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Weather observations inside tornado

| 4:27 pm February 24, 2012

A long time friend and blog reader, Wally Coker, has been keeping 1-minute resolution observations at his house in Clay, just off I-59/Deerfoot Parkway, for several years.  His station ID on the mesonet was KC4ANB.  Since getting 1-min data is tough in the short-term, I have sometimes asked Wally for his data, and he always obliges.  I have used his data in blog posts, conference talks, etc.

Wally’s home was hit by the Center Point-Clay-Trussville tornado of Jan 23.  His house is pictured below.   Fortunately, his family was safe.

His Davis instruments weather system was wireless, and continued taking wind observations until his roof came off the house around 414 am.  Apparently, the barometer is inside the weather station inside his basement, so it took readings for a few more minutes (it and computer must have been on battery back up  and kept running until rain water came in).  His highest observed 1-minute average wind speed was 53 mph.  His highest recorded gust was 79 mph according to an internet site he was linked in to, but given the damage I would say it got a lot higher than that when the roof and the anemometer left.

Here is a trace of pressure and 1-minute average wind speed, then a trace of temperature, both at Wally’s house.

The rapid drop in pressure began even before the tornado arrived, but got worse when it did.  This drop in pressure is due to the rotation in the mesocyclone and then the tornado…centrifugal force literally throws air out away from the center of the rotation, just like you get pushed to the outside of the curve in a car.  The wind averaged 53 mph for the minute ending at 4:13 am, then dropped and went away.

Interestingly, the temperature suddenly rose 2 or 3 degrees as the tornado passed by.  This could be an electronic problem with the sensor due to debris, etc.  But, some have suggested that there are occasionally downdrafts in the middle of a tornado that can actually warm the air right in the middle…so maybe it was real.

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Category: Meteorology 101

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