Rapidly decaying storms last evening over southwestern Iowa produced what appears to be a heat burst event. The featured chart is a time series from the Atlantic AWOS showing a temperature rise above 100 degrees and a dew point drop to 7 degrees, which is a classic heat burst type signature. There is some doubt if the 7 degree dew point is legitimate as other sites in the area only dropped to as much as the mid 40s. Regardless, these events typically also bring damaging winds and a few trees were reported down. Heat bursts are not fully understood by scientists yet, but the common explanation is a decaying thunderstorm encounters a layer of dry air below the storm. Virga then falls into this layer, which quickly cools it by evaporation and the air mass rapidly sinks to the ground and warms along the way.

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Tags:   heatburst   2011