Posted: May 21, 2013 3:44 PM by Rob Perillo
Updated: May 21, 2013 4:02 PM
While this year the tornado season across the U.S. has been a tardy one, activity across the Plains States has caught up with the time of the year, and in a hurry.
Typically severe weather activity and tornadoes increase along the Gulf coast in February with activity slowly migrating northward with the jet stream through April and May and eventually the northern US states in June.
This year has been quite different with a persistent East Coast upper trough that kept dry and stable air in tornado alley for a good part of the spring.
You may have noticed that the weather pattern has changed to a more summer-like mode in Acadiana with breezy southerly Gulf winds traversing the area over the last several days. Unfortunately, this warm Gulf air has met up with the storm track emanating from the Rockies which in turn has manifested into rounds of severe weather across the favored areas.
The graphic below, shows that it is not unusual to have tornadic activity in Texas, Oklahoma and Kansas this time of year.
Unfortunately, while violent EF4 and EF5 tornadoes are generally rare, they do account for more than 80% of all tornado damage and obviously most fatalities in Tornado Alley (Plains to SE U.S.)
As for Acadiana, tornadoes can happen just about any time of the year, with the least amount of activity interestingly enough in July and August.
And because of Acadiana's proximity to the Gulf Coast, most intense severe weather events are influenced and generally dominated by the Gulf marine air that effectively throws a wet blanket on severe weather dynamics.
The graphic below shows all tornado paths recorded in Acadiana area back through 1962.
Blue lines are EF0 tornadoes, green EF1, yellow EF2 and orange, EF3. Not surprisingly, most of Acadiana's tornado hot spots are farther away from the Gulf and to the northwest where some of the "plains dynamics" are still in play before meeting with the more stable Gulf atmosphere.
The next graphic below is a listing of all tornadoes for the last 50 years reported in Acadiana. There has never been a confirmed EF4 or EF5 in our part of the world and only 20 EF3's in 538 reports. Thats less than 4% of all tornadic storms.
While Acadiana can see tornadoes at just about any time during the year, it is somewhat comforting that we appear relatively immune to the most violent that Mother Nature can serve up. Unfortunately during hurricane activity, we can easily generate 10-20 tornadoes of EF2 intensity or slightly better in one event.
The most recent intense tornado that was tracked in Acadiana was related to the back end of Hurricane Gustav in 2005 when 80 degree dew points met up with drier air filtering in from Texas behind the storm. An EF3 tornado was the result in Evangeline Parish with major damage and 2 fatalities the night after Gustav made landfall on September 1, 2005.