06/07/07 FCST: TX / OK / KS / MO / IA / IL / WI

[Brandon Goforth]

It looks as though the SPC is pessimistic on the tornado threat south of IA due to frontal forcing on the cold front producing a squall line. I'm having a lot of difficulty making sense of this assessment, as the surface cold front is forecast to be up in the northern Plains at 00Z! The boundary depicted by the models to be initiating convection in MO/KS/OK is not a cold front, but a dryline. Perhaps they're expecting the models' placement of the surface cold front at 00Z to be off by 200-300 miles, and for the front to have already caught up to the dryline by 00Z instead of closer to 06Z? That doesn't seem likely given the placement of the 500mb vort max at 00Z, but maybe I'm wrong about that.

I too am curious about the reasoning behind this, as the forecast discussion does not address convection along the dryline to the south through KS/OK in the afternoon. This leads me to believe that SPC is expecting the area ahead of the dryline to remain capped, holding off convective initiation until after dark as the front sweeps south with storms firing along a line to the SW...obviously creating primarily a hail/wind threat. Maybe?

 

[Mikey Gribble]

It is beyond me how you come up with a high risk tornado threat from this...
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_overlays.cgi?fcsthr=021&STATIONID=_KRPD
That is from Rice Lake, Wisconsin at 21Z. CAPE and deep layer shear combination are obviously very good for supercells, but the conditions for tornadoes are not that great IMO. There is not much curvature to the hodograph. 1km SRH is only at 134. 1km and 5km SR winds are both good. 1km and 3km EHI are both <4, which is not good at all considering the threat level SPC is putting out there. I don't even know what goes into generating the supercell potential, but it is only at 67%. Am I missing something here? Yeah deep layer shear and CAPE are very good, but once you get into supercell criteria with your CAPE and shear combo there is a lot more that goes into getting tornadoes than just strong deep layer shear. Other ingredients for tornadoes are decent, but not even close to high risk material IMO.
This next forecast sounding is from Stevens Point at 00Z.
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace_overlays.cgi?fcsthr=024&STATIONID=_KSTE
Once again the hodograph is long, but there isn't much curvature. ML LCL is 904m, which is fine, but not extremely low. 1km SR winds are 22kts, which are good, but they could be a lot better. EHI is less than 2 with the GFS, around 4 from the NAM. Supercell potential is at a whopping 35% if you look at the GFS, NAM is 95%. There are significant differences between the NAM and GFS, with the NAM being much more agressive with tornado paramaters, but even going with the NAM solution I still think it is lacking in high end tornado threat criteria. 1km and 5km SR winds are good still, but I would expect another 5-10kts from 1km for violent tornadoes (1km SR winds are 22kts in the sounding).
On top of the paramaters not being extremely favorable for tornadoes IMO, storm mode could be an issue. The WRF has one or two discrete cells in NW Wisconsin early on, but the stuff that fires over central Wisconsin goes linear immediately. It does start to break a bit at 00Z, but they are still linear in nature.
I guess we will just have to wait and see what happens. I know the guys at SPC obviously know far more than I do when it comes to forecasting, but I strongly disagree with them on this one. I think they will have several tornadoes over the high risk area, probably even one or two strong tornadoes, but this is not a high risk setup for tornadoes IMO. I'm not even going to get into the high tornado probabilities they have out for Iowa too, which I very strongly disagree with as well. I think they botched the tornado threat on this one big time. I am eagerly awaiting the reports from this event and desperately hoping I won't need a shoe horn to get my foot out of my mouth lol.

 

[Jeff Snyder]

Can't disagree with most of ya'll... I feel strongly that the tornado risk is greater than the 2% given in the 6z Day 1 outlook across portions of OK and KS, and I also am hesitant about the violent tornado threat for WI. By mid-day, I would expect to see the MDT dragged southward to I40 in central/eastern OK, but I don't want to critique an SPC forecast too much.

