2011-05-22: FCST: WI/IL/IA/MO/OK/TX

[Joe Pudlik]

Note: Mods can add other states as needed.

Concerning S. WI/IL/E. IA...

This is an interesting setup being shown on the models, especially from the 0z runs last evening. Both the 0z GFS and NAM had a decent to nice flow aloft, generally on the order of 40KT+. Moisture and instibility are also in place, with dp's around 65F and CAPE values running AOA 2500 J/KG. The NAM had a nice area of 0-3km SRH on the order of 350-400m^2/s^2 by 0z in N. Illinois, increasing a bit after dark. 0-1km SRH also increased to around 150 by 0z and greatly increased after 0z. The surface flow in the area is southerly and backed to the SE in some areas. As previously mentioned, the wind profile aloft is nice with a gradual turning. The hodo's were also quite nice looking, especially in the Sterling/La Salle/Streator, IL areas.

The issue with the 12z runs is that there is much more early initiation which cause more more uncertainty.

 

[Jason Persoff]

It took all day, but now the rental vehicle fiasco following the deer collision (see yesterday's report) has left me ready to get back out chasing, and I'm surprised that there's little chatter about tomorrow.

My forecast target is the eastern KS/OK borders with a tentative target for Coffeyville, KS. Using the 18z NAM at this point, I like a number of things about this area. At the sfc, strong sfc backing winds in response to a low pressure system migrating into the area with draping dryline will lead to very strong convergence. The 700mb temps will become quite chilly between 21z to 00z leaving almost all of KS and most of NE OK uncapped and ready for intense hail given steep lapse rates. Florida swamp mugginess will lie in wait in advance of the dryline with intense CAPE. A CIN hole will open up in SE KS/NE OK at 2100, though I think the convective temps and forcing will be easy to reach along the dryline. A vort max associated with an H5 westerly focus of 50kt winds coupled with 250mb winds showing a left exit region over the target area by 00z.

I'm really no good at forecasting storm mode at all. Will it all fire at once vs. single cells early that can avoid each other long enough to prevent become congealed like gelatin? I have a feeling storms are going to fire everywhere based on the CAPE, lack of CIN, and strong daytime heating. But the Coffeyville area will be under the influence of intense easterly backing and I expect storms forming around 21z will have a shot at tornadic achievements given low-level veering. Given the broad area expected to be upgraded to MOD, I'm obviously missing an important ingredient that makes my target stick out from all the rest of the areas that will be convective tomorrow. It just has this feeling about it....All that aside, I'm very interested in feedback or thoughts on the reason this target area is good or not so good given tomorrow's setup.

 

[John Farley]

This post focuses on the MO/IL aspects of tomorrow's setup. I am debating two possible targets - one in IL along I-80 from roughly La Salle-Peru eastward, and the other along I-44 in MO in the Rolla-Lebanon area and possibly southwestward. Both targets have good combinations of instability and shear. Per this evening's NAM run, the IL target has more shear, albeit slightly veered surface winds, but less instability. It also has better upper support. However, movement of the storms into the Chicago metro area could be an issue chase-wise, although until/unless that happens, the chase terrain is better than in the MO target. The MO target has stronger instability and, although slightly less shear overall, perhaps slightly more backed surface winds. Overall combination of instability and shear is a little better in the MO target, with EHI of 6-9 in many places from Rolla on down I-44 into OK. This evening's NAM breaks out strong storms in both of my areas of interest, although I think that in the IL target there could be TOO many storms. If that happens with the MO target, though I don't think it is as likely there, moving farther down I-44 and finding a tail-end Charlie might be the solution, as the NAM breaks out less precip farther down toward Joplin and Tulsa. I guess all things being equal I would prefer the MO target, since it will put me in a much better position for the next two days of active weather in OK and/or KS. I think right now I prefer that target anyway due to the slightly better overall parameters in that area and the better chance of avoiding a massive, unchaseable mess of storms everywhere which worries me about the IL target. I do think there is a decent chance of tornadoes in both areas, though. Will decide in the morning based on morning model runs and data. Looks like tomorrow could be a busy day in a number of areas.

 

[Trey Thee]

Man I've gotta be honest here, today sort of snuck up on me. I looked at the models Friday night and yesterday morning and it looked like we'd have a few storms around. Then we got home from a wedding last night and things completely changed.

