Canadian marine warning program: chapter 3

Localized Watches and Warnings

• Squall Watches and Warnings
• Tornado Watches and Warnings
• Waterspout Watches
• High Water Level Warnings
• Special Marine Watches and Warnings

Localized Watches and Warnings are relatively short in duration and are typically issued for a single marine forecast area or portion of a marine area. Localized Watches and Warnings are issued in a special bulletin that indicates the status of the event, using the keywords “new” or “in effect” or “ended.”

Localized Watches and Warnings can be issued for such hazardous events as Squalls, Tornadoes, Waterspouts, High Water Levels and any other undefined event using a Special Marine notice. Localized Watches and Warnings are only issued on short notice (less than six hours in advance) and are ended soon after the prevailing conditions have passed.

Squall Watches and Warnings

Squalls usually occur when conditions, such as severe thunderstorms, are affecting a marine area. Squall Watches and Warnings are relevant to all marine interests and can be issued for all marine areas (coastal, inland and offshore) that have a regular or recreational marine forecast.

Squall Watches come into effect when there is the possibility of sudden, strong, gusty winds of 34 knots or greater over the marine area.

Squall Warnings come into effect when sudden, strong, gusty winds of 34 knots or greater are either forecast or observed over the marine area.

Tornado Watches and Warnings

Tornadoes can develop when conditions, such as severe thunderstorms, are affecting a marine area. Tornado Watches and Warnings are relevant to all marine interests and can be issued for all marine areas (coastal, inland and offshore) that have a regular or recreational marine forecast being produced for them.

Tornado Watches come into effect when severe thunderstorms have developed over a marine area, and the conditions are conducive for the development of one or more tornadoes within the marine area during the time specified in the watch.

Tornado Warnings come into effect when there is evidence of tornado formation (i.e. reliable observation, radar, etc.), or an existing tornado is moving from land to an adjacent marine area. Details about the expected development, movement and duration of the tornado will be provided in the warning message.

Waterspout Watches

Waterspouts can form during unstable conditions when cool air moves over relatively warmer water. Waterspout Watches are relevant to all marine interests and can be issued for all marine areas (coastal, inland and offshore) that have a regular or recreational marine forecast.

Waterspout Watches come into effect when conditions for the development of cold-air waterspouts are forecast over a marine area during the time specified in the watch.

High Water Level Warnings

Abnormally high water levels along coastal regions can be caused by the development of one or more of the following events in combination: tropical or non-tropical storms, strong winds, high waves, and high tides. High Water Level Warnings are relevant to all coastal marine forecast areas that have a regular or recreational marine forecast along the coasts of New Brunswick, Nova Scotia, Prince Edward Island, and Newfoundland and Labrador.

High Water Level Warnings come into effect in order to warn mariners and coastal populations, about the potential impacts of abnormally high water levels or waves on coastal or shoreline areas.

Special Marine Watches and Warnings

All other non-specified marine weather conditions that may warrant a watch or warning being issued will be covered in a Special Marine Watch or Warning.

Special Marine Watches can be issued when conditions are conducive for the development of any other weather-related phenomena that may pose a hazard to local marine operations. For example, a marine forecaster may decide to issue a Special Marine Watch when a small band of freezing precipitation is occurring, or is forecast to occur, over a marine area.

Special Marine Warnings can be issued for any other weather-related phenomena which may result in a hazardous impact on local marine operations. For example, a marine forecaster may decide to issue a Special Marine Warning when an extended period of freezing precipitation is forecast over a marine area that may result in hazardous icing conditions on marine infrastructure.