5/10/10 FCST: TX / OK / KS / CO/ MO

[Rich Thompson]

I can't remember seeing any dewpoint projections that were consistently forecast by the NAM or GFS for a chase day that were way off this year. And in this case the GFS isn't showing a magical leap of moisture. It is showing 48 hours of advection and I can look at a surface chart now and see a good moisture pool already in place over the gulf. I'm considering the moisture quality over the gulf and the amount of time we should get for moisture advection with this setup. If you get 48 hours of moisture advection leading into this, with wind speeds >30kts over the southern plains for the last 24 hours, how far do you think that moisture will travel? I don't consider low 60 degree dewpoints for Monday "super bullish moisture-return predictions". That seems very reasonable to me and I'd be really surprised to see that not verify.

Mid-upper 60 Tds are not a stretch in this coming case for the reasons you stated - 48 hrs of relatively unimpeded advection and the moisture is already present across the wrn Gulf. Of course, there haven't been that many chase days this years in the Plains, but several recent events have featured Tds closer to 3-5 F too high. The difference in those cases was an apparent local source in the model forecast (didn't match the actual local sources, or lack thereof).

Other than some minor EML concerns I have for areas farther south along the dryline, and the fact that I'm working mids, the chase situation looks quite good (and reasonable) for 5 days out.

 

[Logan Karsten]

Indeed, Monday is beginning to look increasingly favorable for a potential tornado outbreak across the plains. 12Z GFS looks good for a Hutchinson to Salina, Kansas target. Forecast soundings from Hutchinson at 00Z Tuesday show over 2600 SB CAPE, 0-1 Km SRH of 350, LCL of under 1000, and 0-3 Km shear of around 50 Kts. There will be a cap throughout the day, but it looks breakable as long as there is enough surface heating in the warm sector. Even the experimental FIM looks very favorable for the same area.

 

[Brian Stertz]

Latest GFS has the dryline immediately west of the US 81 corridor with a very nice triple pt. near Russell KS. Looks to me like the tornado ourbreak will be along and east of a Concordia to Enid to Lawton line. Significant TOR parameters (on my checklist)appear to be in place by Monday afternoon with an approaching strong 700 wave to bust the cap. Looks like the best theta nose is forecasted to poke up just west and southwest of Wichita. Looks like the lfq of the mid-level jet is also favoring C/SC Kansas and NC Oklahoma. This would put my inital target in the Kingman KS area with a watchful eye on the triple pt. near Salina. Looks like mutliple supercell hard targets will be available to spread out the storm chaser/V2 hordes. Definitely time to prepare and plan....

 

[Mikey Gribble]

I just updated my blog so I will just copy and paste that here instead of writing it all out again...

