Derecho

Facts for Prelims

Derecho

News: Recently, a few States of US were hit by a storm system called a Derecho, turning Sky Green. They mostly occur across central and eastern parts of the United States.

About:
• A Derecho 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.
• It is a warm-weather phenomenon that generally occurs in June and July.

Why does the sky turn green?
• Severe thunderstorms result in a ‘green sky’ due to light interacting with the huge amount of water they hold.
• The big raindrops and hail scatter away all but the blue wavelengths due to which primarily blue light penetrates below the storm cloud.
• This blue then combines with the red-yellow of the afternoon or the evening sun to produce green.