2015-05-09 EVENT: TX/OK/KS/NE/CO

[Brett Nickeson]

Several people have mentioned the VBV profile of the hodos, and in many cases I'd agree that this profile leads to fairly messy storms that just can't get it done. But remembering back to June 20, 2011, many people we saying the same thing of that day. And like others have pointed out, models are (very) slightly trending away from the VBV, so the hope is there that it continues to do so.

 

[James Gustina]

The VBV profile seemed almost negligible up into the Woodward-Liberal area on the 00Z/12Z runs of the NAM. Definitely not progged to be worse than say, April 17th which still managed to put out some mammoth supercells.

While this does have April 26, 2009 levels of bust possibility on it I don't think it's gonna be as much of a crapshoot as it's being pegged everywhere I've seen. A very, very sharp dryline with excellent forcing and at least somewhat of an inversion in the not worked over areas further north along the dryline should theoretically yield some pretty intense supercells if everything else pans out as expected (barring convective debris and such).

 

[Jared Orr]

Im not at all surprised. It has 'High Risk' written all over it. That doesn't mean it will be a good chase day of course, since High Risk storm mode/storm motion often leads to epic chase busts, but there will be widespread severe weather Saturday. People can nitpick and find kinks in the hodos all they want, but the big picture (pattern recognition) says outbreak. I hope I'm wrong, cause it will be bad news for the people in the path...

Maybe I was being a little too biased towards "chaseable storms" warranting higher risk levels...when in reality, it doesn't have to be chaseable to warrant a day 3 moderate. However, I would still question the 45% in terms of convection initiating too soon before storms can be surface-rooted.

Or perhaps this could also be like April 14, 2012 where storms fired early and became mature, functional supercells with time.

 

[Jeff Snyder]

The VBV profile seemed almost negligible up into the Woodward-Liberal area on the 00Z/12Z runs of the NAM. Definitely not progged to be worse than say, April 17th which still managed to put out some mammoth supercells.

While this does have April 26, 2009 levels of bust possibility on it I don't think it's gonna be as much of a crapshoot as it's being pegged everywhere I've seen. A very, very sharp dryline with excellent forcing and at least somewhat of an inversion in the not worked over areas further north along the dryline should theoretically yield some pretty intense supercells if everything else pans out as expected (barring convective debris and such).

The most recent few model runs indeed don't show much of a V-B-V pattern south of the first couple tiers of counties in Oklahoma. So, this potential wrinkle appears to be abating a bit. The 12z NAM doesn't show a particularly wide instability corridor owing to very early CI (15-18 z) along the dryline in W OK. This early stuff is progged to move eastward/northeastward, with a second round of convection along the dryline firing by late afternoon. This seems possible, I guess, but there isn't very long recovery period for dryline convection. If the late morning convection holds off an hour or two later, it may hose the area completely; if it holds off 4-5 hours until mid afternoon, it may end up being "the show". Tough to say. We've had issues this year a couple of times with mid-day convection mucking up the environment.

The other potential wrinkle in this setup for chasers is storm speed and the heavy rain that's fallen in the past several days (and may continue to fall through Saturday). The non-paved roads in northern OK were quite suboptimal yesterday around Wakita and Medford. If we see significant chaser convergence this weekend (it's May in the Plains on a weekend, so I suspect we will), we may see folks getting stuck on muddy roads (or dead-ending into a mud pit) trying to follow storms moving 40+ mph.

 

[Royce Sheibal]

Central Plains chasers may want to make note of the 12z NAM4k. Pushing 3k cape into N KS and SE Neb with decent helicity values and hodographs that don't make Jared want to puke. Depending on where morning convection ends up and heating occurs, I think that a northerly target may be the way to go Saturday. Sim. Precip. shows an initial band of storms firing from central KS down to OKC mid-day, moving NE into what could be some juicy air and better hodos. Got a feeling there's gonna be some HP's, however. My target: Hebron, NE around 4pm. I might actually get to go Saturday, we'll see.

 

[Eddie Natenberg]

I looked at the 12z NAM and thought it would be good to give my 2 cents. IMO this is a clear high risk outbreak day. One that may not be worth chasing, because you most likely will be chased . After several days of return flow deep boundary moisture will be sitting above very steep mid level lapse rates, the convection from the previous day will help to modulate convection on Sat with some subsidence during the period of peak heating. I expect the right exit region of the jet to fire early in the day around 2pm in NE and KS with the chance of sig tors. With stronger capping to the south in the middle of the jet region should make for a late show 6-7pm in Oklahoma but still with sig tor chances. Otherwise expect a large area covered by sig severe all the way from NE to TX. Please stay safe everyone, as Jeff mentioned road conditions may be 'quite suboptimal'.

 

[Andrew Stoller]

This is WAY too far out to even mention this, but the 4k NAM simulated reflectivity is now in range; it shows storms firing all along the dryline as early as 18z Sat. Doesn't have anything in the form of early morning grunge to work things over.

