Watching the radar

Posted at 6:56 AM on May 12, 2009 by Craig Edwards

Growing up I studied the clouds and the weather trends n the Fox River Valley of norhtern Illinois. I remember the gravel voice meteorologist on the radio often predicting a chance for afternoon and evening thunderstorms. To cover himself he would also mention fading morning showers. He was likely following folklore of the old rain before 7am ends by 11am.

Nature hasn't changed. Daytime heating makes the air unstable and generates more lift to excite clouds to produce rain. With sufficient vertical motion and low level moisture you can get thunderstorms. And it is true, for the most part, that overnight rain diminishes through mid morning in the warm season.

Today, we have the fun of watching this all enfold on weather radar. You can view how showers form, increase in intensity and coverage and travel across the landscape. What you can't do on your computer is cut and paste a shower over your lawn or garden that badly needs moisture.

But by watching the radar you get a better understanding for how the meteorologist tries to convey rain chances by the use of precipitation probabilities. The best chance for wetness in the metro region comes later today and into Wednesday morning.

Chanhassen radar

Sometimes the radar displays moisture aloft in the mid level clouds about 50 miles from the radar. The other ghost images, close by the radar, are ground clutter. Meteorologists filter the ground clutter on the Doppler to track storms as they move over the local area.

CE

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