Friday, June 14, 2013

Nebraska Heat Burst Sends Temperatures Soaring Earlier This Week

Parts of Central Nebraska had a relatively unusual experience on Tuesday morning.  A heat burst occurred in a number of towns, with temperatures jumping over 20 degrees and dew points dropping from the muggy 60's into the dry 40's or even 30's as gusty winds blew out of a nearby thunderstorm and bounced temperatures significantly higher in the late night hours.

What is a heat burst?   The easiest definition (the NWS has a detailed definition on what they are) is that a heat burst occurs when dry air has exhausted all of the available moisture in a thunderstorm, with air continuing to escape out of the storm out ahead of the storm's track (much like the initial gust front in advance of a storm).  This outflow boundary contains warmer air, heated by its descent through the dry air layer.  These winds can be rather gusty but serve the dual purpose of drying out the atmosphere and drawing in that warmer air that is pulled down from the dry thunderstorm.

While they are relatively uncommon in that any one location often does not see them happen, they do occur a few times a year around the United States.  If one occurs, more often than not they do so in the Plains and Upper Midwest as there's more dry air around to impact thunderstorm complexes.  However, one did occur in the Delmarva in April 2009.