There are several atmospheric warning signs that precipitate a tornado’s arrival:
- A dark, often greenish, sky
- Wall clouds or an approaching cloud of debris
- Large hail often in the absence of rain
- Before a tornado strikes, the wind may diedown and the air may become very still
- A loud roar similar to a freight train may beheard
- An approaching cloud of debris, even if a funnelis not visible
Despite great strides made in meteorology that help us understand and predict tornadoes, there are still many unknown variables. Advance warning and proper precautions are the only certainties.
Tornadoes can occur at any hour but usually strike during the late afternoon and early evening (3 to 9 p.m.). Most move from southwest to northeast but can move in any direction. They have an average speed of 30 mph, but speeds can vary from nearly stationary to 70 mph. Normally a tornado will stay on the ground no more than 20 minutes, however, one tornado can touch the ground several times in different areas.
See Also
Thunderstorm Winds and Derechos