from which water has disappeared after the formation of cracks and thaw holes; during the period of drying, the surface whitens.

Drift Ice/
Pack Ice/
Banquise/
pack

Sea-ice terminology. This term is used in a wide sense to include any area of ice, other than fast ice, no matter what form it takes or how it gets there. When concentrations are high (7/
10 or more) the term pack ice is normally used. When concentrations are 6/
10 or less, the term drift ice is normally used.

Drifting Snow/
Poudrerie basse

Snow raised from the earth's surface by the wind to a height of less than 2 metres.

Drizzle/
Bruine

Precipitation from stratus clouds, consisting of minute, fine water droplets that appear to float.

Dry Lightning/
Foudre sèche

Cloud-to-ground lightning that comes from a thunderstorm and that produces little, if any, rain.

Drydocked Iceberg/
Iceberg érodé

Sea-ice terminology, which describes an iceberg that has eroded in such a way that a U-shaped slot forms near or at water level, with twin columns or pinnacles.

Dust Storm Warning/
Avertissement de tempête de poussière

A warning issued by Environment and Climate Change Canada’s Meteorological Service (MSC) when a prolonged period of reduced visibility caused by blowing dust (of one hour or more) is expected to occur, is imminent, or is occurring.

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E

Easterly Wave/
Onde tropicale (aussi appelée « vague de l'est »)

Also known as easterly waves or African easterly waves, they are a type of atmospheric trough, oriented north to south, which move from east to west across the tropics causing areas of cloudiness and thunderstorms. A tropical wave can develop into a tropical cyclone.

Easy Area/
Zone facile

Sea-ice terminology, meaning a general qualitative expression that indicates that prevailing ice conditions in an area are such that navigation is not difficult.

EF-scale/
Échelle de Fujita améliorée (échelle EF)

The Enhanced Fujita Scale, or EF-scale, is an intensity scale used to rate wind damage. The scale ranges from EF0 (weakest) to EF5 (strongest). It was adopted in Canada in April of 2013, replacing the original Fujita Scale, or F-scale. The EF-scale is more sophisticated than the original F-scale, having a better correlation between wind damage and wind speed and a much greater variety of indicators with which to rate damage.

El Niño/
El Niño

El Niño can be distinguished when the surface waters in the eastern tropical Pacific extending westward from Ecuador become warmer than average. The changing pattern of the Pacific Ocean causes a shift in the atmospheric circulation, which then influences weather patterns across much of the earth. El Nino is like La Niña's brother, the totally opposite.

Event/
Événement

An individual occurrence of a weather or environmental hazard that meets hazard criteria values.

Event Time/
Heure de l’événement

The time at which the criteria value is first met for an event.

Extratropical Cyclone/
Cyclone extratropical

The generic term for the class of frontal low pressure systems. They are unlike tropical cyclones in that they are not symmetric in their temperature, precipitation or wind patterns. The driving mechanism for these systems is the difference in temperature and humidity across the cyclone.

Extratropical Transition (ET)/
Transition extratropicale

The transformation of a tropical cyclone into an extratropical cyclone. More than 40% of Atlantic tropical cyclones undergo such a transformation at the end of their tropical existence. The metamorphosis typically starts as the system begins to be driven by atmospheric temperature differences rather than latent heat release. The cyclone begins losing its tropical characteristics and often develops front-like qualities. During the transformation the rain area usually shifts to the left of the storm track while the strongest winds diminish but become elongated to the right of the storm track. Some extratropical transition events can result in a more powerful storm than the originating tropical cyclone.

Eye of the Storm/
Oeil de la tempête

The roughly circular area of comparatively light winds found at the centre of a hurricane and surrounded by the eyewall. Within the eye, the skies are often clear, despite the fact that winds and clouds continue to rage around the edge of the eye in the eyewall. Over the ocean the sea can be treacherous under the eye because high waves are converging. The eye of a hurricane is often obscured by overriding high cloud by the time it reaches Canadian latitudes. The diameter of a hurricane eye can range from 10 to more than 100 kilometres.

Eyewall/
Mur de l’œil

The ring of thunderstorms that surrounds a storm's eye. The heaviest rain, strongest winds and worst turbulence are found in the eyewall.

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F

Fast Ice/
Banquise côtière

Sea-ice terminology, describing ice which forms and remains fast along the coast. It may be attached to the shore, to an ice wall, to an ice front, or between shoals or grounded icebergs. It can extend between a few metres to several hundred kilometres from the coast. It may be more than one year old, in which case it may be attached to the appropriate age category (old, second year or multi-year). If higher than 2 m above sea level, it is called an ice shelf.

Fast Ice Boundary/
Ligne de démarcation de la banquise côtière

Sea-ice terminology. The ice boundary, which at any given time is found between fast ice and the pack/
drift ice.

Fast Ice Edge/
Lisière de la banquise côtière

Sea-ice terminology, describing the differentiation (at any given time) between fast ice and open water.

Fetch/
Fetch

The distance that wind, usually of uniform speed and direction, blows over the water surface. Fetch length is related to the height of the wind-generated wave heights. The longer the fetch length, the higher the wind-generated wave heights.

Finger Rafted Ice/
Glace imbriquée

Sea-ice terminology, meaning atype of rafted ice in which floes overlap each other in "fingers." This is common in nilas.

Firn/
Névé

Sea-ice terminology that describes old snow that has re-crystallized into adense material. Unlike ordinary snow, particles are joined together (to some extent); but, unlike ice, the air spaces in it still connect with each other.

First-year Ice/
Glace de première année

Sea-ice terminology, meaning sea-ice that has grown for not more than one winter, developing from young ice. It must also be 30 cm or greater. First-year ice may be subdivided into thin first-year ice (sometimes referred to as white ice), medium first-year ice, and thick first-year ice.

Flash Freeze Warning/
Avertissement de refroidissement soudain

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for when arapid drop in temperature to below freezing results in significant ice on road surfaces. This ice is produced by the freezing of residual water from either melted snow or falling/
fallen rain.

Flaw/
Brèche de séparation

Sea-ice terminology, describing a narrow separation zone between floating ice and fast ice, where the pieces of ice are in achaotic state. Flaws form when ice shears, due to astrong wind or current along the fast ice boundary.

Flaw Lead/
Chenal de séparation

Sea-ice terminology, describing a passageway between ice and fast ice, which is navigable by surface vessels.

Flaw Polynya/
unsure

Sea-ice terminology, which describes a polynya between ice and fast ice.

Floating Ice/
Glace flottante

Sea-ice terminology, meaning any form of ice found floating in water. The principal kinds of floating ice are lake ice, river ice and sea ice, which form by water freezing at the surface, and glacier ice that forms on land or in an ice shelf.

Floe/
Floe

Sea-ice terminology. Describes any relatively flat piece of ice that is 20 mor more across. Floes are subdivided according to their horizontal extent, as follows: Small: 20 m- 100 m across Medium: 101 m- 500 m across Big: 501 m- 2000 m across Vast: 2001 m- 10 km across Giant: Greater than 10 km across

Floeberg/
Floeberg

Sea-ice terminology, describing amassive piece of ice composed of ahummock or agroup of hummocks, frozen together and separated from any surrounding ice. They may typically protrude up to 5m above water level.

Flooded Ice/
Glace inondée

Sea-ice terminology. Describes ice which has been flooded and is heavily loaded by water, or water and wet snow.

Flurries/
Averse de neige

Precipitation in the form of snow from aconvective cumulus-type cloud, known as flurries. They are characterized by the suddenness with which they start and stop, by their rapid changes in intensity, and usually by rapid changes in the appearance of the sky.

Fog/
Brouillard

A cloud based at the earth's surface, consisting of tiny water droplets, or under very cold conditions, ice crystals or ice fog. It is generally found in calm or low wind conditions. Under foggy conditions, visibility is reduced to less than 1 kilometre.

Fog Bank/
Banc de brouillard

Fog generally caused by local conditions, which extend over asmall area of some hundreds of metres across, and which reduces visibility to less than one-half (1/2) nautical miles (or five-eighths (5/
8) of akilometre). Multiple fog banks are sometimes referred to as patchy fog or fog patches.

Forecast/
Prévision météorologique

A statement of expected meteorological and environmental conditions for aspecified time or period, and for aspecified area or portion of airspace.

Forms of Ice/
Formes de glaces

Sea-ice terminology:

1. Pancake Ice
2. Ice Cake
3. Floe
4. Floeberg
5. Ice Breccia
6. Batture Floes
7. Brash Ice
8. Fast Ice
9. Icefoot
10. Anchor Ice
11. Grounded Ice

Fracture/
Fracture

Sea-ice terminology. Describes any break or rupture through very close pack ice, compact ice, consolidated ice, fast ice or asingle floe, resulting from the deformation processes. Fractures may contain brash ice and/or be covered with nilas and/or young ice. Their lengths may vary from afew metres to many kilometres long.

