Tornado warning means a tornado has either been spotted on the ground or indicated on radar, and local forecast offices of the National Weather Service issue these warnings for smaller areas.
A warning typically lasts 30 to 45 minutes and signals that people should seek shelter right away, according to guidance in the source material.
By contrast, a tornado watch means conditions are favorable for tornadoes to form and is issued by the Storm Prediction Center, often covering multiple states and giving four to eight hours notice.
A similar watch versus warning distinction applies to severe thunderstorms, which the National Weather Service officially defines as storms that produce hail roughly the size of a quarter, at least one inch across, and or wind gusts 58 miles per hour or higher.
Forecasters may issue a severe thunderstorm watch when they believe storms capable of meeting those thresholds could develop, with the intent to give people time to stay alert and prepare.
Impacts Actions And Forecast Products
Warnings are more localized than watches and are issued when radar or trained storm spotters detect storms that meet the hail and wind criteria, so immediate protective action is advised.
An advisory is used when weather is causing gusty winds, small hail or heavy rain that does not meet severe criteria, and the National Weather Service uses these to flag conditions that could make driving difficult.
Outlooks are the earliest alerts and the Storm Prediction Center issues them days in advance, classifying risk on a one to five scale as marginal, slight, enhanced or high based on how favorable the environment is for severe storms.
In the most extreme situations forecasters may append a tornado emergency to a warning, which is not a separate warning type but rather more urgent wording to convey an immediate and potentially catastrophic threat.
The takeaway in the source material is straightforward, a watch means be prepared while a warning means take action, language intended to give people precious minutes to protect themselves and their families.
