Canadian Hurricane Centre: frequently asked questions

The Canadian Hurricane Centre was formed in 1987.

Canada has a hurricane centre because tropical storms, hurricanes and post-tropical storms can have a significant impact on Canadian weather and on Canadians.

These storms often bring severe rainfall and wind speeds and behave differently than other types of storms and can therefore be quite complex and challenging to forecast. The Canadian Hurricane Centre provides the public with the expertise of specially-trained forecasters and issues tropical cyclone-specific public warnings to warn the public about these potential weather hazards.   

The Canadian Hurricane Centre (CHC) was created in 1987 after it became clear that Canadians needed an expert source for information that was focused specifically on how tropical cyclones affect Canada. Before the creation of the Centre, Canadians relied largely on forecasts from the United States for hurricane-specific information.

A tropical storm watch is a public announcement for a specific geographic area that tropical storm conditions are a possible threat within 36 hours.  This includes sustained winds between 63-118 km/h.

A tropical storm warning is a public announcement that tropical storm conditions are expected in a specific geographic area within 24 hours. This includes sustained winds between 63-118 km/h.  As tropical storms are usually accompanied by heavy rainfall, local flooding can also be expected.

A hurricane watch is a public announcement for a specific geographic area that hurricane conditions are a possible threat within 36 hours. These conditions include average sustained winds of at least 119 km/h, dangerously high water levels, or a combination of high water and waves.

A hurricane warning is a public announcement that one or both of the following dangerous effects of a hurricane are expected in a specific geographic area in 24 hours or less:  (1) average sustained winds of at least 119 km/h; (2) dangerously high water levels, or a combination of dangerously high water levels and exceptionally high waves.  This can happen even if expected winds are less than hurricane force. A hurricane also brings the threat of local flooding from heavy rainfall.

The Canadian Hurricane Centre and the National Hurricane Centre have a well-established practice of regularly discussing and coordinating details on storms expected to affect Canada.  There can sometimes be very small differences in the predictions about storm intensity or track. This can happen due to differences in access to data or the interpretation of the available data. In particular, it can sometimes be challenging to forecast the exact intensity and track of a storm prior to it making landfall, due to the lack of data over the ocean.

Tropical cyclone bulletins are generally issued every six hours once a storm is forecast to impact Canada or Canadian waters within a 72-hour period.  Bulletins are issued at 9:00 p.m., 3:00 a.m., 9:00 a.m., and 3:00 p.m. Atlantic Daylight Time.  Tropical cyclone bulletins provide forecast discussions and wind speed information.

Once a storm begins to have a significant impact on Canada or Canadian waters, intermediate bulletins are issued in addition to the regular bulletins above, at 6:00 p.m., 12:00 a.m., 6:00 a.m., and 12:00 p.m.. These bulletins are brief and state the position, movement and intensity of the storm.

The World Meteorological Organization recognizes the National Hurricane Center in the United States as the official lead hurricane agency for the Atlantic Basin.  However, many countries, including Canada, have weather offices with meteorologists specializing in tropical cyclones.  In Canada, Environment Canada created the Canadian Hurricane Centre to meet our safety and security needs, and the centre is the only Canadian organization authorized to issue tropical cyclone watches and warnings.

No, the Canadian Hurricane Centre forecasters work for the Meteorological Service of Canada, a branch of Environment Canada. The Weather Network is a private company.

The most up-to-date information on tropical cyclones predicted to affect Canada can be found on the Canadian Hurricane Centre, Environment Canada’s Weather Office, Weatheradio Canada and your local telephone recording weather line (Automated Telephone Answering Device).

Local television and radio stations can also be good sources of weather information and their broadcasts will often display and talk about the areas where Environment Canada’s warnings are in effect.

While many local television stations employ trained meteorologists, they are generally not experts in hurricanes or tropical cyclones. However, if you have questions about their qualifications you should check with your local television station.

You can access information on past hurricanes and tropical storms that have affected Canada in the climatology section of the Canadian Hurricane Centre’s website.

In a qualitative sense, the CHC predicts 3-out-of-4 storms reasonably well, while 1-in-4 can pose a particular challenge.  That is to say, 1-in-4 storms track far enough away from land such that they do not cause any significant impact, but warnings were issued because of the storm’s close proximity to land.  There are times when the overall intensity and track of a storm is generally well-predicted, but the impact at a specific location may be different than expected due to complicating factors such as local terrain. 