Fracture Zone/
Zone de fracture

Sea-ice terminology. Describes an area that has agreat number of fractures. Fractures are subdivided as follows:Very Small Fracture: 1m to 50 mwideSmall Fracture: 51 mto 200 mwideMedium Fracture: 201 mto 500 mwideLarge Fracture: Greater than 500 mwide

Fracturing/
Formation de fractures

Sea-ice terminology that describes the pressure process whereby ice is permanently deformed, and rupture occurs. This term is most commonly used to describe the breaking across of very close ice, compact ice and consolidated ice.

Frazil Ice/
Frasil

Sea-ice terminology, meaning fine spicules or plates of ice suspended in water.

Freezing Drizzle/
Bruine verglaçante

Drizzle that freezes on impact to form acoating of clear ice (glaze) on the ground and on exposed objects.

Freezing Drizzle Warning/
Avertissement de bruine verglaçante

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for persistent freezing drizzle.

Freezing Rain/
Pluie verglaçante

Rain that freezes on impact to form acoating of clear ice (glaze) on the ground and on exposed objects.

Freezing Rain Warning/
Avertissement de pluie verglaçante

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for freezing rain.

Freezing Spray/
Embruns verglaçants

Freezing spray occurs when acombination of below freezing temperatures and strong winds, causes awind-generated spray to freeze and accumulate (or build-up) on any marine infrastructure located in or near the vicinity of the water.

Freezing Spray Warning/
Avertissement d'embruns verglaçants

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) if freezing spray is forecast or observed to be moderate or severe. Freezing spray is termed moderate if the ice accumulation or build-up rate on marine infrastructure is between 0.7 and 2cm per hour. It is termed severe if the ice accumulation or build-up rate on marine infrastructure is greater than 2cm per hour.

Friendly Ice/
Glace propice

Sea-ice terminology that describes an ice canopy containing many large skylights or other features, which permits a submarine to surface. There must be more than 10 such features per 30 nautical miles (56 km) along the submarine's track.

Front/
Front

The boundary between two different air masses. Acold front is the leading edge of an advancing cold air mass, while awarm front is the trailing edge of aretreating cold air mass.

Frontal Cyclone/
Cyclone frontal

Any cyclone associated with a front. It is often used synonymously with extratropical cyclone (as opposed to tropical cyclone, which is nonfrontal).

Frost/
Gel

A deposit of ice crystals that forms through aprocess called sublimation.

Frost Smoke/
Brume d’évaporation

Sea-ice terminology that describes fog-like clouds that form when cold air and relatively warm water come in contact with each other. Frost smoke can appear over openings in the ice or leeward of the ice edge, and may persist while ice is forming.

Funnel Cloud/
Nuage en entonnoir

A funnel-shaped condensation cloud caused by the pressure deficit associated with aviolently rotating column of air. It is typically vertically oriented and may extend fully or partially from acumuliform cloud to the surface. Afunnel cloud is often generated by atornado.

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G

Gale Force Wind/
Coup de vent

Wind speed of 34 to 47 knots inclusive; has aBeaufort wind force of 8 to 9.

Gale Warning/
Avertissement de coups de vent

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) if wind speed of 34 to 47 knots inclusive (gale force wind) is forecast or observed over amarine area.

Geostationary Satellite/
Satellite géostationnaire

A satellite that orbits the earth at the same rate that the earth rotates, and as aresult remains over afixed place above the equator.

Glacier/
Glacier

Sea-ice terminology. Describes amass of snow and ice that is continuously moving from higher to lower ground or, if afloat, continuously spreading. The principal forms of glaciers are: inland ice sheets, ice shelves, ice streams, ice caps, ice piedmonts, cirque glaciers, and various types of mountain (valley) glaciers.

Glacier Ice/
Glace de glacier

Sea-ice terminology that describes ice in or originating from aglacier, whether on land or floating on the sea as icebergs, bergy bits, growlers or ice islands.

Glacier Tongue/
Langue de glacier

Sea-ice terminology that describes the seaward extension of a glacier, usually afloat. In the Antarctic, glacier tongues may extend over many tens of kilometres.

Grease Ice/
Sorbet

Sea-ice terminology that describes a later stage of freezing than frazil ice where the crystals have coagulated to form asoupy layer on the surface. Grease ice reflects little light, giving the water amatte appearance.

Grey Ice/
Glace grise

Sea-ice terminology, describing young ice that is 10 cm to15 cm thick, less elastic than nilas, and which breaks on swell. It usually rafts under pressure.

Grey-White Ice/
Glace blanchâtre

Sea-ice terminology, describing young ice that is 15 cm to 30 cm thick. Under pressure, it is more likely to ridge than to raft.

Grounded Hummock/
Hummock échoué

Sea-ice terminology. Defines ahummocked, grounded ice formation. There are single grounded hummocks and lines (or chains) of grounded hummocks.

Grounded Ice/
Glace échouée

Sea-ice terminology that describes floating ice that is stranded in shoal water.

Growler/
Bourguignon

Sea-ice terminology that describes apiece of ice smaller than abergy bit and floating less than 1m above the sea surface. Agrowler generally appears white but sometimes transparent or blue-green in colour. Extending less than 1m above the sea surface, and normally occupying an area of about 20 sq. m., Growlers are difficult to distinguish when surrounded by sea ice or in high sea state.

Gulf Stream/
Gulf Stream

A warm, swift, narrow ocean current flowing parallel to the east coast of North America. The current then turns and flows south of Nova Scotia and Newfoundland and continues towards Europe.

Gusts/
Rafales

Gusts are sudden, rapid, and brief changes in the wind speed. They are characterized by more or less continual fluctuations between the high (peak) and low (lull) speed.

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H

Hail/
Grêle

Precipitation in the form of lumps of ice mainly associated with thunderstorms. Hail ranges in size from that of asmall pea to the size of cherries, but has been observed as large as grapefruit. Hail in Canada occurs most frequently during the summer when thunderstorm activity is at its peak.

Hazard/
Phénomène dangereux

A type of condition (weather or environmental) that has a negative impact on the safety and security of the public.

Haze/
Brume sèche

Consists of fine particles of dust and pollution suspended in the atmosphere, and is distinguished from fog by its bluish or yellowish tinge.

Heating degree-days/
Degrés-jours de chauffage

A heating degree day (HDD) measures how much energy we need to heat abuilding. On aday that is under 18°C, we need to use heating to keep buildings comfortable. The difference between 18°C and a day's temperature, is the HDD needed to keep the building warm. For example, aday with amean temperature of 15.5 °C has 2.5 HDD.On days with amean temperature above 18°C, the HDD is 0, since no heating energy is required to keep the building comfortable. For example, aday with amean temperature of 20.5°C has zero heating degree-days.

High/
Anticyclone (aussi appelé << zone de haute pression >>)

Region of the atmosphere where the pressures are high, relative to those in the surrounding region at the same level. In the Northern Hemisphere, winds around ahigh move in aclockwise fashion.

High Water Level/
Niveau élevé des eaux

Abnormally high water levels or waves along coastal or shoreline areas.

High Water Level Warning/
Avertissement de niveau élevé des eaux

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) to warn mariners and coastal populations of potential impacts caused by abnormally high water levels, or waves along coastal or shoreline areas.

Hillock/
Monticule

A small hill or mound.

Hostile Ice/
Glace hostile

Sea-ice terminology that describes an ice canopy containing no large skylights or other features, and as aresult submarines are unable to surface.

Humidex/
Humidex

The humidex is a tool we use to describe how hot, humid weather feels on your skin. It combines the temperature and humidity into one number, and it can be a better measure of how hot the air feels than temperature or humidity alone. The hot, humid air masses, which cause such uncomfortable weather, usually come from the Gulf of Mexico or the Caribbean.

How to use the humidex as a guide:

Range of humidex: degree of comfort

• 20 to 29 °C: little discomfort
• 30 to 39 °C: some discomfort
• 40 to 45 °C: great discomfort; avoid exertion
• above 45 °C: dangerous; heat stroke possible

Any value over 40°C is an extremely high humidex reading. At that point, you should reduce all unnecessary physical activity.  

For a humidex reading above 30 °C, you should limit or modify outdoor exercise, depending on:

• your age
• individual physical limitations
• the type of clothes you are wearing, and
• other weather conditions

Extremely high readings on the humidex are rare except in the southern regions of Ontario, Manitoba, and Quebec. Learn how to calculate the humidex in your region with the humidex calculator.

Humidity (also called Relative Humidity)/
Humidité

Humidity is the amount of water droplets (vapour) in the air. On ahumid day, sweat on your skin cannot cool you down because it cannot evaporate quickly. As aresult, ahigh humidity day feels hotter than adrier day at the same temperature.

