4/06/06 FCST: KS/NE/IA/MO/OK/AR/TX

[Matthew Havin]

A quick addition and I'm off to bed:

Taking a look at soundings.....from BIE TO LNK at 21Z....LFCs are 1000-1100m above ground, with LCLs slightly below that. Not bad. Also has a ridiculous 3800+ CAPE on both (which will be believed when seen). Best part is storm motions are NNE at around 30-35mph.....much better than the rat race I went on in SE KS last Thursday. Cap is shot by 21Z.......being eroded by the model quickly between 19-21Z. CINH at 21Z= 0. Be ready for a quicker than expected start.

 

[Mike Peregrine]

Going to call the prelim target for me tomorrow from St. Joseph to Kansas City, Missouri, though storms will likely initiate a bit further to the west along the DL in northeast Kansas. Will be out the front door after work again. Everything in this area appears to be coming together for a fairly strong to major tornadic episode. Here's why, based on 0z NAM:

>275 m*2/s*2

>2000 MLCAPE

>3, 0-1km EHI

>45 kt BL-6km shear

LCLs of <1000

LFCs <1500

Moisture appears to really pile up along the state line by 0z. It just doesn't get much more favorable as far as tornado production is concerned than the numbers we see here. As it currently stands, I think we're potentially looking at some bad ones around home base again tomorrow. Missouri will be in for yet another long afternoon/evening. Hopefully storm motions will remain at the current forecast 30-40kt range, though I expect these to speed up as time goes on to the previously expected 50-60kt range. Will really be following the obs coming in tomorrow late morning.

 

[Kevin Polston]

Well I agree with Todd that I think tomorrow will be a major tornado outbreak. I also agree with Todd and Alex in their call on the area farther south...into eastern OK and AR. The ETA and GFS are very similar in their depiction of the 500 trough coming out a little further south with the strong vort max located near AMA at 18Z and then moving quickly to southeast KS by 00Z. The jet max really "punches" through eastern OK into AR and southwest MO around 00Z.

My scenario in my head is for thunderstorms to develop quickly near the upper low over central Nebraska early in the afternoon...developing eastward during the next few hours. With the surface low still rapidly deepening and being in close proximity to the triple point, and with the environment being favorable I would expect to see tornadic storms over east central and southeast Nebraska moving into southwest Iowa. The storm motion should be roughly north to north-northeast during the afternoon...with the tornado threat obviously being augmented as the storms interact with the warm front. However....the storm motion should prevent anything from becoming long track...as the storms move into cooler air north of the front.

By mid-late afternoon thunderstorms should develop down the dryline in KS as the cap is quickly eroded. These storms have the potential to become tornadic but I think the better potential is when they move into western MO...where the surface winds will be backed and LCL's a little lower (around 1000 m as opposed to 1200 m back in KS). Really impressive is the LFC height forecast.....with LFC's being less than 800m by 00Z in southeast NE and generally 1200-1400 m from western MO into AR.

My biggest concern though is probably from the evening through the overnight hours from far eastern OK into AR and sw and sc MO.This is when the jet really punches into the area....and I would expect to see big tornadic supercells in this area overnight. Something that caught my eye was the 700-500 lapse rates....they were very steep over the western high plains at midday and then wrapped around the low and extended east at 00Z to intersect the moist axis over southeast KS/sw MO. With the LLJ strengthening as the sun goes down as well as LCL's lowering from cooling....and the trough punching out...it just seems like a very bad situation for this area. Especially at night.

I've attached a graphic showing my rough outlook. I think a high risk will be forecast from Nebraska/Iowa south into OK/AR and I think there could very well be another major tornado outbreak. Certainly is a very impressive synoptic pattern.....the 500 mb diffluence is very very impressive over a large area as the trough swings out......and there should be 60 dewpoints over a large area by 00Z.

 

[Chad Ringley]

NCEP 00 UTC 4.5 km WRF NMM (output at http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/ ) develops convection first in a NE/SW line from NW MO SWWD to SW MO between 16-18 UTC. Surface based convection blows up between 21-22 UTC in an arc (E/NE of sfc low and along dryline) from North Central KS SE to just E of ICT, then SWWD through Central TX. Many supercells a roarin in this model simulation!

4.5 km (no Cp scheme) Sfc (Lowest Model Sigma) DBZ (21 UTC 06 April 06)

4.5 km (no Cp scheme) Sfc (Lowest Model Sigma) DBZ (01 UTC 07 April 06)

This solution suggests that this hi-res model doesn't mix the dryline too far E of I-35 before convection initiation. In addition, the model must erode CIN quite substantially to get that much convection with SWWD extent along the dryline. If this is realized, I'd think quite a few long tracked supercells/tornadoes would be very likely.

Good luck to all venturing out tomorrow!

 

[Chad Ringley]

This model has done exceptionally well with convection so far this year. What's scary? Take a look at this...

