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Doppler Radar lights up despite no rain in area

Published: Friday, September 29, 2017 @ 8:32 PM

Doppler radar systems across the region are detecting what appears to be precipitation, but there is no rain anywhere nearby. The stagnant late September air along with a temperature inversion is likely to blame for radars lighting up.

You may have opened your WHIO Weather App recently to check Live Doppler 7 Radar and thought it was falsely detecting precipitation all over the Miami Valley.

WHIO Doppler 7 Interactive Radar

But don't be fooled. The radar is working -- and it’s working quite well, Storm Center 7 Chief Meteorologist Eric Elwell said.

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There has been no significant rainfall in the Miami Valley or the region over the last 10 days, he said, and even though a series of cold fronts has crossed the region, the cooler air has been quite shallow. 

That means the overall atmosphere in the region is quite stagnant.

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When air becomes stagnant, it can collect dust and other microscopic debris, such as pollen. In the summer, air pollution advisories are sometimes issued because of the stagnant air. 

So what does that have to do with what radar is detecting? 

Elwell said the dry field conditions have been perfect for area farmers to start harvesting crops. The dust created by the tractors has been lifted into the air and can remain airborne for long periods as it is picked up by the winds.

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Many of the National Weather Service Doppler radars, along with WHIO-TV’s Live Doppler 7 radar, are sensitive enough to detect the increased dust particles in the air.

It also turns out that an increase in late summer/early fall insects are also likely being detected, he said. 

Stink bugs are one of those insects likely being picked up being moved around by the breezes. With farmers working in the fields, this will also force those insects that are feeding on crops to take flight. 

When those insects and the field debris become concentrated enough, Doppler radar is able to detect it. 

Elwell said that despite what radar may show the next few days, rainfall is not expected in the region until late next week.