10/30/09: FCST WI/MI/IL/IN/OH/KY/TN/MS/LA/TX/AR/MO

[Adam Lucio]

This event is starting to remind of of March 8th. Where we had tornadic storms racing across southern IL at 9am moving NNE at 70mph to the IN/OH border region by 4pm. I think if this becomes a chase it would play out like that.

Both the 12z NAM and GFS bring the low way into Canada by 0z. The GFS is still showing impressive bombogenesis from 1000mb to 972mb. Moisture and shear certainly wont be a problem but both models show the area socked in precip.

Not as excited as I once was. Its going to be a tough call for me since Ill be ditching a wedding in order to chase this one.

 

[Andrew Pritchard]

I see a couple trends that are discouraging. The biggest is in the GFS. Seems each run it more and more wants to close off the southern portion of the trough and just sit there for a bit. Even hinting at it you can really see how much it weakens things at the surface. Instability was not as much of an issue when you were dealing with a system of insane dynamics. If we start dealing with more of a closed off upper low situation in the arklatex region the severe threat seems negligible north of the Ohio River. Just look how it affects the wind fields. I'm not sure how you can spin the 12Z GFS wind fields to look good. Yeah, they're roaring at all levels. But even the surface winds are veering to the SW by the lunch hour. Even pockets of 0-3 km cape aren't going to get you anywhere with roaring unidirectional speed shear.

I think this is almost certainly a non-event right now. It would take -drastic- changes at this point for even a marginal tornado event in the midwest. Event the deep south looks shot right now.

 

[Bob Hartig]

I'm not sure how you can spin the 12Z GFS wind fields to look good. Yeah, they're roaring at all levels. But even the surface winds are veering to the SW by the lunch hour. Even pockets of 0-3 km cape aren't going to get you anywhere with roaring unidirectional speed shear.

I think this is almost certainly a non-event right now. It would take -drastic- changes at this point for even a marginal tornado event in the midwest. Event the deep south looks shot right now.

I wouldn't be too quick to write it off. There are a number of model runs between now and Friday, and veering surface winds aside, the 12Z GFS showed ample directional turning up to around 550 mbs in the eastern part of Michigan (if you're thinking in a Michigan mode)--though with the 18Z run in, I have to agree that the outlook has deteriorated.

Again, the 18Z NAM paints a rosier picture. I'm in a wait-and-see mode. After all, this thing is still three days out.

 

[Robert Dewey]

It looks like the models are phasing the Plains wave and the Canadian wave earlier, which is causing a further north SFC low. I doubt the models are sampling the Canadian wave with any accuracy... and statistically, the models don't handle "phasing" all that well to begin with.

With that said, I think we could see big variability (positive or negative) up through 12z THU.

 

[sebenste]

Robert Dewey and Bob H. have it right. Now, check this out: European ensemble runs...finally available to the public! Slide 3/4 of the way down the page:

http://www.hpc.ncep.noaa.gov/training/SDs/

Irony alert: The link has "SDS" in it.

But folks, this trough has heights of over 5 standard deviations lower than average. That is to say, there's a .006% chance of that happening! That's truly wild. So for the models to get the details right this far out is asking way too much. Do not get your hopes up or down at this point. The models are going to struggle with this in a big way for another 36 hours. Hang tight and keep watching...

 

[cdcollura]

Good day all,

In my opinion, I think everyone should be focused on the possibilities in TX on Wednesday (the 10/28 thread). I see the upper level dynamics pulling a bit far north and weak lapse rates for the south central US ... But 10/30 is still 2 days out.

 

[Scott Weberpal]

I love love love tonight's NAM. It goes with the slower solution for Friday and really puts E. IL/W. IN through KY into TN in a sweet spot for possible supercells. Forecast soundings in SE IL show ~750 j/kg SB CAPE with an absolutely incredible amount of low level and deep layer shear. Caveat is obviously instability, but it won't take much to get tornadoes in that environment. If SB CAPE can nudge up toward 1000 j/kg, with decent 0-3km CAPE and there could be a significant tornado or two.

This continues to remind me of the Nov. 15, 2005 setup when I witnessed (albeit from a distance) an F3 tornado near Washington, IN. SB CAPE that day was <1000 j/kg with a very similar shear profile.

Still keeping my eye on Friday as the better of the 3 days.

 

[Skip Talbot]

There is a glimmer of hope there, but I am not sold at all...

There is a promising trend with tonight's run. I'd shift my target further east and north from where I had it a couple days ago (MO bootheel) to the Carbondale area between 18-21z. 3km and SBCAPE are nosing into this area between these hours. I probably won't be able to keep up after that when the cells cross into southern IN.

There is an excessive amount of speed shear with 40 knots of 1km shear still being plotted over the target area. 1km SRH looks impressive at 200-300, however, taking a look at the hodos makes my heart sink. The winds are unidirectional and veered from the surface up to the midlevels right on the front (looking at Effingham at 21z where the cold front is forecasted to be). Winds look like they are more backed ahead of the front, but given what looks like piss poor lapse rates on the forecast sounding, the displacement of the upper level dynamics to the west, the mess of ongoing precip, and a cap east of the front, we probably won't see any prefrontal initiation where the hodos are more favorable.

It does look like the WRF is trying to setup a warm front across central IL and IN. I don't see the surface winds backing along it, however. Its also well north of any of the instability. However, if this warm front does set up, and the instability backs into it, I'd say its game on for tornadic supercells. Otherwise I think we're dealing with a messy squall.