10/26/2010 FCST: IN/MI/OH/IL/KY/TN/MS/AL/GA/PN

[Skip Talbot]

I didn't believe the GFS four or five days ago when it had a bombing 968 mb low tracking past the great lakes. Its held in there from run to run with NAM now picking up on it as well with a 972 mb low over southern MN/northern IA at 21z 10/26. Along with the low, a 100+ knot mid level jet is forecast to eject over the OH river valley. The deepening low is forecast to advect dewpoints into the mid 60's well into Michigan. Instability is forecast to remain minimial, probably because of the massive amount cloud cover the trough is going to kick up. However, with such extreme forcing and dynamic lift, little to no instabily may be needed. If we do get some pockets of sunshine in there, we may be looking at a severe weather outbreak. Along with this system a very fast moving cold front is forecasted to sweep through the area, with marginal veering with height along the front. We'll probably have a big undercut squall line moving through that may pose a threat for damaging winds. Hodographs are gigantic curves just ahead of this front though. If we can get discrete initiation ahead of the line and some low level instability in there, I think we may see a tornado outbreak across portions of MI/IN/OH and into the southern states depending on when this system moves through. The GFS is a little more progressive as always, but overall I'm impressed with the run to run consistency and agreement between the models on such a dynamic system with the crazy numbers its spitting out. Its not going to be a pretty chase with your typical grey, grungy high shear/low cape high risk type events, but it might be fun to try and get out of ahead of the line and catch something as it races past.

 

[Andrew Pritchard]

I generally hate playing the "this reminds me of such and such" game, but I can't help but think of October 24 2001 when looking at this system because of the time of year and similar strength/position/movement of this guy.

I generally agree with Skip's analysis of the system. Things will need to get ironed out in coming model runs as data becomes more clear. If we can get it to slow down a little, which isn't uncommon in such deep systems (the October 24th system slowed down quite a bit in the 24 hours before the event) we may be looking at a potential heightened risk for severe weather across eastern Illinois into the Ohio Valley. 10/24/01 was a difficult chase day, mostly resulting in embedded supercells with rain wrapped tornadoes, and I expect no different should this one become a chase day.

It looks as if convection could ignite along the cold front fairly early in the period (again, similar to 2001 where we had tornadic supercells initiating near St. Louis before noon) in a likely linear fashion across western Illinois. Best case scenario, we hope for clearing in advance of the front resulting in higher instability to support some embedded supercells, perhaps even a couple supercells ahead of the line, because as Skip said hodos are just insane.

There are still a couple changes I'd like to see take place, but if this does end up being a chase day it appears it could be a fairly widespread event in which you've got red boxes in effect before the lunch hour. I hate relying on change, but slow the arrival of this thing by 6-12 hours and we could be talking about some tornado producing rockets.

 

[Mike Kovalchick]

From the APX Gaylord MI forecast discussion,

"..INTERESTINGLY... LATEST HPC DISCUSSIONS ARE COMPARING THIS STORM TO THE GREAT
ARMISTICE DAY STORM OF NOVEMBER 11TH 1940..."

Latest HPC extended discussion:

http://www.hpc.ncep.noaa.gov/preepd/preepd.html

That particular storm may have been worst storm ever recorded on Lake Michigan. (Mostly due to an extremely long fetch over water due to a Southerly gale.)

This system definately worth watching. Not sure if chasing will be possible will crazy storm motions but this will be interesting setup depending on the exact timing of the cold front. For Michigan a later in the day passage on Tuesday will certainly help the cause.

 

[Adam Lucio]

Interesting that the NAM brings the best CAPE into IL in the pre 18z timeframe. It also brings one heck of a squall line through in a 60kt sheared environment. Given the rapid deepening and strong linear forcing along that cold front it looks like at the very least we will see a high end wind event. Best case scenario has been already mentioned and that is the system slows down a tad and allows for some better instability to creep ahead of the front, if that happens whoa boy. Van Wert version 2010 anyone?

 

[James Gustina]

I definitely agree. The speed shear is forecasted to be insane with that jet max(err speed max?) rolling in over the Indiana/Ohio/Michigan area. The hodographs the NAM spat out look like fish hooks almost. But like what was said above, the storms are gonna be going insanely fast with this and the amount of forcing on the front is gonna turn this into one intense looking squall line.

