States of Nebraska, Minnesota and Illinois in the U.S. were hit by a storm system called a derecho.
What is it?
- As the storm hit, it turned the skies green, with even many experienced storm chasers claiming to have never witnessed such atmospheric optics.
- A derecho, according to the US’s National Weather Service is “a widespread, long-lived, straight-line windstorm” that is associated with a “band of rapidly moving showers or thunderstorms”.
- The name comes from the Spanish word ‘la derecha’ which means ‘straight’. Straight-line storms are those in which thunderstorm winds have no rotation unlike a tornado. These storms travel hundreds of miles and cover a vast area.
- Being a warm-weather phenomenon, a derecho generally – not always – occurs during summertime beginning May, with most hitting in June and July.
- For a storm to be classified as a derecho it must have wind gusts of at least 93 km per hour; wind damage swath extending more than 400 km. The time gap between successive wind damage events should not be more than three hours.