11/15/06 FCST KY, MO, TN, ARK, OK

For several runs now, the GFS and the ensembles have been fairly consistent with what I think maybe one nasty outbreak of severe weather for the mid mississippi valley, specifically, KY, TN and west into MO. for this next Wednesday the 15th. Lots of parameters still need to fall in to place and of course the models may still jump around a bit on the position of the storm system.

My hunch is... is that this will be a doozy, this is the peak secondary season for tornadoes in the mid south, historically there has been alot thats happened this time of year and I think this will be no exception.

As of now, moisture will be more than adequate, temps. will likely be at least in the 60's perhaps 70's ahead of this system... shear with a system like this likely be significant.

As of now, I would be watching areas from Little Rock to St. Louis southeast to Nashville, down to Jackson and back into Arkansas for the late Tuesday thru Wednesday time period.

I'm hoping we'll pick up some precip. here in Oklahoma... we're getting parched again and this system if the GFS is correct, will be predominately a high wind event for here in cntrl Okla. ... if this upcoming system can dig a little farther south and come out slower, then we may get some much needed rain... perhaps some svr wx for the eastern sections.


Rocky&family
 
The 15th is the anniverary of the horrible tornado outbreak last year. The PAH area was hit hard. It appears that the models are having a difficult time with deciding how far to dig this next storm system. With an intense jet coming in from the Pacific and diving to the southeast it appears that the storm could dig pretty far south. Earlier runs had it passing into Southern Illinois and the latest models take it further south...more like Memphis and then northeast from there. So there are definately some differences in timing and placement of the low.

The intensity of the jet should favor the storm digging pretty far south and perhaps a bit slower than the models are showing.

We are getting within the 72 hour time frame (Tuesday Night). There are major differences in the GFS and NAM - as far as storm intensity.

PAH One year ago
http://www.crh.noaa.gov/crnews/display_story.php?wfo=pah&storyid=4215&source=0


Will be keeping an eye here in Paducah.
 
Four days out...lots can change between now and then. System looks like it's going to be a fast mover. My current feeling is it'll stay south...Memphis/Tupelo/Birmingham/Huntsville for starters with most of the storms in the afternoon for once. Definitely worth keeping an eye on.
 
Thismornings GFS (06Z) has the storm system developing a little farther south around the Arklatex by Tuesday eve. then starts to bomb out during the day on Wednesday as it slowly heads up into the Ohio Valley.

Whats interesting here is that the NAM greatly disagrees with the other models on the strength of this system. Given the incredible upper level energy poised to dive south from the gulf of Alaska... I can't see how this can be. I'm sticking to my belief of a strong vortmax taking shape over southern Ark. maybe northern LA. by Tuesday night then swinging northeast by Wed. evening.

The GFS shows doomsday for Alabama and especially GA. up into east TN. by 0Z Thurs. Shear profiles are absurd, whatever storms can form ahead of a squall line will have a high likelihood of producing tornadoes. Potential negatives maybe the amount of instability and perhaps lapse rates as cold air behind this system is not that great... but with a potential 984mb. low near by... and climatology for what can happen this year......??

Regardless of what the NAM says... I still think this bares watching
 
Instability in VERY short supply. Would like to see a little bit better return of moisture as well. Certainly has potential but as most NWS Offices have mentioned there is very little in the way of instability. Appears portions of Eastern Alabama, Florida Panhandle, and Georgia would be under the gun. Very impressive 500 mb winds across the Southlands. Nasty squall line should race across the above areas...high wind event for many?

Let's see if the storm can manage to sqeeze out a bit more in the way of instability.
 
This looks like a classic cool-season Gulf Coast severe weather setup, but as mentioned, workable moisture is going to have a hard time getting north of the southern Tennessee border. I can see this event having potential only about 100 miles inland from the Gulf. The low looks deep enough for great shear, but (according to the GFS) it looks like it occludes too quickly, moves north and separates from the juicy air.

If anything I'm inclined to start looking at the cold-core possibilities with this. In that case I hope the GFS is right. NAM/WRF is keeping the low too far south for anything to happen away from the Gulf coast.
 
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Think I'm tweaking south just a bit. GFS is showing that little moisture spike up along the MS/AL border. Temps look a bit cool, but I'm beginning to get a little more used to cold core setups. Lots of shear, but not much else going for this one. Too soon to call a specific target, but the area betwen Jackson, MS and Montgomery AL is looking interesting. Any descrete cells that form early would definitely stand a chance on going tornadic. After that, it looks to be the squall line from Hades.
Keeping an eye on it...
 