Hummock/
Hummock

Sea-ice terminology, meaning ahillock of broken ice which has been forced upwards by pressure; it may be fresh or weathered.

Hummocked Ice/
Glace hummockée

Sea-ice terminology that describes ice piled chaotically, one piece over another, to form an uneven surface. When weathered, hummocked ice has the appearance of smooth hillocks.

Hummocking/
Formation de hummocks

Sea-ice terminology. Describes the pressure process by which ice is forced into hummocks. When the floes rotate in the process, it is termed screwing.

Hurricane/
Ouragan

Hurricanes are tropical cyclones with maximum sustained surface winds of at least 118 kilometres per hour. Hurricanes are known as typhoons in the western Pacific, very severe cyclonic storms in the North Indian Ocean, and severe tropical cyclones in Australia. There are 5 classes of hurricane intensity as outlined by the Saffir-Simpson Scale.

Hurricane Force Wind/
Vent de la force d'un ouragan

Wind speed of 64 knots (118 km/h) or greater, not necessarily in association with atropical cyclone, with aBeaufort wind force of 12.

Hurricane Force Wind Warning/
Avertissement de vents de force ouragan

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for awind speed of 64 knots (118 km/h) or greater is forecast or observed over amarine area.

Hurricane Season/
Saison des ouragans

Hurricane season in the North Atlantic runs officially from June 1 to November 30 when almost 95% of all tropical cyclones occur. About 85% of "landfalling" tropical cyclones in Canada occur during August through October.

Hurricane Warning/
Avertissement d’ouragan

An announcement that one or both of the following dangerous effects of a hurricane are expected in a specified area in 24 hours or less: (a) average sustained winds 118 kilometres per hour or higher; (b) dangerously high water or a combination of dangerously high water and exceptionally high waves, even though winds expected may be less than hurricane force. By nature a hurricane also implies the threat of local flooding from heavy rainfall.

Hurricane Watch/
Veille d’ouragan

An announcement for a specific area that a hurricane or an incipient hurricane condition poses a possible threat within 36 hours. This watch does not mean that a hurricane is definitely going to strike. It means that everyone in the area covered by the watch should watch more carefully for the hurricane and be prepared to act quickly if definite warnings are issued that a hurricane will strike.

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I

Ice Blink/
Halo glaciaire

Sea-ice terminology, describing a whitish glare on low clouds above an accumulation of distant ice.

Ice Boundary/
Ligne de démarcation des glaces

Sea-ice terminology that describes the differentiation at any given time between fast ice and floating ice, or between areas of ice of different concentrations, types and/or floe sizes.

Ice Breccia/
Mosaïque de glace

Sea-ice terminology, describing ice pieces in different stages of development that are frozen together.

Ice Cake/
Glaçon

Sea-ice terminology that describes any relatively flat piece of ice less than 20 m across.

Ice Canopy/
Voûte de glace

Sea-ice terminology, meaning ice seen from the point of view of the submariner. (I.e. underwater looking up at the ice)

Ice Cover/
Couverture de glace

Sea-ice terminology. Describes the ratio of an area of ice to the total area of water surface within alarge geographic area. This area may be global, hemispheric, or defined by aspecific oceanographic entity such as Baffin Bay or the Barents Sea.

Ice Deformation Process/
Processus de déformation des glaces

Sea-ice terminology.Includes the terms: Fracturing Hummocking Ridging Rafting Finger Rafting Weathering

Ice Distribution/
Distribution des glaces

Sea-ice terminology. Includes the terms: Ice Field Large Ice Field Medium Ice Field Small Ice Field Ice Patch Ice Massif Belt Tongue Strip Bight Ice Jam

Ice Edge/
Lisière des glaces

Sea-ice terminology, which describes the differentiation at any given time between open water, and sea, lake or river ice - whether fast or drifting.

Ice Field/
Champ de glace

Sea-ice terminology that describes an area of floating ice, consisting of floes greater than 10 km across.

Ice Free/
Libre de glace

Sea-ice terminology, meaning "no ice present." If ice of any kind is present, this term will not be used.

Ice Front/
Falaise de glace

Sea-ice terminology. Describes the vertical cliff that forms the seaward face of an ice shelf or other floating glacier. It varies in height from 2m to 50 m or more above sea level.

Ice Island/
Île de glace

Sea-ice terminology. Describes alarge piece of floating ice protruding about 5metres above sea level, which has broken away from an Arctic ice shelf. Ice islands have athickness of 30 m to 50 m, and an area of afew thousand square metres up to 500 sq. km or more. They are usually characterized by aregularly rolling surface giving aribbed appearance from the air.

Ice Island Fragment/
Fragment d’île de glace

Sea-ice terminology, describing apiece of an ice island that has broken away from the main mass.

Ice Jam/
Embâcle

Sea-ice terminology that describes an accumulation of broken river ice or sea ice that is not moving, due to aphysical restriction and its resistance to pressure.

Ice Keel/
Quille de glace

Sea-ice terminology that describes adownward-projecting ridge on the underside of the ice canopy; the submerged counterpart of aridge. Ice keels may extend to as much as 50 metres below the surface.

Ice Limit/
Limite de glace

Sea-ice terminology. A climatology term that refers to the extreme minimum or extreme maximum extent of the ice edge in any given month or period, based on observations over anumber of years. This term should always be preceded by minimum or maximum.

Ice Massif/
Mer de glace

Sea-ice terminology that describes avariable accumulation of pack or very close pack, covering hundreds of square kilometres and found in the same region every summer.

Ice Motion Processes/
Mouvement de la banquise

Sea-ice terminology. Includes the terms:Diverging,Compacting, Shearing.

Ice Patch/
Banc de glace

Sea-ice terminology, meaning an area of ice which is less than 10 km across.

Ice Pellets/
Grésil (aussi appelé << granules de glace >>)

Tiny particles of ice formed when supercooled raindrops freeze before reaching the ground.

Ice Rind/
Glace vitrée

Sea-ice terminology. Describes abrittle, shiny crust of ice formed on aquiet surface by direct freezing, or from grease ice, usually in water of low salinity, with athickness of about 5centimetres. Easily broken by wind or swell, it commonly breaks into rectangular pieces.

Ice Shelf/
Plateau de glace

Sea-ice terminology. Describes afloating ice sheet of considerable thickness that is visible 2metres or more above sea level, and is attached to the coast. They usually have great horizontal extension, and alevel or gently rolling surface. Ice shelf growth occurs with annual snow accumulation and by the extension of land glaciers over see. Limited areas of the ice shelf may be attached to land. The edge facing the sea is termed as ice front.

Ice Stream/
Coulée de glace

Sea-ice terminology. Describes the part of an inland ice sheet in which the ice flows more rapidly and not necessarily in the same direction as the surrounding ice.

Ice Surface Features/
Caractéristiques de la surface

Sea-ice terminology. Includes the terms:Level IceDeformed IceIce Deformation ProcessesIce Motion Processes

Ice Under Pressure/
Glace soumise à la pression

Sea-ice terminology describing ice in which the deformation processes are actively occurring. This form of ice is also apotential impediment or danger to shipping.

Ice Wall/
Mur de glace

Sea-ice terminology that describes an ice cliff forming at the seaward margin of aglacier that is aground.

Iceberg/
Iceberg

Sea-ice terminology. Alarge, massive piece of floating or stranded glacier ice of any shape detached (calved) from the front of aglacier into abody of water. An iceberg extends more than 5m above sea level and has the greater part of its mass (4/5 to 8/9) below sea level.

Iceberg Limit/
Limite des icebergs

Sea-ice terminology, meaning the limit at any given time between ice of land origin and the open sea or sea ice.

Iceberg Tongue/
Champ d’icebergs échoués

Sea-ice terminology describing amajor accumulation of icebergs that are projecting toward the coast, held in place by grounding and joined together by fast ice.

Ice-Bound/
Bloqué par les glaces

Sea-ice terminology. A harbour, inlet, etc. is said to be ice-bound when ships cannot navigate within it due to the ice. In some cases, navigation is possible with the assistance of an icebreaker.

Icefoot/
Banquette côtière

Sea-ice terminology describing anarrow fringe of ice attached to the coast, unmoved by tides and remaining after the fast ice has moved away.

Iceport/
Port de glace

Sea-ice terminology describing abay of ice, often of atemporary nature, where ships can moor alongside and unload directly onto the ice itself.

Intermittent Rain/
Pluie intermittente

Rain that starts and stops repeatedly, although not as abrupt or as frequent as showers.

Isobar/
Isobare

A line connecting points of equal pressure on amap.

Issue Time/
Heure d’émission

The time at which an alert has been transmitted by aforecaster.

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J

Jammed Brash Barrier/
Barrière de sarrasins

Sea-ice terminology. Describes astrip or narrow belt of new, young, or brash ice usually 100 m to 5000 m across, formed at the edge of either floating or fast ice, or at the shore. Heavily compacted, mostly due to wind action, ajammed brash barrier may extend 2m to 20 m below the surface.

