Warnings and watches are two levels of alert issued by national weather forecasting bodies to coastal areas threatened by the imminent approach of a tropical cyclone of Tropical Storm or Hurricane intensity. They are notices to the local population and civil authorities to make appropriate preparation for the cyclone, including evacuation of vulnerable areas where necessary. It is important that interests throughout the area of an alert make preparations to protect life and property, and do not disregard it on the strength of the detailed forecast track. Tropical cyclones are not points, and forecasting their track remains an uncertain science.
The following terminology used by the US National Hurricane Center is the model for countries around the North Atlantic and in the Caribbean basin:
Tropical Storms
Before the 1987 Atlantic hurricane season Tropical Storm alerts were described as Gale Watches / Warnings, not distinguished from non-tropical storms.
Tropical Storm Watch
A tropical storm watch is issued when tropical storm conditions, including winds from 39 to 73 mi/h (35 to 64 knots, 63 to 117 km/h) pose a possible threat to a specified coastal area within 36 hours.
Tropical Storm Warning
A tropical storm warning is issued when tropical storm conditions (as above) are expected in a specified coastal area within 24 hours or less.
Hurricanes
Hurricane Watch
A hurricane watch is issued for a specified coastal area for which a hurricane or a hurricane-related hazard is a possible threat within 36 hours.
Hurricane Warning
A hurricane warning is issued when a hurricane with sustained winds of 74 mi/h (65 knots, 118 km/h) or higher is expected in a specified coastal area in 24 hours or less. A hurricane warning can remain in effect when dangerously high water or a combination of dangerously high water and exceptionally high waves continues, even though the winds may have subsided below hurricane intensity.
Where the intensity or track of a forecast cyclone are uncertain, a Tropical Storm Warning and a Hurricane Watch may be in force at the same time on parts of the coast.
Inland Wind advisories
The following alerts are issued for inland areas that may see tropical storm or hurricane force wind conditions, but are not located along the coast.
Inland Tropical Storm Wind Watch
Issued for inland areas when sustained winds of 39 to 73 mph associated with a tropical storm are anticipated beyond the coastal areas though the actual occurrence, timing and location are still uncertain.
Inland Tropical Storm Wind Warning
Issued for inland counties when tropical storm conditions are anticipated beyond the coastal areas in the next six to twelve hours.
Inland Hurricane Wind Watch
Issued for inland counties that sustained winds of 74 mph or greater associated with a hurricane are anticipated beyond the coastal areas though the actual occurrence, timing and location are still uncertain.
Inland Hurricane Wind Warning
Issued for inland counties that sustained hurricane force winds are anticipated beyond the coastal areas in the next six to twelve hours.
Other advisories
Other advisories are also commonly issued in association with tropical cyclones, but are not specific to them. Tropical cyclones often produce tornadoes, prompting the issuing of severe thunderstorm and tornado watches and warnings. Heavy rains associated with tropical systems often result in flood advisories. Gale warnings are typically issued for areas surrounding the storm but where it is unlikely to travel. Still lighter winds carry a small craft advisory.
Regional notes
Before the 2004 Atlantic hurricane season, these warnings were not issued in Canada (who simply issued standard wind and rain warnings). That policy was changed due to the lack of warning from four storms in 2003 that affected different land and offshore areas of Canada, the worst of which was Hurricane Juan in Nova Scotia. The inland watches and warnings are not differentiated from the coastal watches and warnings in Canada; the hurricane and tropical storm watches and warnings can be issued for any forecast area.
External link
NHC - watches and warnings