On average, 12-hour forecasts of the storm centre location are accurate to within 100 km, 24-hour forecasts to within 150 km, 36-hour forecasts to within 200 km, and about 250 km for a 48-hour (2-day) forecast.  In other words, the centre of the storm may be located anywhere between Fredericton and Halifax based on a 2-day forecast.  Some storm tracks can be easier to predict, and the uncertainty for a 2-day forecast may be less - for example, the distance between Halifax and Moncton.

What makes predicting tropical cyclones particularly challenging is that their behaviour and structure changes quickly over the ocean, where there are very few weather observations.

It is important to note that in terms of preparing for a tropical cyclone, the precise track of a storm is less important, as the area impacted can be quite dispersed from the actual storm.  It’s also important to remember that the measures that should be taken to prepare for this kind of storm are very similar whether or not you are directly in the “path of the storm” and regardless of the predicted strength.

Environment Canada’s scientists and meteorologists are constantly working to improve our understanding of these complex storms and adjusting our forecast tools and techniques accordingly to make sure that our forecasts are as accurate and as useful as possible.  

The most up-to-date and accurate hurricane forecasts can always be found on the Canadian Hurricane Centre website; on Environment Canada’s Weather Office website, via the Weatheradio Canada network and through the Automated Telephone Answering Device for your location. You can also sign-up to receive tropical cyclone bulletins, and tropical storm and hurricane watches and warnings via the Weather Office website.

There are many reasons why radio stations could be broadcasting different or conflicting information. If you are concerned about the accuracy of the information you are receiving from your local radio station it would be best to check with one of Environment Canada’s sources, either via the website or by listening to Weatheradio.

A tropical cyclone is a low-pressure weather system that draws its energy from heavy showers and thunderstorms (known as convective clouds). Warm water temperatures greater than 26º Celsius are usually necessary for a tropical cyclone to form or persist.

The term “tropical cyclone” is a general term used to describe storms that originate in the tropics, including hurricanes and tropical storms. Tropical cyclones include storms of different intensity that are categorized based on wind speed.  

A hurricane is a tropical cyclone with maximum sustained wind speeds of at least 119 km/h (64 knots). 

A tropical storm is a tropical cyclone that has maximum sustained wind speeds between 63 and 118 km/h (or between 34 and 63 knots). 

A tropical depression is a tropical cyclone with maximum sustained winds less than 63 km/h (34 knots).

The term extratropical storm can refer either to a storm that developed outside the tropics, or to a tropical cyclone that has moved outside of the tropics. These storms draw energy from the differences in temperature between warm and cold air masses across the storm and are often called “Nor’easters”, bringing wind, rain, snow or freezing rain, depending on the season. It is important to note that tropical cyclones can become extratropical and still bring tropical storm- or hurricane-force wind speeds.

A post-tropical storm on the other hand, began as a tropical cyclone and then moved into an area where it came into contact with colder air. Post-tropical storms have qualities of both tropical cyclones and extratropical storms.  It should be noted that, as tropical cyclones become post-tropical storms, under certain circumstances they can actually intensify and bring greater impacts to the affected areas. Post-tropical storms should not necessarily be dismissed as being less dangerous than hurricanes.

Sub-tropical storms or sub-tropical depressions are cyclones that exist in the tropical or subtropical latitudes.  These weather systems usually have less organized cloud structure than purely tropical systems and form in somewhat cooler environments and over cooler water temperatures. Like tropical cyclones, sub-tropical cyclones get most of their energy from heavy showers and thunderstorms (known as convective clouds).   

A subtropical depression has maximum sustained winds less than 34 knots or 63 km/h (gale force). A sub-tropical storm has maximum sustained winds of 34 knots or 63 km/h (gale force) or higher. A storm is named once it has been identified as sub-tropical.

The amount of rain depends on a number of factors including: the size of the storm, whether or not the storm is mostly tropical or post-tropical, the speed of the storm and the storm’s intensity. Generally a tropical storm or hurricane that is tracking over or is close to land in Canada will give rainfall amounts of 100 millimetres or more.

Hurricanes are categorized based on wind speed using the Saffir Simpson Hurricane Wind Scale, which classifies hurricanes in five categories.

Category 1:  sustained winds of 119-153 km/hr (64-82 knots).

Category 2:  sustained winds of 154-177 km/hr (83-95 knots).

Category 3:  sustained winds of 178-209 km/hr (96-113 knots).

Category 4:  sustained winds of 210-249 km/hr (114-135 knots).

