Q: Some years ago, a tornado warning meant that a tornado had been spotted and to take cover. Now it seems that tornado warnings are given over a broad area when there is a potential for a tornado ... that used to be a tornado watch, as I recall. Why has there been a change, if in fact there has been?
-- Martha Hunt, Hoschton
A: The terms “watch” and “warning” are sometimes confused by people despite their common usage since at least the late 1960s, WSB Radio meteorologist Kirk Mellish said, and the meanings have not changed.
Watch means a tornado is possible sometime in the next two to six hours. A warning means it is imminent within minutes. A tornado watch may cover large parts of one or more states indicating atmospheric conditions are favorable for possible tornado formation, he said. A warning will cover all or parts of one to three counties, and it means immediate danger.
Mellish said the confusion may arise from the use of Doppler radar to trigger a tornado warning. That practice began in the 1990s. Before Doppler, a warning would be issued only when a tornado was spotted on the ground. Nowadays, if Doppler indications are strong enough, a tornado warning will be issued despite no eyewitnesses. The weather bulletin will state: Doppler radar indicates a severe thunderstorm capable of producing a tornado. If a tornado has been confirmed by eyewitnesses, the bulletin will say so.
Lori Johnston wrote this column. Do you have a question about the news? We’ll try to get the answer. Call 404-222-2002 or e-mail q&a@ajc.com (include name, phone and city).
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