This is looking like a potent Sunday setup. At this point in time I would target the NE quarter of Oklahoma. East of 35, North of interstate 40. CAPE values are impressive, lifted index is also impressive, wind profiles also look decent to good. Helicity values could be better but they are definitely adequate. One of my big concerns at this point is the proximity of some of these features in relation to Tulsa. The NAM paints some interesting points of interest just to the North and West of Tulsa. North of 412 in the highway 20 area, helicities, cape, lifted index etc all seem to be amplified in this area. A small deviation and this could be over the Tulsa metro, which would put 900,000 people under a fairly significant tornado threat IMO.

Having said that, it appears the hail with these storms is going to be downright nasty. I would not be surprised if we had numerous instances of baseball size hail reported today. People need to be paying attention this afternoon and evening.

I really believe the entire eastern half of OK and SE KS will provide ample chase opportunities. I would target the Chandler or Stillwater area for initial staging.

If SPC hasn't gone MDT yet, I believe they will at their 8am update.

 

[Jason Persoff]

This am's data hasn't changed my overall thinking...yet...I spent time reviewing topography and satellite images over NE OK and SE KS within 50miles of Coffeyville. The road network immediately SE of Coffeyville is sparse, but since I'm looking for ENE movement of storms that form, so long as we're north of the OK border we'd be okay, or alternatively so long as we were further S near Vinita on I-44 corridor, there appears to be a lot of farmland and roads are meager, but reasonable given projected slow storm motions.

12z RUC shows possible mesolow backing along I-35 near ICT while temps soar (CDS today has progged temps of 105 (!)). For whatever reason, the dryline appears quite mushy with gradual decrease in Tds from E to W along a vaguely N/S orientation with peak dewpoint temps along a tongue east of I-35 in SE KS/NE OK. Would roughly guestimate the area to be in the 80s over upper 60s which still would give fairly large initial dewpoint depressions.

Current SAT shows rapid loss of cloudcover over the target area which should allow ample daytime heating. A prominent OFB seen on SAT and radar drapes NE to SW from KC to ICT which is slowing down as it moves SE. Hint of mesolow formation with weird, limited 5-10kt SE/E winds forming east of ICT today on RUC sfc suggests that this is likely going to be an area of good convergence. Current radiosonde data suggest that all of E OK and SE KS will be in the left exit region of a 250mb streak.

While we're not looking at the forecast Hindenberg-potential CAPE in E OK (? >7000 J/kg ?), we'll be sitting in 1500-2000 J/kg near a CIN hole by 21-00z. Last: 00z WRF suggests the potential for a tail-end storm to evolve from a line of convection starting due east of ICT by around 20z.

I just don't have the courage to chase SE OK, and C TX feels too far away for me starting from ICT this morning. Today was not initially on my eyeballs until yesterday's down day for me. High CAPE, low shear, and reasonable focusing mechanisms. Will continue to target a 50mile radius around Coffeyville KS.

 

[Rocky Rascovich]

First off, thanks to all who showed up yesterday to the picnic, and especially being able to successfully intercept the tornadoes near Ada! On to today's set up, I'm a little confounded on my target for today (what else is new?) Looked at the short range models including the HRRR, SREF and NAM. All agree that CIN will not be overly apparent, robust amounts of CAPE, surface CAPE over 4K j/g.. both speed and directional shear adequate for rotating storms. One thing that I thought stands out is the lack of any catalyst like short waves in the mid/upper levels that kick off convection, at least from what I see, what is interesting is that based on the Twister Data site, looking at the EHI's, they are almost off the scale basically in the eastern half of Okla. by 21Z, and with CINH's minimal, CI should result as early as that time. According to the simulated radars from NAM, RUC and HRRR, there is a hint that convection will happen by then and probably will be isolated to scattered at best, still would like to see a couple more runs of the HRRR on that to see a consensus on what MAY happen. Will obviously look at real time surface features as the day progresses as I refuse to live and die by models alone. So.. as of now, Mark McGowen and I will likely head up the Turner TP. toward TUL or east on I-40 and reevaluate from there. I think there is a high likelihood that we'll have a set up at least as good as yesterday and with the CAPE/EHI numbers progged, one thing I'll be avoiding at all costs will be the gargantuan hail (4"+) that could occur with the most vigourous updrafts. Will make the best out of today as the rest of the week is questionable for me to chase due to work commitments.

 

[Tim Marshall]

Another marginal chase day but even less so than yesterday. For example, winds at 500 mb are weaker than yesterday. I also don't like the veered forecast winds (RUC) in MO and IA, so I will once again remain in the high CAPE region in the south. Much of my chase target is in the hills and trees of southeast Oklahoma, which I don't like. So, I will try to stay toward I-35 in southern OK and north TX. Target town at 9am valid for 00z is Atoka. There is an outside chance of me staying around the DFW area. So, I will continue to monitor.