Jet Stream/
Courant-jet

Relatively strong winds, concentrated within a narrow band in the upper atmosphere.

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K

Killing Frost/
Gel destructeur

A frost severe enough to destroy annual plants and new growth on trees (in the spring), or to end the growing season (in the fall).

Kilopascal/
Kilopascal

The internationally recognized unit used by the Environment and Climate Change Canada's Meteorological Service (MSC) for measuring atmospheric pressure.

Knot/
Nœud

The unit of speed used in the marine environment, which is equal one (1) nautical mile per hour. One (1) knot equals 1.852 kilometres per hour.

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L

La Niña/
La Niña

An extensive cooling of the waters in the tropical eastern Pacific Ocean. It is the climatic opposite of the El Niño.

Labrador Current/
Courant du Labrador

A cold, strong ocean current flowing parallel to the east coast of Labrador.

Lake Ice/
Glace de lac

Sea-ice terminology describing ice formed on alake, regardless of where it ends up.

Land Breeze/
Brise de terre

This coastal breeze blows from the land to the sea, lake or river, and usually occurs at night when the temperature of the water is often warmer than the nearby land. The water heats the air above, which rises and is replaced by cooler air from the land. (See also sea breeze)

Landfall/
Arrivée à terre

When the eye, or physical centre of the hurricane, reaches a coastline it is said to "make landfall." The term "landfall" is generally not used when post-tropical storms move inland because they typically do not have an eyewall and the worst impacts of the storm have already spread out at a distance from the storm centre.

Large Ice Field/
Grand champ de glace

Sea-ice terminology describing an ice field that is over 20 kilometres across.

Large Iceberg/
Gros iceberg

Sea-ice terminology that describes apiece of glacier ice extending 46 mto 75 mabove sea level, and with alength of 121 mto 200 m.

Latent Heat/
Chaleur latente

Heat that is stored in water vapour in the atmosphere. When water vapour rises, cools and condenses into liquid water, it releases this heat into the surrounding atmosphere. This is the driving mechanism for tropical cyclones.

Lead/
Chenal

Sea-ice terminology describing any fracture or passageway through ice, which is navigable by surface vessels.

Lead Time/
Préavis

The difference between the time that an alert is issued, and the actual event time.

Leeward/
Sous le vent

A term that means, "is situated away from the wind;" in other words, downwind and opposite of windward.

Level Ice/
Glace plane

Sea-ice terminology describing ice that is unaffected by deformation.

Light Nilas/
Nilas clair

Sea-ice terminology describing anilas that is more than 5cm in thickness and lighter in colour than dark nilas.

Light Wind/
Vent léger

Wind speed of 11 knots (20 km/h) or less, with aBeaufort wind force of 0to 4.

Lightning/
Éclair

Generally, any and all of the various forms of visible electrical discharge that are produced by thunderstorms; often seen as abright flash of light in the sky.

Lightning Flash/
Coup de foudre

A scientific term used to describe lightning, which consists of more than one individual stroke of lightning (and as many as 20 single lightning strokes within asingle flash). This causes the "flickering" effect sometimes seen in lightning.

Lightning Flash Density/
Densité de foudroiement

The number of lightning flashes detected per square unit of area (usually per square kilometre or mile) and unit of time.

Lightning Strike/
Foudre

Another term for cloud to ground lightning.

Lightning Stroke/
Décharge

A scientific term used to describe asingle discharge of lightning. There can be many individual strokes of lightning within asingle lightning flash.

Limit of Known Ice/
Limite de toutes les glaces connues

Sea-ice terminology that describes the limit at any given time between icebergs and/or sea-ice infested waters, and ice-free waters.

Line Squalls/
Ligne de grains

Squalls that occur along aline or within an elongated area, such as an organized area of squalls in the vicinity of acold front.

Low/
Dépression (aussi appelée << basse pression >>)

Region of the atmosphere where the pressures are low, relative to those in the surrounding region at the same level. In the Northern Hemisphere, winds around alow move in acounter-clockwise fashion.

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M

Maximum Iceberg Limit/
Limite maximale des icebergs

Sea-ice terminology, describing the maximum limit of icebergs, based on observations over a period of years.

Mean Ice Edge/
Limite moyenne des glaces

Sea-ice terminology that describes the average position of an ice edge in any given month or period, based on observations over anumber of years. Other terms that may be used are mean maximum ice edge, and mean minimum ice edge.

Mean Iceberg Limit/
Limite moyenne des icebergs

Sea-ice terminology. Describes the average position of the limit of icebergs at any given time, based on observations over anumber of years.

Median Ice Edge/
Limite médiane des glaces

Sea-ice terminology describing the position of the ice edge, where its frequency of occurrence is 50 per cent.

Median Iceberg Limit/
Limite médiane des icebergs

Sea-ice terminology describing the position where the historical or statistical frequency of occurrence of the iceberg limit is 50 per cent.

Medium First-year Ice/
Glace moyenne de première année

Sea-ice terminology meaning ice that is 70 cm to 120 cm thick.

Medium Ice Field/
Champ de glace moyen

Sea-ice terminology meaning an ice field that is 15 km to 20 km across.

Medium Iceberg/
Iceberg moyen

Sea-ice terminology meaning apiece of glacier ice extending 16 mto 45 mabove sea level, and with alength of 61 mto 120 m.

Medium Lake Ice/
Glace de lac moyenne

Sea-ice terminology meaning ice that is 15 to 30 cm thick.

Mesopause/
Mésopause

Top of the mesosphere situated at about 80-85 km above Earth's surface. It corresponds to the level on minimum temperature.

Mesosphere/
Mésosphère

Region of the atmosphere, situated between the stratopause and the mesopause, in which the temperature generally decreases with height.

Millibar/
Millibar

A unit for expressing the atmospheric pressure. Average global sea level pressure is about 1013 millibars (101.3 kilopascals).

Minimum Iceberg Limit/
Limite minimale des icebergs

Sea-ice terminology that describes the minimum limit of icebergs based on observations over aperiod of years.

Microburst/
Microrafale

A downburst less than 4km in horizontal dimension. Microbursts tend to have ashorter lifetime and be more intense than larger downbursts and can result in damage intensity similar to that associated with a strong tornado.

Mist/
Brume

Very small to microscopic-sized water droplets that are suspended in the atmosphere, usually in association with precipitation, and causing obstruction to visibility from one-half (1/2) to five (5) nautical miles, inclusive.

Moderate Wind/
Vent modéré

Wind speed of 12 to 19 knots inclusive, with aBeaufort wind force of 4to 5.

Multi-year Ice/
Glace de plusieurs années

Sea-ice terminology that describes old ice that has survived at least two summers worth of melt. Hummocks are smoother on multi-year ice than on second-year ice, and the ice is almost salt-free. Where bare, this ice is usually blue in colour. The melt pattern consists of large, interconnecting, irregular puddles and awell-developed drainage system.

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N

Nautical Mile/
Mille marin

The unit of distance used in the marine environment. One (1) nautical mile is equal to 1.852 kilometres.

New Ice/
Nouvelle glace

Sea-ice terminology. This is ageneral term for recently formed ice that includes frazil ice, grease ice, slush, and shuga. These types of ice are composed of ice crystals that are only weakly frozen together (if at all) and have adefinite form only while they are afloat.

New Lake Ice/
Nouvelle glace de lac

Sea-ice terminology describing recently formed ice, which is less than 5cm thick.

New Ridge/
Nouvelle crête

Sea-ice terminology that describes aridge with sharp peaks and sides that has aslope of 40 degrees or more.

Nilas/
Nilas

Sea-ice terminology. Describes athin, elastic crust of gray-colored ice that is formed on acalm sea, and is easily bent by waves and thrust into apattern of interlocking fingers (known as finger rafting). Nilas has amatte surface, is up to 10 cm in thickness, and may be subdivided into dark nilas and light nilas.

Nip/
Pressé

Sea-ice terminology. Ice is said to nip when it forcibly presses against aship. When avessel is caught in this way, though undamaged, it is said to have been "nipped".

Normal/
Normale

The long-term average value of aclimate element for acertain area, averaged over a30-year period. Elements can include temperature, precipitation, hours of sunshine, etc.

Normal High/
Température maximale normale

The climatological average high temperature for agiven day.

Normal Low/
Température minimale normale

The climatological average low temperature for agiven day.

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O

Old Ice/
Vieille glace

Sea-ice terminology describing sea-ice that has survived at least one summer's melt. The surface of old ice is generally smoother than first-year ice. Old ice may be subdivided into second-year ice and multi-year ice.

Open Drift/
Banquise lâche

Sea-ice terminology that describes floating ice in which the concentration is 4/10 to 6/10, with many leads and polynyas. Floes are generally not in contact with one another in open drift.