With true tropical air in place in the low-levels (mT airmass), and cooler 700mb and 500mb temps compared to Wednesday, I don't really foresee the cap to be that big of an issue. This notion is supported by NAM and GFS CINH forecasts, which indicate the depletion or complete removal of the cap (GFS and NAM forecasts, respectively) by 00z. I think the primary limiting factor for storm coverage may be convergence in the low-levels to force surface-based parcels to their LFC. The 00z NAM now shows much better southerly surface winds across southeastern KS and OK east of the dryline, as opposed to southwesterly surface flow that was shown previously. In addition, QPF charts indicate at least a couple of cells likely in central and eastern OK near and shortly after 00z. In fact, I'm almost willing to issue a Tornado Warning for Cleveland and Oklahoma counties, and I urge those who live in Moore to take their tornado precautions... Why? Check out the 4.5km explicit-convection WRF, a graphic from which (valid at 23z) is here --> http://www.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/tcolc_f23.gif ... Of course, I'm half-kidding, but it does go to show that supercell mode seems to be preferred in this part of the risk area... That particular runs shows a couple of large supercells in central and eastern OK that move very little between 22z and 6z.
Lower LCLs Thurs compared to Weds should also increase the tornado potential. Now, we'll just have to see if the surface winds can stay southerly or even SSErly through the afternoon. It's amazing to see this strong of mid-level and upper-level flow this time of year in this part of the country, that's for sure.

 

[Eddie Natenberg]

Well I'm oviously up too late, but whatever.

My brief thoughts "It looks impressive."

I completely agree with the high risk, but with tornado potential a bit farther SSE(IMO). Synoptic forcing is not the issue anymore as the jet streak will elongate over the base of the trough (due to the intense thermal gradient at H700) and help decrease the amount of linear forcing and increas the large scale lift as well as subsidence ahead of the trough will help keep skies clear. The lack of boundaries along a trough axis at the sfc is going to play a large role of keeping supercells isolated, as well as the impressive deep layer shear that can help induce storm scale subsidence. I'm also not worried about the winds at the surface backing mostly because the flow at the upper levels is so strong causing SR winds look very good with a deep inflow layer. I looked at the NAM 24 hr forecast for DVN, it looks fantastic to say the least with a similar loaded gun shape (without the CIN).

http://www.emc.ncep.noaa.gov/mmb/soundings.nam/images/744550nam.sndf24.gif

The 4km WRF is a little overboard I think and my guess is south of IA linear mode might seem favored. But the farther north you go storms should fire in isolated small clusters with intense mesocyclones. A long tracked tornado is not out of the question because of storm motion and a very saturated boundary layer.

Target: 10 miles west of Freeport, IL along route 20.

OK thats my 2cents.
Best of luck to all that go out.

 

[Dick McGowan]

LOL @ day 1.

I'll take my chances on EC KS today. ETA to Lawrence, KS 5:00 a.m. Storms will be hauling anywhere you chase tomorrow.

I'm not thrilled on the setup, but I'm off of work:


Chanute, KS 0z.
Pretty near where I'll be.
http://beta.wxcaster.com/cgi-bin/parse_skewt_trace.cgi?model=NAM&fcsthr=024&STATIONID=CNU

 

[Brandon Goforth]

In fact, I'm almost willing to issue a Tornado Warning for Cleveland and Oklahoma counties, and I urge those who live in Moore to take their tornado precautions... Why? Check out the 4.5km explicit-convection WRF, a graphic from which (valid at 23z) is here --> http://www.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/tcolc_f23.gif ... Of course, I'm half-kidding, but it does go to show that supercell mode seems to be preferred in this part of the risk area... That particular runs shows a couple of large supercells in central and eastern OK that move very little between 22z and 6z.

Wow, showing a monster cell there over central OK. It'll be nice if this holds true, although you hate to see significant supercells ripping through populated areas. However, this is consistent with what I've seen as well with a couple of isolated supercells developing along the dryline in OK as far south as possibly the Red River. Hmmm, it will be interesting to see how this looks by noon and I wouldn't be surprised to see tornadic probabilities increased in this area. If we get isolated storms firing before dark I would expect a decent tornado risk throughout OK based on what I've seen, but then again I'm certainly no expert in forecasting. Given the setup, a tornado risk of 2% seems very low IMO.

 

[Ilya Neyman]