Category 5:  sustained winds of greater than 249 km/hr (135 knots).

It is important to note that the category of the storm does not alone determine how “bad” a storm will be and the extent of the damages. Also, it is important to know that the category of a hurricane does not reflect the amount of rain. Storm impacts depend on a number of factors including: local geography, specific vulnerabilities of a particular area and previous weather conditions.  For example, a particular location may be more vulnerable to flooding conditions if there have been recent heavy rainfalls, or more vulnerable to breaking trees and power outages if there have been recent very high winds.

Hurricanes at or above Category 3 have never been documented in Canada on land. However, measured wave heights in Canadian waters have been higher than what Category 3 or higher hurricanes normally produce in the tropics.

Wind speeds are based on a calculation of the forward motion of the storm and the counter-clockwise motion of the winds surrounding the centre of the storm, at any given point in the storm’s track. On the right-hand side of a storm’s track, the rotating winds and the forward motion of the storm are moving in the same direction. These two readings combine to give the actual wind speed that we feel near ground/ocean level. On the left side of a storm, the rotating wind speed and the forward motion of the storm are moving in opposite directions. So, the resulting wind speed is determined by subtracting a certain proportion of the forward motion of the storm from the rotating wind.  

The Atlantic hurricane season officially starts on June 1 and ends on November 30. This is because very few tropical cyclones form after November 30 or before June 1. It should be noted however, that most of the tropical cyclone activity in Canada occurs during August and September.

Yes, tropical cyclones do occasionally form outside of the hurricane season. During the extremely active hurricane season of 2005, there were two tropical cyclones which formed outside the hurricane season:  Hurricane Epsilon and Tropical Storm Zeta. Both formed in the tropical Atlantic.

No, it is not possible to get snow from a tropical cyclone at any stage of development, including a hurricane. However, it is possible for a post-tropical storm to bring snow late in the year if it interacts with very cold air.

As of 2011, the most intense (as defined by sustained wind speed) tropical cyclones on record in the Atlantic Basin were Hurricanes Camille (1969) and Allen (1980), with maximum sustained wind speeds estimated near 305 km/h (165 knots).  Hurricane Wilma in 2005 had the lowest atmospheric surface pressure of any hurricane in the Atlantic Ocean - 882 millibars - with maximum sustained winds of 297 km/h (160 kts).  Typically, the lower the surface pressure - the higher the wind speeds.

Several typhoons in the Pacific Ocean had winds measured or estimated to be near 305 km/h, including Typhoon Tip (1979) which holds the world record for the lowest atmospheric surface pressure in a tropical cyclone - 870 mb.  The most extreme wind gust in any tropical cyclone occurred in Cyclone* Olivia that struck northwestern Australia in 1996. A weather station on Barrow Island registered an incredible peak wind of 408 km/h (220 knots) - about 2½ times stronger than the highest gusts during Hurricane Juan in 2003!

*Cyclone is what a hurricane is called in that part of the world.

The answer to this question is complicated because it depends how you define “strongest”. The most recent example of a strong hurricane affecting Canada was Hurricane Juan in 2003. This storm made landfall near Halifax, Nova Scotia and greatly impacted portions of the province as well as Prince Edward Island. Hurricane Juan was a Category 2 storm at landfall (maximum sustained wind speed near 155 km/h - 85 kts) and was responsible for two direct fatalities, four indirect fatalities, widespread power outages, record coastal water levels and major tree damage along and just to the right of its track.

Historical records indicate that storms of similar intensity to Hurricane Juan affected Atlantic Canada before, in the early 20^th century and late 19^th century.  The hurricane with the strongest winds at landfall in Canada is Hurricane Ginny in 1963 with maximum sustained winds near 175 km/h (95 kts).  Ginny made landfall near Yarmouth Nova Scotia on October 29^th.

The hurricane in Canada with the highest number of human fatalities on land was Hurricane Hazel in 1954. Hazel was responsible for the deaths of 81 people in Ontario, mainly from flooding.

The hurricane in Canada with the highest observed wave heights was Hurricane Luis in 1995. A Canadian buoy reported a peak wave height of 30 metres (98 feet) during this storm.  

Finally, the hurricane with the highest reported wind strength in Canadian territory (over the ocean) was hurricane Ella in 1978. This storm moved into Canadian offshore waters as a Category 4 storm with maximum sustained winds of 215 km/h (115 knots), making Ella’s winds the strongest in over 100 years of record inside Canadian territory.