 

[jcooper]

Yeah this is gonna be very fast...storm motions poss. upwards of 60-70 knots.It will be intresting to see what ends up.I think at the very least you get a crazy intense squall!

 

[James Gustina]

And if the HPC Front/Pressure charts are correct that low is gonna deepen a lot and the cold front is gonna be from Illinois to Virginia in the course of 24 hours.

 

[David Mikulec]

Louisville LMK is drawing comparisons to November 10, 1998 in calling this a potential major wind event for Tuesday afternoon. May not have to chase very far if it does make its way down here. I'll be watching their discussions for changes.

STORM SYSTEM IS VERY SIMILAR TO
THE NOVEMBER 10, 1998 EVENT WHICH PRODUCED QUITE A BIT OF WIND
DAMAGE ACROSS THE MID-MS VALLEY AND THE NORTHERN PART OF THE OHIO
VALLEY. IN PARTICULAR...THE 24/18Z NAM RUN WAS QUITE BULLISH ON
STRONG/SVR STORMS HERE TUE AFTERNOON/EVE.


historical information: http://www.crh.noaa.gov/mkx/document/wind/wind_11-10-98.php

 

[Jesse Risley]

The 0z GFS has come a bit more into alignment with the 0z ECMWF and the 03z SREF, at least in showing a slightly more progressive nature to this system than what the 0z run of the NAM from last night is showing, with the deepening area of low pressure making headway into Ontario by 0z Wednesday (NAM keeps the system centered over central MN at 0z WED). This would position the surface front further east than what the NAM is showing, clearing the eastern OH River Valley by early evening. It should also be noted that the 0z runs of the GFS and the NAM are <= 960 mb in regards to the intensity of the system.

The 0z NAM is also more bullish on the amount of CAPE the system has to work with, though that will probably be somewhat dependent on the position of the cold pool in relation to the front. Strong winds in the lowest 1km, with a notable portion of the vector perpendicular to the line, will probably sustain a healthy squall line in advance of the CF. The threat for at least isolated tornadoes shouldn't be ruled out this far in advance of the system, as there are some favorable hodographs across the OH River Valley and points northward. Storm motions look to be sustained at 45-60 kts across a wide portion of the warm sector, which doesn't make for the most favorable long-term chasing event.

 

[Robert Dewey]

A closer look at the 12z NAM shows pockets of 600-800j/kg worth of CAPE from southern MI southward, between 18z-0z TUE. With the degree of shear and forcing, this is more than sufficient for severe thunderstorms. The features are fairly similar to the 19981110 system, although this system is a bit deeper (960-965mb) and slightly further NW. Looking at radar imagery from that date, much of the warm sector was plagued by a large area of rainfall, with a solid squall line embedded along the cold front. With that said, widespread wind damage was still realized. Back to the future, the NAM is showing very little precipitation preceding the cold front.

I can definitely envision an embedded squall line - perhaps with little thunder - producing widespread wind damage, as was the case back in 19981110. Anything more significant (i.e. a 20011024 type of event) would be highly dependent on instability.

 

[L.B. LaForce]

The HPC disco for today was talking about a possible seiche on the great lakes.

INTENSE GREAT LAKES/UPPER MS VALLEY REGION STORM WITH FORECAST
EXCEPTIONALLY LOW SURFACE PRESSURE READINGS SUPPORT STORM FORCE
GREAT LAKES WINDS TUES INTO WEDNESDAY DIMINISHING THURSDAY. 11 NOV
1998 AND ARMISTICE DAY STORM OF 1940 REMAIN ANALOGS WITH THIS ONE
HAVING LOWER FORECAST PRESSURES. PROLONGED WIDESPREAD VERY HIGH
WINDS WILL OCCUR OVER THE AREA FROM THE DAKOTAS TO IA AND THE ERN
GREAT LAKES WITH A LIKELY STRONG SEICHE/SLOSH EFFECT OVER THE
GREAT LAKES. HEAVY RAIN EXPECTED OVER NRN MN WITH THE WRN
PERIPHERY ACROSS THE DAKOTAS SEEING LIGHT SNOW. SEE LOCAL NWS
DISCUSSIONS/ADVISORIES AND WARNINGS FOR THIS ENTIRE REGION.

 

[Mike Kovalchick]

The HPC disco for today was talking about a possible seiche on the great lakes.

