The Storm Prediction Center (SPC) has issued an Enhanced Risk for severe weather today across the western part of Oklahoma and the eastern Texas Panhandle.
Associated with the Enhanced Risk is a 5% Tornado Threat ring.
The SPC is basing this threat on a strengthening surface low over the southern High Plains and its interactions with a dryline that will form later this afternoon. There will also be an upper-level impulse that travels around the trough, which will add to the possible convection in this area.
Synoptically speaking, the 300 mb NAM chart (from Unisys) shows an upper-level low over the Great Basin. The trough dips south around the low and ejects into the Enhanced Risk area.
The 500 mb chart does not show much Positive Vorticity Advection (PVA) at all today. This is a bit surprising, considering the approaching trough.
The 700 mb NAM chart shows very little rapidly-rising air today as well. This is also surprising.
The 850 mb NAM chart shows strong Warm Air Advection (WAA) into the Enhanced Risk area. Notice how the winds blow directly across the thermal gradient from warm to cold. This will boost convection in the area by 0Z.
The 12Z upper air sounding from Amarillo, TX, does not show a particularly unstable air mass as of yet. There was no Convective Available Potential Energy (CAPE), and the surface dewpoint was only 49 F. There is a slight capping inversion in place, and 0.94 inches of precipitable water present in the column. However, the 0-3 km average lapse rate was only 3.5 C/km.
The deep-layer shear was 37 kts, and the low-level shear was 26 kts. The shear at all layers was mostly due to speed changes. The low-level shear is enough to support tornadoes and the deep-layer shear is marginal for rotating storms, but it will probably increase throughout the day as the nose of the jetstreak makes its way into the Enhanced Risk area.
The 12Z upper air sounding from Dodge City, KS, shows a saturated atmosphere. Dewpoint depressions are low and there was 1.09 inches of precipitable water present in the column this morning. There was 2 J/kg of CAPE present, only a slight capping inversion, and the 0-3 km average lapse rate was 3.5 C/km.
The deep-layer shear was 21 kts, and the low-level shear was 35 kts. The low-level shear was mostly directional, and was more than enough to support tornadoes though the deep-layer shear was not enough to support rotating storms.
TwisterData.com shows that CAPE is not expected to become very explosive today, though it may be adequate for severe storms.
Currently, the surface observations (from the SPC Mesoscale Analysis Map) show the dryline running through the eastern part of New Mexico, dropping 10 degrees between stations as you move west. There is southeasterly flow at the surface, which is acting to advect moisture into Western Oklahoma and the Texas Panhandle. The radar overlay shows some leftover precipitation clearing out of the Enhanced Risk area, so perhaps there will be a few outflow boundaries to work with as well.
The Supercell Parameter is expected to increase to 4 over the next six hours in the central Texas Panhandle, according to the RAP. I expect it will increase beyond that after the six hours as well.
The visible satellite imagery shows that much of the Enhanced Risk area is under cloud cover this morning. The time spent under clouds will limit diurnal heating and thus convection.
The enhanced infrared satellite imagery shows that many of the clouds in this region are not very thick, so perhaps they will mix out over the next few hours.
The water vapor satellite imagery shows the trough, but I am not seeing the upper-level impulse at this time. Perhaps I need more practice identifying it.
Overall, I am slightly regretting going to work today instead of to western Oklahoma, but some of that is just jumping the gun to get on the my first real storms of the season. I don’t think conditions are that explosive today; limited PVA is one weakness with today’s setup. However, storms are quite possible, and it wouldn’t surprise me to see that a few tornadoes struck later this afternoon.
Thank you for reading my forecast.
The upper air soundings and mesoscale analysis plots are from the Storm Prediction Center website.
The forecasted upper air soundings are from TwisterData.com.
The surface observation and upper level charts are from Unisys Weather.
The satellite data is from NASA – MSFC