5/13/09 FCST: IA/IL/MO/OK

[Adam Lucio]

00Z NAM looks better IMO. It brings a narrow tounge of 2000+ CAPE into IL by 0Z Thursday and this is as good as Ive seen it.

Shear doesnt look too unidirectional to me especially once you get into central and southern IL, nice curved hodographs too.

t/td spread is sick...under 10 degrees it looks like. Were gonna be dealing with some ground scrapers iif thats the case

The only thing I dont like is the simulated reflectivity as it keeps allot of junkvection around. Although it shows some more intense "blobs" within the mess...perhaps embedded sups or maybe even isolated ones...after 0Z thursday though it does transition the whole mess into a massive line which is what we pretty much expected.

I like this run better than last though, now lets wait for the 0Z goofus to chime in.

 

[Mike Brady]

You have to remember what time this forecast was issued (2:30am this morning) that is still a long way out of the event. Discussing supercells that early in the game can be risky (especially in this part of the country). Especially with the model spread that was still and still is evident. I will be interested to see what the folks at SPC have to say tomorrow morning outside of an obvious wind event.

I would have to agree with you on this please keep in mind that many severe outbreaks have been slight up to the day of the out break and several High/Moderate Risks have come and gone with little to no effect.

...Looking at the model runs as of 00z I think that the best area for storms will be late afternoon into evening I will be calling a preliminary targeting near Springfield along I 72 But will obviously adjust as needed. Wind profiles from the runs on Sunday were more impressive than those today as far as turning with height However 00z data has brought the turning back as well as sufficient instability I look forward to seeing how this one pans out in future model runs...

 

[Dustin Wilcox]

My attention is turning more from a conditional IL target to an equally conditional OK target. The 12KM NAM seems to point at a somewhat favorable environment just SW of OKC. The model progs a 995mb low in the E TX panhandle and wraps in a nice bulge along I-40 by the 21-0Z time frame with 4000+j/kg CAPES progged across the area. At the same time a subtle little wave is working over the area with H5 winds at 35-40kt, LL's (mainly 850) veer more than I normally like to see, but the model hints at some SE sfc winds near and along I-40, and more than sufficient helicity. The lack of a nice vort max along with the overall shy of strong flow keeps it far from an ideal setup, but I'll too now be keeping my eye on the are near and just WSW of OKC.

 

[Dan Rupnow]

Unidirectional?

SFC / 500 Crossover

SPI sounding at 0Z

2000 j/kg sfc cape nosing into my "near STL" initiation point as well.

My thoughts exactly! I think if anything, the 00Z NAM runs tonight show even better backed surface winds, and thus turning with height over C IL. I don't think shear is something we have to worry about with this setup. Knock on wood the models don't change that.

 

[Jarrod Cook]

Shear is definitely not an ingredient that will be lacking in this event. The 00z NAM still does have me concerned though about the usual IL grunge and low CAPEs. This run also has less of a cap in place in the early afternoon than the 12z did.

The best CAPES per the 00z NAM run from STL along I70, which is farther south than I'd like to see. Hopefully the GFS will maintain what it showed on its last run.

 

[Jesse Risley]

I don't see shear being the main concern with this setup, even on the 00Z NAM. I believe the major caveat is and will continue to be potential instability (or lack thereof), and when and if any storms fire off of existing boundaries prior to the linear show.

The 00Z NAM is a bit further SE with the higher progged CAPE values, but I also noted that little money shot just to the NW, up near KSTL. As usual with these systems, if the GFS doesn't verify, I would at least expect some pockets of clearing somewhere in an area bounded by KUIN, KSTL and KSPI, which would yield higher CAPE values in that region.

 

[Dick McGowan]

The main problem on the Illinois target is the suggested ongoing convection/precipitation from 12z - 0z depicted by the NAM: http://www.rap.ucar.edu/weather/model/displayMod.php?var=eta_sfc_prcp&hours=hr36hr39hr42hr45hr48

Another, is the amount of instability that will or won't be allowed to recover after that first (or ongoing) round of precipitation. The shear is obviously the best in Illinois, while the best instability is further SW into SW MO, SE KS and NC OK. That being said, I think on a day like Wednesday you have to meet it somewhere in the middle. Right now, I think Central Missouri into perhaps extreme W. IL would be where I'd chase, if I decide to pull the trigger...and I'm geographically unbiased, choosing the place for highest probabilities of tornadoes .

Overall though, I'm not excited for what should be mostly a large hail and damaging wind threat over a decent area. There will probably be a lot of tornado warnings issued, but I'd expect a small amount of the reports to actually verify...at this point.

 

[Mike Hollingshead]

Talk about the year of "I'll chase it because it looks like crap afterward anyway". That is what I feel on hmmm pretty much every chase I've went on this year. Sure not really remembering an excited feeling from any of them. And this one won't be any different(maybe if crapvection is looking friendly on the way).

I can see the morning off already. Wake up, see crapvection everywhere and wonder, will that get better? No time to wait and see, get on the road or not chase. Even pretending crapvection is not much of an issue I wonder if there will be much of anything to fire storms ahead of the cold front. Doesn't look like a very convergent warm front even with crapvection. Upper flow looks like it plummets south of I70 at all. I also don't know what to make, if anything, of the converging look to the 500mb winds all along. Can that help keep crapvection down or not?

