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Name: David C.
Status: other
Age: 40s
Location: N/A
Country: N/A
Date: 2001


Question:
I have always wondered why it oftentimes seems to rain harder immediately following a thunderclap. After reading explanations of the water-producing thermodynamic possibilities in the questions-answered section, it occurred to me to ask. Does rain get shaken out of the atmosphere, is it thermodynamically produced, or is it just coincidence that the rain falls more densely after the thunder? Thanks.


Replies:
Dear David-

The observation that the heaviest rain occurs after thunder is mostly coincidental. The heaviest rain in a thunderstorm does fall near the strongest updraft part of the storm, and this is also where the lightning and thunder is produced. So it is likely that thunder may be heard during the heaviest rainfall in a thunderstorm.

Wendell Bechtold, meteorologist
Forecaster, National Weather Service
Weather Forecast Office, St. Louis, MO


David,

The heavier rain after or just about the time of more frequent lightning is probably not a coincidence. Research on lightning frequency and rainfall suggests that the action of hydrometeors (rain and hail) being carried around in the thunderstorm (in updrafts as well as downdrafts) creates electrical charge buildup in the clouds. The more active the storm and the more hydrometeors there are, the more electric charge is built up and the more frequent the lightning is. The more hydrometeors there are, the greater the likelihood of heavy precipitation, although it may occur after most of the lightning, as a downdraft has to set up or the updrafts decline to allow the hydrometeors to fall towards the ground.

David R. Cook
Atmospheric Research Section
Environmental Research Division
Argonne National Laboratory


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