In 1995 Hurricane Luis produced a peak wave of 30 metres (98 feet), according to measurements from a buoy south of Newfoundland. This record height is likely close to the highest waves capable of being produced by tropical cyclones in Canadian waters.

The waves produced by Luis were higher than the waves typically produced by much more intense hurricanes in the tropics. This is because storms in the Atlantic Basin (like Luis) move faster and further north which keeps the strong winds over the waves longer, allowing the wave heights to continue to grow larger.

Storm surge is an unusual rise of water generated by a storm, over and above the predicted astronomical tides.  Storm tide happens when the water level rises due to a combination of storm surge and the astronomical tide. This rise in water level can cause extreme flooding and significant damage in coastal areas particularly when storm surge coincides with normal high tide.

The frequency of tropical storms and hurricanes in the Atlantic varies greatly from year to year. In addition, patterns suggest that hurricane formation is cyclical; with an increase in storm activity for a 25 year period, followed by a decrease in storm activity for 25 years. While there is no evidence of a long term (greater than 25 year) increase in the number of tropical storms, the data suggests that we are currently in a more active cycle (since the mid nineties).

The seasonal outlooks, or the predictions of the number of tropical cyclones expected in any given season, apply to the entire Atlantic Basin, which includes the Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico.  Regardless of the overall number of storms forecast for the entre Atlantic Basin, in an average year the CHC responds to four or five tropical cyclone events with one or two of those affecting Canadian soil. There is very little correlation between the number of storms that form in the North Atlantic and the number that make their way into Canadian waters.  

Therefore Canadians should be less concerned about the number of storms predicted for the overall Atlantic Basin, and more focused on the one storm that could affect them. People living in areas vulnerable to tropical storms and hurricanes or post-tropical storms should always be prepared for a storm to affect their location.

No. Whether a given location is affected by a tropical storm, post-tropical storm or a hurricane is dependent on storm formation and track. The warmth of a Canadian summer does not affect this.

However, if a warm Canadian summer leads to warmer than usual water temperatures, then a tropical storm or hurricane tracking over these warmer waters may be more intense. That said, the storm’s track and location of the impacts wouldn't be affected by the previous summer’s weather, but instead by the large-scale pattern of the jet stream and other pressure systems at the time of the storm.

Yes, if a hurricane tracks close to your location, you can be affected by very strong winds even if the hurricane itself remains offshore. Even if a hurricane tracks quite far (offshore) from your location, you can still be affected by very heavy rainfall resulting in localized flooding.

You should consult the latest weather information from the Canadian Hurricane Centre and follow the advice of your local and provincial emergency services organizations. You should be prepared for extended power outages and have emergency supplies on hand. Check out Get Prepared for more information about preparing for hurricanes.

In September 2010, a state of emergency was declared in approximately 30 Newfoundland communities after Hurricane Igor hit as a Category One storm. Igor brought wind gusts of nearly 140 km/h and more than 200 mm of rain in some places. Severe river flooding over the entire eastern portion of Newfoundland washed away numerous bridges and left giant chasms in most major roads, resulting in a fatality and causing major disruptions for several weeks after the event. With total damage estimated near $200 million Igor was by far the most damaging tropical cyclone to strike the island of Newfoundland in the modern era.

In 2003 the Halifax Regional Municipality (HRM) declared a state of emergency in the hours following the arrival of Hurricane Juan, a storm that has been described as the worst storm to hit Halifax since 1893.  The near-160 km/hr sustained winds caused widespread structural and vegetation damage across the region, especially in the HRM. Thousands of felled trees blocked streets and knocked down power lines and Canadian Forces personnel were called in to help with the clean-up. Thousands of homes and businesses suffered property damage and some weaker structures were destroyed. Juan's passage resulted in eight fatalities and over $300 million in damage.

Yes, a tropical cyclone typically brings more than 100 mm of rainfall in some areas and in some cases more than 200 mms. In addition, the rain often comes in torrential downpours with a lot of rain falling in a short period of time. Road washouts, flooded basements, and overflowing streams and rivers are common in the areas where the heaviest bands of rain occur.

Yes, just because a storm has been classified as being “post-tropical”, it doesn’t mean it’s any less dangerous.  Not only can post-tropical cyclones maintain their strength, they can also intensify as they move north toward Canada and interact with colder air (very similar to common fall storms). However the tropical heat and moisture brought by post-tropical storms can lead to a much more severe storm than a typical fall storm.