Open Water/
Eau libre

Sea-ice terminology describing alarge area of freely navigable water in which ice is present, with aconcentration less than 1/10. In open water, no ice of land origin is present.

Openings in the Ice/
Ouvertures dans les glaces

Sea-ice terminology. Includes the terms:

1. Medium Fracture
2. Large Fracture
3. Crack
4. Tide Crack
5. Flaw
6. Lead
7. Shore Lead
8. Flaw Lead
9. Polynya
10. Shore Polynya
11. Flaw Polynya Recurring Polynya

Other Surface Feature Definitions/
Autres caractéristiques de la surface

Sea-ice terminology. Includes the terms:Standing FloeRamBare IceSnow-Covered IceSastrugiSnowdrift

Outlook/
Aperçu

A term used by meteorologists to refer to anticipated weather conditions in the future. Usually, an outlook covers aperiod of time that goes beyond anormal forecast.

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P

Pancake Ice/
Glace en crêpes

Sea-ice terminology. Describes (predominantly) circular pieces of ice that are 30 cm to 3m in diameter and up to 10 cm in thickness, which have raised rims due to the pieces striking against one another. Pancake ice may form on aslight swell from grease ice, shuga or slush, or as aresult of the breaking of ice rind, nilas or, under severe conditions of swell or waves, from grey ice.

Perigee (Lunar)/
Périgée (lunaire)

The point in the moon’s orbit that is closest to the Earth. Opposite of apogee.

Period/
Période des vagues

The time between two successive crests or troughs of a wave.

Pinnacled Iceberg/
Iceberg pointu

Sea-ice terminology that describes an iceberg that has acentral spire or pyramid. This pyramid can have one or more spires.

Polar Low/
Dépression polaire

An intense storm system that usually forms in polar regions during outbreaks of very cold air, over relatively warmer ocean waters. Typically spanning from 400 to 800 kilometres across, and usually existing for only one or two days, polar lows can result in severe blizzard-like conditions, with heavy snow and gales force winds over affected marine areas.

Polar-orbiting Satellite/
Satellite en orbite polaire

A satellite whose orbit closely parallels the earth's meridian lines, and thus crosses the polar regions on each orbit.

Polynya/
Polynie

Sea-ice terminology. Describes any non-linear-shaped opening enclosed by ice. May contain brash ice and/or be covered with new ice, nilas or young ice. Submariners refer to polynyas as "skylights".

Post-Tropical Storm/
Tempête post-tropicale

A storm system that used to be tropical but has since lost most of its tropical characteristics. Since the remnant system may or may not be an "extratropical cyclone" (a term set aside for a specific breed of cyclone) the term "post-tropical" is a convenient communication term to permit the ongoing use of the storm name. This is important because storms with a tropical pedigree seldom lose all of their tropical characteristics, such as intense rainfalls and high wind gusts.

Precipitation/
Précipitation (s)

Precipitation is aliquid or solid form of water falling from the atmosphere to the earth's surface. Examples include rain, freezing rain, hail, and snow.

Predicted Astronomical Tide/
Calcul des marées astronomiques

The height of tides at various locations and times based solely on astronomical calculations. These are the values printed in tide tables. These values do not account for effects such as wind, atmospheric pressure or waves.

Prevailing Winds/
Vents dominants

The wind direction most frequently observed during agiven period of time.

Puddle/
Mare

Sea-ice terminology that describes an accumulation of water on ice, mainly due to melting snow. However, in the more advanced stages puddles can also be due to the melting of ice.

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R

Radar/
Radar

Radar is an acronym for Radio Detection And Ranging. It is used in the meteorological environment to detect and locate the presence of clouds and precipitation.

Rafted Ice/
Glace empilée

Sea-ice terminology, describing atype of deformed ice, formed by one piece of ice overriding another.

Rafting/
Chevauchement des glaces

Sea-ice terminology describing the pressure process whereby one piece of ice overrides another. Most common in new and young ice.

Rain/
Pluie

Moisture condensed from atmospheric vapour that falls to earth in drops.

Rainfall Warning/
Avertissement de pluie

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for ahazardous, prolonged or intense short-duration of rainfall. It may be amajor factor in the cause of disasters, such as floods, flash floods, and landslides.

Ram/
Éperon

Sea-ice terminology. Describes an underwater protruding piece of ice that has come from an ice wall, ice front, iceberg or floe. Its formation is usually due to amore intensive melting and erosion of the un-submerged part.

Recurring Polynya/
Polynie récurrente

Sea-ice terminology for apolynya which recurs in the same position every year.

Relative Humidity (also called Humidity)/
Humidité relative

Relative humidity (RH) is the percent of water droplets in the air compared to the maximum amount of water the air could hold at that temperature. As the temperature changes during the day, relative humidity also changes. One hundred percent relative humidity means the air is completely full of water droplets, and you will probably have mist, fog, dew, or precipitation (rain, snow, hail, etc.).

Ridge/
Crête

An elongated atmospheric area of relatively high pressure, extending from the centre of ahigh pressure region; the opposite of atrough.

Ridge (Ice)/
Crête de glace

Sea-ice terminology describing aline or wall of broken ice forced up by pressure that may be fresh or weathered. Also see ice keel.

Ridged Ice/
Glace tourmentée

Sea-ice terminology describing ice that is piled haphazardly, one piece over another in the form of ridges or walls. Usually found in first-year ice.

Ridged Ice Zone/
Zone de glace tourmentée

Sea-ice terminology that describes an area of many ridges with similar characteristics.

Ridging/
Formation de crêtes

Sea-ice terminology that describes the pressure process by which ice is forced into ridges.

River Ice/
Glace de rivière

Sea-ice terminology that describes ice that is formed on ariver, regardless of where it is observed.

Rotten Ice/
Glace pourrie

Sea-ice terminology that describes ice which has become honeycombed and is in an advanced state of disintegration.

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S

Saffir-Simpson Scale/
Échelle de Saffir-Simpson

The scale used to give public safety officials an assessment of the potential wind and storm surge damage from a hurricane. Scale numbers are available to public safety officials when a hurricane is within 72 hours of landfall. Scale assessments are revised regularly as new observations are made. Public safety organizations are kept informed of new estimates of the hurricane's disaster potential. Scale numbers range from 1 to 5.

Sastruga/
Sastruga

Sea-ice terminology. Describes sharp, irregular ridges formed on asnow surface by wind erosion and snow accumulation. On floating ice, the ridges are parallel to the direction of the wind that was present at the time they were formed.

Sea Breeze/
Brise de mer

This is the breeze which blows from the sea or alarge lake, to the land. The breeze is set off when the temperature of the land is higher than the temperature of the water. The land heats the air above, which rises, and it is then replaced by the cooler air from over the water. (Opposite to the land breeze).

Sea Fog/
Brouillard marin

Fog which forms in the lower part of arelatively moist and warm air mass as it moves over arelatively cooler water surface. This process cools the water vapour to such an extent that it condenses into the suspended water droplets that create the fog. It reduces visibility to less than one-half (1/2) nautical miles. (See also advection fog).

Sea Ice/
Glace de mer

Sea-ice terminology describing any form of ice found at sea, which has originated from the freezing of water.

Sea Smoke/
Fumée de mer

A fog that forms when an outbreak of cold air settles over an expanse of open, relatively warmer water, reducing visibility to less than 1kilometre. Also known as steam fog. (See also arctic sea smoke, and advection fog or sea fog)

Sea State/
État de la mer

Overall state of agitation of alarge expanse of ocean or sea due to the combined effects of wind-generated waves, swell waves, and surface currents.

Second-year Ice/
Glace de deuxième année

Sea-ice terminology. Describes old ice that has survived only one summer's melt. Thicker than first-year ice, it stands higher out of the water. In contrast to multi-year ice, summer melting of second-year ice produces aregular pattern of numerous small puddles. In this case, bare patches and puddles are usually greenish-blue.

Severe Thunderstorm Watch/
Veille d’orages violents

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) that outlines a "watch zone" where conditions are favourable for the development of thunderstorms, some of which have the potential to become severe thunderstorms.

Severe Thunderstorm Warning/
Alerte d'orages violents

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) when at least one thunderstorm that produces hail large enough to cause damage (at least 2cm in diameter), heavy rain, and/or damaging winds, is imminent. This is indicated by radar and/or observation reports.

Shearing/
Cisaillement

Sea-ice terminology. An area of floating ice is subject to shear when the ice motion varies significantly from its main direction, subjecting the ice to rotational forces. These forces may result in phenomena similar to aflaw.

Shoal/
Haut-fond

A place where the depth of water is shallow, especially where the seafloor is visible at low tide.

Shore Lead/
Chenal côtier

Sea-ice terminology meaning alead between ice and the shore, or between ice and an ice front.

