Heatbursts are rare meteorological events that occur across the Great Plains of the United States. They happen when a complex of thunderstorms dissipates during the late night or early morning hours.

The dying storms produce a downdraft of very dry air that is heated through compression as it rapidly descends to the surface of the Earth. Heatbursts are accompanied by a rapid increase in temperature, a marked decrease in relative humidity and strong winds at the surface.

A remarkable heatburst event occurred during the early morning hours on August 14, 2002 in San Angelo, Texas. At midnight local time, the temperature in San Angelo was 70 degrees F with a dew point of 63 degrees making the relative humidity 79 percent. Winds were from the south at 13 mph.

The 12:35 a.m. observation reported winds from the south at 31 mph gusting to 40 mph. By 1:05 a.m., the temperature had risen to an amazing 94 degrees with a dew point of 45, making the relative humidity a dusty 19 percent! By 1:20 a.m., things had returned to somewhat normal, with a temperature/dew point of 73/61, but strong and gusty winds continued during the early morning hours.

The peak wind gust observed during the event was from the south at 53 mph at 2:07 a.m. Heat burst usually occur further to the north, but can occur as far south as North Texas.

The Sunday map discussion video is on the web, and available on iTunes:

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I guess I really understated the weather situation in yesterdays map discussion video. It sure looked like we were headed for a wet day with the way radar looked in the morning, but the elongated area of rain began to break up by mid-morning and by afternoon we were into a sunny situation with temperatures reaching only the upper 80s for most places - lower 90s in some spots. All-in-all, quite a nice day yesterday. Some localities in west central Alabama got rain totalling over two inches according to radar estimated values. The Birmingham airport recorded 1.55" during the morning.

Today we are starting off rather gray - not the usual August day. The clouds are a result of a weak wedge pattern. The wedge occurs when high pressure is centered off to our northeast - generally over New York and Pennsylvania. The clockwise circulation around the high brings usually cooler and often moist air across northern Georgia and into Alabama. The stationary front has migrated further west and south of Central Alabama, so the liklihood of showers today has diminished though isolated showers or thunderstorms are still possible.

The upper air pattern over Alabama will remain somewhat flat for the next several days with a ridge building stronger by mid-week. A weak disturbance located off the North Florida coast from Jacksonville will move westward during the next week enhancing chances for rain along the northern Gulf coast and into Texas by the end of the week. It will be interesting to watch this weak disturbance to see if it can generate anything tropically. It would appear that the position is too close to land to actually gel up a tropical depression, but it will be something to watch.

At the surface, a weak front Tuesday and Wednesday may help to increase rain chances in Central Alabama from the daily outlook of isolated showers. But after that we settle back into a summer time pattern into next weekend as the upper ridge becomes somewhat stronger.

The tropical scene is still quiet. Latest satellite imagery shows thunderstorms in the southern portion of the Windward Islands. There does not appear to be any sign of organization in that disturbance at this time, but we are into the most active part of the Atlantic hurricane season. Also wanted to note that NOAA updated their hurricane season forecast this week. They are sticking with an active season forecasting 12 to 15 names storms, but those numbers are lower by one then their previous forecast at the start of the season.

I hope you have a great Sunday and have the opportunity to spend time with your family. James will be back tomorrow morning bright and early with the next web video map discussion. God bless.

-Brian-

”We have met our Andrew,” said Charlotte County Emergency manager Wayne Sallade after Category Four Hurricane Charley made landfall near the towns of Punta Gorda and Port Charlotte on this date in 2003. The hurricane made a beeline for the Southwest Florida coast after crossing Cuba the night before. The storm strengthened only slowly during the morning hours before intensifying rapidly in the three hours just before landfall, deepening from 965mb to 941 mb.

The hurricane began turning from a northerly course to a more north northeasterly one during the morning hours, drawing a bead on the Southwest Florida coastal area. An Air Force reserve Hurricane Hunter plane gave the only notice of the catastrophic intensification when it transmitted a report a 162 mph flight level wind to the National Hurricane Center. This allowed forecasters to upgrade the hurricane from Category 3 to Category 4 nearly two hours before it reached land. This gave a small window of precious time for last minute evacuations.

The hurricane’s tight core made landfall near Charlotte Harbor, Florida with winds of 145 mph and a central pressure of 941 mb. The retirement town of Punta Gorda, Florida was especially hard hit. Many residents who lived in several mobile home parks around the area ignored evacuation orders and were severely injured or killed. Twenty people died in the storm. Up to eighty percent of the buildings in Charlotte County were damaged. Charley would cause extensive damage all the way across inland sections of the Florida Peninsula. A wind gust to 105 mb was measured in Orlando. Charley was the strongest storm to affect Southwest Florida since Donna in 1960.