3/23/09 FCST: NE, KS, OK

[Rocky Rascovich]

I'm now quite confident that the first significant outbreak of severe weather is on tap culminating on this day for Monday March 23. Strong cyclogenesis will be occurring across eastern CO. on Sunday which could be "the day before the big day" But I will emphasize this post for Monday. Examining mostly the latest GFS data from 0Z 18Mar suggests that moisture return should be ample with surface temps in the 70's across most of the outlook area with dewpoints into the low 60's as far north as the ICT area for Monday afternoon. If we don't get too gunged out with cloud cover, which may be something to deal with, instability will be moderate with cape values in the 1200-1500 j/kg. range. Shear parameters look very favourable for rotating storms accompanied by large hail and a few tornadoes.. if model trends continue, a couple of violent tornadoes are possible. Best chances for severe weather is right here in central OK. if these last few GFS runs verify.

Lots can change of course as the day draws close, but I think the chances for at least a few decent storms to observe looks decent. I hope to be out and about getting my chase season started. Meanwhile, I'll be watching this close.

BTW: I'm really liking the site: http://twisterdata.com/ You may want to keep abreast for your data needs with that great site.

 

[Connor McCrorey]

Thanks for starting this thread Rocky. It seems nearly everyone freaked out when they saw the 0Z GFS tonight! If nothing were to change, I would be chasing in N TX Monday. Better moisture down here, and the shear looks excellent. If instability gets any better we could have an excellent chase day. As usual though, I have school until 4:15, so I'll have to hurry to make any storms

 

[Danny Neal]

http://northernilstormchaser.com/ I threw a quick map on my web page homepage. It is still pretty early to speculate on the type and intensity of the severe weather associated with this system but as I said in the other thread, I like the dry line play as I think there may be too much forcing up north and it will be a linear mess. Further south we may be dealing with a decent cap. So I outlined an area I felt was in between that sees the greatest potential for severe weather from SC KS into W OK and down into NE TX. The red in my map is the "greatest" potential ATTM IMO. The blue is just a broad area of thunderstorms that I feel will develop and may or may not be severe. My map (as always) will be subject to change.

 

[Derek Weston]

Thanks for starting this thread Rocky. It seems nearly everyone freaked out when they saw the 0Z GFS tonight! If nothing were to change, I would be chasing in N TX Monday. Better moisture down here, and the shear looks excellent. If instability gets any better we could have an excellent chase day. As usual though, I have school until 4:15, so I'll have to hurry to make any storms

As is...according to the 0z GFS.... we're talking CAPE < 750 for the area you mention. (not to pick on you -- just making a point about the setup I'm seeing) As well as very meager mid level winds. (500s...) Just a bit disorganized yet.

Agree this day has potential... but, I think we've got to hope for something a little better than what we're seeing on this run. (the following day, however, could be insane.. if things come together correctly)

 

[Brett Roberts]

As is...according to the 0z GFS.... we're talking CAPE < 750 for the area you mention. (not to pick on you -- just making a point about the setup I'm seeing) As well as very meager mid level winds. (500s...) Just a bit disorganized yet.

Agree this day has potential... but, I think we've got to hope for something a little better than what we're seeing on this run. (the following day, however, could be insane.. if things come together correctly)

I was worried about moisture/instability on earlier GFS solutions that ejected the upper trough into the Plains on Sunday, but with both models now honing in on Monday, I think another full day of return flow should help mitigate that problem. As for the CAPE values, my completely subjective impression over a few years of following severe weather on the models is that the medium-range GFS will often underestimate the extent and magnitude of instability. The surface dew points on the 00z GFS look nearly comparable to, say, 2007-03-28 (in no way am I suggesting a repeat; just that moisture does not seem like the primary issue, as long as these current slower solutions verify).

As for lacking mid-level winds, I'm not really seeing that either on any of the 00z models. In fact, the wind profiles almost look scary over much of OK/KS/NE. Someone more experienced can correct me if I'm wrong, but it seems to me that if you take current model output of the overall synoptic situation as being fairly close to on-the-mark (which is always a stretch at 144 hrs., of course), the only real question marks standing in the way of a significant event would be timing and storm mode.

 

[Tony Laubach]

the only real question marks standing in the way of a significant event would be timing and storm mode.

Brett, I agree with you.. moisture and upper level winds don't seem to be the biggest factors in deciding this event. The GFS has a good 500mb punch moving over the region with decent moisture to work with below that.

My concern with this being such a dynamic system is explosive development into a line or cluster. I think areas along the dryline in western Oklahoma and points south have the best potential for discrete storms as opposed to areas further north.

I like the setup as it stands right now, and think it definitely has good potential to become a good chase setup. How insane it all turns out remains to be seen, but I definitely think the overall lack of a major outbreak is pushing us as forecasters in a much more favorable direction to make this a big deal. I do think this will be the best chase setup so far this year, but unfortunately that says very little considering what we've had to work with.

 

[John Cameron]

Wow... this has become rather interesting in just the last 24 hours. Would love to see the the upper wind maxima more perpendicular to the dryline, but we are talking late March here. My concern right now is just a big nasty squall line. The Td fetch does look nice though.

 

[Michael O'Keeffe]

My concern with this being such a dynamic system is explosive development into a line or cluster. I think areas along the dryline in western Oklahoma and points south have the best potential for discrete storms as opposed to areas further north.