The GFS continues to show an extraordinary setup for next Monday. The million dollar question is whether or not if will verify. I’ve seen a lot of really good setups go to absolute crap inside of 72 hours, so I am being cautious about fully buying into some of the paramaters being forecast for Monday. It is tough not to get excited though because this is the best setup I’ve seen for the plains since 2008.
The GFS and ECMWF are in pretty good agreement with the timing and overall intensity of the trough that should eject into the plains on Monday. They have been pretty consistent with each other and to a lesser degree the timing over the last several runs. They have had some significant differences on how to handle the evolution of the upper air pattern, with the GFS flopping back and forth from a one large trough to a two smaller waves solution, but that hasn’t really had any impact on Monday’s setup (it has to do with any potential chases beyond Monday). So while there have been some differences, the models seem to be doing a good job with Mondays forecast.
I think everybody is starting to pick up on the fact that Monday is looking exceptionally good. The paramaters are great all across the board. If the models were breaking out precip along the dryline and LCL’s could lower by about 200m, this would literally be as close to a perfect setup as you’re going to get. There is a lot that can change between now and then though. I haven’t seen any reason to doubt the model forecast for Monday yet, but just going off past results you know its a little dangerous to buy into details this far out.
Again in this mornings run the GFS places a surface low over southwest Kansas (north of its placement in yesterdays run) with a dryline running south from there across western Oklahoma. Dewpoints are being forecast in the low 60’s across the warm sector. I think us getting dewpoints >60 along the dryline is highly likely, so moisture is of no concern for me with this setup. It would be nice to get dewpoints up to about 65 to help bring the LCL heights down a tad, but they are plenty good enough right now to support a strong tornado threat on Monday.
Surface temps are in the low 80’s ahead of the dryline which brings CAPE up into the 3000J/kg range, which is pretty damn good for this time of year. Deep layer shear and the CAPE being forecast will create an environment extremely favorable for supercells. The shear vectors are normal to the boundary, so discrete supercells will be the mode of convection.
It is still too far out to consider the specifics affecting tornado potential with this setup, but I’ll go over some of them just because they are so impressive.
0-1km SRH is forecast to be >400m2/s2 along the dryline with >600 closer to the triple point. To put that in perspective you usually look for >100 for a solid tornado threat. We cover that four times over with this setup. With good directional shear and almost 50kts at 850mb the shear profile will be very favorable for strong to violent tornadoes.
The GFS shows 1km EHI at 8 over the warm sector and a significant tornado probability of 15.9. Those are off last nights run because they haven’t updated yet, but those numbers won’t drop with the 12Z run.
The hodograph for Monday will be amazing if this holds together. Once you get off the dryline into the warm sector surface winds are out of the southeast at around 20kts. 850mb winds are out of the south at 45kts. 700mb winds are out of the southwest at 55kts. And 500mb winds are out of the WSW around 60kts. The best hodograph I remember ever seeing was the NAM forecast sounding from the night before the Greensburg tornado and this one would give it a run for its money if it verified.
When you consider everything the GFS is showing this setup looks great for cyclic tornadic supercells capable of strong/violent long-track tornadoes. It is easily the best setup I’ve seen for the plains since May of 2008. It is important not to get too comfortable with what the models are showing this far out though. For our last setup the GFS was overdoing wind speeds by about 20kts at 850mb. 20kts makes a huge difference in a setup like this. That being said I am extremely optimistic, but I’m not signing off on this yet. If it verifies though and the cap can break, it would be a major tornado outbreak.
My biggest concern by far with what the GFS is showing is the cap. At 00Z there is still a fairly significant cap in place and none of the model runs have shown precip breaking out. Now with the earlier model runs a couple days ago when it was showing the trough just barely nosing into the plains on Monday I could see a cap bust happening. I don’t think that is a very probable outcome in this situation since you have upper level support and a rapidly deepening surface low. Even though that is the case any time the models aren’t showing convection it should be a cause for concern.
This is an extraordinarily good setup for tornadoes. I am extremely pumped to see the potential for violent tornadoes with the models because it is a very rare thing. Like I mentioned earlier I haven’t thought a setup was capable of violent tornadoes since the Greensburg outbreak. There is still a lot that can go wrong with this though so I’m keeping my hopes in check for now. I will continue to watch this very closely and I will probably update my blog a couple more times today after I have a chance to go over more details.

 

[Stephen Jones]

Giving my two cents on the possible event...

It looks as of the 12Z GFS that it's defiantly going to be a big tornado potential setup! Especially just west of I-35 in OK and along I-135. The main worry about this system is the CAP. But I personally believe that by 6pm the CAP should break in Southern Kansas and slowly break into Northern OK! CAPE values per the GFS are going to be sufficient enough to break through the moderate cap (>2750). Moisture return is looking like that it should not be a worry. The GFS has fared well with the last couple events concerning dew points, and from experence being in Arkansas this past weekend during the High Risk, it was more than enough moisture.

Wind Shear itself per GFS is not a problem, their will be enough directional shear and speed shear to get violent tornadoes in Northern OK and Southern KS. My initial Target area as of right now would have to be Kingman, KS to Harper, KS area. Still a lot will change within time.

