Analyzing Today’s Tornado Threat
After an MCS (mesoscale convective system) mitigated the tornado threat somewhat on Thursday, there is a lot of concern about something similar happening today. Despite the concerns, radar imagery from 9:30 a.m. shows only a few thunderstorms in the far western panhandle of Texas. Although there appears to be a boundary from Lubbock to just north of Abilene with some showers attempting to form along it, radar is much different now than 24 hours ago. Although it is still possible and perhaps even probable that clusters of thunderstorms develop into a complex by midday across the Texas panhandle to northwest Texas, that by no means writes off today’s threat. While the threat may not be able to reach it’s full potential, there is still a distinct possibility of a few significant (EF-2+) tornadoes in the area by late afternoon.
Breaking down the morning environment:
Starting with a look at 9 a.m. surface observations, an objective analysis shows a remnant outflow boundary draped from near Lubbock eastward to central Texas. Along and south of this boundary, which is advancing north, temperatures are generally in the mid-70s with dew-points in the mid to upper 60s and nicely backed near-surface winds. To the north, there is some drop-off in dew-points, particularly toward the Texas Panhandle. Near the Red River along the Texas/Oklahoma border, dew-points remain in the mid to upper 60s and there is enhanced low-level wind shear, with winds out of the east-southeast at several stations.
The 14z mesoanalysis was showing upwards of 1000-2000 J/kg of CAPE with 40-50kts of bulk shear and enhanced 0-1km SRH over 200 m2/s2 across southwest Texas. As the aforementioned boundary lifts north, this environment will advect north-northeast and conditions will continue to destabilize.
Evolution of the convective setup through this afternoon:
Showers and thunderstorms will continue to develop along the boundary lifting through Texas. The HRRR and NAM/WRF models show convection blossoming as it reaches a line from Amarillo to Wichita Falls, likely becoming severe in spots in terms of hail and isolated damaging winds by early afternoon. (As I’m typing this, a Tornado Watch has just been issued and that echoes the thoughts here. The initial threat is hail/wind, but a tornado threat should increase during the afternoon.) That boundary is expected to continue moving north, while the environment to the south continues to prime. With the above ingredients and stronger winds in the mid to upper levels than previous days, any warm sector thunderstorm initiation would likely be supercellular. It gets a bit more complicated with the ongoing thunderstorms. A few scenarios could play out, but it appears most probable that a mixed storm mode will exist by mid-afternoon. Assuming moderate to strong instability is observed by late-day, an increasing low-level jet should produce an environment supportive of significant tornadoes between 22z and 03z. Based on what I am seeing, I am on the fence about the severity/extent of the threat. As mentioned, while it appears to be mitigated somewhat, the setup today is more conducive than some guidance had been suggesting earlier. If the storm mode does tend to be more discrete, or if a few cells can remain discrete/isolated, there could be multiple instances of strong and/or long-lived tornadoes.
Area to watch and probabilities:
The general area is essentially about 75 miles on either side of the Red River from just west of Childress, east to about I-35. On the northern side, there are some concerns about a messy/mixed storm mode. The southern side would appear to have the greater threat of more discrete cells, so if splitting hairs here, I do somewhat favor along/south of the Red River. Some threat may exist east of I-35, as dew-points are in the lower 70s near to just north of Dallas, but displacement from the greater shear does not place that area in the greatest threat.
For probabilities, I would set an expectation of 80% that there will be at least five (5) tornadoes in the outlined area. A 60% probability of at least one (1) significant (EF-2+) tornado.
The evolution of the setup over the next few hours will be key. Past events this season have, at times, appeared messy, but were still able to produce. While a few setups, like yesterday, did not seem to produce as much as some had expected, the environment today should be considerably more conducive. The HRRR has consistently been progging impressive STP (Significant Tornado Parameter) values of 5+ feeding into this area across northwest Texas. A quick look at radar as of 10 a.m. continues to show limited coverage/struggling convection approaching northwest Texas, so I will remain cautiously optimistic about the tornado threat later today.
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