Derecho windstorms

Derecho is a widespread windstorm associated with a line of severe convective storms. To be classified as derecho, the windstorm must exhibit wind gusts exceeding 25 m.s-1 on a major axis length more than 400 km, with minimal three wind gusts exceeding 33 m.s-1 . Various mechanisms play a main role in the formation of these widespread windstorms, which interrelate and can together be responsible for the formation of derecho. However, the occurrence of derechos is not only the domain of the USA, but also of Europe, China and South America. Conditions for the formation and development of derechos in Europe are different from those in the USA and their occurence is not concurrently as frequent as in the USA. Warm season derechos in Europe occur at lower instability than derechos in the USA and at higher deep layer wind shear values. In respect of the extent of the damaged area, the cold season derechos in Europe hit larger areas than derechos in the USA. Warm season derechos in Europe are related to the area of the front side of the upper trough and develop ahead of the cold front near the convergence line. Conversely, cold season derechos are related to the significant cold front. One of the most significant warm season windstorms in the Central Europe occurred on 4th July 1929. This event was..