 

[Michael O'Keeffe]

Not much to add here as I agree with much of what has been said but wanted to add some graphics from wxcaster showing the incredible 0-1km helicity values and 0-1km EHI from todays 12z GFS.

http://beta.wxcaster.com/models/gfs/central/CENTRAL_GFS_0-1KM_SRH_108HR.gif
0-1km Helicity

http://beta.wxcaster.com/models/gfs/central/CENTRAL_GFS_0-1KM_EHI_108HR.gif
0-1km EHI

http://beta.wxcaster.com/models/gfs/central/CENTRAL_GFS_ATMOS_STP-NEW_108HR.gif
Sig Tor Parameters

 

[Andrew Stoller]

Let us now pray that this verifies.

 

[Warren Faidley]

Skew-t looks wild, but storm speed could be a problem... 41.7 Kts.... ouch!

W.

 

[Chris Vagasky]

You said it Warren...00z GFS still has storm motions of 40+ knots...makes it difficult to chase and even a bit more dangerous should any supercells tornado...

00z GFS still on track for a big event...

Dryline along a line from FDR - CLK - AVK - PTT, with impressive directional and speed shear (S/SSE/ESE winds @ 15-20kts at SFC, S winds @ 40kts at 925, S/SSW @ 50+ kts at 850...you get the drift...)

Forecast soundings ahead of the dryline...See KCHK, KRQO, KWDG, KOUN, KICT...and to a lesser extent KHUT...show 3000-4000 J/kg CAPE...0-3k Helicity >400 m2/s2...low LCLs (750-1250m)...EHIs >9...and STPs approaching 20 (KRQO = 17.4 for 00z 11 May 10!)...but storm motions approaching 50 knots...

The cap looks relatively easy to break all along the dryline, especially with decent convergence along it.

Should this verify...the OKC and ICT Metros could be in for some significant severe weather in the evening hours...

Like Mikey said above...I don't think I've seen a set up this good in quite a long time. At least across the Southern Plains. Now, this is just me, but I would probably set up in El Reno, able to move north towards Enid or south towards Chickasha if I need to, and be able to book it east towards OKC along I-40.

 

[Jason Boggs]

I also think it looks good for Monday, but i think the GFS has things too far east. I think when the NAM takes hold, it will pull the moisture and higher CAPE westward near the TX-OK line. Of course this is only my opinion, but I've already seen it happen a couple of times this year.

Pretty much everything looks good to me for a potential outbreak on Monday. A couple of cold fronts will go through the area before Monday, but the moisture should recover nicely. Shear looks incredible with really good speed and directional shear in all levels. The cap will be moderately strong (700mb temp 8-12), but I think with daytime heating along with high moisture values, it should be overcome.

I agree that storm speed may be a problem with any storms that develop, so we'll definitely have to stay on our toes and pay attention to road options and escape routes.

Shamrock, TX to Sayre, OK may be a good starting point with good road access in all directions. Of course things will change, but this is my thinking at this point.

 

[Chris Wilburn]

This has the chance to be significant for sure. The shear just looks amazing that's for sure. I am not sure if I could make up a scenario where the wind shear looks better. Plenty of moisture, moisture depth and CAPE will be on display. I can't imagine the cap not being able to be overcome with such parameters in place. It has happened before though so nothing is for sure. The cap may be a bit more of a problem in SW OK to western OK where 700mb temps are forecasted 10-12C. Northern OK into KS they are forecasted 8-10C so the cap may be a bit more friendly in this area.

Wind shear, moisture and instability are just insane for this setup! I am not going to go too much into all of those parameters because it is almost perfect and doesn't have me worried at all. 0-1 and 0-3 SRH/EHI values definitely support strong tornadoes. I agree this is the best setup we have seen in a while. Maybe May 22nd or May 23rd of 2008? Hopefully it will verify and I see no reason to think that it will not do just that. I guess you never know about capping so that will need to be monitored. Long tracked, cyclic tornadic supercells look likely with a few strong and long lived tornadoes possible as things stand now and things don't change.

I too am anxiously awaiting the NAM like Jason mentioned. I too wouldn't be surprised to see it pushed back to the TX/OK border area. I am thinking western OK for an early target. This may change to the KS/OK border area say near Medicine Lodge if I think the cap will be an issue further south into OK. The NAM should be out in about 7 hours so it will be nice to have it to compare to the GFS. I did forget to mention the worries about 40-45 kt storm motions as talked about above. This is pushing the 45mph to 50mph range and isn't ideal for sure. This will cause problems keeping up with storms. It would be nice if the 500mb jet was only 50kts instead of the projected 75-80kts, but you can't have it all perfect I guess.

