Guide to marine weather forecasts: chapter 9

Interpreting the Wording of a Marine Forecast

As mentioned in Section 1 of this Guide (Types of Marine Forecast), there may be up to four marine weather elements included in regular or updated marine forecasts. At times the marine forecast can become quite lengthy, particularly during the winter storm season as extra wording may be required to convey the meteorological and warning information comprising the marine forecast.

As such, in the interests of brevity and utility for the end-user, the marine forecast will exclude wording that may be redundant, or that does not provide additional information for the end-user.

Since the marine forecast is worded in such a way so as to minimize length, end-users should note that insignificant changes in marine weather elements, such as wind and visibility, are not usually mentioned so as to avoid unnecessary or redundant wording. However, significant changes to marine weather elements are explicitly stated to ensure the forecast information is conveyed.

• Example 1:  Significant changes to winds occurring part-way through the forecast period then winds remain unchanged for the remainder of the forecast period:

If the last significant change to the wind forecast occurs on Day 1, the wind statement will not be repeated in the Day 2 wind forecast. To illustrate, refer to wind statement of the following marine forecast:

FQCN13 CWUL 190700
MARINE FORECASTS FOR THE ST. LAWRENCE AND SAGUENAY RIVERS ISSUED BY ENVIRONMENT CANADA AT 3:00 A.M. EDT THURSDAY 19 MARCH 2009 FOR TODAY TONIGHT AND FRIDAY.
THE NEXT SCHEDULED FORECASTS WILL BE ISSUED AT 3:00 P.M.

FOG IMPLIES VISIBILITY LESS THAN 1 MILE.

MONTREAL TO TROIS-RIVIERES.
WIND WEST 15 KNOTS DIMINISHING TO LIGHT EARLY THIS EVENING. HIGH TODAY PLUS 3. LOW TONIGHT MINUS 12. HIGH FRIDAY MINUS 1.

Note that the stated period of coverage for the above forecast is TODAY TONIGHT AND FRIDAY, and that the wind forecast states WIND WEST 15 KNOTS DIMINISHING TO LIGHT EARLY THIS EVENING. Since there is no further mention of changes to the wind after early this (Thursday) evening, this implies that light winds are expected beginning early Thursday evening and persisting through to midnight Friday.

• Example 2: A marine forecast in which there is no change in the wind speed or direction during the entire forecast period:

In this case there is no significant change in the wind during the forecast period, and the marine forecast will notrepeat the same wind forecast for subsequent times of the forecast part-periods (this afternoon, tonight, etc). To illustrate, refer to wind statement of the following marine forecast:

FQCN13 CWUL 190700
MARINE FORECASTS FOR THE ST. LAWRENCE AND SAGUENAY RIVERS ISSUED BY ENVIRONMENT CANADA AT 3:00 A.M. EDT THURSDAY 19 MARCH 2009 FOR TODAY TONIGHT AND FRIDAY.
THE NEXT SCHEDULED FORECASTS WILL BE ISSUED AT 3:00 P.M.

FOG IMPLIES VISIBILITY LESS THAN 1 MILE.

MONTREAL TO TROIS-RIVIERES.
WIND WEST 15 KNOTS. HIGH TODAY PLUS 3. LOW TONIGHT MINUS 12. HIGH FRIDAY MINUS 1.

Note that the stated period of coverage for the above forecast is TODAY TONIGHT AND FRIDAY, and that the wind forecast states WIND WEST 15 KNOTS. Since there are no further stated changes, this implies that 15 knot westerlies are expected to persist during the entire forecast period, from 3 AM Thursday morning through to midnight Friday.