Jason's Texas Weather and Adventure Blog

May 7, 2019: Moderate Risk in the Texas Panhandle

The Storm Prediction Center has drawn a moderate risk for severe weather in the Texas Panhandle today, with all modes of severe weather (i.e. tornadoes, large hail, and damaging winds) likely. SPC even mentions that a few strong tornadoes will be possible. My hypothetical chase target today would be near Pampa, TX where the High-Resolution Ensemble Forecast system (HREF) paints a high probability of updraft helicity exceeding 150 m^2/s^2. To explain a couple terms here, the HREF is what is known as an ensemble forecast model. It’s not really its own model, but really shows the forecast for a bunch of different models. Because it uses multiple models, if several models are in agreement on something, it will show up as higher probabilities as mentioned above. Updraft helicity is the amount of spin within the updraft, and values higher than 150 meters squared per second squared are typically indicative of a strongly-rotating supercell. My discussion for today is below.

HREF probability of updraft helicity exceeding 150 m^2/s^2

Strong ascent ahead of a negatively-tilted upper-level trough over the western CONUS will spread east into the High Plains today. This ascent is quite apparent on GOES-16 water vapor channel imagery. At the surface…13Z manual analysis revealed a 1009 mb low near [Borger, TX]. A warm front extends northeast from this low towards [Hutchinson, KS]-[Kansas City, MO]. A dryline extends to the south back towards the NM/TX border. The warm sector is characterized by dewpoints near 60 and into the mid 60s. High-resolution model guidance is in strong agreement that convection will initiate along and ahead of the dryline by 21Z-00Z…and quickly spread northeast. Forecast soundings show impressive low-level hodographs…with effective [storm relative helicity] forecast to exceed 300 m2/s2. Combined with large instability…including 0-3 km [convective available potential energy] values in excess of 100 J/kg…tornadoes will be likely…with a significant tornado or two not out of the question. The one potential caveat is that given the very strong upper-level ascent and deep-layer shear vectors somewhat parallel to the dryline…convection will likely grow upscale into a [quasi-linear convective system] within a few hours of convective initiation. Still…there should be enough of a window for discrete supercells to lead to a tornado threat across central and eastern portions of the TX Panhandle.

My forecast discussion for May 7, 2019

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