2020-01-10 EVENT: TX/LA

[Drew Terril]

The first major event of 2020 looks to be shaping up for Friday and Saturday. An intense mid/ upper level trough will be ejecting over the Southern plains, and ample moisture flow north appears to be in play. As the trough ejects, a surface low will likely develop over north Texas. A cold front will be pushing south and eastward during the day and into the night Friday, which should prompt development of a QLCS. With that said, impressive shear values, especially in the lower 6km, will exist out ahead of the front, as will dew points in the mid to upper 60 degree range. Any storms that can develop in the warm sector will have ample moisture and shear to work with, and all hazards are in play.

Most likely, storm motions will be rapid, as is typical this time of year, and East Texas/Northern Louisiana is not great from a terrain or road network perspective. A large portion of this event will take place after dark as well, which will place additional challenges for those still chasing after nightfall.

Most likely, I will be chasing this event, unless factors out of my control with work on Thursday interfere. My initial target will either be near Tyler, TX, or further north in the Sulphur Springs area. With the way things are trending, I won't be surprised if I have to adjust a little to the west as the CAMs come into range.

 

[Dan Robinson]

Tons of lift with this system which means widespread clouds and early precip, not much of a dry slot at the moment on any models. Low-level lapse rates and instability suffer as a result. The main jet streak is shown hanging back a little, which will help that some as well as slightly slowing storm speeds, though it appears not by any meaningful amount. Watching this one, though I am not motivated to stray too much farther south than the MO/AR border.

 

[Patrick K]

I want to like this setup, but it's still a positively tilted system with storm motion parallel to forcing gradient, widespread clouds/crapvection, instability a bit on the low side, and 12z NAM3k hinting at only modest pre-frontal convection and not really aligned with the best parameter space. Even if we get a storm to root in the warm sector, the storm motion parallel to the forcing tends to lead to storm interference. As usual, we'll have to see how things play out, but I wouldn't get my hopes up on this one. That said, if I had to choose a target, it would be along the SH-19 corridor between I-20 and I-30.

 

[Drew Terril]

As I expected (and mentioned in the initial post), things have trended westward as time goes on. Given the history, anything with the Nam3km I take with a grain of salt, so that in and of itself is not a dealbreaker for me. With the consistent trend to the west, more of the warm sector will fall under better upper level support. The early onset of a stout LLJ, and the unusually steep (for this time of year) mid level lapse rates, along with indications of an EML at play, are additional factors that I think will have an influence as the event unfolds.

As is typical for this time of year, there are always parameters/composites that aren't necessarily ideal by springtime standards, but there are also a few items of note that you typically do not see in a Dixie type setup such as this; things that we're more accustomed to seeing during the traditional Plains season. Will it be messy? Most likely. Will it be a difficult chase? Yes, and those of us who have done our share of chasing in the Southeast (my first tornado was in KY in 06, mind you) know full well what we're dealing with. Given the dynamics, the FWD and SHV forecast discussions are right to be very concerned with pre frontal convection, in addition to the QLCS that will form along the front.

 

[Randy Jennings]

When I looked at lunch today, several models had temps at 700 mb warmer than I would like, but that could work to our advantage too. But if you pick apart every setup, you will never chase. I"ll be out for sure.

 

[Randy Jennings]

This morning runs still have some questions at the 700 mb level - not only with warm temps, but also weaker winds that are putting kinks in otherwise sickle shaped hodos. The Euro and HRRR seem to resolve these questions to the severe wx side, but the GFS and 3k NAM indicate there could be some limiting factors. This mornings observed soundings from West TX and NM do indicate a pretty warm inversion just above the surface that is likely to be transported above the target area by Friday . Having said that, other model parameters are just thru the roof and it is already unseasonal warm and moist at the surface here in DFW. This setup seems too good for us not to get something worth chasing. I'm just not convinced that it will be as high end as some folks think it will be. Having said that, we all know that a stronger caps that breaks in the afternoon can produce big events, so this event does have to be taken very seriously.

 

[James Gustina]

The 12Z Euro has almost 14C H85 temps in the morning which provides a relatively stout cap for the time of year (although the EML is not exceptionally deep meaning it should be relatively easy to break as the front approaches/mixing throughout the day). The shear vectors unsurprisingly become less orthogonal from 18Z to 00Z with time as the jet streak noses in from the west, but assuming that jet streak ejects more slowly as the NAM and Euro are both progging right now, I could see somewhat more favorable shear profiles materializing ahead of a broken line/QLCS. Modest instability should be available ahead of the front (1000-1250 j/kg ML) but as Dan noted, the forecast sounding profiles throughout DFW and to points east suggest a pretty dense layer of cloud cover/potential drizzle at least through 18Z. I doubt anything other than a broken line of transient supercells manages to get going in the warm sector due to messy storm interactions/fast speeds out of favorable environments but we'll see.

 

[Andy Wehrle]

This morning runs still have some questions at the 700 mb level - not only with warm temps, but also weaker winds that are putting kinks in otherwise sickle shaped hodos. The Euro and HRRR seem to resolve these questions to the severe wx side, but the GFS and 3k NAM indicate there could be some limiting factors. This mornings observed soundings from West TX and NM do indicate a pretty warm inversion just above the surface that is likely to be transported above the target area by Friday . Having said that, other model parameters are just thru the roof and it is already unseasonal warm and moist at the surface here in DFW. This setup seems too good for us not to get something worth chasing. I'm just not convinced that it will be as high end as some folks think it will be. Having said that, we all know that a stronger caps that breaks in the afternoon can produce big events, so this event does have to be taken very seriously.

Agreed. I've seen an awful lot of gnarly veer-back between 850 and 500mb on a lot of the NAM forecast soundings, especially over TX tomorrow. Based on the soundings I've looked at off the NAM and EURO, the best vertical wind profile for supercell tornadoes will be over southern MS/AL/the Florida Panhandle Saturday afternoon and evening; and the first sniff of a CAM into that timeframe (3KM NAM) is in line with that thinking.

 

[James Gustina]

12Z FWD soundings looks pretty impressive, an over 1 km deep moist layer with a reasonable enough cap to possibly suppress early crapvection. The only noticeable issue is that weakness in flow around 750 millibars. The shear profile is likely going to get a lot wonkier as the main jet approaches, causing some veering but at least some semi-discrete supercells along the I-35 corridor seem like a good bet at this point.