Derechos are heard about now more then ever. What is a Derecho? What is the Definition of one and what can be done to better warn people of this threat?
Derechos can cause hurricane force winds, tornadoes, heavy rains, and flash floods. Convection-induced winds take on a bow echo (backward "C") form of squall line, forming in an area of wind divergence in upper levels of the troposphere, within a region of low-level warm air advection and rich low-level moisture. They travel quickly in the direction of movement of their associated storms, similar to an outflow boundary (gust front), except that the wind is sustained and increases in strength behind the front, generally exceeding hurricane-force. A warm-weather phenomenon, Derechos occur mostly in summer, especially during June, July, and August in the Northern Hemisphere, within areas of moderately strong instability and moderately strong vertical wind shear. They may occur at any time of the year and occur as frequently at night as during the daylight hours.
There are four types of Derechos:
Derechos depending on your location is more or less frequent to occur. One of the most Devastating Derechos in the last 5 years occurred on June 29/30 2012. This Derecho was powerful with 28 deaths, 2.9 million in damage and very High Winds some of which occurred in Roanoke VA where at the airport an 80 mph plus wind occurred. My weather station Recorded 91 mph matching the highest official gust of 91mph in Fort Wayne, Indiana
Areas with the most Derechos
Research by Meteorologist Dean D Davison for the National Weather Association Conference will be presented in Norfolk VA in September.