11/14/05 (late)-11/15/05 NOW: Midwest-Mississippi Valley

[Gabe Garfield]

Well, here's the explanation I have been waiting for as to why I look outside here in Norman and see nothing but clear skies. This is from the latest OUN short term frcst:

AN UPPER AIR BALLOON RECENTLY RELEASED AT NORMAN FORECAST OFFICE INDICATED A STRONGER CAPPING INVERSION EXPANDING INTO THE AREA. SATELLITE IMAGERY CONFIRMED THIS
BY SHOWING A RELATIVE LACK OF CUMULUS CLOUDS FROM OKLAHOMA CITY...SOUTHWARD TOWARD ARDMORE AND MARIETTA.

Guess we'll miss it again here in Norman.

This actually bodes worse for the high risk area. Insolation should be at a maximum tomorrow, which could yield very strong instabilities (>3000 j/kg). Throw in an outflow boundary or two, let 'em cook in the sun, and you've got a recipe for disaster. I have the feeling that this will be an historical tornado outbreak.

Gabe

 

[Justin Bailey]

historical outbrake during an historical year. makes perfect sense.

 

[Jonathan Whitehead]

for those that are interested, OUN launched a special wx balloon at 6Z and is available for viewing at the cod page by simply clicking on off time soundings at the bottom left.

 

[J West]

Any bets that those cells starting to fire in far NW Arkansas become a problem within 30-45 minutes?

Last radar loop I looked at about an hour ago showed that area was clear, but now that handful of returns popped up.

 

[Mike Umscheid]

This actually bodes worse for the high risk area. Insolation should be at a maximum tomorrow, which could yield very strong instabilities (>3000 j/kg). Throw in an outflow boundary or two, let 'em cook in the sun, and you've got a recipe for disaster. I have the feeling that this will be an historical tornado outbreak.
Gabe

I agree that there should be decent insolation especially south of the Mason-Dixon line. 3000 J/kg is very unrealistic in this environment later today. A worst-case thermodynamic setting I could possibly produce for the corridor from MEM to PAH is 74/66F. Lifting this SB parcel yeilds at the most 1300 J/kg given the fairly warm 500-400mb temps advecting out across much of the warm sector. You don't start getting into real cool temps in the mid trop until you get into the STL-SPI area. For mid November, -12C is kinda warm at 500mb... acting as a CAPE robber. Just look at the sounding, it's a narrow looking CAPE profile. Not atypical this time of year though

This time of year, worrying about 1300 J/kg vs. 3K is moot. The kinematic environment is outrageous with significant broad scale ascent and high shear everywhere. Storm motion of 55 kts are likely. If anyone thinks about chasing this stuff... well... my best to you! It'll be interesting to see how this pans out today. I can't disagree with a High.

EDIT: modifying 21z MEM profile for 77/67 yeilds ~1700 J/kg, which may be more reasonable for this latitude in the warm sector.

EDIT #2: Below is the NAM12 fcst hodograph valid 21z for Memphis. Unmodified... truncated at 2km AGL. Note the degree of curvature... which would tend to favor more discrete supercellular processes..

<img src=http://www.underthemeso.com/wxmisc/NAM12_hodograph_valid21z_MEM.gif>

Mike U

 

[George Tincher]

I am now glad I took a nap yesterday evening. I have this strange feeling that I am going to be awake at least 36 straight hours. While I am normally excited about the prospects of severe weather, this system is just different somehow. It's giving me a bad feeling and I am just afraid something really horrible is going to happen. And there's lots of cities in the path of this thing. I wish I had tried to sleep a bit more tonight, but I just couldn't go to bed considering the crazy parameters that are in place. This thing could go at any time and when it does, we are going to see a powderkeg unleased I am afraid.

Everyone stay safe today and if you know anyone in the threat areas, please alert them to the seriousness of this situation and advise them to pass the word along.