Think I'm tweaking south just a bit. GFS is showing that little moisture spike up along the MS/AL border. Temps look a bit cool, but I'm beginning to get a little more used to cold core setups. Lots of shear, but not much else going for this one. Too soon to call a specific target, but the area betwen Jackson, MS and Montgomery AL is looking interesting. Any descrete cells that form early would definitely stand a chance on going tornadic. After that, it looks to be the squall line from Hades.
Keeping an eye on it...

Can that be defined as cold core? I thought cold core only dealth with areas of the 500 mb low to the north of the primary low?

Modified MT air is what this is dealing with along the gulf.
 
Can that be defined as cold core? I thought cold core only dealth with areas of the 500 mb low to the north of the primary low?

Modified MT air is what this is dealing with along the gulf.

Sure, it's usually in reference to a cold core upper low which the models are showing here (18-22C at 500hPa). The wind profiles look fairly intense 85-100kts at 500hPa and 45-60kts at 850hPa. Obviously there are problems with the moisture avaliable, though the strength of the jet should be able to bring in a decent moisture profile considering the nature of the setup. Particularly interested in the area near the low and WF. While instability appears fairly low on both models, both also show some decent levels of 0-3km CAPE (starting fairly high in in the 15z-18z timeframe and working down). Given the intense wind profiles and the potiental for fairly significant low level buoyancy (and boundaries), I certainly would believe that this event has some potiental.

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Sure, it's usually in reference to a cold core upper low which the models are showing here (18-22C at 500hPa). The wind profiles look fairly intense 85-100kts at 500hPa and 45-60kts at 850hPa. Obviously there are problems with the moisture avaliable, though the strength of the jet should be able to bring in a decent moisture profile considering the nature of the setup. Particularly interested in the area near the low and WF. While instability appears fairly low on both models, both also show some decent levels of 0-3km CAPE (starting fairly high in in the 15z-18z timeframe and working down). Given the intense wind profiles and the potiental for fairly significant low level buoyancy (and boundaries), I certainly would believe that this event has some potiental.
But if the 500mb low is up in AR and TN wouldn't that be the cold core area. Is anything north of the warm front considered the cold core? If so then Southern MS/AL would be in the warm sector - well in it. A bit confused by what he meant I guess. I thought to be a cold core outbreak it had to be further north along the 500 mb low region. This case that would be much further north.

Curious...on definitions here.
 
Looking at the latest NAM forecast, it appears that any 'cold-core' setup would be in the TN/KY/southern IL/southwestern OH areas. 2m T and Td forecasts indicate that the areas south of TN are in more of a true warm-sector environment. In this case, the low / cyclone is almost completely vertically-stacked, with the surface low located very near the center of the 500mb low. The latest CAPE plots would indicate some marginal instability developing ahead of the surface low in a relatively standard cold-core fashion, but I don't like the very stacked nature of the low. I haven't looked at this event much, and an examination of forecast skew-Ts would help shed additional light.

If you haven't read it, and you have an interest in cold-core events, I strongly suggest reading through the following preprint:
Environment characteristics associated with tornado events near closed cold core 500 mb lows - Guyer and Davies (2006) AND
A Preliminary Climatology of Tornado Events with Closed Cold Core 500 mb Lows in the Central and Eastern United States - Davies and Guyer (2004)
 
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Sounds good. I added that area to my "concern" region earlier this evening. Could be a few spinups in the areas you mentioned.

One thing that I noticed about tonights runs is that the low is further south and has a bit better opportunity to tap into the better dew points/moisture. Defin would be concerned across portions of Central and Southern MS/Central and Southern AL. Looks nasty on the soundings. Helicities are over 500. CAPE is decent now. The further south that low can go then the better opportunity to tap into the better moisture field. Something to watch.

Also note that both models are painting an enhanced area of CAPE across West TN.

Looks like a rough Wednesday ahead.

Also starting to look like there might be potential for a high wind event as this thing moves into the Middle Atlantic and Northeast.
 
Cold core prospects look doable if a good dry slot develops and allows surface heating in the vicinity of the occluded frontal boundary. As Jeff mentioned, there will need to be an offset between the 500mb low and surface low as noted by Davies/Guyer. I think getting a good dry slot is not going to be easy though.
 
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