Shore Polynya/
Polynie côtière

Sea-ice terminology describing apolynya between ice and the coast, or between ice and an ice front.

Shower/
Averse(s)

Precipitation characterized by the suddenness with which it starts and stops, by its rapid changes in intensity, and usually by the rapid changes in the appearance of the sky.

Shuga/
Shuga

Sea-ice terminology meaning an accumulation of spongy white ice lumps that have adiameter of afew centimetres across. Shuga are formed from grease ice or slush, and sometimes from anchor ice rising to the surface.

Sky and Air Indications/
Indices de glace dans le ciel et dans l'atmosphère

Sea-ice terminology. Includes:Water SkyIce BlinkFrost Smoke

Skylight/
Claire-voie

Sea-ice terminology. Describes the thin places in an ice canopy, usually less than 1meter thick, that appear from below as light, translucent patches in dark surroundings. The under surface of skylights are normally flat. They are termed small or large; if they are big enough for asubmarine to attempt to surface through them (120 meters wide or more) they qualify as large.

Slush/
Gadoue

Sea-ice terminology describing snow which is saturated and mixed with water on land, on ice surfaces, or as athick floating mass in water, after aheavy snowfall.

Small Ice Cake/
Petit glaçon

Sea-ice terminology that describes an ice cake that is less than 2m across.

Small Ice Field/
Petit champ de glace

Sea-ice terminology that describes an ice field that is 10 km to 15 km across.

Small Iceberg/
Petit iceberg

Sea-ice terminology that describes apiece of glacier ice extending 5m to 15 mabove sea level, and with alength of 15 mto 60 m.

Smoke/
Fumée

Suspension in the atmosphere of small particles, produced by fire.

Snow/
Neige

Precipitation of ice crystals, isolated or as part of acluster, falling from acloud.

Snow Grains/
Neige en grains

Minute, white and opaque grains of ice. When they hit hard ground, they do not bounce or shatter. They usually fall in very small quantities, and never in the form of ashower.

Snow Pellets/
Neige roulée

Snow pellets are brittle and easily crushed; when they fall on hard ground, they bounce and often break up. They always occur in showers. They are often accompanied by snowflakes or rain drops, when the surface temperature is around zero Celsius.

Snow Squall/
Bourrasque de neige

A moderate to heavy snow flurry, which is driven by strong, gusty winds. Visibility during snow squalls is usually poor.

Snow Squall Warning/
Avertissement de bourrasques de neige

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for localized, limited duration, intense snowfall that reduces visibility significantly and may be accompanied by strong, gusty winds and (in some cases) lightning. These weather conditions are produced by the passage of cold air over an open body of water (open water squall) or the passage of acold front (frontal snow squall). Local snow accumulations may be significant during this type of event.

Snowbelt/
Ceinture de neige

Areas where prevailing onshore winds are responsible for heavy snowfall is known as asnowbelt, and usually refers to regions southeast of open water.

Snow-Covered Ice/
Glace recouverte de neige

Sea-ice terminology meaning ice that is covered with snow.

Snowdrift/
Congère

Sea-ice terminology. Describes an accumulation of wind-blown snow that is deposited in the lee of an obstacle. Acrescent-shaped snowdrift, with ends pointing down-wind, is called asnow barchan.

Snowfall Warning/
Avertissement de neige

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for an expected snowfall that is heavy enough to cause significant inconvenience and hazardous conditions.

Special Marine Warning/
Avertissement maritime spécial

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) to warn mariners of any undefined marine weather phenomenon that could pose ahazard to marine navigation or safety.

Special Marine Watch/
Veille maritime spéciale

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) to notify mariners that conditions are favourable for the development of any undefined marine weather phenomenon that could pose ahazard to marine navigation or safety.

Special Weather Statement/
Bulletin météorologique spécial

A type of alert from Environment and Climate Change Canada's Meteorological Service (MSC) where:A warning or watch is not warranted because the expected conditions are less menacing than those of awarning or;A warning or watch is not yet practical to issue because of the high degree of uncertainty of occurrence, location and/or timing of the possible hazardous condition(s)A special weather statement can be used to describe any hazard (unlike an advisory). The statements do not have a formal "in effect" status, since there is no requirement to update or end them.

Spicule/
Aiguille de glace

A spike of ice that has needle-like crystals, which is formed during the freezing of water.

Spiral Rain Bands/
Bandes spirales de pluies

Bands of thunderstorms and intense rain that wrap around a hurricane.

Squall/
Grain

An atmospheric phenomenon characterized by an abrupt and large increase of wind speed within aduration of minutes, that suddenly diminishes. Squalls are usually associated with thunderstorms, and as such are often accompanied by heavy showers, thunder, and lightning.

Squall Warning/
Avertissement de grains

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for forecast or observed wind gusts of 34 knots or greater, that are associated with aline, or an organized area, of thunderstorms. (See also squall)

Squall Watch/
Veille de grains

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) to give advance notice of conditions that are favourable for the development of squalls.

Stages of Development of Lake Ice/
Stades de formation de la glace de lac

Sea-ice terminology. The stages are:

1. New Lake Ice
2. Thin Lake Ice
3. Medium Lake Ice
4. Thick Lake Ice
5. Very Thick Lake Ice

Stages of Development of Sea Ice/
Stades de formation de la glace de mer

Sea-ice terminology. The stages are:

1. New Ice
2. Nilas
3. Young Ice
4. First-Year Ice
5. Old Ice

Stages of Melting/
Phases de la fonte

Sea-ice terminology. The stages are:

1. Puddle
2. Thaw
3. Holes
4. Dried Ice
5. Rotten Ice
6. Flooded Ice

Standing Floe/
Floe dressé

Sea-ice terminology that describes aseparate floe standing vertically or inclined, and enclosed by rather smooth ice.

Steam Fog (also called Arctic Sea Smoke)/
Brouillard d'évaporation (aussi appelé « fumée de mer arctique »)

A type of fog that forms when an outbreak of cold Arctic air settles over an expanse of open, relatively warmer water (See sea smoke, arctic sea smoke and advection fog, or sea fog)

Storm Force Wind/
Vent de la force d'une tempête

Wind speed of 48 to 63 knots inclusive, with aBeaufort wind force of 10 to 11.

Storm Surge/
Onde de tempête

The positive or negative difference in sea level from the predicted astronomical tide, due to the forces of the atmosphere. The two main atmospheric components that contribute to storm surge are air pressure and wind. Deep low pressure systems can create a dome of water under the storm (much like the low pressure in a vacuum on a carpet). High winds along a coastline can also elevate the water levels at the shore, depending on the direction of the wind with respect to the coast. For powerful storms like hurricanes, the abnormally high water levels are due mostly to the high winds and high waves at the coast.

Storm Surge Warning/
Avertissement d'onde de tempête

A warning that significant wind-forced flooding is to be expected along low-lying coastal areas if weather patterns develop as forecast.

Storm Track/
Trajectoire de tempête

The line of movement (known as propagation) of the storm's centre through an area.

Storm Warning/
Avertissement de vent de tempête

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) if wind speed of between 48 and 63 knots inclusive, is forecast or observed over amarine area.

Stranded Ice/
Glace jetée sur la côte

Sea-ice terminology describing ice which had been floating and is then deposited on the shore by retreating high water.

Stratopause/
Stratopause

A boundary or zone of transition separating the stratosphere and the mesosphere; it marks areversal of temperature change with altitude. It is located at the height of roughly 50 km.

Stratosphere/
Stratosphère

The region of the atmosphere extending from the top of the troposphere (the tropopause), at height of 10-17 km to the base of the mesosphere (the stratopause), at aheight of roughly 50 km.

Stratus/
Stratus

Generally grey cloud layer with afairly uniform base, which may produce drizzle, ice prisms or snow grains.

Stress/
Tension (aussi appelée contrainte)

A surface force measured per unit area, for example, the force due to the transport of momentum by turbulent fluid motions.

Strip/
Cordon

Sea-ice terminology. Describes along narrow area of pack/drift ice, about one (1) km or less in width, usually composed of small fragments detached from the main mass of ice, which run together under the influence of wind, swell or current.

Strong Wind/
Vent fort

Wind speed of 20 to 33 knots inclusive, with aBeaufort wind force of 5to 7.

Strong Wind Warning/
Avertissement de vent fort

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) if awind speed of 20 to 33 knots inclusive, is forecast or observed over coastal or inland water bodies during the recreational boating season.

Sublimation/
Sublimation

The process by which solids are transformed directly to the state of vapour or vice versa, without passing through the liquid phase.

Subtropical Ridge/
Crête subtropicale

A large belt of high pressure located around 30 degrees latitude in both hemispheres and characterized by mostly calm winds. Air flows out from the ridge toward the upper and lower latitudes of each hemisphere, creating both the trade winds and the westerlies. A change in the ridge position of the Atlantic subtropical ridge (often referred to as the "Bermuda high," or "Azores high") has a direct impact on the tracks of tropical cyclones which typically form to its southern and western periphery.