I forgot to mention one thing. It may be best to get as far north as you can due to storms speeds. This way you can sit in one spot and pick storms up as they come in from the southwest. If you play too far south along the dryline you may only have one or two storms come and go and be left with nothing else. This has me thinking more southern KS now, but will see how things evolve over the next few days.

 

[J Allen]

Still a few days out, but I really like what I am seeing.

The storm motion of 40+knots looks like the only thing making this chase day less attractive....and perhaps the strength of the CIN in terms of kicking things off. The prior of these points may be a serious issue for V2, as I believe they would struggle to complete the intended plan with such a high rate of motion...the process is complicated enough as it is.

Instability and CAPE looks fantastic and concentrated with a really solid updraft potential, and fairly strong chance of hybrid microbursts from the look of DMAPE. From that forecast sounding, hail is going to be of little concern, with the updraft likely too saturated to generate a growth to large hail sizes, despite the strength of the updraft through the growth layer.

LCL looks to be in the sweet spot at 900mb, which is definitely a positive given the speed of storm propogation. I would go as far to say as that chasing might be limited to intercepting the storm where possible and letting it go, but that hodograph and SRH might convince some people otherwise.

Definitely going to be interesting to watch for how the NAM and GFS take this one over the next few days. I will be interested to see if the moisture backs off in either of them as it has to some degree in events so far this year.

 

[Brian Stertz]

My take on storm motions is that they will be slower as they have a tendency to move right and slow down when the supercells mature into solid sfc based tornado producers. The parameters off the 00z GFS point to supercells from C. Kansas down into C. Oklahoma with a less cap scenario in the C. Kansas triple pt. zone...where the better lapse rates and strongest convergence will be to break cap with violence (if the GFS solution is right). I was thinking Kingman KS earlier, but am leaning more towards a Salina KS target attm given more favorable Sig Tor checklist parameters. All in all, it looks like a very active tornado day from about 5pm onwards. Plenty of adjustment time ahead...have the day off Monday so will go where things eventually point the weather finger...and hopefully not the middle one.

 

[Bart_Comstock]

Wedgefest 2010!? :O

As others have mentioned it appears as if the NAM is bringing the system in slower than the GFS. More than likely I see the NAM's speed being more accurate as the GFS does have a track record of being a bit to quick with a system until day 2 or 3 when it starts to slow it down.

The CIN is certainly looks like a minor "uh oh" with this system but with the CAPE values so high and wide spread I see no reason that storms will be unable to fire and thrive. If anything the increased CIN will help prevent too many storms for firing and promote discrete storms with more than enough space between them to be able to each do their own things without killing their northern counterpart.

Although the system will likely slow back towards the OK/TX boarder I would still favor a Harper, KS to Enid, OK target due to the forecasted storm motion. This way you will not have to rapidly rush to get in position ahead of the storm and with the potential for such strong tornadoes I would much rather be able to comfortable position instead of rushing to get south if the storm of your choice goes up to your SW.

Really there isn't much about this system that I don't like other than the speed at which these storms will be racing across the plains. The shear is outstanding and the HODO's are frightening. I honestly haven't been this excited over a system this far in advance since late May of 08. Geographically speaking this system reminds me a lot of the one that spawned the Red Rock, OK F4 and the Andover, KS F5. It would be interesting to go back and compare the two which I will do later if I have the time.

Oh and did I mention that I love ski jumps?

 

[Jason Boggs]

Well, my gut feeling was right. Here is the latest NAM for 18Z on Monday. Looks to put the dryline in the central TX Panhandle. I believe it will move near the TX-OK border by game time. The dryline may punch a little east, but as it gets east, it will slow down due to deeper moisture.

The GFS has the dryline way too far east. I believe the NAM has a lot better handle on the setup than the GFS. Way to go NAM!!!