WRAL WeatherCenter Blog

Please explain again the difference between a storm warning and a storm watch. Thanks!

Posted July 2, 2007 11:20 a.m. EDT

MIKE MOSS SAYS:       Julie,   It varies a litle depending on the type of storm (tornado versus hurricane versus winter storm, etc) but for the most common types we will deal with in the next few months, here are the guidelines:

For severe thunderstorms (those with winds reaching 58 mph or more and/or hail three quarters of an inch or more in diameter) and tornadoes, a watch is issued for a sizable area whenever general atmospheric conditions appear favorable for possible formation of those types of storms. These watches are usually in effect for about six hours or so, and they simply mean that people in the affected area should be alert to the chance that a severe storm or tornado could form, and should be prepared to take the appropriate actions in that event. When a severe thunderstorm or a tornado is actually observed, or is indicated based on radar signatures, then a warning is issued for a much smaller area than the watch. The warning means that a severe storm or torndado is underway and may affect locations in the warned area very shortly. Therefore, people in the warned area should be prepared to take cover immediately.

The situation is a little different with hurricanes because of the large size and long life span of those storms, along with the uncertainties inherent in forecasting their track and intensity. A hurricane watch means that hurricane force winds and the associated bands of heavy rain are POSSIBLE within the next 36 hours for the affected area. A hurricane watch is upgraded to a warning, or sometimes a warning may be issued initially, when hurricane conditions are considered LIKELY within 24 hours.