Expert: Donald Rosenfeld - 9/12/2010

Question
Dear Mr Rosenfeld,

I am doing some research into the language used to describe sunshowers, but I would quite like to be able to include some meteorological information within the text I am writing. The problem is, the scant information I can find on the Internet seems to disagree on why sunshowers occur: some talk about the angle of sunlight; some say it's because the wind sweeps away the clouds before the rain can fall; others talk about cloud size as being an important factor...

If you could help to clear this up, I would be most grateful.

Best Wishes,
Camila

Answer
Hi Camila

Sunshowers are rain that falls during daylight hours from cumulus clouds that are moving at a high rate of speed with sunlight visible in proximity to the rain.

To expand:

"Daylight hours" allows for the sun light to be visible.

"Cumulus clouds" allows for breaks between clouds which allows for sunlight to be present.

"Cumulus clouds" can be any type of cumulus clouds as long as it has sufficient height to allow creation of rain.

"Cumulus clouds" of this height typically are cumulonimbus clouds.

"High rate of speed" is necessary to get the cloud out of the way for a person to see sunlight associated with the slower falling rain.

"Rain" can be light, moderate or heavy, in the shower.

"Shower" can be of a duration of less than a minute to several minutes.

The "amount of rainfall" can be a trace up to a half an inch or more.

For more info, see:

http://www.snopes.com/luck/superstition/sunshower.asp

http://timestranscript.canadaeast.com/news/article/1122164

http://www.weatherbyemail.com/sun-shower

http://en.wikipedia.org/wiki/Sunshower

http://web2.iadfw.net/danb1/clouds.htm