2012-04-13 FCST: KS/OK/NE/IA/TX

[Warren Faidley]

Potential horse-sized fly in the ointment for today's risk seems to have departed. Recent satellite images do not show hints of early convection that was forecasted by some models. Thus, there seems to be decent chase possibilities for today. Target will be defined by initiation and any low level shear enhancements, including any early storm outflows moving back west if the dry line does not progress east. Initial target will be near Shamrock.

W.

 

[Juston Drake]

Today's setup looks to have some major complications to it that I don't think the models are handling that well. One problems that models are definitely having is when and where convection will initiate. They were having that problem yesterday and it seems to be happening again. Both days, the models are showing no cap over a very large area with precip firing all over the place. I'm starting to wonder if, like yesterday, storms will have trouble initiating along the dryline in OK. From just looking at the soundings, I ruled out the cap being a major and/or only issue, due to the fact the 700 mb temps aren't really that high and the fact the convective temperatures in the area weren't too high also. What I think may have been the main problem yesterday and also might end up being the deal breaker today is the subsidence that is over the region. Per the 12z OKC sounding, there is an inversion that is located at the 550 mb level. At this same time, there is also an inversion in the 650 mb level in the AMA sounding. These are signs of some subsidence in the area. Couple that with the fact that the early morning shortwave up in NE/SD has already moved through, and there will be shortwave ridging behind it and also some larger scale ridging between that system and the much larger shortwave back in CA, which can be seen on the 12z 500 mb and particularly the 700 mb upper air maps, and I'm worried subsidence is really gonna kill today's setup. There has to be a reason why all the morning convection the models were forecasting didn't end up developing, and I'm thinking that may be the reason.

With all that said, the morning convection not firing will definitely help out with instability this afternoon. If enough instability can develop, and maybe if there is the presence of a minor wave in the larger scale flow, then storms will still be able to develop right before dark despite all the subsidence that will be occurring in the area. Storm Riders will be heading out in W. OK and be stationed out there for a while just in case something does end up going up. We just don't believe at this time the chances of something going up before dark are very good.

 

[Greg McLaughlin]

That is a valid concern Juston. I am noticing surface pressure falls in northwest/west central Oklahoma attm. I am guessing this may partly be in response to a mid-level speed max which appears to be nosing out of New Mexico. Hopefully this feature and moisture convergence along dryline as it retreats back to the northwest are enough to get things going.

 

[Mike Johnston]

Goodness, gracious...live video and TWC, together with SRVs on radar indicating a tornado coming into Norman, OK now!

 

[Tim Vasquez]

I have not watched any media at all, but I have been tracking this thing closely on GRLevel2. Definitely a tornadic vortex signature which appears to have started around W 36th & Main, moving toward the western downtown area and now (as I type this) near Hall Park. The gate-to-gate velocities have broadened quite a bit so the risk has probably diminished, but the shear was extremely tight as it went through western Norman and a debris plume was quite obvious on the spectrum width products.

EDIT: Referring to Norman OK.

Tim

 

[Trey Thee]

I have not watched any media at all, but I have been tracking this thing closely on GRLevel2. Definitely a tornadic vortex signature which appears to have started around W 36th & Main, moving toward the western downtown area and now (as I type this) near Hall Park. The gate-to-gate velocities have broadened quite a bit so the risk has probably diminished, but the shear was extremely tight as it went through western Norman and a debris plume was quite obvious on the spectrum width products.

EDIT: Referring to Norman OK.

Tim

Tim, there was a confirmed touchdown in Norman according to Newson6 here. They just showed the video from News9. Looked like an EF1 but it was partially rain wrapped for much of its time on the ground. Minor damage being reported in Norman including the OU campus according to reports I just got three minutes ago.

 

[Tim Vasquez]

As of 2211 UTC (right now) storm #2 appears to be lined up to hit Norman.

The one thing that concerns me is that storm #1 did lay down an outflow (mostly generated by the RFD) which appears to have stalled ENE-WSW just south of Highway 9 in southern and southeast Norman. I am in rural southeast Norman near Highway 9 and we have extremely weak northwest winds at the moment. It's difficult to tell where exactly this boundary is, but it is there. I'm wondering whether storm #2 will interact with this boundary and to what extent as it continues moving eastward.

Is OU-PRIME up? It would almost certainly pick up the boundary, but I tried loading WeatherScope and it is dead as a doornail as far as products go.

Tim

 

[Tim Vasquez]

Interesting structure on the spinning-top supercell northeast of Altus. These are some notations on the radar imagery as of 2348 UTC (6:48 pm CDT):

The S-shaped line is a very prominent RFD/outflow feature showing up strongly on the lowest level velocity imagery, kind of trailing under the FFD area itself. To me this is suggestive of a rather cool RFD.

 

[James Aydelott]

Tim, persistent meso along that e/w outflow boundary in SW OK. LLJ now increasing rapidly. Think tornado threat should continue or even increase next few hours in SW and Central OK

 

[Jacob Ferden]

Keeping an eye on it from here in Norman. Hoping the earlier cells stabilized the air enough to preclude any appreciable nocturnal tornado threat in the metro, but time will tell. Very impressive couplet on that storm at the moment.

 

[brice.coffer]

Is OU-PRIME up? It would almost certainly pick up the boundary, but I tried loading WeatherScope and it is dead as a doornail as far as products go.

Tim

http://arrc.ou.edu/ouprime/status/

OU Prime has been down since March 19th when it got struck by lightning. This is not the first time this has happened either.