I agree with you Tony. That's why I am liking the latest ECMWF more than the GFS. It is showing a more SW flow double barrel low setup and SE 850mb winds over a massive area. VERY VERY similar to March 13, 1990.

http://bangladeshtornadoes.org/UScases/031390/03149000zh5.gif

However even if the GFS verifies I have seen these early season fairly unidirectional setups verify over the Plains, namely 3/28/07, so ya never know.

 

[jamesmseitz]

I too have been following these days for awhile. I am too leery that the Clouds, like mentioned before, will have to break up in OK, KS to have decent shot. GFS now has storms possibly starting that day before. If so, will the atmosphere clear out in time to give some good ground heating. I am also concerned that the strong front that will likely follow will cause linear formations rather the discreet cells . These 2 factors make me think that pre frontal storms might have issue getting to the upper winds to give us those right turning cells we all love to see. Time will tell but this does warrant attention.

 

[Brandon Lawson]

Timing with this system is looking really iffy at the moment, with all the forcing arriving early monday morning. At least there are 5 more days for the models to surprise us. I'd expect to see something similar to what the Euro is already showing. If that were to verify, we could still see some good storms. If the system held off, even for just 6 more hours, that would be amazing. Maybe I'm having too much fun looking at the models, but these 850mb winds on the latest 12z gfs run are insane

 

[Chris Lott]

My main concern from looking at the models so far is there maybe too much shear with a very narrow band of minimal CAPE. I'm afraid storms will get sheared apart quickly. I really don't think the cap will be an issue, but rather the storms being able to sustain themselves with the amount of shear that is forecast. Based solely on what I see now, I'm liking an area from Wichita Falls up through W. Oklahoma ahead of the dryline for the best development.

 

[Bob Hartig]

Just got done looking at the 12Z GFS. Like Brandon said, the 850s are looking pretty stout. It's too early for me to worry much about timing; right now, I just feel excited about the prospects of a dryline chase next week. At the moment, southwest OK looks to be the place. Farther north, the mid to upper winds line up increasingly from the south, pointing to a bunch of storms raining on each others' parade.

For us Great Lakes chasers, Tuesday also could keep us occupied on the way home.

 

[Skip Talbot]

The GFS is showing wind fields that are quite similar to 3/28/07. The major concerns with that setup when it was being forecasted several days in advance were moisture return and storm mode. I remember the dews were forecasted to be in the mid to upper 50's, but that was more than enough for tornadic supercells given the higher terrain. Also, with the flow nearly paralleling the dryline, a quick squall line evolution was forecasted. This was not the case, however, as there was ample directional shear with highly backed surface winds, SE 850's and SSW 500's with the storms being able to space themselves nicely. One major difference is the instability, where 3/28/07 had many areas near 3000 J/Kg, and the GFS is forecasting 750-1000 J/Kg for this setup. I, however, don't put much stock in the GFS's CAPE plots. Its one of the more inaccurate forecasts that you can look at this far out. With the orientation of this trough and the forecasted moisture return, we could see severe weather from NE down to the panhandles along the dryline.

 

[Dick McGowan]

The GFS is showing wind fields that are quite similar to 3/28/07. The major concerns with that setup when it was being forecasted several days in advance were moisture return and storm mode. I remember the dews were forecasted to be in the mid to upper 50's, but that was more than enough for tornadic supercells given the higher terrain. Also, with the flow nearly paralleling the dryline, a quick squall line evolution was forecasted. This was not the case, however, as there was ample directional shear with highly backed surface winds, SE 850's and SSW 500's with the storms being able to space themselves nicely. One major difference is the instability, where 3/28/07 had many areas near 3000 J/Kg, and the GFS is forecasting 750-1000 J/Kg for this setup. I, however, don't put much stock in the GFS's CAPE plots. Its one of the more inaccurate forecasts that you can look at this far out. With the orientation of this trough and the forecasted moisture return, we could see severe weather from NE down to the panhandles along the dryline.

My thoughts exactly. GFS, IMO, is always too low for the forecasting of instability. I've just quickly glanced at the 12z run and it is strikingly similar to the 3/28/07 setup. Being geographically unbiased of this setup, I'll likely be out, (assuming it doesn't go to sh**) wherever the chances are maximized for tornadoes. Still a long ways to go....

 

[Michael O'Keeffe]

Very true Skip, here is the SPC's day 2 outlook for March 28, 2007. It mentions the same general concerns as with this upcoming setup.

THE PRIMARY UNCERTAINTY THIS FORECAST IS THE CONVECTIVE MODE OWING
TO THE TENDENCY FOR MID AND HIGH LEVEL WIND FIELDS TO BACK WITH
APPROACH OF UPPER SYSTEM. THIS WOULD SUGGEST THAT STORMS WOULD
EITHER INITIATE AS LINE SEGMENTS OR QUICKLY EVOLVE TO THIS TYPE OF
MODE AS A RESULT OF SEEDING EFFECTS AND POTENTIAL FOR COLD POOL
REINFORCEMENT ALONG INITIATING BOUNDARY. STRONGEST LOW-LEVEL SHEAR
IS FORECAST TO EXIST OVER PORTIONS OF N-CNTRL/NWRN KS INTO WRN/CNTRL
NEB INVOF OF WARM OR STATIONARY BOUNDARY WHERE LOW-LEVEL WIND FIELDS
WILL HAVE MORE OF AN ELY COMPONENT. IT DOES APPEAR THAT THERE WILL
BE SOME TEMPORAL WINDOW ALONG DRYLINE FOR INITIAL SUPERCELLULAR
INITIATION WITH THE PRIMARY SEVERE THREATS BEING LARGE HAIL /SOME
SIGNIFICANT/ AND A FEW TORNADOES