4/23/07 FCST: TX / OK / KS / NE

[Mikey Gribble]

Assuming clouds clear and western Oklahoma gets good insolation, I think there will be a tornado outbreak. The only thing that bothered me was 500mb winds being weak until near dark, but there is still 40kts of deep layer shear which is just fine for supercells. The one other thing that bothers me a little is that things don't become real favorable for tornadoes until around 00Z. Other than that, virtually everything thing is there. LCL's should be around 700m, with dewpoints in the low to mid 60's. After looking at surface obs and soundings along the Gulf, I am confident the 60 td's should verify. Directional shear is great. There should be 1km SR winds >30kts from Altus to Elk City by 00Z. The hodograph for Altus at 00Z is very impressive. I think strong tornadoes are a good possibility tomorrow IF this unfolds right.

 

[Bill Hark]

I really wish I could chase Monday which may be a better day than Tuesday. Approaching trough with SW winds at the 500 level across the Texas and Oklahoma panhandles. The winds will be approx 40 for the late afternoon evening. Unfortunately, the higher 50 kt winds with a slightly more SW component won't arrive until well after dark (NAM 00 init) but I think there will still be sufficient upper level support in the early evening. The better backed winds are to the north near the warm front. Forecast helicities are huge (300) for NE Texas Panhandle and to the NW into the OK Panhandle, also SW into OK also according to the NAM. Predicted CAPE of about 1000 in the Oklahoma Panhandle, slightly higher to the south. My target for tomorrow is Perryton to the north of the predicted dryline bulge. Elk City is my secondary target but I am concerned the best storms will be after dark in that area and points southward.

Bill Hark

 

[Jeff Snyder]

I haven't had a whole lot of time to look through the setup for tomorrow, but I agree with most others' thoughts. My primary concern is actually the premature removal of the cap. The 00z NAM shows no cap over much of the risk area by 18z. I've chased on days during which was saw no capping by noon or early afternoon, and most of those saw early initiation that prevented the buildup of strong instability. Now, the models don't really show this occurring, but they do show little or no CINH by early afternoon.

A second concern is the mid-level flow. If the shortwave trough slows down any, the >35kt 500mb flow won't really make it into the warm sector until after dark. Deep-layer is sufficient (40-45kts 0-6km, per 00z NAM), but certainly not strong. In the absence of stronger CAPE, I think we may start with multicells that consolidate into supercells. I'd be a little happier if we were looking at 3000-4000 j/kg CAPE, but the ~2000 j/kg CAPE should at be sufficient for significant supercells.

Now, despite what I've written, I am almost certainly going to be chasing tomorrow, and I expect at least several tornadoes on at least a couple supercells across western OK and maybe western north Texas. The forecast hodographs are impressive across southwestern and western Oklahoma (the only places I looked, admittently), with a very favorable shape. I expect to see the MDT risk continue, with a High risk (or, rather, a high-end tornado event) likely inhibited by the absence of stronger CAPE and deep-layer shear.

EDIT: 4km explicit-convection WRF run from NCEP shows a honkin' supercell in the northeaster TX panhandle tomorrow, with no convection in western OK. See http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/tcolc_f25.gif as an example.

 

[Brandon Lawson]

I'd have to agree with you Jeff; I'll definitely be out tomorrow as well. The latest GFS run, unlike the NAM, has the cap holding in place a little longer. My fingers are crossed. As of the latest model runs I'll be targeting somewhere close to Clinton, OK (just in case I need to drop south), or possibly a little north of there.

According to the latest GFS, the 500mb winds are less veered and more out of the southwest in NW Oklahoma by 0z. It shows better backing with the 850mb winds there as well. This has me hesitant about heading further south, but who knows what tomorrow will actually look like.

It seems that, while no single parameter tomorrow is going to turn any heads, they are at the very least, adequate and more than sufficient for supercell storms. With any luck, maybe the models will underforecast the CAPE values. Good luck to everyone chasing tomorrow and a special WOOT for all of us in Oklahoma who have been waiting to chase a little closer to home.

 

[Jim Bishop]

I haven't had a whole lot of time to look through the setup for tomorrow, but I agree with most others' thoughts. My primary concern is actually the premature removal of the cap. The 00z NAM shows no cap over much of the risk area by 18z. I've chased on days during which was saw no capping by noon or early afternoon, and most of those saw early initiation that prevented the buildup of strong instability. Now, the models don't really show this occurring, but they do show little or no CINH by early afternoon.

