Wednesday, August 19, 2009

Beaumont Tornado

Life in the northwest corner of Beaumont, TX was interrupted Tuesday afternoon by an unexpected tornado that caught many off guard. The tornado that developed around 2:00pm Tuesday afternoon formed with no warning as the parent storm showed no signs of rotation. By analyzing radar data and looking at the storm environment, it appears a “landspout” tornado, much like a waterspout, formed rapidly under an intense thunderstorm updraft. A landspout, a term used to describe non-mesocyclone tornadoes, forms when an area of surface vorticity, or rotation, is stretched vertically when it encounters an updraft of a developing storm. Doppler Radar from Lake Charles, LA shows that on outflow boundary was stalled out across Jefferson County Texas and this would be the source for the surface vorticity.

This boundary was formed from a collapsing storm off to the northeast of Beaumont. This boundary moved southwest until it encountered strong enough winds to stop its forward progression. It was the interaction of northeasterly winds on the east side of the boundary and the southwesterly winds on the west side of the boundary that caused areas of surface rotation to form. As this rapidly developing updraft moved across this rotation it stretched it into the vertical causing the tornado to form. You can see from this radar loop how fast the storm which caused the tornado developed.

Next you can see the volumetric scan of the storm just north east of Beaumont. Watch the rapid development of dark red colors over the area where Kohl’s is located. This shows the storm had rapidly moving updrafts that were able to ingest the surface vorticity, rotation, and pull it upward causing the rotation to rapidly increase developing into the tornado.

Just a reminder to always be on the watch for the possibility of severe weather and even tornadoes under rapid thunderstorm development, especially near stalled boundaries.

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