2/16/06 NOW: Midwest and Great Lakes Region

[nickgrillo]

Thunderstorms are now developing ahead of the rapidly progressing cold front stretched from the surface low in northern IL back through MO and into OK. Substantial insolation / convective mixing in the pre-convective airmass has allowed the moist boundary layer to develop upward and diabatically destabilize with surface-based CAPE of at least 250 J/kg (per SPC mesoanalysis) ahead of the cold front (and will continue to increase through the afternoon).

Kurt Hulst, are you out there?

 

[David Draun]

I gotta say something since stuff is happening near my home. Southern sections of the Chicago-metro area are under a tornado watch, on February 16th!! The radar doesn't look too impressive, though there are some pockets of higher reflectivity. Judging by the air temperature in Chicago right now these storms are probably dumping accumulating small hail or sleet. The temperature just a few counties south however is in the 60's! :shock: What a spread, and those things are firing right on the front it seems. Any tornado threat would be from mini-supercells ahead of or imbedded in the line. Pretty cool stuff nonetheless. It appears, judging by the radar, downtown just got hammered by an intense and gusty cell. Wow!

EDIT: I just animated the radar. The line is not moving east, there is a train of these things tracking over the same area. :shock: I'm noticing flood watches as well now. Ugly stuff

 

[Andrew Revering]

I'd be watching northwest Arkansas pretty closely over the next hour or so. I think the stuff firing there is going to take off pretty quickly.

It's fun to look at the mesoanalysis stuff with this. If you use GR and have an Allisonhouse account, overlay the F5Data lid strength (cap strength) index over radar, and you'll see that the line developed just as it go outside of the 2c lid strength line. Pretty cool to watch things fire just when they're suppose to.

 

[Andy Wehrle]

"Tail-end Charlie" cell approaching the St. Louis metro with hook echo and intermittent couplet.

 

[Sam Sagnella]

20z modified sounding for KSTL yields CAPE of ~500j/kg of the 'tall, skinny' variety with 0-3km SRH ~300m2/s2 (0-1km ~250m2/s2)...small CIN layer remains though LFC has dropped ~500m in the last hour, so tornado threat still not imminent though definitely looks to be on the increase.

 

[nickgrillo]

This storm has been sustained for well over an hour and has displayed well-defined hook echoes and inflow notches. It has appeared to develop stronger rotation in the lower levels in the past few scans, and given that it's in a populated area -- I am suprised LSX doesn't have a TOR issued on it.

Tha background environment is characterized by 500 J/kg SBCAPE and about 250m2/s2 of 0-1km SRH -- and the storm will move into an enhanced area of low-level CAPE (3km CAPE of about 75 J/kg) as it progresses east.

Originally posted by Andy Wehrle
"Tail-end Charlie" cell approaching the St. Louis metro with hook echo and intermittent couplet.

 

[Tony Laubach]

Reports of baseball sized hail with the St. Louis storm in northern sections of town according to the latest Severe WX Statement from that warning.

 

[Simon Brewer]

I think the St. Louis NWS office is dropping the ball on this one! Most meteorologists know it's hard to detect low-level rotation in low-topped supercells; especially ones travelling at 50 mph!

At least the Lincoln, IL office has torn warnings for cells in their area, but the best cell so far only has a Severe-t-storm warning!

 

[Jeff Snyder]

That's a nice supercell up there! Tilt 1 SRV not showing a whole lot, but then again, Tilt 1 for an area very near the radar is pretty close to ground-level, so you may not see much there until tornadogenesis...

That storm also has a nice bounded weak echo region (BWER) evident on Tilt 3 and Tilt 4 BREFs... See HERE for Tilt 4 BWER and HERE For tilt 3 BWER


EDIT: Hoisting a tornado warning for a major metro area carries a lot of risk! There are a LOT of businesses, schools, etc, that enact their 'emergency' plans. I'd imagine that it'd be incredibly important to be confident in your warning, since false alarms in metro areas (with hundreds of thousands of people) are likely quite detrimental to the warning response system.

 

[Simon Brewer]

Finally they issued a warning for that storm! Maybe someone reported their house blowing away? They should have issued the warning a little earlier in my opinion....once again my opinion; not fact, but opinion, okay.

EDIT: I know issuing a tornado warning for a major city is a large risk, but issuing one too late is even greater.....people would much rather have some warning instead of being caught off guard; lives could be saved. I've been chasing and seen storms with tornadoes on the ground doing damage with no tornado warning far too many times in the past 7 years.

 

[beaudodson]

I believe that is actually a different cell...the one that moved through St Louis with the baseball size hail is now up in Madison County. I believe that is the cell that has been most impressive over the past few hours. This new tornado warned cell is a sep one.

 

[Jeff Snyder]

I am a bit surprised by the intensity of the reflectivities from many of these storms. With RUC mesoanalysis indicating only <500j/kg SBCAPE over most of the region, I was expecting to see more of a winter-like convective regime -- relatively shallow convection with 50-55dbz max reflectivities. With the intense low-level shear (pockets of >400 m2/s2 0-1km SRH), updrafts are ingesting this rich low-level streamwise vorticity leading to decent updraft rotation, which in turn enhances updraft strength courtesy of vert. perturbation pressure gradients. Decently-low wet-bulb zero levels and enhanced updrafts are leading to storms with respectable very large hail which is contributing to the very high reflectivities... I've seen a few storms with >70dbz cores this afternoon... The supercells are also staying relatively discrete, though there is a slow progression to more solid linear convection).

 

[Robert Dewey]

I'm really hoping to get some action in southern MI... The warm front is right at my door, with 55-60F temperatures about 35-50 miles south (Td's also in that value range). VAD profiles already indicating 2K FT winds increasing to 55-60KNTS at IWX, and the main threat appears to be damaging winds. It won't take much to bring things down a bit later.

Those parcels are impressive for MI in February!

EDIT: Didn't see the TOR out for SW MI... Ouch :lol:

 

[Marko Korosec]

First tornado report from Atwood, IL!

That's really an impressive squall today, I also didn't image I can see >70dBz in February, totally insane lol!

 

[Scott Olson]

Take a look at the 18z KILX sounding:

http://www.spc.noaa.gov/exper/soundings/06021618_OBS/

Wow, not bad for mid Feburary!