A second concern is the mid-level flow. If the shortwave trough slows down any, the >35kt 500mb flow won't really make it into the warm sector until after dark. Deep-layer is sufficient (40-45kts 0-6km, per 00z NAM), but certainly not strong. In the absence of stronger CAPE, I think we may start with multicells that consolidate into supercells. I'd be a little happier if we were looking at 3000-4000 j/kg CAPE, but the ~2000 j/kg CAPE should at be sufficient for significant supercells.

Now, despite what I've written, I am almost certainly going to be chasing tomorrow, and I expect at least several tornadoes on at least a couple supercells across western OK and maybe western north Texas. The forecast hodographs are impressive across southwestern and western Oklahoma (the only places I looked, admittently), with a very favorable shape. I expect to see the MDT risk continue, with a High risk (or, rather, a high-end tornado event) likely inhibited by the absence of stronger CAPE and deep-layer shear.

I've noticed in the past that as long as you've got 25 knots at 500mb and 50 knots or greater at 300mb, deep layer shear is sufficient for supercells that won't just rain themselves out. It would seem reasonable to assume 30-35(ish)knots tomorrow would be sufficient to support significant tornadic supercells given the 50+knots at 300mb and the 40knots at 700mb.

The main concern I see is the cirrus deck currently over Northern Mexico and Southwest Texas. That could be the wild card that really inhibits and outbreak from occuring. But both GFS & WRF models indicate the clear slot will move east of the dryline sometime after 18z. I'd watch the timing of that clear slot very closely as it could be a key factor.

I think once that uncertainty is eliminated we are talking about several tornadic supercells across the extreme Eastern Texas Panhandle & Western Oklahoma. I wouldn't be surprised if a high risk is issued at the 1300z or 1130z update if it's more certain that the cirrus don't won't be an issue. At any rate it's hard not chasing this one, but it's a Monday and I've gotta get back to work..

 

[Ray Walker]

WOW, is it just me or did SPC just do a complete turnaround with the day one outlook. I totaly disagree with what they are thinking. They have the moderate risk WAY back to the north and west. From the models I looked at this is very confusing because the main targe areas should be across western Oklahoma. Is it just me or do others agree? I will definatly be sitting this one out if this is what is going to actually happen. Also take a look at the Hail, tornado probabilitys across colorado. They have the moderate risk well into colorado but the probabilities they have out for the same area comes no were close to matching up with there moderate risk thinking, only 10% tornado probs, and a small area of 30% hail graphics? This outlook just makes no since to me.

 

[Billy Griffin]

WOW is right! That's about a 300+ mile move on the graphics from earlier, but I suppose anything's possible. They certainly explain it in the discussion, but it sure doesn't match the day two MOD text from yesterday. Only time will tell, I guess.

 

[Brandon Lawson]

LOL I don't think anyone saw that coming. The only thing I can say is that, even with a slower system, the NAM and GFS both have precip breaking out across western Oklahoma by or before 0z. With the forecasted wind shear, dewpoints, and CAPE, you'd have to expect, at least, supercells and possibly tornadoes. The EHI values for tomorrow will be around 2, if not greater later in the evening, thus supporting a favorbable enviornment for supercells.

The 4km WRF has storms breaking out much further west, but I still am not sure if I would put all my money on it.
http://www.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/

I'm going to sleep now, but will be very curious to see what tomorrow morning's new outlook shows.

 

[Andrew Pritchard]

Things change guys. I agree with their outlook, I'm not sure what you're seeing that doesn't say that their highlighted area is the best? Western Oklahoma and the eastern Panhandle of Texas would probably be my target for the day, but I think supercells with an associated tornado threat are possible in an arc back into eastern Colorado, which goes well with the day 1 outlook.

It might not be a repeat of the Day 2 outlook that was in effect, but based on the current model run I think they have highlighted the main threat area perfectly. They still put your target area of western OK in a moderate, but have expanded to cover areas further NW too that also share a tornado/supercell threat.

