06/09/09 DISC: KS/OK/CO

[Bill Schintler]

Arguably, the best chasing storm today in KS/OK was that which fired just west of Dodge City around 5-5:30 PM while producing a left-split early in its life cycle, and then tracked east-southeast to just north of Greensburg (where it produced a brief tornado), and then towards Pratt, by which time it rapidly weakened and fell apart. What happened to this storm to cause such a rapid demise? A few observations of my own:

1) The storm crossed over to the north side of the front/OFB west of Greensburg, where the capping inversion was strong.
2) More importantly, the LLJ was virtually non-existent at that time and location – so if the inflow-portion of the storm crossed over into the cooler air, there was nothing above the boundary layer to sustain it.

Thoughts? - bill

 

[Paul Austin]

I would agree, Bill. I was watching this cell on GR3 at home. I didn't pull up surface obs, but it appeared to begin riding along the boundary shortly after its split toward the SSE for some time before taking a jog across the boundary toward the ENE and then NE as it dissipated. Additionally, I don't believe SBCAPE was quite as robust this far west as it was further east, so that might have played a role as well. Not quite so much energy to tap into and difficulty tapping into it with the boundary pushing further south. Very interesting storm.

I was also a little surprised at how long the storm seemed to show strong rotation on lowest SRV without acquiring a tornado warning. The warning seemed late to me, but perhaps the proximity to DDC and spotters/chasers in the area relaying ground truth (no tornado for quite a while) had a role to play in this.

I had actually contemplated heading out to KS for this day, but decided against a $400+ price tag for a single day with setup question marks. I'm glad I stayed home, as I probably would have been in the Wichita area perhaps southward into OK with almost everyone else.

 

[CZandbergen]

I was wondering the same thing regarding the DDC storm and also the convection to the SE of ICT. One thing I noticed last night as I was watching GR3 and the RUC and it looked like the surface winds and the winds aloft at 500mB were causing the storms to have a hard time maintaining a decent updraft. You can see this in the link below which is the 22Z RUC run for 0Z yesterday.

http://www.twisterdata.com/index.ph...nglemap&sounding=n&output=image&archive=false

Also, to your second point the LLJ was much better in the area to the SE of ICT and those storms were able to sustain themselves even though there was little rotation and they turned into a mess rather quickly. I was watching the cell that went tor warned to the NW of Sedan and there wasn't much there in terms of storm relative velocity when the warning was issued. Link to the LLJ and 500mB cross over below.

http://www.twisterdata.com/index.ph...nglemap&sounding=n&output=image&archive=false

I would be interested in hearing others thoughts on why the storms SE of ICT turned into such a mess. What changed from the earlier model runs?

 

[Stephen Locke]

OK I've got the weakest meteorology of anyone on here but I'll join this conversation in hopes of learning something. I was too busy chasing and trying to make a decent photograph to monitor mesonet but I am always wetting my finger and holding it up in the air. And I use the plethora of American flags to monitor wind directions. On my way to Pratt I pulled up east of ICT because that is where the atmosphere seemed agitated. Surface temps were 82F but from the North. I figured storms were eminent on the east side but would be fed by the LLJ. I continued toward Pratt. West side of Wichita winds were from the south and 92F. I felt that was an improvement. Closer to Kingman winds were from the West. At this point I did not know what to do. I went south along I-35 were winds were at least consistently from the south and storms were initiating in OK. Toward evening it looked to me as if a dryline had advanced east rapidly. The southern and western storms seemed to evaporate. And the atmosphere really cleared out.

 

[Andy Wehrle]

TWC was really harping on the persistent cirrus clouds, which I'm sure played a role in the failure mode yesterday. When they talked to Howard Bluestein, he also mentioned the veering surface winds. In 2009, when it's not ridged solid, all the good-looking setups find a way to fall apart at the 11th hour (go back to April 26th high risk).

Vortex2 should be very glad that they had the right combination of luck and skill to successfully deploy on what may well turn out to be the only really chaseable, long-lived, photogenic tornado in the Plains during their operating window.

 

[Dustin Wilcox]

Without a doubt IMO it was purely the boundary surging South, you could visually see the boundary sagging south of its location. It was interesting to watch the updrafts as they were influenced by that boundary. The updraft near Wellington shot up in a hurry as it interacted with the boundary and it appeared visually it (at least for a brief time) rooted itself on the boundary and caused it to stall or maybe even lift North near I-35, while further to the West the boundary continued to sag South. I think had the boundary been a true WF and or just stationary, the storm out of DDC would have been a long lived monster...

I will say it's neat (though still disappointing as it means the end of a chase) when supercells die in that shrinking barber poll fashion. I never hope for it, as it normally means a once impressive beast is no more, but I'd much rather watch a supercell slowly spin itself to death, as opposed to watching one gust out and do the whole MCS, cold pool thing.

