Durant Damage: Not a Tornado

(This blog might get some folks upset, but please realize the opinion given below is based on the available information we have and is consistent with the meteorology of the event. Here goes.)

I had received several e-mails and phone calls from viewers convinced that a tornado caused the June 3, 2009 wind damage event in Durant. I do not believe this is the case. Here’s why:

I spoke with Marlin Blankenship of Bryan County Emergency Management; he personally conducted a damage survey; he said there was no indication of a consistent “circulation” within the damage.
The radar data from before and after the event supports this:  A strong (but not severe) thunderstorm was approaching Durant from the west-northwest at 3:36a.m. It “spiked” very quickly and then collapsed shortly thereafter. 
The wind came from the front of the storm, while a very high percentage of tornadoes come from the rear quadrant. It is likely that this sudden decrease of the storm intensity produced the destructive down-burst, more commonly known as a microburst, of straight-line winds. These may have exceeded 70mph, which is sufficient to knock over large trees.
The saturated ground conditions from recent rains likely contributed to the trees falling with less wind than it would take in dry conditions.
Good folks have said that they saw the trees “turning” or “spinning”, proving it was a tornado.
However, even straight-line wind currents twist and tumble as they interact with buildings, trees, other air currents, and the ground itself;  this is not a reliable guide to whether it was a tornado or not.
Finally, the sound of a locomotive has often been offered as “proof” of a tornado. If you will consider that the tornado makes these sounds because of strong winds, a straight-line gust of sufficient velocity is likely to make a loud noise too.
The three most accurate ways to determine tornado versus not tornado is:
1) Was a tornado spotted by credible eyewitnesses? Of course this is the best way.
2) The damage path: does it “fan out”, but generally all point within 90 degrees of the same direction (such as NE, E or SE), or does it have a clear circular pattern of “throw” around the entire compass as you travel along the path?
3) Was there a hook or velocity signature on the radar?
The Durant storm fails all three tornado tests.  It was very likely a microburst.
Take Care,
Steve LaNore
Chief Meteorologist
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  • by Steve LaNore Location: KXII-TV on Jun 8, 2009 at 07:12 PM
    Chad, the storm probably did not “spin up” since the damage was inconsistent with tornado damage. Smaller tornadoes often form and die very rapidly, but this damage was very likely from a collapsing thunderstorm. As the updraft weakens and the precipitation held aloft by the updraft begins falling, the downward motion of the air mass creates a gusty wind when it hits the ground. Wind speed can be further increased by evaporation of the rain into drier air which is sometimes pulled from outside. This evaporation cools the air, making it denser so that it falls even faster. While not everything is understood about a downburst (microburst), the radar signature and the damage pattern point that way for the Durant storm. Take Care, Steve
  • by chad Location: Ardmore on Jun 7, 2009 at 05:08 PM
    Hey Steve could that storm do a quick spin up befor the storm fell apart? And when the storms fall apart where does that wind come from?
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