 

[Ilya Neyman]

I think this has to do with a bit of uncertainty with regards to how far south and east convection manages to fire. However, BOTH the GFS and NAM indicate initiation occurring at least as far south as the SE TX panhandle, with the NAM indicating a large pre-dryline initiation scenario well into the heart of Oklahoma by 00z. Curtis McDonald pointed out that this outlook has to be in response to the NSSL's Experimental 4km WRF (which I saw a frame of) showing one monster storm in the NE TX panhandle and not much else to the south. Certainly the other parameters are very conducive to significant severe potential provided storms develop to the south i.e. SW OK. Another thing may be the large area of cirrus advecting across Mexico in relation to the strengthening subtropical jet. I think the MDT down to at least Altus/Childress would be certainly well warranted at this point in time. This looks to be a day of constant mesoscale observations to garner a better idea as to what exactly looks to be taking shape. It would also not be out of the question to get storm development initially as far west as the Caprock that would then move more NE-ENE vs N/NNE as in recent events with nearly westerly 500mb forecasted flow, which is plenty strong enough 35-45 kts (addressing earlier posts) for big-time storms. I have been watching the area of SW Kansas for a couple days as a good bet for at least one chase zone exhibiting a triple-point setup, with good backed surface and 850 flow on the nose of increasing moisture. However, this could be a scenario featuring multiple storms firing up and down the dryline in which case any of them would be game with the further south options working with potentially higher moisture and CAPE. Tricky and challenging!

 

[Jim Tang]

Hmmm... I was just trying to type a degrees symbol by using alt-0-1-7-6 but that automatically took me to the back button, which erased the post I had. Oh well.

The 0Z NAM shows a fairly deep moist layer in the TX Panhandle at 18Z. That says to me that the dryline should once again have a pretty hard time mixing east. So having the dryline crash into OK doesn't make much sense. Especially when it's had a bias of mixing the dryline east too far, for about a million times already. GFS certainly does not mix it east as much, and I pretty much agree with SPC in that area.

As for why the SPC didn't go further south with its outlook, a quick look at 0Z NAM fcst soundings indicate convective temperatures around 80 degrees, pretty high for this time of year. Without any upper air support (southern TX Panhandle is in between two shortwaves), chances of initiation are rather slim in that area.

As for CO, a quick look indicates strongly backed sfc flow and upper air support leading to large scale ascent. The shear profiles are undoubtedly very impressive in that area. Only question is instability.

 

[Ray Walker]

Guys this still looks really fishy to me. The tornado probs are not really all that high in CO under the MOD risk and neither are the hail probs wich should fall under slight risk so I dont know what to think. I really think yesterdays outlook was much closer to what is going to happen compared to todays, albiet a tad bit further west than what was proged for yesterday.
Ya I really thing that the new outlook is a fluke. The GFS shows precip breaking out acros SC SW Kansas down into SW Oklahoma tomarrow afternoon. Also it doesnt even show dewpoints to make it into the 50's across Colorado!!!!!!! I think we will see a new outlook much closer to yesterdays day 2 outlook. SW Oklahoma and the Eastern panhandles on up into southern Kansas look primed for tornadic supercells today a suptropical Jet streak moves into the region. I still think we could be dealling with a tornado outbreak later on today.

 

[Mark Farnik]

Ahem, gentleman... I believe you are GREATLY mistaken. As long as we can get the stratus deck to break up before noon and allow for maximum solar heating, the MOD for eastern CO is perfectly justified. The shear profiles are simply ridiculous, helicities are forecast to approach 300 ms/2 by late afternoon over the better portion of eastern CO, and we have strongly backed east/southeast flow at the surface pumping higher dews back in from western KS. Remember, this IS Colorado; you tend to not take our significantly higher elevation into consideration. High 40's or low 50's dewpoints with a 65-68 air temperature will be more than sufficient.

I think there will be tornadic supercells this afternoon from eastern CO all the way down to the east TX Panhandle/western OK, with damaging tornadoes a good possibility. It's just a matter of whether you pick the southern posion with greater instability but poorer shear profiles, or the northern poison with greater shear profiles but less instability.

 

[Tim Marshall]

TARGET: HEDLEY, TX TIME OF DEPARTURE: 9:30 AM. This is another classic tornado situation along the dryline. I do not see any negatives about the day. Ample moisture is in place and a dryline bulge is forecast to develop in the CDS area by 00z. Although the main dynamics with this system is still in the Rockies, there will be just enough upper support to allow storms to develop along the dryline by 0z. Expect storms firing along the caprock will move northeastward a bit slower than on Saturday.TM

 

[cedwards]

The NMM WRF run for SPC shows a nice cell popping up at 22z NE of Dumas, TX one left split moves north and the cell with a kidney bean shape moves almost due east. I don't ever recall seeing a simulated reflectivity forecast that looks that good. Now, hopefully it will verify. The other WRF model doesn't make any since to me. Pricip is random and moving just west of due north.