Still really intrigued by the OK region for late Thursday afternoon into the evening. Shear and cape combo is quite astounding and with a roughly 90 over 75 setup somewhere not too far away from I-35 there is some major juice for this airmass to work with. Provided initiation takes place, and by all indications per GFS, NAM, 4km it will, look for a significant severe threat quickly materializing late Thursday afternoon somewhere across or very near to central OK. I am fully expecting a 10-15% hatched tornado probability within a MDT risk to cover the I-35 corridor of OK and points east. This is a scenario where an isolated one or two storms could explode off of the dryline and reach significant severe levels very quickly. The probability of significant severe, including destructive hail, damaging wind, and even strong, possibly violent tornadoes exists across this region including the OKC, Norman, and Tulsa areas for late Thursday afternoon into the evening hours. A curious development is that the 4km wrf fires a discrete cell that in essence practically sits in one place near the OKC metro for several hours, despite winds that would propel it eastward at 35-40kts?! The best explanation for this is that the model may be forecasting such a storm to backbuild into the wind / propagate toward the west as winds feed extreme moisture and instability into it. A past example of something even resembling this would be Jarrell, TX, but that environment was quite different from this one on the synoptic level. Either way, if convergence/instability overcome relatively strong cap explosive supercell thunderstorm development is highly likely. Models have been consistently hinting at this for a couple days already. The other scenario would be for capping to hold off initiation until the cold front undertakes the dryline overnight. In this case intense thunderstorms would develop posing a mainly large hail, heavy rain and some wind threat. But the prospects of late afternoon initiation across the aforementioned area IMO are quite high.

Look out Oklahoma.

 

[Jason McIntosh]

Well not much to say but...

HIGH RISK for WI!!!

Me and my bud will be heading up towards the Eau Claire area. Looks to be no issue with instability. That is rare for WI severe weather. Usually we have rain in the AM and a warm front moves in that produces tornadoes. This whole thing is almost too good to be true. The wind shear of 60-80 knt 0-6 km is rediculous. What has really become the main ingriediant for tornadoes is the 0-1 km winds now forcast to be 20-25 knt. These storms will have to resist a lot to eventually become a Dercho type event, but i feel that two areas of severe will form. The supercell/tornadic threat from SE MN up into C WI and the linear/wind damage event from E IA/S WI/N ILL. The moisture will be in play today; so where that dp line sets up will be important. Let the chase begin!

 

[Dustin Wilcox]

FWIW, last nights 4KM seemed to handle the evolution of convection today in C NE pretty well, as it nailed location, timing and to an extent storm mode far better then any of the other model solutions, if it verifies again many will have a succesfull chase, it will certinly be interesting to watch the southern end of this setup evolve if LL winds can avoid severly veering I think KS into OK holds great potential.

 

[Brandon Sullivan]

Well.. Not surprised at all with the high risk.. Only concern for me is the cloud cover possibly limiting heating across the area.. Other than that. All systems are go for a dangerous severe weather outbreak later today and tonight.. Again, all be safe and good luck chasing!!!

 

[Scott Weberpal]

What a beautiful thing waking up in Southern Wisconsin to bright blue skies, and a screaming southerly surface wind.

Though I agree with the concerns of those looking at the relatively long, straight hodos, and fairly unidirectional deep layer wind field; storm relative winds look great for at very least embedded mesocyclones and attendant tornadoes. Everything else has been touched on well in this FCST thread.

A note to anyone chasing in WI not from the area. West of I-94 and north of Hwy 8 are virtually unchaseable. The area from Eau Claire to Wausau is quite flat, and still has a sizeable amount of tree-less farm area. Otherwise, have fun and bring a chain saw.

 

[Johnathan Brouwer]

INCHASE strated out early, then after re-reading all spc products, today just is missing the events needed for a higher percentage of SS and tornadic development. Our Original target area was the Davenport to Waterloo, IA area. BUT after the latest Day 1 we decided to call today off. As much as we wanted to get out, we'd rather turn around than to get smacked around and pelted...Back to Fort Wayne we go!

Go luck to all today and BE SAFE!

 

[Bill Doms]

No issue with surface heating. Clear here with 71/62 in Buffalo, MN about 30 minutes west of the Minneapolis metro. Like due to some weak subsidence from overnight elevated severe which moved through about 3am. Focusing on two areas today after looking at surfaces obs and sat data (oh I wish I had awips today), North Branch, MN and another area south of the metro near Faribault, MN. With either, river crossings and A LOT of trees are going to come into play aside from getting on the cell(s) right at initiation before going flying into tho cursed earth to the east/northeast. Oh well, I still haven't used my day passto enter WI yet this year. Might as well be today.

 

[Michael O'Keeffe]

The new SPC outlook pulled the better tornado parameters south in SE KS/NE OK. I like the Chanute area for today and will probably start there. SPC mentions supercells with very large hail and tornadoes. We shall see as the day goes on how this pans out.

 

[Helge Tuschy]

This finally could be a rare reason to issue a PDS SEV
(PDS severe thunderstorm watch)
Shear is outstanding for June and storms should have a nice speed. Good luck to all and stay safe !

Helge