Today marks the three year anniversary of a huge plains tornado outbreak. On March 28, 2007 over a hundred tornado reports came in from Nebraska down through Texas as a powerful storm system moved in from the west and fired off dozens of supercells along a dryline. Check out my chase log from the day:
As we look back on this day, I can’t help but notice a similar pattern in the upper level winds forecasted on the weather models for Friday this week. Although Friday’s forecast is subject to change being several days out, and there are other things to consider than just a similarity in the upper level pattern, its still a reminder to me that Spring is here and the models are hinting at severe weather.
The GFS has been showing a high amplitude trough over the southern Plains for several runs now. The ECMWF is in fairly good agreement with the position of this trough, and then NAM out to 84 hours (two days before the event) matches up fairly closely with the GFS at 84 hours with the trough coming on shore from the Pacific. There’s also been good consistency on the moisture return. The GFS has been showing 60′s dewpoints spreading across TX and maybe into OK and forecasted cape at 1000-2000 J/Kg. The 12z NAM is even more bullish with the moisture showing 60′s dewpoints established into OK two days before the event. If these models do verify it looks like we are going to have a dryline setup from south central OK down through TX with more than enough shear, moisture, and instability for severe weather including supercells. A big concern I see with the setup is the southerly 500 mb winds a high amplitude trough would create. With a strong southerly LLJ also forecasted to be in place, we might be lacking in the directional shear and wind up with a big linear line training along the dryline. Today marks the three year anniversary of the March 28, ’07 outbreak, which was also characterized by a high amplitude trough and dryline. Similar concerns were voiced about storm mode and movement but in the end it wound up being a huge tornado event. With bulk shear over 50 knots and a chance at 2000 J/Kg this is a setup you definitely don’t want to turn your back on. If we do wind up getting a training line, there still might be some decent play at initiation before everything congeals. It might also be wise to setup further downstream to the north and move south, letting the storms come to you where you might be able to catch a break in the line or tail end charlie. So in conclusion, the models are all pointing at decent parameters for a severe weather event in the southern Plains this Friday. The biggest concern I have at this time is storm mode.
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