You can see a HOOK...classic supercell on the MODEL RUN. Unbelievable. Persists into the next frame too. I'm feeling a bit more confident in my forecast now.
[/b]

The WRF's pride and joy...the ability to model convection explicitly at hi-resolution. Wish the time step was shorter and more output was generated...because 1 hr reflecitivity...we know alot happens in the model between output times. We'll have full fields when the 4 km WRF Spring/Summer Exp. gets started on April 18.

But so far, the WRF-NMM has done really well with convective mode and evolution this year, and since this run is made FOR the SPC....I wouldn't be shocked to see a much larger risk area in the SWODY1.

 

[Scott Lincoln]

This model has done exceptionally well with convection so far this year. What's scary? Take a look at this...

http://www.emc.ncep.noaa.gov/mmb/mmbpll/ce...v2/refc_f25.gif

You can see a HOOK...classic supercell on the MODEL RUN. Unbelievable. Persists into the next frame too. I'm feeling a bit more confident in my forecast now. Even if it isn't a hook, just a weird anomaly, the model is picking up on the discrete modes south which is exactly what I expected. Very cool though if that is a hook, but it sure looks like one if it isn't.

and now i see the same image was posted above haha sorry B)
[/b]

Well i'm not 100% sure how that model does its DBZ simulation but i'm pretty sure you aren't seeing a hook, just something that resembles it. A hook echo as we know it would be kinda hard to resolve on a 4.5km model, especially when it doesn't calculate storm level rotation and storm level parameters to my knowledge.

Regardless... i would still be leary. I'm not saying the potential isn't there for something big, but the models are not really keeping it all that consistant, and the fact that WRF breaks out precip like that makes me happy, but also makes me worried becuase the ETA forms the precip differently. The best course of action would be to see how the RUC forecasts are tomorrow morning and see which scenario it starts to follow. And i still recommend not chasing the stuff towards the early stages of this, as the dryline in KS and OK on the last few runs hasn't jumped out at me as something tornado outbreakish. I think the real chances lie along the warm front and moreso along the dryline later in the day towards nightfall IF the cap doesn't become an issue.

 

[Jason McKittrick]

SPC day 1 should be out any time now. I think there will be a high risk but I would bet that it will be over western MO and northwest AR. Models from 00z seem to be in agreement holding warm front along the IA/MO boarder area. Looks like hail and wind for Omaha. Looking at the SREF output, southern MO and northern Arkansas seems to have the best tornado threat now. 3km shear vectors perpendicular to the dry line at 50knts. Mid sixty dew points forecast to be as far north as west central MO. Looks like a fast moving tornadic supercell event again for MO. I still think I will stay in Nebraska $$gas and fast storm speeds are quite the deterrent

 

[Chad Ringley]

A hook echo as we know it would be kinda hard to resolve on a 4.5km model, especially when it doesn't calculate storm level rotation and storm level parameters to my knowledge.
[/b]

4.5 km is a bit coarse, but research simulations done using the 4 km WRF can resolve mesocyclones and hook echoes when the time step and output are at a much higher frequency.

Regardless... i would still be leary. I'm not saying the potential isn't there for something big, but the models are not really keeping it all that consistant, and the fact that WRF breaks out precip like that makes me happy, but also makes me worried becuase the ETA forms the precip differently. The best course of action would be to see how the RUC forecasts are tomorrow morning and see which scenario it starts to follow. [/b]

Keep in mind that both the ETA and the RUC use the Kain-Fristch cumulus paramertization package becausee of coarser grid resolutions (12 km). Thus, the convective precip product from the ETA/RUC and the simulated dBZ shown here are going to be quite a bit different. The 4.5 km WRF has no cp scheme, and thus, if you are looking for convective precipitation evolution, the WRF, because of grid resolution and model physics, does a better job at resolving developing convection than the grid-saturation, CAPE dependent CP schemes.

 

[Ryan McGinnis]

I'm liking SE Nebraska near the triplepoint, if the 60 tds really make it up here. Will have to data check tomorrow morning. For one thing, I'm already here, and nothing annoys me more than driving a long way only to miss the home storm. Another is that E KS and NW MO is the other nearby play, and dear Lord do I hate NW MO.

The storm motion seems much more timid in SE NE according to Bunkers, at 20 to 30 kts, which is a relief.

The Skew-T for KLNK at 21Z isn't too bad, though I wish there was a little more directional shear:

http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=klnk

The Beatrice Skew-T for 18Z is a bit better, if anything has popped by then:

http://www.wxcaster.com/modelskewt.php3?mo...&STATIONID=KBIE

CINH is only in the 30s, so maybe. Gonna have to wake up early tomorrow to make the final call, but right now I'm good with staying put, maybe ducking a little south. That way, if worst comes to worst, I can always pick the dryline up in KS and follow it into... ugh... can't... say... it... northwest Missouri.

