Friday morning, may 8, 2009
A very serious severe thunderstorm situation appears headed toward southwestern KY. Large, powerful derecho has been creating widespread damaging winds (80 mph plus), and a few tornadoes, over southern Missouri. System will probably weaken very slowly as it moves across extreme southern IL into southwestern KY by early afternoon. Widespread wind damage should continue with this system.
While this system is bad news for western and southern KY, it is good news for the WAVE 3 viewing area. Derecho system will pass south of us - dropping into central TN by early evening IF it can last that long. That path is important. North of the system's path, there will be plenty of rain and thundershowers, but any severe weather is unlikely. The potentially dangerous weather is along and south of the path.
Some information of derechos from the Storm Prediction Center...
What is a derecho?
A derecho (pronounced similar to "deh-REY-cho" in English is a widespread and long lived windstorm that is associated with a band of rapidly moving showers or thunderstorms.
Because derecho is a Spanish word the plural term is "derechos".
What is the origin of the term "derecho"?
The word "derecho" was coined by Dr. Gustavus Hinrichs, a physics professor at the University of Iowa, in a paper published in the American Meteorological Journal in 1888.. Dr. Hinrichs chose this terminology for thunderstorm induced straight-line winds as an analog to the word tornado. Derecho is a Spanish word which can be defined as "direct" or "straight ahead" while tornado is thought by some, including Dr. Hinrichs, to have been derived from the Spanish word "tornar" which means "to turn".
DERECHO PRODUCING STORMS
What kind of storms cause derechos?
Derechos are associated with a band of showers or thunderstorms that are often "curved" in shape. These bowed out storms are called "bow echoes". A derecho can be associated with a single bow echo or multiple bow echoes. The bow echoes may vary in scale and may die out and redevelop during the course of derecho evolution. Further, derecho winds can be enhanced on a smaller scale by embedded supercells within the derecho producing storm system.
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