INTENSE GREAT LAKES/UPPER MS VALLEY REGION STORM WITH FORECAST
EXCEPTIONALLY LOW SURFACE PRESSURE READINGS SUPPORT STORM FORCE
GREAT LAKES WINDS TUES INTO WEDNESDAY DIMINISHING THURSDAY. 11 NOV
1998 AND ARMISTICE DAY STORM OF 1940 REMAIN ANALOGS WITH THIS ONE
HAVING LOWER FORECAST PRESSURES. PROLONGED WIDESPREAD VERY HIGH
WINDS WILL OCCUR OVER THE AREA FROM THE DAKOTAS TO IA AND THE ERN
GREAT LAKES WITH A LIKELY STRONG SEICHE/SLOSH EFFECT OVER THE
GREAT LAKES. HEAVY RAIN EXPECTED OVER NRN MN WITH THE WRN
PERIPHERY ACROSS THE DAKOTAS SEEING LIGHT SNOW. SEE LOCAL NWS
DISCUSSIONS/ADVISORIES AND WARNINGS FOR THIS ENTIRE REGION.

Some of the model runs have intensified this as low 955 mb. The lowest pressure ever recorded in the US outside a hurricane is 958mb in Cleveland in 1978. In this case the lowest pressure will occur North of the border so the record won't be threatened.

 

[Robert Dewey]

MAY ALSO WANT TO START THINKING OF NAMING IT. I MAY BE MISTAKEN...BUT I BELIEVE THAT IF IT ACTUALLY DOES INTENSIFY TO AROUND 960 MB THIS WILL LIKELY BE THE STRONGEST GREAT LAKES CYCLONE SINCE THE ARMISTICE DAY STORM OF 1940!

It will definitely be interesting to see how this plays out. Not much change from my original thoughts; I still expect a solid line of severe wind gusts along the cold front. Whether it's in the form of thunderstorms remains to be seen.

 

[Andrew Pritchard]

Is it just me or does the 0z NAM look a little more interesting for some early period rotating storms on Tuesday? No yeah, it's probably just me.
We've gone from almost complete agreement between the major models, to a completely different story between the 0z NAM and GFS solutions. The NAM offers a slightly weaker, but perhaps more favorable for severe weather solution. In sacrificing a few MB and somewhat delaying the bombogenisis, the NAM has dropped the placement of the surface low further south by about 100 miles, placing it over central Wisconsin now around 15z, rather than near the Canada border. This allows things to destabilize a little more before the cold front sweeps through, and keeps us in the highly sheared unstable warm sector a lot longer.

I'm still not ready to talk tornado outbreak, but the significant wind damage threat just took a big increase if you buy into the slower NAM solution (which I eluded to being a possibility in my earlier posts). While the GFS did well picking up on the extreme bomb, it's not uncommon for it to be too progressive, so seeing the NAM slow down on the 18z, and then even more now at 0z is not a huge surprise. I just hope it's on to something, and not out to lunch.

Things will become more clear tomorrow certainly, but I like the direction we're moving. I'm afraid the SDS is getting to me and I'm getting a little too gungho, but I think the severe weather threat that had taken a backseat to the super-bomb story may be making a resurgence. Could be a day where we find areas of central and southern Illinois into Indiana under tornado watch boxes shortly after sunrise.

It still looks like an obvious linear and wind damage biased event, but with increased instability, and a little more time before the cold front blasts through I like the increasing odds at a few embedded rotating storms. As was the case on 10/24/2001, close attention to any subtle surface perturbations will be required for any potential trouble areas.

Forecast soundings for central and northern Indiana now showing at or just above 1000 j/kg of the good stuff, which with the insanity aloft could be enough.

I'm not sure how far I'd be willing to chase such a ridiculous setup, but perhaps dropping into eastern Illinois or northern Indiana would be a decent excuse to try out my new jet pack.

 

[ahaberlie]

Looking at the forecast soundings for MKX I was a bit underwhelmed until I saw the overnight details.. things could get downright dangerous for people living in southern WI and northern IL as the instability increases from the incredible moisture advection starting way after dark. ( and 50 kts of 0-1 km shear around 5 am .. yikes)

Another interesting thing is they are forecasting pressure gradient related wind gusts approaching severe thunderstorm levels. This system isn't messing around.