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

[Derek Weston]

Dang it, I had been posting in this thread thinking 00 UTC Monday. Still amazed at my ability to get dates screwed up this way.

(maybe that will make some of my comments a little more coherent sounding)

Anyhow... yes, the southerly 500s are very worrisome when considering storm mode. As of last run, had to go to Texas to get some SWerly 500 flow. Shear is going to be insane -- one of those days where things teeter on being unidirectional and going crap-fest on us or being a major tornado outbreak.

Latest 12z GFS.... still narrow tongue of CAPE... SW Oklahoma looks best... flow parallel to the dryline is worrisome...

 

[Mike Hollingshead]

There's still a pretty fair difference in how the ECMWF handles the trough and the GFS, especially regarding the backing of the mid-level winds. GFS has them southerly through most of the plains. The ECMWF hasn't been doing that as bad. Or the lower resolution of the COD graphics for the ECMWF just make it look that way. 0z run of that still looks nasty to me. How that pans out is the biggest difference maker in my book. I'm not terribly concerned about much else. Clouds and whatnot usually have a way of working themselves out somewhere with large systems like this.

GEM ain't been as bad with that either...at least not over such a big area.

 

[Brett Roberts]

There's still a pretty fair difference in how the ECMWF handles the trough and the GFS, especially regarding the backing of the mid-level winds. GFS has them southerly through most of the plains. The ECMWF hasn't been doing that as bad. Or the lower resolution of the COD graphics for the ECMWF just make it look that way. 0z run of that still looks nasty to me. How that pans out is the biggest difference maker in my book. I'm not terribly concerned about much else. Clouds and whatnot usually have a way of working themselves out somewhere with large systems like this.

GEM ain't been as bad with that either...at least not over such a big area.

Just to throw another foreign model into the mix, here is the 00z UKMET output valid at 00z Tuesday:

http://meteocentre.com/models/ukmet_amer_00/GZ_D5_PN_120_0000.gif

It's nice to see that the GFS is alone at this point, among the operational models, in depicting such a sharp H5 trough with the closed low so far south and putting the entire length of the dryline under meridional mid-level flow. Needless to say, there are other issues to work out, and the overall timing seems unfortunate (i.e., when I look at the model forecast H5 maps valid 12z-18z Monday I think "wow, that looks classic..."). Hopefully we can slow things down a bit and not get widespread junk by lunchtime Monday. Hey, at least it's still four days out, and not much is set in stone!

 

[Andrew Stoller]

Yea, I hope the ECMWF pans out instead of the GFS. The 12Z GFS looks even worse now IMO. 500 mb winds are even more backed, and further south. The GFS is now even faster with the system and there's precip all day along the dryline. There's a bit more instability showing up along the KS/OK border with up to 1,500 J CAPE.

But the windfield to me just doesn't lead to discrete convection. It's funny, we're always wanting backed winds, but not this much!

Lets hope the GFS DOES NOT continue with it's consistency, because with each run, it looks consistently crappier.

 

[Michael O'Keeffe]

Yea I agree the GFS is not looking that good, but I remember May 22 and that was looking horrible on the GFS just before it showed up on the NAM and when it went on the NAM it looked like all hell could break loose. Could that be the case again, maybe or maybe not, but still we got time, I mean the setup this coming Sunday was showing 750 j/kg of CAPE on the GFS with maybe a small pocket of 1000 j/kg of CAPE, but when it hit the NAM there is 1500 j/kg and a widespread instability across from the Panhandles to Nebraska with at least 1000 j/kg of CAPE.

 

[Tom Dulong]

A vigorous early season closed system stacked from the surface clear up to 200Mb over eastern CO with a stretched advection tongue wrapping around through NE screams cold-core for me. Though the timing is a bit uncertain the feature has been pretty consistent through recent runs.

If I were able, Sunday night would find me in one of Tucumcari's cheap motel rooms, rising early and planning on running ahead of the vort max through central-western KS to Kearney, NE.

I think you are still on the right track, David. What past event the GFS "looks like" seems to change with each successive run. However, the 03/19/09 12Z run is almost a dead ringer for the 10 April 2005 event in Kansas.

Per Mr. Davies, this was a classic cold core low...which produced several tornadoes in a narrow s-n corridor of north central/northwest KS. If this GFS run was a perfect forecast, I would position myself near Hays, KS Monday morning and be prepared to run north or even northwest as the shallow supercells developed along the occluded front. Pretty good chance to put a few more notches in your belt.

