Thursday, July 23, 2009

Severe Storms Pound East Texas

Tuesday night’s storms across East Texas provided much needed rain to many but also brought with them a round of severe weather. Numerous reports of wind damage accompanied these storms as they developed along the I-30 corridor and moved south into the Tyler Longview area. There were even a few reports of hail up to the size of quarters in Upshur County and yours truly experienced penny size hail along Cumberland Road in Tyler.

The first photo below was taken off of Hwy 155 north of Big Sandy looking towards Gilmer. Lots of low hanging clouds giving an ominous appearance to the approaching storm.

Looking Towards Gilmer Just North Of Big Sandy

The next photo taken was taken in the same spot but looking more to the east than northeast, under the updraft base. Weak rotation was seen but nothing to signal the possibility of a tornado developing.

Looking Towards Gilmer Just North Of Big Sandy

As the storm continued south it continued to strengthen producing numerous cloud-to-ground lightning strikes and very strong winds. We were continuously buffeted by winds between 50 and 60 mph. Limbs were being snapped off and a few trees were knocked down along Hwy 80 as we raced east from Big Sandy to Gladewater. Below are a few photos sent to me from Mack and Jeanette Rose of Gilmer.

Once in Gladewater we took Hwy 271 southwest towards Tyler. Just south of Interstate 20 we saw a feature that really caught our eye. There appeared to be a tornado on the leading edge of the storm but after watching it for a minute it was easy to see there was no rotation and this feature was what we call scud, or scattered cumulus under deck. Many times this feature will take on the shape of a funnel or tornado. Below is a shot of this feather as it moved north of Interstate 20.

Low clouds called scud becoming a tornado look-a-like

The storm we had been chasing began to weaken as we moved into Smith County but another storm along the Smith Wood County line began to strengthen. It is this storm that would produce the widespread damage and power outages across South Tyler. Below are a couple of radar animations. One, of the storm as it moved through the Tyler area, and the other is a volumetric scan where you can see the collapse of one storm which helped develop the Tyler storm. Then you can see the Tyler storm collapse which could have caused even more damage in the form of a microburst.

Now let’s take a look at the velocity data from Tuesday night’s storms, or speed and direction of the wind flow in the storms. In these photos the green colors are winds blowing towards the radar and the red colors are winds blowing away. The brighter the color, the stronger the wind. Another important fact to understand is these images are sampled in the storm around 13,000’ above the ground, so we don’t know exactly what was occurring at the surface. In the 1st photo we see red colors over Tyler indicating winds blowing away from the radar site indicating inflow to the developing storm along the I-20 corridor. Also you notice a large area of green east of New Chapel Hill indicating winds blowing towards the radar from outflow of a weakening storm over northwest Rusk County.

Over the next two frames, it looks as though this westward moving outflow boundary may have induced rotation in the Tyler storm as it continued to move south-southwest. The second of the two frames shows a tight couplet forming over southern Tyler near the intersection of Cumberland and Broadway. I was at this intersection and witnessed an abrupt change in the winds from the north to the south to around 60 mph. So there could have been rain wrapped rotation moving through south Tyler.

Over the next 15 minutes from this point the storm rapidly died down and can be seen with much weaker wind speed in the last velocity frame.

So was there a tornado in South Tyler Tuesday Night? Well, radar data hints that there was rotation in the storm 13,000’ above the surface which means there was a possibility this rotation reached the ground. I will tell you that all the damage I was able to see the next day indicated the most likely scenario was straight-line winds. I saw very little evidence of swirling wind from damage. However, radar data and the abrupt change in wind speed and direction makes me think there could have been a weak tornado moving through South Tyler. Officially tough this one will go down as a severe thunderstorm with straight-line wind damage.

Damage Photos from Tyler.

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