Monday, April 27, 2015

Why April Is a Dangerous Month for Tornadoes

An average April jet stream is strongest over the southern U.S., over that warm and humid air.  
A common outbreak scenario involves a pronounced southward dip in the jet stream, or upper-level trough, that plows east into the Plains or South with winds aloft spreading apart, forcing strong upward vertical motion in the atmosphere.  
The jet stream also provides deep wind shear, or changing wind speed and direction with height, supportive of rotating supercell thunderstorms.  
If wind shear is particularly strong in the first few thousand feet near the surface, these supercells would more likely produce tornadoes. 
http://www.weather.com/storms/tornado/news/april-tornadoes-history-explained 

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