 

[Gabe Garfield]

I agree that there should be decent insolation especially south of the Mason-Dixon line. 3000 J/kg is very unrealistic in this environment later today. A worst-case thermodynamic setting I could possibly produce for the corridor from MEM to PAH is 74/66F. Lifting this SB parcel yeilds at the most 1300 J/kg given the fairly warm 500-400mb temps advecting out across much of the warm sector. You don't start getting into real cool temps in the mid trop until you get into the STL-SPI area. For mid November, -12C is kinda warm at 500mb... acting as a CAPE robber. Just look at the sounding, it's a narrow looking CAPE profile. Not atypical this time of year though

Looking at this morning's soundings, I agree. The lapse rates were a lot better on the 00z soundings at places like Denver, CO and Riverton, WY. I'm not exactly certain what physically caused this, but the lapse rates look a lot less impressive in this morning's soundings. As you mentioned, though, it will hardly matter with the impressive dynamics associated with this system. Even 500 j/kg will likely be sufficient to produce some major-league tornadoes (given a discrete surface-based storm.

Gabe

 

[Nick Parker]

Look like we have Tornado Warnings for:
POSEY COUNTY IN SOUTHWEST INDIANA.
WHITE COUNTY IN SOUTHEAST ILLINOIS

NWS PAH is saying it is doppler indicated.

Moving to the northeast at 60 mph!

 

[George Tincher]

Look like we have Tornado Warnings for:
POSEY COUNTY IN SOUTHWEST INDIANA.
WHITE COUNTY IN SOUTHEAST ILLINOIS

NWS PAH is saying it is doppler indicated.

Moving to the northeast at 60 mph!

That cell had a strong couplet a few scans ago, looked like 90-100 knts gate to gate. But it didn't remain that strong very long. However, it may have been long enough, as there's word of a possible touchdown in Posey County.

 

[Melissa Moon]

Argh and I'm having trouble loading the NWS page for Paducah...anyone else having similar difficulties right now?

Tornado warnings already out this early in the morning. Can't say I'm surprised though. Today is going to be a very interesting day!

 

[nickgrillo]

Mesoanalysis at 15Z showed the warm front spread across southern IL and IN and then stretching westward. Clusters of convection have evolved along the warm front and continue to push northeast very quickly across southwest IN. A supercell structure east of KEVV has shown significant low-level rotation for the past several scans -- with a rotating wall cloud and funnels reporred by spotters. Meanwhile, more isolated supercell structures should develop to the north as the morning / afternoon progresses across southern/central IL and IN. Strongly backed surface flow pattern along/near the warm front combined with west-southwest upper flow continues to yield very strong deep-layer shear in excess of 50-60kts in the warm sector -- with 400-700m2/s2 0-1km SRH continuing the potential for tornadoes with any surface-based thunderstorm. Any localized pockets of stronger surface-based instability will be to support a violent tornado today...

 

[George Tincher]

Argh and I'm having trouble loading the NWS page for Paducah...anyone else having similar difficulties right now?

Tornado warnings already out this early in the morning. Can't say I'm surprised though. Today is going to be a very interesting day!

Mel, just tried NWS PAH and it loaded ok for me.

http://www.crh.noaa.gov/pah/

-George

 

[nickgrillo]

New severe thunderstorms are developing over southcentral MO (along and south of the warm front) where a line has developed -- with a embedded supercell structure northeast of Ava with +71KT gate-to-gate shear. Very strong deep-layer and low-level shear and even some marginal surface-based instability remains extremely favorable for tornadoes across this area...

 

[Gabe Garfield]

Thus it begins...

Storms are beginning to show signs of becoming surface based over AR/MO at this time. High reflectivities now extend through the lowest tilt and a storm ~30 mi to the E of Springfield has already been tornado warned due to a strong velocity couplet.

Other storms are rapidly developing to the WNW of Little Rock, and though they have a linear configuration, are becoming stronger with each volume scan.

As can be seen from the MO storm, these storms will organize in a hurry.

Best wishes to those in pursuit today.

Gabe

 

[Scott Weberpal]

I'm currently at a rest stop along Interstate 57 between Champaign and Effingham, IL - moving south again soon. Not exactly interested in the current convection moving across S. IL. Playing my cards that the clearing trend in SE MO/NE AR will continue northeastward into S. IL. I guess I'll pick a storm, let it cross my path, and hope it tornadoes while in my vicinity.

Beautiful...PDS issued as I'm typing