The most recent Atlantic Canadian example of the potential impacts of a post-tropical storm is Hurricane Igor in September 2010.  Hurricane Igor transitioned to a post-tropical storm as it passed over the eastern coastline of Newfoundland’s Avalon Peninsula. However, the damages sustained were extreme. Large stretches of roadways were completely washed out by severe flooding, including a portion of the Trans-Canada that left about 150 communities completely cut off for days. One death has been attributed to the storm and total losses are estimated in the range of $200 million.

No, hurricanes can occur at any point in the tide cycle.  The track or existence of a hurricane has no dependence on the phase of the natural tides.   Certainly a hurricane that affects the coast will likely have a large storm surge that results in elevated water levels. However, if a hurricane hits near low tide and has a big storm surge, the total water level may simply appear as a regular high tide.

Yes, the track of any given storm has no bearing on the track of a future storm. There is evidence indicating that in 1891 two hurricanes hit almost exactly the same location on Nova Scotia’s Eastern Shore.

Since 1951, 23 hurricanes or hurricane-strength post-tropical storms have made landfall in Canada (about 1 every 3 years). Over the last few years, the average number of hurricanes that have entered Canadian territory have been increasing. Since 2000, we’ve seen about one land-falling hurricane every other year and 1-2 storms of tropical origin moving over land each year   However, we should remember that it is not the overall number of tropical storms or hurricanes forecast to move into the Canadian response zone that is important, but the one storm that can actually have an impact on you. To find more detailed information on tropical cyclones that have affected Canada since 1900, please visit our website or see A Climatology of Hurricanes for Eastern Canada.

A hurricane stronger than Category 3 (Hurricane Katrina was a Category 5) is virtually impossible in Canada because our water temperatures - even when they are warm - are simply too cold to support such a storm.

However a Category 3 hurricane is believed to be remotely possible in Atlantic Canada under the right conditions. First, a Category 3 (or higher) hurricane would have to be moving rapidly towards Atlantic Canada, with warmer-than-usual coastal waters and the right atmospheric conditions to be present for the storm to keep its strength.

No, areas of central Canada can be affected by gusty winds and torrential rain when hurricanes move across the United States after moving inland from the Gulf of Mexico or the Atlantic Ocean.

A recent example is Post-tropical Storm Irene, which had a significant and deadly impact on Quebec this past season (2011). Covering a broader area than a typical hurricane, slow-moving Irene brought a massive rain shield which extended from Kingston, Ontario to Halifax, Nova Scotia and from New Jersey to Newfoundland-Labrador.   At its worst, Irene’s winds topped 113 km/h east of Quebec City on Île d'Orléans and rainfall amounts approached 170 mm in just a few hours around Montmagny - L’Islet. Pounding rains inundated several communities and fast-moving waters flooded basements, collapsed roads, washed out culverts and triggered landslides and soil slumps.  Storm winds also uprooted trees and downed power lines. Nearly 250 000 Quebec residents were left in the dark (half for more than 24 hours). Sadly northeast of Montreal a motorist drowned after a landslide sent a chunk of roadway and two cars tumbling into the Yamaska River.

Another example is Hurricane Hazel which in 1954 caused tremendous flooding in the Toronto area, killing 81 people, and ultimately becoming the deadliest inland storm of tropical origin in Canadian history.

Finally, hurricanes in the Pacific Ocean can help provide energy to storms affecting British Columbia leading to increased wind and rainfall.

How climate change may be affecting hurricane activity is currently being studied. Although one might expect global warming to lead to more tropical storms and hurricanes, the heat balance in the ocean and atmosphere is very complex. The effect of global warming on thunderstorm clusters in the tropics which lead to the development of tropical cyclones is simply not yet known.

Studies have shown that during El Nino there are fewer tropical storms and hurricanes in the Atlantic Basin. Since there are fewer tropical storms and hurricanes during El Nino, then one would expect that there would be fewer storms available to move towards Canada. However, there is generally very little relationship between the number of tropical storms and hurricanes in the Atlantic Basin and the number that actually affect Canada, in a particular season. Therefore, El Nino has little impact on whether a hurricane will travel far enough to affect Canada.

The frequency of tropical storms and hurricanes in the Atlantic varies greatly from year to year. In addition, patterns suggest that hurricane formation is cyclical; with an increase in storm activity for a 25 year period, followed by a decrease in storm activity for 25 years. While there is no evidence of a long term (greater than 25 year) increase in the number of tropical storms, the data suggests that, as of the mid nineties, we are currently in a more active cycle.