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

[Derek Weston]

This mornings 4km WRF run makes a few interesting statements:

1) It breaks out no convection in IL up to 00z.
2) It shows a massive supercell-type blob in SW IN at 22z
3) It makes SE IA appear to be the prime area for potential tornadoes breaking out a broken line of storms in the 22-23z range.
4) Illinois is completely clear of overnight convection by 16z-17z.

Not that the 4km WRF is above and beyond any other model, but it does have a positive track record in regard to where initiation is likely to occur, along with timing.

These are time sensitive links:
http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/12/refd_1000m_f34.gif
http://www.emc.ncep.noaa.gov/mmb/mpyle/cent4km/conus/12/refd_1000m_f36.gif

That's very interesting... agree this model has done a good job in the past and I value it above what the NAM/GFS usually spit out for reflectivity/precip.

The sparse convection seems to indicate capping through out part of the day that I just didn't imagine. Seems like a strong forcing day considering our shear profiles, had imagined things would be going faster earlier.

In regards to Illinois... by the time storms sweep in that were fired off the CF in Missouri, we might be looking at a very linear bow echo sort of setup. (SPC thinks mode might be this) Wondering if we might not see more isolated convection pop initially in SE IA south through Missouri... while Illinois does have the most favorable shear in 0Z time frame it seems, we're going to need an active WF or OFB interaction to fire discrete activity... as what IA/Mizz brings might not be the desired mode. But this is just my personal conjecture...

(personally, liking the trend for SE IA)

 

[Jason Bolt]

Who'da thunk it. Illinois chasers interpret all the models that Illinois will be the bullseye tomorrow. Oklahoma chasers chime in that the Sooner State will be the best play. Any Alaska chasers care to comment?

I think tornadoes will be a good bet tomorrow anywhere from STL to Springfield back to the northwest part of Illinois. Things likely will go linear quickly and that poses the question if there will be chaseable tornadoes. Then, if there are chaseable tornadoes, will they be of the rain wrapped buried somewhere in a line non photogenic tornadoes. Most likely. I guess since geographical bias is the flavor of the day, I think there will be a string of nice isolated sups trailing down I-44 all the way to tulsa. They will all track NE at about 30 kts so I can watch sup after sup right here from my porch!

 

[Steve Worthington]

I`m not an Alaska storm chaser "but" I flipped my coin and it landed on heads, I guess we`ll go towards Oklahoma tomorrow
Anywhere is better then here in all this mist and fog.

 

[Jeff Russell]

I`m not an Alaska storm chaser "but" I flipped my coin and it landed on heads, I guess we`ll go towards Oklahoma tomorrow
Anywhere is better then here in all this mist and fog.

I don't buy the flip of the coin. How bout two out of three?

I'm heading towards Pana, IL from Atlanta. I'll post my forecast tonight when I get back from the GT and UGA baseball game at Turner Field.

 

[Steve Worthington]

Ok, I also looked at a few other things
But, I`ll know more as time goes on because I`m gonna wait and see how things look tonight before I point one way or the other.

 

[Andrew Pritchard]

Gah, I don't know what to do with that WRF data.

18Z NAM is in and still just screams Litchfield, IL starting point, tracking into central Illinois during the evening. LL Helicities are peaking over 600 m2/s2 right over the central part of the state. I just can't bring myself to target the cold front. With convective initiation on any boundary in the environment ahead of the front in IL, OFB, warm front, whatever, it will go nuts. The odds coupled with roads/terrain still have me favoring the hometown target.

Like I said, I just can't see myself targeting the cold front. Not until we're an hour from sunset and I'm sure that the warm sector is not going to do anything.

 

[CZandbergen]

Seeing as I live about a mile from I44 it just might color my judgment a bit! That said, I am not liking the 18Z NAM run very much for the southern target. Surface winds have gone from slightly backed to veering. Looks like the NAM is trying to speed things up a bit. I still like the chances for a few chaseable cells tomorrow afternoon in the I44 corridor starting west of OKC, however they are looking more like hailers which is not so good.

Looks like the better environment may be further east which while closer to home will also lend its self to a night chase which does not excite me. Waiting for the 18Z GFS to see if it heads in the same direction as the latest NAM run.

 

[Toni Scholz]

I don't buy the flip of the coin. How bout two out of three?

I'm heading towards Pana, IL from Atlanta. I'll post my forecast tonight when I get back from the GT and UGA baseball game at Turner Field.

Jeff,

I'm guessing you're going to be the BMOC tomorrow, but I'm going to place my target just slightly northwest in SE IO around Centerville and Ottumwa.

 

[Michael O'Keeffe]

I'm with Pritchard, the 18z is painting an ominous picture in C Illinois with a small pocket of 3000 j/kg of CAPE and some insane helicity. The directional shear looks even better and it is still breaking out precip in an E-W fashion along what I'm guessing is the warm front as well as the cold front in MO and IA, while it may look like a squall line who knows what that could be, I wouldn't put much faith into any precip model except for maybe the 4km WRF the day of.