Subtropical Storm/
Tempête subtropicale

A subtropical storm is a cyclone that has characteristics of both a tropical storm and an extratropical cyclone. Subtropical cyclones can form in waters normally too cool for tropical cyclones ... therefore they are not as restricted to the hurricane season months. With time the subtropical storm can become tropical.

(Les) Suête -Cape Breton Highlands/
Suêtes (Hautes-Terres-du-Cap-Breton)

Les Suête is an Acadian expression, local to the west coastal highlands area of Cape Breton Island, and used to describe the very strong Southeast winds common to that area.

Supercool/
Surfusion

To cool a liquid (e.g. water) below its freezing point without solidification (e.g. ice).

Swell/
Houle

Undulating movement of the sea surface that persists after the originating cause (wind-generated waves) of the motion has ceased.

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T

Tabular Iceberg/
Iceberg tabulaire

Sea-ice terminology describing aflat-topped iceberg; most tabular icebergs show horizontal banding.

Target Lead Time/
Préavis recherché

The target lead time is Environment and Climate Change Canada's service goal for the timeliness of alerts. The target lead time is intended to provide enough time for the public to take appropriate action when alerted of apredicted event. Other factors, such as the predictability of an event, and the ability of the public and media to receive notice of the message, may influence the actual lead times provided.

Temperature/
Température

In meteorological terms, temperature refers to the degree of heat or cold of the air, as measured by athermometer.

Temperature Anomaly/
Anomalie de température

The deviation of temperature in agiven region over aspecified period from the long-term average value for the same region.

Temperature index/
Indice de température

When we combine aweather condition with the air temperature to help describe how hot or cold the air feels, this is atemperature index. For example, humidity combined with the air temperature helps describe how hot the air actually feels on our skin (see the humidex). We also combine other weather conditions with air temperature to describe how temperature actually feels, such as wind (see wind chill index), and solar radiation.

Terms Related to Submarine Navigation/
Termes relatifs à la navigation sous-marine

Sea-ice terminology. Includes:Ice CanopyFriendly IceHostile IceBummockIce KeelSkylight

Terms Related to Surface Shipping/
Termes relatifs à la navigation de surface

Sea-ice terminology. Includes:BesetIce-BoundNipIce Under PressureDifficult AreaEasy AreaIceport

Thaw Holes/
Trous de fonte

Sea-ice terminology describing vertical holes in the ice formed when surface puddles melt through to the underlying water.

Thermosphere/
Thermosphère

Layer of the Earth's atmosphere, above the mesopause, in which the temperature generally increases with height.

Thick First-year Ice/
Glace épaisse de première année

Sea-ice terminology which describes ice that is between 30 cm to 70 cm thick.

Thick Lake Ice/
Glace de lac épaisse

Sea-ice terminology which describes ice that is between 30 cm to 70 cm thick.

Thin First-year Ice/
White Ice -First Stage/
Glace mince de première année/
glace blanche -premier stade

Sea-ice terminology which describes ice that is 30 cm to 50 cm thick.

Thin First-year Ice/
White Ice -Second Stage/
Glace mince de première année/
glace blanche -deuxième stade

Sea-ice terminology which describes ice that is 50 cm to 70 cm thick.

Thin Lake Ice/
Glace de lac mince

Sea-ice terminology which describes ice that is 5cm to 15 cm thick.

Thunder/
Tonnerre

The sound that results from the formation of lightning. This burst of lightning expands air around it, producing an effect similar to an explosion, thus creating the noise.

Thunderstorm/
Orage

A local storm, usually produced by acumulonimbus cloud, and always accompanied by thunder and lightning.

Tide/
Marée

Sea-level instability/movement in an approximately daily or twice daily period. The movement is caused by the difference of the gravitational attraction between celestial bodies and the centrifugal acceleration of their rotation, and is periodic because it is related to the motion of the sun, earth, and moon.

Tide Crack/
Fissure de marée

Sea-ice terminology. Describes the crack at the line of junction between an immovable ice foot or ice wall, and fast ice. The fast ice being subject to rise and fall of the tide.

Tongue/
Langue

Sea-ice terminology meaning an extension of the ice edge up to several kilometres in length, caused by wind or current.

Tornado/
Tornade

A tornado is aviolently rotating column of air that extends from acumuliform cloud to the surface. The pressure deficit in atornado often results in the formation of afunnel cloud that extends fully or partially from the cumuliform cloud to the surface. Atornado is typically also made visible by rotating debris near the ground or aspray ring near the water surface.A tornado can be tens to hundreds of metres wide and have alifespan of minutes or hours. In terms of size and area, it is one of the least extensive of all storms, but in terms of how violent storms can be, it is the world's most severe.Canada has the second highest tornado occurrence rate in the world, behind the United States. In Canada, tornadoes occur mostly on the Prairies and in southern Ontario with apeak frequency in late June and July.

Tornado Warning/
Alerte de tornade

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC), when at least one tornado is imminent, as indicated by observations, reports and/or radar scans.

Tornado Warning (Marine)/
Avertissement de tornade (maritime)

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC), when tornadoes are forecast or observed over alocalized marine area, or when an existing tornado is moving from land to an adjacent marine area.

Tornado Watch/
Veille de tornade

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) when severe thunderstorms are forecast, and conditions are favourable for one or more tornadoes to be spawned from those thunderstorms within adefined “watch zone.”

Tornado Watch (Marine)/
Veille de tornade (maritime)

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) to give advance notice of conditions that are favourable for the localized development of tornadoes over, or in the vicinity of amarine area.

Towering Cumulus Clouds/
Cumulus bourgeonnant

Cauliflower-shaped clouds associated with intermittent-type precipitation (showers). They may appear to be tall and towering, or tall and broad, and can either be isolated, or grow from agroup of lower cloud called cumulus.

Trade Winds (also called Tropical Easterlies)/
Alizés (parfois appelés « vents d'est tropicaux »)

The belts of winds on either side of the equator, blowing from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. In both hemispheres the winds become more easterly closer to the equator.

Tropical Cyclone/
Cyclone tropical

The generic term for the class of tropical low pressure systems, including tropical depressions, tropical storms, and hurricanes. These non-frontal cyclones originate over tropical or sub-tropical waters and are identified by organized showers and thundershowers and a cyclonic surface wind circulation. They are unlike extratropical cyclones in that they are generally symmetric in their temperature, rain and wind patterns. Rainfall with tropical cyclones is not dependent on the intensity of the storm. The driving mechanism for a tropical cyclone is the release of latent heat. These systems typically last a week or more.

Tropical Cyclone Information Statement/
Bulletin d'information sur les cyclones tropicaux

Routine bulletins issued by the Canadian Hurricane Centre when a tropical cyclone could bring high winds or seas to Canadian waters, or high winds, heavy rain, dangerous coastal waves or coastal storm surge to Canadian territory within the next 72 hours.

Tropical Depression/
Dépression tropicale

A tropical cyclone with maximum sustained surface winds of 37 to 62 kilometres per hour. It does not typically have the organization or the spiral shape of the more powerful storms. When a tropical cyclone reaches this stage it is given a number.

Tropical Disturbance/
Perturbation tropicale

An organized region of showers and thunderstorms in the tropics - generally 200 to 600 kilometres in diameter - that maintains its identity for at least 24 hours but does not have a closed wind circulation.

Tropical Easterlies (also called Trade Winds)/
Vents d’est tropicaux (parfois appelés « alizés »)

The belts of winds on either side of the equator, blowing from the northeast in the Northern Hemisphere and from the southeast in the Southern Hemisphere. In both hemispheres the winds become more easterly closer to the equator.

Tropical Storm/
Tempête tropicale

A tropical cyclone with maximum sustained surface winds of 63 to 117 kilometres per hour. When a tropical cyclone reaches this stage it is given a name.

Tropical Storm Warning/
Tropical Storm Warning

An announcement that tropical storm conditions, including possible sustained winds within the range 63-117 kilometres per hour, are expected in specified areas within 24 hours or less. By nature a tropical storm also implies the threat of local flooding from heavy rainfall.

Tropical Storm Watch/
Veille de tempête tropicale

An announcement for a specific area that a tropical storm or an incipient tropical storm condition poses a possible threat within 36 hours.

Tropical Wave (also called Easterly Wave or African Easterly Wave)/
Vague de l'est (aussi appelée « onde tropicale »)

Also known as easterly waves or African easterly waves, they are a type of atmospheric trough, oriented north to south, which move from east to west across the tropics causing areas of cloudiness and thunderstorms. A tropical wave can develop into a tropical cyclone.

Tropopause/
Tropopause

The boundary between the troposphere and the stratosphere, where an abrupt change in lapse rate usually occurs.