 

[Kiel Ortega]

CINH is only in the 30s, so maybe.
[/b]

That's what would worry me most about tomorrow...looks like the area near the north TA have little CINH. Under a nice little low kicking out like we'll have, anything and everything will go up. I'm still uneasy about saying anything about an outbreak, especially with the hodographs as they are currently. Helicity is going to be limited (as per models and some eyeballing)...further with the shear vectors as they are, I would worry that the storms are going to rain right into the areas that they are moving into. I agree with some previous posts about the linear mess that will probably be up north. Down south is a little different, the only concern I have is the width of the CAPE that will be around tomorrow (shear vectors look nice for getting things off the dryline and on their own). The models have been consistent over the past day about a fairly limited horizontal extent of CAPE off the dryline in the OK/AR target area. Also, it looks as if the models didn't get the greatest dewpoint intializations, as they have 60s up towards NE...current obs and 00Z obs don't really support that as a mix of stations have some 60s with most in the mid-upper 50s.

We'll have to see tomorrow though!

 

[Jeff Snyder]

My forecast thoughts align quite well with the new SWODY1. With a westward shift in dryline forecast position in this evening's model runs, I'm back into chase mode. I'm not a huge fan of strongly meridional mid and upperlevel flow (southerly / southeasterly), so I''m not too hot on the area north of the OK/KS border. It does appear as though a secondary warm front will set up from near Hebron to Kansas City to Springfield by 0z, with southeasterly surface flow supporting some better low-level shear profiles. Between that warm front and the OK border, however, winds and wind shear will largely be unidirectional (at least through 500mb), courtesy of southerly 500mb flow. These setups with veering low-level , backing mid-level , and veering upper-level profiles tend to make forecasts quite tricky, with the possibility of anticylonic and cyclonic mesos in the absence of stronger low-level helicity.

Farther south into OK, the 500mb flow is progged to be more veered, yielding a better looking deep-layer shear vector orientation relative to the dryline (SW, compared to almost due S in eastern KS). This should help favor discrete activity. Im still concerned about surface dewpoints, since we've seen several times this year that the models have overforecast Tds by 3-7F. Since we're already on the high side of LCLs (with T-td of 20+F degrees possible), I do think we need all the CAPE we can get. Not to mention, in such a strongly sheared environemnt (deep-layer shear of 50+kts), storms can struggle when deprived of strong CAPE. This may have been a reason why storms took a little while to organize into supercells on 3/12. Regardless, my preliminary target is Bartlesville, OK. The cap may be an issue, but this area will be in the left-exit region of a strong upper-level jet streak, yielding upper-level divergence and vertical motion (if any is needed in light of intense DPVA ahead of the vort max). The 0z NAM and WRF (as noted above) initiate precip all along the dryline before 0z. Low-level shear isn't particularly strong south of the warm front, so any backing of the surface flow that we can muster would be quite helpful.


Prelim target: Bartlesville, OK (need to be downstream from the dryline a ways given forecast storm motions)

 

[Daniel Christianson]

Despite feeling like crap this morning with chest pains, i have to work and will be working as fast as i can, right now im estimating the time i get done it will be close for storms to get going im prb going to stick around here in Omaha, or maybe head south... i agree with most as tornadoes for MO AR and what not them people have had enough already!... good luck to all who chase today and be cautious

 

[Matthew Havin]

300+ 0-1km SRH and 1500+ MUCAPE sitting over NE KS. Water vapor imagery is extremely impressive with massive dry air rounding the trof..... I'd say this looks like HIGH RISK material for SE NE/NE KS/NW MO.

Oh wait... IT IS!!

http://www.spc.noaa.gov/products/md/md0435.html

Enjoy!

 

[bbarjenbruch]

Wow, that's got to be some of the strongest wording I've ever read in an SPC discussion. It's on!

KTOP and KOAX soundings from this morning exhibit much better 0-1 km shear than anticipated. However, our suspicions about lower dewpoints seems to have come true by a few degrees as well. Low pressure is centered somewhere in the vicinity of Columbus NE... farther East than I had anticipated, with a weak secondary warm front extending to it's SE. The Fairbury profiler is quite interesting with 500m winds out of the WSW at 20 knots. Surface winds are due south if not a bit southeast... Wow.

My current target is not to move much at all from Lincoln. I could easily see the best chase options being just north or just south of lincoln early. It's going to be a heckuva day. Keep a heads up, an eye on your back, luck in your pocket, and a prayer on your lips, and enjoy the chase!

 

[Marc Austin]

Good luck to everyone out chasing today! From the looks of some of those radar simulations, it seems as though some cities may see more than one round of severe weather, as has happened in recent severe weather outbreaks. Look out Springfield, MO and Sedalia, MO. Actually, I would probably just go to Sedalia and wait... Anyway, can't wait to see what pans out and to get some reports! All the ingredients are coming together a little to nicely...