 

[David Reimer]

With the 12Z NAM now out until 0Z Monday (7 PM Sunday) one interesting thing caught my eye, the NAM has a much higher amount CAPE then the GFS. It will be interesting to see if the trend continues onto Monday. I still believe that the GFS is under doing the CAPE, as it has done several times this year, but off course it will depend on the cloud cover and precipitation that present themselves with the returning moisture, however, for five days out, I wouldn't be too worried with what the GFS is presenting until it can be compared with the NAM.

David Reimer

 

[Mike Hollingshead]

12z ECMWF indicating more of a piece coming out Monday than the entire thing, which should lead to less backing of the mid-level winds. That is what needs to happen. I'm almost glad it's still doing that a bit early as some room is left for the somewhat typical slowing down still possible between now and then. I'd rather deal with a little early than a little late.

12z GEM out and also showing less of the backing mid-level stuff.

 

[Stan Rose]

The 12Z EC is still holding tough with its 'dumbell' low solution, and certainly looks a lot better than the gfs. The general trend of the gfs has definitely been deeper and slower with the low, and the NAM at 84 hours is even showing much deeper and slower than the GFS. Id have to go with the gfs, the EC has been lousy all winter with these systems. The gfs is showing a ton of shear red river and OK, but its looking very linear to me and theres not enough CAPE to match. Im definitely biased since we need moisture big time in E CO, and i cant chase Mon--though if i could, i would definitely take my chances!

 

[Andrew Stoller]

I don't even know why I'm model watching so much (yea I do, SDS!).

Twisterdata's 18z GFS is out and it still looks the same - this sucker just digs in, closes off, and vertically stacks all day Monday. Short of any cold core type action, west central OK and points south into northern TX look doable. 500s are at least out of the SW and there's a decent crossover to southeasterly as you get to the surface, with up to 1,500 J CAPE. 60 degree dewpoints are finally showing up in southern OK as well. After 00z, the GFS breaks out a ton of precip/squall line, but there may be a brief window before sunset of discrete convetion ahead of the pacific front.

 

[Michael O'Keeffe]

I think I may throw the GFS away because even the NAM even though it only goes out to 06z Sun it showing the trough still back near S California while the 18z GFS has the trough plowing into the High Plains at 06z Sun. So it appears that every model run the NAM, Euro, and GEM models are all in agreement with the GFS the outlier.

 

[Andrew Stoller]

I just looked over the GEM and it indeed is in agreement with all the others, except the GFS.

I hate the GFS but it's the only model that goes medium/long range with any kind of decent resolution from various web sources.

The 00z NAM will be fun to gander at tonight. The 18z run has the system a little slower then the GFS which will help things tremendously.

 

[Fred Gossage]

I think I may throw the GFS away because even the NAM even though it only goes out to 06z Sun it showing the trough still back near S California while the 18z GFS has the trough plowing into the High Plains at 06z Sun. So it appears that every model run the NAM, Euro, and GEM models are all in agreement with the GFS the outlier.

Your "analog" from the first page of this discussion is pretty interesting. Here's the 12Z run of the SPC MARS. Note the top 850-mb analog...

 

[Rich Thompson]

The Hesston case as an analog for Monday is a pipe dream. 3/13/90 featured an extended return flow scenario with record high temps along the Atlantic coast, and widespread low-mid 60s Tds from TX-NE.

The moisture return is still a serious concern for Monday. It looks like we'll pump another slug of relatively dry air swwd into the Gulf basin in the wake of the system crossing the Atlantic coast now. This will result in low-level trajectories from within the large surface ridge just off the SE Atlantic coast through early Monday. That leaves little opportunity for the tropical trajectories, so I suspect we'll see more of the somewhat marginal Tds (mainly in the mid-upper 50s, perhaps near 60 F). The GFS is probably full of you-know-what in keeping surface temperatures so cool Monday. Low-level saturation and thick low clouds seem like a bit of a stretch given that we won't see a maritime tropical air mass surging back into a cool, continental air mass across TX.

If the warm sector ends up looking marginal in terms of instability, a reasonable play could be the "cold core" from KS into NE. Still way too much time to haggle over the details...

 

[Fred Gossage]

Yep, moisture return is a big big big issue. Will be interesting to see if we get enough warm sector instability to spark off stuff...or if we're limited to cold core activity.