 

[Mike Smith]

I have, printed in front of me, the Lamont, OK profiler for 18Z (1pm) yesterday. It is, for all intents and purposes, perfect from the surface all the way up.

Based the bullseye over Augusta of upward vertical motion and better surface backing at 2pm, we headed east to Howard. We saw the weak wave on the boundary east of IAB about 4pm and picked the storm that originated on it. "Surely this will produce a tornado," I thought.

We caught two very nice funnels, one with strong rotation, near Moline. But, neither got to the ground and I can't figure out why. The ICT -88D did show weak to moderate rotation and surface conditions seemed OK. In fact, temperatures rose from 71° to 75° as the storm approached. FYI, based on past experience, tornadoes do occur with high clouds. By themselves, I don't think high clouds make much difference.

I am hoping Vortex spends as much time on the null cases (plenty of those this year!) as they do the "big one" in Wyoming Friday.

Many years ago, when SPC was NSSFC and was in KC, one of the long-time forecasters told me, "some airmasses want to rotate and some don't." I was out April 26, was out yesterday, and was out for the multiple funnel cloud show west of Winfield on April 25.

It seems that 2009 could be summed up with air masses that "don't" (want to rotate).

Mike

 

[Paul Austin]

I'll agree with Dustin on this one. Having watched a bit more video of the storm, I think another hour without being cut off and this cell would have produced a nice sustained tube. I was surprised that the early MCS stuff and trailing cells seemed to spin like crazy as they approached or crossed the KS/MO line. I know most of this was not especially chaseable and rather messy. But it was interesting nonetheless, as I expected cells going up further west to get rooted on the boundary and produce something at least briefly.

 

[Derrick Herndon]

We also set up in Pratt and had the decision to dive a little south for the storm just south of the OK near Alva which at the time was isolated and looked good, or stay put for something on the boundary. I saw the storm near DDC but thought that the Alva storm would hit the boundary, turn East and spin. My concern with the DDC was the orientation of the boundary such that it would have to turn hard to the SE to stay along the boundary instead of moving up over the boundary. Of course the Alva storm became a multi-cell mess while the DDC underwent a nice split and rotated for a bit. I regret not seeing the nice structure as it was the best storm of the day. My question is why the boundary continued to sag south the way it did instead of lifting North? We left the Alva mess when we saw the DDC storm improve. I counted on it moving along the boundary but as soon as I saw how far south the boundary had sagged I knew it was toast. It appears from the surface obs that a meso low developed along the boundary south of ICT which enhanced the Northerly flow, pushing the boundary farther South instead of it lifting North. Perhaps terrain played a role here? I am trying to imagine a drainage wind situation looking at the topography.

 

[Chris Allington]

The eastern storms to the east of the Wichita area seemed doomed because of the orientation of the boundary relative to the storm motions there. The outflow boundary/ warmfront was set up from NW to SE in this area while storms that were initiating were moving NE/ENE. They would pop right on the boundary, then the bases would elongate and eventually cross to the cool/ stable site of the boundary and elevate and chop off there surface inflow. We saw this a few times before the storms in Greenwood and Elk Counties were finally able to take a more ESE motion along the boundary. The problem after that was too many storms went at the same time, and the more intense ones couldn't control their outflow production. If the boundary would have remained more E-W oriented and our surface winds wouldn't have veered to the area west of ICT, I think it would have been a much more favorable situation. We gave up and anything firing west of ICT because of the veered surface winds and the evaporating cu field.

 

[Jeff Duda]

I have, printed in front of me, the Lamont, OK profiler for 18Z (1pm) yesterday. It is, for all intents and purposes, perfect from the surface all the way up.

Mike,
Were you looking at this sounding? (http://www.spc.noaa.gov/exper/soundings/09060918_OBS/)

If so, it doesn't look perfect at all to me. Granted, CAPE looks good and 500 mb winds are acceptably strong, but LCLs are a little high, there's no 0-3 km CAPE, and next to no SRH anywhere in the lower half of the storm according to this sounding. I was watching the SRH and shear parameters all day in the area, and until about 00Z there was next to no even decent shear in the low-mid levels in NE OK or ext. SE KS. That probably contributed to the storms not rotating much, or for long, and going outflow dominant immediately.

I was on the storm that got tornado warned near Sedan and it looked fantastic for about 15 minutes before puking its guts out with outflow. I had to get >5 miles away from the base of the storm before I could get in front of the outflow boundary. It was pathetic.

 

[Derrick Herndon]

The bases near Alva where high, perhaps 4,500 ft. I am a weather observer so a decent judge of heights (or at least I was). I dont think you got the lower bases until up near the boundary.

 

[Chris Allington]

Heres what I was talking in my earlier post, just look how stretched out that updraft is with the lower portion on the better side of the boundary. Same thing again later on in Greenwood county with one of the storms: