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Thursday Heat Burst Event

04 May 2012 05:46 AM
Some locations in Iowa just to the southeast of Des Moines near Pella experienced a somewhat rare phenomena known as a heat burst. The signature for these events can easily be identified when high resolution in time observation data is available. They are marked by a period of rapid increase in temperature, decrease in dew point, and typically gusty winds. They are caused by rain showers that rapidly decay causing very warm and dry air to rush to the ground. The featured chart presents a time series from the Twin Cedars KCCI-TV SchoolNet site near Bussey. The period shaded in blue is roughly the length of the event, just 18 minutes. Other observation stations in the vicinity recorded this event as well with a wind gust topping out at 78mph (Pella RWIS) and a temperature rise of 14 degrees Fahrenheit (Pella SchoolNet). With once per hour observations, these events typically go unnoticed. Our period of active weather will continue into the weekend!

Voting:
Good: 84
Bad: 25

Tags:   heatburst   schoolnet  


more details here: NWS statement

High resolution

03 May 2012 06:01 AM
Parts of northern Ames were hit hard early Wednesday morning by a thunderstorm complex producing straight line winds upwards of 80 mph. The KCCI SchoolNet8 site in Ames sampled this event at about 6 second resolution and its data is presented in the featured graph. Data for only a seven minute period is shown between 1:49 and 1:56 AM. The peak wind gust of 61 mph occurred very briefly with wind speeds a few seconds later back down to around 20 mph. The pressure trace shows the jump in pressure as the colder thunderstorm air rushes by. The wind direction also shows an organized change from south to westerly winds. While not definitive proof, this plot would not indicate the presence of a nearby tornado as there probably would have been a pressure oscillation and more pronounced change in wind direction.

Voting:
Good: 55
Bad: 8

Tags:   schoolnet   ames   gustfront