Troposphere/
Troposphère

The lowermost layer of the atmosphere, in which air temperature falls steadily with increasing altitude. The troposphere begins at ground level and ranges in height from an average of 11 km (at the International Standard Atmosphere) at the poles to 17 km at the equator.

Trough/
Creux

An elongated area of relatively low pressure, extending from the centre of alow pressure region. It is the opposite of aridge.

Tsunami/
Tsunami

A very large wave caused by ashallow submarine earthquake but can also be caused by submarine earth movement, subsidence, or volcanic eruption.

Turbulence/
Turbulence

The vertical motion of the air, at times violent, which can cause the up-and-down movement of aplane.

Typhoon/
Typhon

The name given to hurricanes in the western North Pacific Ocean, west of the International Date Line.

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U

Ultraviolet (UV) Radiation/
Rayonnement ultraviolet (UV)

Invisible electromagnetic radiation with afrequency between that of visible violet light and x-rays.Most of the ultraviolet component of sunlight is absorbed by the ozone layer of the atmosphere, however UV-B radiation can cause sunburn and skin cancer, and UV-A radiation can cause photosensitivity reactions and possibly skin cancer.

Universal Thermal Climate Index/
Indice universel du climat thermique

The Universal Thermal Climate Index (UTCI) is atemperature index that describes the “feels-like” temperature to the human body. It uses air temperature, humidity, wind, and solar radiation. Unlike Humidex and Wet Bulb Globe Temperature (WBGT), UTCI can be used for both hot and cold ““feels-like” temperatures. The UTCI is most often used in research, looking at thermal stress on the human body.

Unstable/
Instable

A turbulent, convective state in the atmosphere, resulting from arapid decrease in air temperature with the altitude.

UTC/
TUC

UTC is the international abbreviation for Coordinated Universal Time. It is the local time at the Greenwich meridian (0°), situated in United Kingdom. The World Meteorological Organization (WMO) has adopted the UTC as the standard time for use in reporting of all meteorological data. Times in UTC sometimes get the suffix "Z", i.e. 16Z. From the "Z" suffix came the mnemonic "Zulu" (as used in international marine communications standards).

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V

Veering Wind/
Vent dextrogyre

A clockwise change in wind direction. For example, from southeast to southwest, through south. It is the opposite of backing wind.

Vertical Wind Shear/
Cisaillement vertical du vent

The condition produced by a change in wind velocity (speed and/or direction) with height. Vertical wind shear can weaken or destroy a tropical cyclone by interfering with the symmetric nature and organization of the deep convection around the cyclone centre.

Very Close Pack/
Drift/
Banquise très serrée

Sea-ice terminology that describes floating ice in which the concentration is from 9/10 to less than 10/10.

Very Large Iceberg/
Très gros iceberg

Sea-ice terminology. Describes apiece of glacier ice that extends more than 75 mabove sea level, and has alength of more than 200 metres.

Very Open Drift/
Banquise très lâche

Sea-ice terminology describing ice in which the concentration is 1/10 to 3/10 and water dominates over ice.

Very Thick Lake Ice/
Glace de lac très épaisse

Sea-ice terminology describing lake ice that is greater than 70 cm thick.

Very Weathered Ridge/
Crête très érodée

Sea-ice terminology describing aridge with tops very rounded. The slope of its sides is usually from 20 to 30 degrees.

Virga/
Virga

Wisps or streaks of precipitation that evaporate before reaching the ground.

Visibility/
Visibilité

The greatest distance at which ablack object of suitable dimensions can be seen and recognized against the horizon sky during daylight. It could also be seen and recognized during the night if the general illumination were raised to the normal daylight level.

VR/
N/A

Abbreviation for winds that are variable in direction.

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W

Warm Front/
Front chaud

A transition zone where acold air mass retreats and is replaced by awarm air mass.

Warning/
Avertissement/
alerte

A type of alert issued by Environment and Climate Change Canada's Meteorological Service (MSC), where ahazardous weather or environmental event that poses asignificant threat to public safety and property is certain or imminent.

Watch/
Veille

A type of alert issued by Environment and Climate Change Canada's Meteorological Service (MSC), where conditions are favourable for the development of weather or an environmental hazard that poses asignificant threat to public safety and property, but the occurrence, location, and/or timing of the expected hazardous condition(s) is still too uncertain to issue awarning. It is intended to heighten public awareness of the potential impact of the event, and serves as alead-up to awarning.

Water Sky/
Ciel d'eau

Sea-ice terminology. It describes dark streaks on the underside of low clouds, indicating the presence of water features, in the vicinity of ice.

Waterspout/
Trombe marine

A tornado that occurs over water. Unlike tornadoes over land, they can occur frequently in the fall months when water temperatures remain warm relative to air temperatures in the lower atmosphere.

Waterspout Watch/
Veille de trombe marine

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) to give advance notice when conditions are favourable for the development of waterspouts over amarine area.

Wave Height/
Hauteur des vagues

The vertical distance between the trough and crest of awave.

Wave Period

The time it takes two successive wave crests to pass a fixed point.

Wavelength/
Longueur d'onde

The distance between two successive crests or troughs of a wave.

Weather/
Temps (aussi appelé << conditions météorologiques >> ou << conditions atmosphériques >>)

The condition of the troposphere (lower atmosphere) at any particular time and place.

Weather and Meteorology/
Temps et météorologie

Meteorology is the science that studies the processes and phenomena of the atmosphere. Weather is the state of the atmosphere at agiven time and place with regard to temperature, atmospheric pressure, humidity, wind, cloudiness, and precipitation. The term weather is used mostly for conditions over short periods of time.

Weather Summary/
Sommaire météorologique

A bulletin issued by Environment and Climate Change Canada's Meteorological Service (MSC), which contains apost-event summary of aweather event, especially one that has received significant media attention.

Weathered Ridge/
Crête érodée

Sea-ice terminology describing aridge with peaks slightly rounded, and slope of its sides that is usually 30 to 40 degrees. Individual fragments of ice are not visible.

Weathering/
Érosion

Sea-ice terminology. Describes the processes of ablation and accumulation, which gradually eliminate irregularities in an ice surface.

Wedged Iceberg/
Iceberg biseauté

Sea-ice terminology. Describes an iceberg that is rather flat on top, with steep vertical sides on one end, sloping to less steep sides on the other end.

Westerlies/
Vents d'ouest

The dominant west-to-east motion of the atmosphere, centered over the middle latitudes of both hemispheres.

Wet Bulb Globe Temperature/
Température au thermomètre-globe mouillé

The Wet Bulb Globe Temperature (WBGT) is an index that uses air temperature, humidity, wind, and solar radiation to estimate the effect of heat exposure on humans. The WBGT is most often used in sport and occupational heat exposure.

Wind/
Vent

The horizontal movement of air, relative to the earth's surface.

Wind Chill/
Refroidissement éolien

Chill that results from aspecific combination of wind speed and air temperature, expressed by the loss of body heat in watts per square metre (of skin).

Wind Chill Index/
Indice de refroidissement éolien

Index used to determine the relative discomfort resulting from aspecific combination of wind speed and air temperature, expressed by the loss of body heat in watts per square metre (of skin).

Wind Shear/
Cisaillement du vent

The change of wind speed and/or wind direction over agiven distance.

Wind Warning/
Avertissement de vent

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for sustained winds of speeds that pose asignificant threat to public safety and property.

Windward/
Au vent

Windward or upwind, is the direction from which the wind is blowing; the opposite of leeward.

Winter Storm Warning/
Avertissement de tempête hivernale

A warning issued by Environment and Climate Change Canada's Meteorological Service (MSC) for amajor snowfall, or significant snowfall combined with freezing rain, strong winds, blowing snow, and/or extreme wind chill. The mix of these winter weather conditions poses athreat to public safety and property. Winter storm conditions are not necessarily restricted to the winter season, but may occur in the late autumn and early spring as well.

Winter Storm Watch/
Veille de tempête hivernale

A watch issued by Environment and Climate Change Canada's Meteorological Service (MSC) in advance of awinter storm warning, to alert the public of the possibility of apotential winter weather storm.

Wreckhouse Winds/
Vents de Wreckhouse

Wreckhouse is located between Cape Ray and St Andrew's in Southwestern Newfoundland. This area is, at times, subject to extremely violent southeast winds, which have been strong enough to blow railcars off their tracks.

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Y

Young Coastal Ice/
Jeune glace côtière

Sea-ice terminology. Describes the initial stage of fast ice formation consisting of nilas or young ice; its width varying from a few metres up to 200 metres from the shoreline.

Young Ice/Jeune glace

Sea-ice terminology that describes ice in the transition stage between nilas and first-year ice. It is of between 10 cm and 30 cm in thickness, and may be subdivided into grey ice and grey-white ice.