Srain Posted February 15, 2012 Share Posted February 15, 2012 Nice LLJ developing this evening across SE TX. Discuss... Link to comment Share on other sites More sharing options...
tornadotony Posted February 15, 2012 Share Posted February 15, 2012 Link to comment Share on other sites More sharing options...
Srain Posted February 15, 2012 Author Share Posted February 15, 2012 Meh...some like to post in our sub forum for these events. We'll see how it goes...) Link to comment Share on other sites More sharing options...
David Reimer Posted February 15, 2012 Share Posted February 15, 2012 Meh...some like to post in our sub forum for these events. We'll see how it goes...) I just noticed that severe weather threat was in the primary forum. No offense to Tony, but screw that. I'm all for staying local.... A complicated setup for tomorrow from a chasing standpoint. I'll say off the bat that it's a marginal day. Heck, if it were any more marginal it would be nothing but a few rain showers. However, I'm seeing a few things that are keeping me interested in chasing tomorrow. Hot off the 0Z North American Model (NAM) we have our Surface Based CAPE (Convective Available Potential Energy)... These are always the hardest setups to forecast for regarding the possibility of severe weather. Instability values are quite marginal, even for a cool season event. Never the less, we do have some surface based instability at 3 PM on Wednesday. From the Red River south to about Madisonville, TX is a narrow corridor of instability values in excess of 500 joules per kilogram. South of Madisonville, our instability axis tends to widen out as we're closer to the gulf coast and higher amounts of moisture. Values are generally around 600 to 800 joules per kilogram. Those values are still marginal for cool season events, but just high enough that I believe there is some threat of organized, low-topped convection. In lieu of a complete analysis of the wind fields, which I'll be publishing later on my website, I'll stick to the three kilometer Storm Relative Helicity Index. This graphic is also for 3 PM on Wednesday. Our primary low level jet will already be ejected off eastward into Louisiana and Arkansas, with a secondary area of westerly winds at 850 millibars in place across most of Central/East Texas. In terms of turning with height, forget about it. By tomorrow afternoon, everything looks quite linear across Texas. That's a different story across Louisiana and Southern Arkansas where low level winds are more southwesterly verses southerly. A few models have backed surface winds, creating pretty large hodographs in those areas. However, models continue to advertise little to no surface based instability in AR/LA, preventing any sort of surface-based convective threat. However, there are two things I noticed on the 0Z NAM verses earlier runs. There seems to be slightly more instability across LA then earlier runs and wind shear seems to be lower across East Texas then earlier runs at 3 PM. At this time, I have two chase targets in mind if I were to go chasing tomorrow (which is a big if). My primary chase target would be close to the Gulf Coast in Southeast Texas. Instability values are higher and there's the possibility of mesoscale boundaries in place due to coastal effects (sea breeze, convective outflow, etc) that could briefly enhance updrafts and allow them to become briefly capable of producing a low level circulation. My second target is across Central/Northern Louisiana. My concern about heading out east is that models indicate widespread precipitation across those regions most of the afternoon hours, severely limiting instability and atmospheric recovery. With all that said, I believe the severe weather threat for tomorrow is fairly marginal. If we can get elevated supercells to form later tonight and during the first half of Wedensday across North Texas and Oklahoma, there could be a decent hail threat due to increased instability values. After sunrise, instability values tend to decrease as upper forcing begins to eject northeastward and widespread convection forms thanks to warm air advection. I believe any afternoon severe weather threat will depend greatly on any localized areas of clearing, creating localized differential heating, along with any boundaries that may be in place. The 12Z High Resolution WRF indicated a QLCS type system forming across Southeast Texas. I wouldn't be shocked to see that occur. If that is the type of setup we deal with tomorrow, I would say there is a brief tornado threat with any QLCS spinup (much like we saw back a few weeks ago). Otherwise, spotty damaging winds and sub-severe hail would be the primary issues. We'll see what happens overnight tonight and what the high resolution models say in a few hours. I don't expect tomorrow to be substantial, but after our event back in January, I'm going to expect the unexpected. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 15, 2012 Share Posted February 15, 2012 Euro 18Z skew-T similar to GFS really, more a hail threat than a tornado thread, but I think all modes would be possible. SREFS hold out the possibility. Edit to add- that tiny little blue area where all the SREFs have a SigTor greater than 1, that would be Steve's neighborhood if I read that correctly. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 15, 2012 Share Posted February 15, 2012 I think hail is the main threat, the 12Z GFS sounding seemed to suggest individual cells would go QLCS fairly quickly, and near surface instability was fairly meager. MUCAPE and deep shear, high total-totals, and speed shear in the fat part of the CAPE region, hail seems the main threat. If 0Z runs repeat 12Z runs, GFS will be most enthusiastic about severe, with the EURO silmilar but not quite as good. Not totally tornado proof. . Link to comment Share on other sites More sharing options...
David Reimer Posted February 15, 2012 Share Posted February 15, 2012 This is coming off the Rapid Refresh (scheduled to replace the RUC next month) and shows 925 MB winds at 3 PM this afternoon. If this is right, I'll be out chasing. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 15, 2012 Share Posted February 15, 2012 HGX disco says leaving severe out of the zones. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 15, 2012 Share Posted February 15, 2012 I still think hail is the biggest risk in SE Texas, oddly enough, SPC seems to give hail and tornadoes near equal odds. Link to comment Share on other sites More sharing options...
Ed Lizard Posted February 15, 2012 Share Posted February 15, 2012 Yes, 15% hail on 1630 SWODY1 update! Link to comment Share on other sites More sharing options...
DoctorMu Posted February 15, 2012 Share Posted February 15, 2012 We're getting trained a bit in CLL.. Some lightning displays and intermittent heavy downpours. Nothing severe yet, but some street flooding is being reported. Rain expected to end shortly though. Link to comment Share on other sites More sharing options...
David Reimer Posted February 15, 2012 Share Posted February 15, 2012 I ended up sitting today out and am enjoying the 75° post dryline temperatures here in Dallas. NEXT STORM! Link to comment Share on other sites More sharing options...
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