Maybe there will be a boundary east of the cold front with a slight change from sw to s sfc winds to pop a couple storms off(doesn't look like it on Earl's stuff as much as RAP). Or maybe the surging moisture won't need a nice looking front to it. Seems like to me a pretty small area will be favorable with the huge IF regarding crapvection earl on. Heck take that out and I'd probably still end up on the cold front lol.

Look at about any extended model, I guess a chaser able to chase this one almost has to, regardless of the ifs(not sure this chase motivation/mindset has ever paid off for me). I hope the crapvection at least doesn't make things south of I70. Or maybe that is what is killing the upper flow, doesn't really look like it. Given about any better pattern down the road I think I'd find this one easy to sit out. Friendly crapvection with a friendly OFB from it though, would certainly make for some big fun for someone in this setup. Since low level shear out ahead of the cold front will be off the charts with south sfc winds...toss in crazy low lcls like it looks will happen and well.

My forecast for myself this day. Drive 8 or so hours to watch a ground scraping shelf go by me at 60mph. A very intense wind storm would be worth it to me though. I hope to at least see that.

 

[Scott Weberpal]

The main problem on the Illinois target is the suggested ongoing convection/precipitation from 12z - 0z depicted by the NAM: http://www.rap.ucar.edu/weather/model/displayMod.php?var=eta_sfc_prcp&hours=hr36hr39hr42hr45hr48

Unfortunately the QPF at 42 hours is a 6 hour accumulation - so any precip between 12z and 18z is going to show up. The 45 hour (3 hour accumulation) shows a break between ongoing precip and new development into western IL.

I'm holding out hope that there'll be a 4 km WRF run for Wednesday at some point, and we'll have a better idea of hourly precipitation trends as the NAM is absolutly horrible at trying to decipher breaks between a major MCS and convection later in the day.

 

[Andrew Pritchard]

Generally agree with McGowan, but have more faith in the Illinois target. Call me geographically biased, or whatever, but I'd still drive to the best tornado target myself on Wednesday. I'm sticking again, to my target near Intertate 55 just north of St. Louis.

There will be a ton of convection in IL on Wednesday. The bulk of the main complex should track east into Indiana by early afternoon, allowing for clearing behind it, along the E-W boundary laid down. I'd look along this boundary in EC MO and SW IL for new supercellular development. Likely around Columbia, Missouri, tracking into western and southwestern Illinois. A high cape / theta-e area will be nosing into this area with sbcape nearing 2000 j/kg. That along with helicity values above 350, nearing 500 closer to Interstate 72 will be more than adequate for discrete thunderstorms (talking ahead of the cold front here, folks) and potentially tornadoes. There will be a strongly forced line of thunderstorms along the cold front by nightfall, but I don't intend to be anywhere near the cold front during the chase.

I'll continue eyeing an area in SW Illinois near Litchfield, along Interstate 55 south of Springfeld and north of St. Louis.

 

[Danny Neal]

I have been talking to Andrew, Adam. David, and a few others about this set up for the past couple of days. Generally we all believe there will be chase-able storms in the area (E MO/W IL).

However, speaking for myself now...... I am still skeptical about this MCS. The NAM simulated plot showed a mess but as Scott said above, it is generally an accumulation totaling 3 to 6 hours of precip. I had two general IL targets plotted. One being up north near Bloomington and one being further south near Vandalia and points W of there. CAPE from 00 UTC run shows a nice tongue nosing up near STL and definitely swings the favor of the Vandalia-ish target. Still AOA 10 degree T/Td spreads in the area so as Adam said it will likely be a very scary looking storm approaching. (I would expect to see some scudnado reports Wednesday) I am optimistic for supercells. Shear is not a question, moisture is there, and IF the 2000+ CAPE can be established I call it a no brainer. GFS precip plot is quiet at 00z and erupts in the next three hours. Even LI's are spiking around STL.

As I noted before.... oh where oh where will the MCS go.......

 

[Andrew Pritchard]

For what it's worth - GFS has no grungy precip and 2500+ cape over the entire warm sector in Illinois and eastern Missouri.

Target area.

 

[Jarrod Cook]

For what it's worth - GFS has no grungy precip and 2500+ cape over the entire warm sector in Illinois and eastern Missouri.

Not only that, but a stout cap in place until a couple hours before 00z in W. IL. GFS definitely still holding strong. Quincy to SPI to STL looking like a fairly decent target area based solely off the GFS.

 

[Joel Wright]

If we can keep most of the morning crap away from central IL we may be in for a big day. With 2000j/kg+ nosing up into a highly sheared, low LCL environment we should have no problem getting at least a few tornadoes in central IL. I'm thinking there will be a broken line of supercells that will eventually evolve into a very powerful squall line with embedded meso-vorticies. Certainly some very damaging wind potential with those.

The two biggest questions for me is the ongoing morning convection, and just how quickly the mode goes linear. With as much shear progged I would hope for at least a few hours of decent supercells.

 

[Danny Neal]

http://wxcaster4.com/nam/CENTRAL_ETA212_ATMOS_STP_48HR.gif - Well uh...hey there bullseye!