3/5: FCST: Friday MI/KY/TN/OK

[Robert Dewey]

I see where your coming from Rob. I don't get how the ETA can have a temp of 70F, dewpoint on lets say 56F, and cold air at 500mb, yet have such little CAPE?

Actually though, I have seen severe storms occur (mainly low topped, squall lines), with CAPES less than 500j/kg. An event such as this occured in December 6 of 1998 or 1999 right here in lower MI (your in Lansing, I think it may have developed just east of you). My location had a wind gust of 82MPH, and numerous trees were down over a widespread area. The temperature during that even was 45F, and obviously when temps are that low, dewpoints don't really matter. The squall line was mainly dynamically driven, which could be the case FRI for the Chicago area...

Robert

 

[rdale]

My GEMPAK hiccupped today (actually one of my daughters reset it) so I don't have all the 18Z stuff in yet ;> Anyways I know storms can form a squall line in that environment, but you were talking about supercells forming ahead of the line and that's very difficult to do in a low-CAPE environment.

Also anything elevated would not be a tornado risk.

- Rob

 

[Robert Dewey]

Yeah, I seen that after I posted that you were talking about thesupercells/tornado threat, sorry...

Your run GEMPAK at your house also? I have several shell scripts to receive data from FTP - how do you get your data?

Robert

 

[rdale]

FTP to NCEP for model / satellite, HTTP to NCEP for NIDS, HTTP to universities for surface / profilers / upperair / watches / warnings / etc. More info on my homepage.

- Rob

 

[nickgrillo]

This system looks pretty dang good I'm definitley taking a day off on Friday for this one

 

[Robert Dewey]

Yeah, I just checked the 500mb RUC analysis, and it actually looks like the storm is on track. I am getting anxious for the 00Z data to come in, which the ETA should probably be in within 2 hours from now, GFS about 3 hours. Nick...Did you read the AFD from GRR for this afternoon? "...SW MI GETS INTO THE WARM SECTOR WITH SOME
INSTABILITY ONCE THE WAA PCPN LIFTS OUT...THEN SVR WX WILL BECOME A
CONCERN. ALL OF THE CLASSIC SYNOPTIC INGREDIENTS APPEAR TO EXIST FOR
A DECENT OUTBREAK OF SVR WX CLOSE BY... BUT INSTABILITY WILL BE THE
KEY...". That sums it up pretty well. My AIM username is TornadoChaser200 if anyone wants to chat.

Robert

 

[rdale]

00Z Wed Eta

Running some 18Z Friday Eta soundings through NSharp and all I can say is -- if this was April I might be evacuating friends and neighbors ;> Not enough juice through the column to kick off supercells, but one heck of a squall line is a nice bet as things stand...

 

[Robert Dewey]

Checked the latest 00Z data, and I think the ETA has actually slowed some, as has the GFS, just a bit. ETA is a bit more unstable than the 18Z ETA, but nothing spectacular. Would really like to see CAPE above 1500 for supercells, and at this point it is impossible to say whether this will happen. ETA still has temps >65F for most areas in the warm sector, and dewpoints approaching 60F (up a few degrees from the 18Z run). Storm system deepens to 982MB by 0Z SAT. Right now, I have to agree with Rob, that it looks like a massive squall line or derecho situation. Wind profiles show extreme speed shear, with an 89KNT jet maximum above OH/IN/MI 18Z FRI! This is probably why the 0-3km helicity is running around 300-350m2/s2, since directional shear will not be too strong. IF instability looks a bit better than the current ETA suggests, a couple of supercells may be possible, especially right ahead of the line of main convection, where SFC winds may still be more southerly. Behind the system, late FRI/FRI night, it looks like the system will transition into a wind machine for lower MI, with ETA suggesting 10m winds sustained at 30-40knts, and some mixing of 50KNT winds possible (gusts to 55MPH).

P.S. 10 more model runs until the event (4 model runs per day), can they hold??

Robert

 

[rdale]

With the 12Z Eta in, nothing terribly different compared to 00Z - timing just about the same, SLP a few mb higher, wind speeds slightly lower -- but all-in-all nothing that's going to stop me from preparing for an overnighter Thursday into the day Friday around northern IN / southern MI...

 

[Amos Magliocco]

N IN / S MI

With the 12Z Eta in, nothing terribly different compared to 00Z - timing just about the same, SLP a few mb higher, wind speeds slightly lower -- but all-in-all nothing that's going to stop me from preparing for an overnighter Thursday into the day Friday around northern IN / southern MI...

How is the visibility and road network up there?

Amos

 

[rdale]

Vis is fine in N Indiana, hit-n-miss in southern MI. Roads are fine in both locations. I usually shoot down I-69, if I have a target out west or south I'll either cross the Toll Road or continue on I-69 -- if I'm meandering I usually take US20 across.

- Rob

 

[Tim Stoecklein]

Hmmm, chaser convergence in Michigan??? I'm in. They have given a good description of the downstate roads and such. If you get too far west, it can get a little tougher with trees and such. Of course when you come from Kansas, as I do, any trees are more than you are used to.

Anyway, let us know who is going to be out and about. I've already hit my 40 hour mark for the week since we've got intramural basketball playoffs going, so I'm not planning on coming to the office on Friday. I'm planning on heading down that way.

Tim

 

[Robert Dewey]

I have to agree with Nick and Rob...MI does have some good areas as far as visibility and road networks. Extreme Northern Oakland County and Macomb county (north of Romeo) are good areas, as well as south of Detroit.

I am having trouble viewing the 12Z data in full, as the only site with graphics is NCEP. The other sites such as RAP/UCAR and COD didn't produce any 12Z data...

From what I see on NCEP is like Rob said, conditions are pretty much the same, SFC low is a bit weaker, but I think 850mb Temps are slightly higher. As far as SFC temps etc., I have no graphics to go by.


Robert

 

[Robert Dewey]

Ok, the latest 18Z data is in for the ETA and GFS, and it is looking good. The 18Z GFS has slowed somewhat, leading to more confidence in the ETA solution. Still thinking that two waves of severe weather will occur. Late tomorrow night will feature a squall line from about KIND southwestward...with little or no severe weather further north.

By FRI afternoon, the 18Z ETA remains with its 65-70F SFC T and upper 50's to near 60F Td. Big difference in instability this go around...With the 18Z ETA showing SFC based CAPEs of 1000j/kg widespread across southwest lower MI and extreme northern IN, with max CAPEs of 1500j/kg near Grand Rapids MI. LI index also goes down to -4. I believe the reason for the increase in instability is the fact that 500mb trough is more rounded and there is better CAA, so temps are around 3C lower than the 12Z run. Speed shear is excellent...60KNTS at 850mb, 80-90KNTS 700mb, and 115KNTS at 500mb. Looking at helicity fields, 0-3km helicity is strongest right along the cold front with values of 300-400m2/s2. If SFC winds can back to the south or southeast a bit more, then helicity may be even stronger. So, if instability does get that high in the afternoon, then I believe a derecho or significant squall line is likely from about KIND northward to Central lower MI, with the potential for isolated supercells. If instability remains weak however, then I would still expect a decent dynamically driven squall line, but supercells will probably not occur.

Robert

 

[Brandon Redmond]

Hey, i'm from Eastern Indiana near Muncie, brand new to the board. I agree rdewey that it does look like the main threat will be in the form of a squall line. I think some elevated convection may develop during the day on Thursday and a storm or two may become strong if it can become surface based, but generally, the main severe weather event should be Thursday Evening, Night and into Friday.