Right now I'm going to look at a target E/NE of St. Louis somewhere, maybe Litchfield as well.

 

[David Toner]

Really not much to add. I agree with Pritchard and O'keeffe. I have been struggling as to if we should go northeast into Illinois or chance targeting Oklahoma. I'm familiar with Oklahoma and Kansas as for the most part chased that area for the past several years. I have never chased very far east of here (Springfield, MO). Until the last NAM run I was having trouble not being biased towards familiarity.

As long as things keep looking like the latest NAM there's no doubt as to where we'll chase tomorrow. Great CAPE and helicity along with good shear and hopefully at least a few OFB's and /or the warm front has me targeting the area northeast of STL as well. Good luck to everyone and unless things change maybe we'll see some of you tomorrow.

 

[Paul Hadfield]

Initially I picked Taylorville being that you have good directional options dependent upon initiation and because I felt to be slightly E of the NAM/GFS bullseye's of yesterday was a wiser move. I'm of the opinion that models are great for pinpointing best updraft initiation but not so with isolating storm maturation which would actually be at a distance away dependent upon downstream forward speed and direction of movement. No special knowledge just opinion based on experience in reviewing past events from where they were forecast to go down versus where they actually did. I trust ILX wording when closest to the day of and has moved things further WNW so I am not so sure. It's too bad things are expected to congeal so rapidly otherwise having an initial target wouldn't be so critical. Ultimately I would prefer a nice uncluttered backlit lowering with the 4PM sun but will of course take whatever. Ultimately I hope to at least meet a few of you. FWIW, there are no good NE options through Decatur so avoid it if you can. Either shoot E from Macon to Dalton City along Andrew street and then N along country roads to US36 or take the I-72/51 loop. As you make your way E, there are some good restaurants at I-72/US 51 just N of Decatur if anyone cares to rendezvous later. Specifically, there is a Texas Roadhouse in the event anyone earns a steak tomorrow

 

[Greg McLaughlin]

As has been the case so far this May, I can find many things I don't like about the setup tomorrow. For the Illinois target it appears everything is in place, except a good cap. I wouldn't be at all surprised to see ongoing convection ruin an otherwise favorable environment for tornadic supercells. If morning convection can clear out and redevelopment can hold off long enough for a solid instability axis to develop by mid-afternoon then things could get interesting up in Illinois, however without much of a cap its possible too much convection could go up at once.

Further southwest into OK I am more concerned about the warm sector being too far removed from the upper support. While the cap will be strong enough to hold off convection most of the afteroon, the models insist on storms exploding by early evening ahead of the dryline and along the front in central OK. While there appears to be sufficient veering with the wind profiles, mid-level winds appear to be rather weak. The weak mid-level winds and the orientation of the instability axis and low-level jet appear favorable for the development of a severe MCS.....possibly a derecho....?

 

[Derek Weston]

Agree that on the 18z -- traditionally don't like this run -- St Louis area is looking best... however, to the E and S we have better CAPE and better backed 850s. The only negative being that the helicity target seems to be further north. And there will be no WF plays down that far south. Central Illinois is also better chase terrain as compared to southern Illinois, from what I understand. I think there are plusses and minuses for both N and S Illinois...

Also worth noting that the 18z seems to continue the trend here of keeping things a bit further west, it seems, especially where good CAPE is concerned... in the 0z time frame most of the good CAPE still seems to be in the vicinity of the Mississippi river... back on west into Missouri.

Again seeming to indicate that significant initiation will take place back across Missouri...where the CF will have only eclipsed the NW part of the state by 0z.

Good news is that with the CF back further to the west, the region of Illinois we're speaking of shouldn't see linear forcing ripping things up initially... however... what forcing are we going to have in the area ahead of what is in Missouri? There ought to be storms out west into Missouri, invof the CF... are we going to have to rely on this complex of storms moving into the area? If we can get a few isolated storms to pop in this area near 0z... I think we've got a great chance for a tornadic sup.

(far E Iowa, into N Ill and S Wisc should be active due to the orientation of the front through the region... also... any sort triple-point-esque action should be present in this region... not so much C/S Illinois and Missouri)

 

[Joel Wright]

With as much wind shear forecasted for tomorrow I really don't see a squall line developing until several hours into the main event. I think we'll end up seeing several short ENE/WSW oriented lines of convection stretching ahead of the cold front from northern IL down through MO. Along these ENE/WSW oriented lines there should be some embedded supercells.

My initial target of Peoria may end up a tad too far east if trends continue. I may end up a tad further west over towards the Galesburg/Macomb area. These storms will likely initiate west of the Mississippi River and quickly push east into IL. Anything that can manage to fire on an old boundary over central IL will go absolutely crazy if there's enough instability. Which hopefully there will be. Any gravity wave type action could easily spark off something like this.

Tomorrow is gonna be fun! Good luck to everyone who heads out!

 

[Darren Stephens]

SPC is hinting of a possible Moderate upgrade tomorrow to the southern portions of the risk area. I think that there is a good chance we will be lucky and catch a "Tail End Charlie" from this system if nothing else.