 

[Jeff Duda]

FWIW, the 00Z MPAS forecast shows MCSs originating in almost the same area (eastern TX PH/NW TX/SW OK) in the late-morning to early afternoon three days in a row, starting today (Thursday) through Saturday. Today's forecast appears to be verifying, although the MPAS forecast was a few hours late in initiating the MCS. These MCSs totally wipe out the CAPE during peak heating and the atmosphere never recovers. As @Jeff Snyder mentioned, the timing of early CI will make a big difference.

I have also noticed the veer-back pattern slowly fading away or being limited more towards 500 mb than before. However, as I said before, this day still has bust potential. The large scale pattern certainly fits an outbreak, but the devil is always in the details, and those details matter.

 

[Ben Holcomb]

Saturday looks to be an extremely potent day across a large amount of the plains and the hype from the SPC and media seems to be warranted. This might be one of the better setups I have seen in quite a long time. 70 knot jet at 500mb slamming into a heck of a moist sector. Not a lot of negatives, although convection today and tomorrow and saturday am could ruin things, but it seems like it could be a day where even that doesn't matter much.

Forecast soundings from Kansas to Central Oklahoma are extremely impressive, with 200-300 m2/s2 0-1 SRH.

Concerns are less with the chance of an outbreak but with the following:

• Storm motions will be booking, with storm motions on the order of 40-45 knots
• Roads are flooded and washed out. It will be hard to get off pavement anywhere, including pulling off the side of the road.
  
• Chaser traffic will be horrendous. A day 3 MDT on a weekend after a pretty long outbreak drought spells some of the worst chaser traffic we have ever seen.

I have commitments in Norman until at least noon, so the central OK target seems more appealing to me. I don't believe i will have to go far from OKC Metro.

Most importantly, everyone please be courteous of other chasers and drive safe.

 

[Ben Holcomb]

Here's some forecast sounding eye candy. The first one is 7pm at Dodge City, KS, the second is 6pm at Watonga, OK

 

[Dean Baron]

One thing that has been making me leery of making that long drive is that surface temps don't really warm very much. You have to get into central Oklahoma before you start sniffing an 80 degree air temp. I realize early in the season strong hearing isn't quite as crucial but it's still concerning considering it may be the result of models picking up on earlier convection. The 4km NAM precip hasn't shown much of anything substantial on Saturday either fwiw.

 

[Stan Rose]

FWIW, the 00Z MPAS forecast shows MCSs originating in almost the same area (eastern TX PH/NW TX/SW OK) in the late-morning to early afternoon three days in a row, starting today (Thursday) through Saturday. Today's forecast appears to be verifying, although the MPAS forecast was a few hours late in initiating the MCS. These MCSs totally wipe out the CAPE during peak heating and the atmosphere never recovers. As @Jeff Snyder mentioned, the timing of early CI will make a big difference.

I have also noticed the veer-back pattern slowly fading away or being limited more towards 500 mb than before. However, as I said before, this day still has bust potential. The large scale pattern certainly fits an outbreak, but the devil is always in the details, and those details matter.

Yep, if I were chasing instead of working id be terrified of the 12z NAM which shows convection rapidly being wiped out to the east as it encounters the 'wiped out' CAPE area. I still think dynamics will win out here. At worst, it will just shift the chase target.

 

[Patrick Martin]

I am chasing Saturday, but the trending of the models has me rethinking quite a bit. As mentioned above, the 12z NAM makes me question a wrn KS dry line play, and further south starts to put it out of my out and back range. Last couple runs has me starting to seriously consider taking a gamble on the surface low play in northeast CO into SW NE. Still time to hammer out details, but keeping options open.

 

[John Peters]

I am chasing Saturday, but the trending of the models has me rethinking quite a bit. As mentioned above, the 12z NAM makes me question a wrn KS dry line play, and further south starts to put it out of my out and back range. Last couple runs has me starting to seriously consider taking a gamble on the surface low play in northeast CO into SW NE. Still time to hammer out details, but keeping options open.

Same dilemma as you Pat. I'm coming out of Ft. Collins.

GFS based 4km guidance from CSU (along with some other GFS based high-res guidance I have seen) does show isolated supercells initiating in the TX/OK panhandles region and entering SW KS near what I will call the "secondary triple point." Going to perch in Garden City tonight and then make the call tomorrow morning as to fall back on the CO/NE/KS boarder play, or stay south in KS.

http://schumacher.atmos.colostate.edu/weather/csuwrf_4km.php

 

[Bill Hark]

I am impressed with the set-up for Saturday which should produce some nice tornadoes for those willing to brave the Saturday May crowds. Unlike Friday, upper level winds will be much higher across the forecast area with expected southwesterly midlevels as high as 60 kts across the panhandles by 00Z I also like the south to southeasterly 850s. I think anywhere along the dryline in Texas and Oklahoma offers potential. If I was out chasing, I would personally target the better CAPE further to south. Wellington, Texas would be my starting point. An alternative target would be Guymon which is closer to the low and at the northward extent of somewhat higher dewpoints. Farther northward in Kansas toward the low may be more risky but could yield some really photogenic storms. Dewpoints are forecast to be much lower but should be sufficient in that area. As I await the 00Z GFS, my biggest concern is the NAM showing large areas of precip crossing the area in the morning. Faster storm motion will also make chasing more difficult.