9/30/07 FCST: IA/NE/KS/MO/WI

[Dustin Wilcox]

I got the cougar gassed up and am ready to hit the road, might need every last Horse out of that V8 engine to keep up with storms tomorrow; I love how the NAM's pulling the 60-65 dp's all the way up into the low, I do wish H5 temps were progged to be a little colder to make this a true cold core setup, NAM has -14C associated with the wave at 18Z across NE but those vanish as the wave pushes E into IA, although I suppose -12 should be suffice. Depending on what transpires tomorrow I'm thinking I may just chill out here in Arlington, wait until the lows about to move over me around noon and then just lead it ENE right up highway 30, I'm not ruling out the possibility of storms near or just East of the river in the early afternoon, will be interesting to see what convective debris is leftover and what impact it may play, 4km paints a decent picture for NW to NCNTRL IA.

 

[scott r currens]

I think most of the slight risk area will be a bust today. Too much shear not enough instability. That being said I do like two targets. My first choice is just NE of the surface low close to the cold are aloft and strong vortmax. My second choice target is the one that Jeff mentioned yesterday. Southeast Kansas where the shear wont be too overpowering and instability will be better than most of IA and MO.

 

[Brian Stertz]

Heading off on the chase trail

My target is Denison IA and will be heading off in a few mins. from West Des Moines. Looks like these low topped supercells should move at a pretty clip as they fire over NE/EC Nebraska and move into W. Iowa. I want to give these storms some distance for them to organize and so they do not rocket by me. I would expect that by the time 3-4pm rolls around, these should be full fledged and potentially tornadic on the IA side of the Missouri River.

 

[Mike Peregrine]

Not sure why I'm even trying today, as I have to be in St. Louis tonight, which forces me to be way south of the best shot. I like Brian's target ... the area just east of the low, over western Iowa. Decent shot at supercells in that area. Dewpoints and instability look marginal, even for low-topped standards. But I suppose 50-60 TDs and CAPE of 1000 or so is still do-able on a day like this. The low is just over 1000mb, and lots of shear with surface winds around 25-35 kts and 500 mb at around 40-50. The storms will be moving, but it's really not as bad as some early spring rocket days. Have fun up there ... guess I'll be stuck with the southern end of things.

 

[Jeff Snyder]

I'm very much on the fence today, but it looks like moisture won't be a big issue, at least in the southern part of the SLT risk area. Tds are in the 68-71F range across much of central and eastern OK, and the 12z OUN sounding showed a pretty good depth of this good moisture as well. Granted, mid-level lapse rates won't be particularly steep, but we should have >1000 j/kg MLCAPE by late afternoon.

The SE KS / SW MO / NE OK area will be on the southerly periphery of stronger mid-level westerly flow, which models forecast to result in 35-45kt 0-6km shear. My primary hesitation attm pertains to surface winds. For the most part, sfc winds west of a TUL - EMP line are veering to the southwest, leaving only northeastern OK and far eastern KS (and pts eastward) in southerly flow. If it appears that southerly sfc winds can be maintained in those areas, then I'll probably head out in an hour or so. If sfc winds look as though they'll veer to SW as well, I'll probably stay back (given that sw sfc winds will reduce low-level shear and increase storm motion given faster ENE mean tropospheric flow). A few of the NAM forecast soundings I looked at showed an inversion in the 400-500mb layer (IIRC), which may act as the equilibrium level (giving us relatively low-topped supercells).

So, the gist of this is that I'm eyeing the Nowata to Chanute area, holding back to see if the sfc winds turn southwesterly. The last RUC I looked at showed a sliver of favorable low-level shear ahead of the front come late afternoon and evening, so I'm crossing my fingers.

 

[Ryan Pfannkuch]

4-county target area in south central IA: Warren, Clarke, Lucas, Marion
Including the cities of: Indianola, Osceola, Chariton and Knoxville

Well I'm not going to be driving east today to deal with storms moving 45-55 mph AWAY from me...but after taking a long hard look at the 12z and 15z RUC and various high-res WRF runs from last night I'd say south central IA certainly looks fairly intriguing for the 21-00z time frame. SFC low is progged to be near Omaha at 21z and near Carroll at 00z. This puts the area named above in an area roughly 80-100 miles SE of the surface low track and along the arc of the advancing surface front punching in from the SW...which in my experience is often not a bad place to be. I was originally thinking farther west...but with storm motions likely to be at least in the 45-55 mph range...this seems like a good day to hedge a little east and let things develop and race toward you.

Big negative today would seem to be the fact that the sfc low appears to be gradually weakening as it moves across IA...leading me to wonder if the models may be a bit optimistic in backing the low level flow ESE of the low track. At any rate, I would like to see a little stronger surface low to get me excited about a tornado day versus linear mode...but with kinematics this strong you just never know.

 

[Brandon Ivey]

I was not going to chase today, but since things have slowed down some I think I will venture out for a while. The front, in SC KS, is currently located from the Reno/Harvey county line down into western Harper County. This is shows up good on radar. Nice area of convection going up northwest of Wichita. I will be heading out in an hour or so to follow the front into eastern Kansas. Looks like a big linear event. Nice speed shear profiles but not much in the way of directional shear. I would expect to see 60-70 mph winds and up to golfball sized hail today. The ruc has slowed this system down a tad (maybe by 50 miles) since the early morning runs. They also just issued a thunderstorm watch for Wichita eastward. Better pack the gear. Good luck to those chasing in Iowa today!!!