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Tornado - April 7th, 2002 - Amazing Tornado |
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Chase Account by: Jonathan Garner
Brian Thalken and I decided to take a chance on what appeared to be a fairly potent set-up in Texas, with the potential for dryline thunderstorms developing underneath a westerly upper-level jet streak. However, the dryline pattern didn't quite set-up the way we expected on Sunday, which we realized after analyzing an hours worth of data Sunday morning in a University of Oklahoma computer lab. Needless to say, the results of this chase were outstanding as we turned our attention to a baroclinic boundary in North Central Texas.
After our data analysis, we headed southwest down the H. E. Bailey Turnpike, with lots of drizzle and low-level cloudiness present. Our initial target was the Abilene, Texas area, however, as soon as we got an hour south of Wichita Falls, Texas, the skies cleared with temps in the mid to upper 70s, turkey towers developing to our east, and a line of storms developing off to our southwest. We passed the DOW team, and then parked a few miles south of them so that we could get an update from our nowcaster back in Lincoln, NE. The storms to the west appeared to be lining up from a radar viewpoint, so we decided to pursue the towers to our east. After we got gas in Haskell, TX, we went east on highway 380 towards Throckmorton, TX. We stopped every so often to get pictures of the developing convection building around us, but nothing too spectacular was going on. However, we did notice a thin line of whispy scud just to our south, which I thought might have been the southern edge of a boundary.
Just before 3 pm, we called in to Lincoln for another update, and our friend Dave (who did a great job
nowcasting) described what the cells to our west were doing. These cells were strong with a few T-storm warnings being issued for one in Haskell County, but they still didn't look too organized. But, it was the only thing going on around us, so we went west in order to investigate. Just after 3 pm, a severe thunderstorm warning was issued for a cell in Throckmorton County, (this cell was just a few miles to our west). We noticed what appeared to be a shelf cloud (some type of lowering) produced by outflow, and I thought that the show was over and things would line up quickly. However, this low-level feature began to fill in, and took on the appearance of a developing wall cloud. So we parked on top of a hill with a great view over a valley at 3:04 pm (our position was 8 miles west of Throckmorton, TX), and set up the tri-pod/video equipment (we were about 2-3 miles east of the storm). During the next 30 minutes, we watched the rain-free base evolve, organize, and develop a broad-scale rotation (the mid-level rotation was a bit more obvious). This rain-free base was very well defined, and scud was being sucked in from the forward-flank downdraft. The surface winds were due east (enhanced low-level shear due to the boundary or just good old fashion inflow), and by 3:20 pm, the low-level rotation really got its act together.
By 3:28, a well defined, very low wall cloud formed, with scud rapidly ascending into the base. At 3:29 pm, we heard over our radio that the National Weather Service issued a tornado warning for this cell, and at 3:31 pm, the first condensation funnel formed and connected with the surface. A few vortices danced around the wall cloud, but no dominant funnel was present.
During the next 5 minutes, the developing tornado moved northeast across the highway and into an open field. Then, a larger, more well defined condensation cloud developed, and the tornado began to mature/grow larger. The clear slot was spectacular, and a collar cloud was present around the tornado cyclone, bulging out away from the center of rotation (it appeared to be associated with the clear-slot). After 10 minutes or so, the tornado grew much larger and began to take on wedge size proportions. It was at this point that we began to hear the tornado as it moved almost parallel to the highway we were on (we were only 1/2 mile from this tornado). The sound was something like rushing water, or a wind gust moving through a tree and blowing its leaves.
The RFD continued to advance east and eventually reached our location. It was a very warm RFD, maybe even slightly warmer than the storms inflow (e.g., Markowski et al., VORTEX results). The tornado continued to move east-northeast until we were eventually southwest of it. A few minutes later, it went into its rope stage and then dissipated soon after (the tornado lasted at least 19 minutes, from 3:31 pm to 3:50 pm). Another large funnel was present to the north of the old one, but it didn't manage to develop any further.
In my short chasing career (7 years), this event definitely tops everything else I have observed so far. In addition, some of the findings coming out of VORTEX during the last few years seemed to fit in well with this event. There was a baroclinic boundary, a persistent updraft (the supercell which moved north over the boundary), and a warm RFD. But besides the educational benefits of this chase, I think I can summarize by saying that this was simply a beautiful, very photogenic, intense tornado.
Watch the tornado video HERE.
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