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

[nickgrillo]

Wow... ETA bringing in some decent instability into the Great Lakes on Friday (with >1000j/kg CAPE in some spots) with some pretty good 0-1km SRH for the development of tornadoes (>200m2/s2 across southern MI during the afternoon).

Discuss FRI:

 

[rdale]

The model consensus (as the Americans catch up to the EC ;> ) is that the system will be in the Oklahoma area on Thursday - wouldn't this need to be a S PLAINS thread for Thurs and Midwest / Great Lakes on Friday instead?

Regardless of where it's at, I see no reason to compare this to the SuperOutbreak...

- Rob

 

[Robert Dewey]

Im not saying we will have a Super Outbreak, since conditions cannot be identical. I was just noting that the past runs of the GFS looked very similar at 500mb in respect to trough location, depth, and wind field. The sfc forecast is somewhat similar, not as much as the 500mb level, since both featured a sfc low of ~990MB southwest of Chicago (maybe has something to do with the 500mb being similar?). That is only at one timestep, however. During the Super Outbreak, the 500mb trough was actually much stronger on April 1 into April 2, the trough was closed off and the heights were less than 540/536. By April 3 and 4, the 500mb trough weakened and opened up, and that is the timestep that looks like the current model runs - the weaker opened up wave around KS/MO. So the big difference is, the Super Outbreak system was weakening, while this one is strengthening. Another huge difference, is the fact that I am using the actual analysis from April 1-4 1974, while for our forecast, I am using un-reliable models.

I just like to bring up old events, and compare them with ones that are forecast to occur, whether they are similar or not.

Robert

 

[Dan Cook]

SPC day 3 outlook has a slight risk from Texas all the way to Illinois.

 

[rdale]

FYI The second topic on this forum always links to the SPC graphics so there's no need to repost in each thread... Anyways I think that might be a little rushed bringing it all the way into southern MI before daybreak Friday. Just starting to get the new stuff in now and it looks like a farther west track of the low would lead to a slowing down of the sevwx threat. At least it's something worth looking forward to!

- Rob

PS Although NWS disagrees with all of us - Detroit, Grand Rapids and Northern Indiana make no mention of thunderstorms, let alone severe, for the end of the week!

 

[Joel Wright]

PS Although NWS disagrees with all of us - Detroit, Grand Rapids and Northern Indiana make no mention of thunderstorms, let alone severe, for the end of the week!

They are often a little gun shy about the thunder wording early in the year.

 

[rdale]

I understand the value in being 'gun shy' -- but how you can look at this system and say 'no need to mention the threat of thunder' is beyond me?!? The HWO is intended to give people a heads-up on possibilities at the extended range, and GFS/ETA both giving 850 winds of 75+kts, 400ft winds of 45 kts and plenty of juice headed in I find it hard to believe there's no chance for getting storms -- let alone a threat for severe.

At least GRR & DTX are mentioning the possibility of heavy rain, but Northern Indiana says no heavy rain, no thunder, and therefore no severe (yet SPC includes them in the outlook?!?)

Anyways enough of my NWS rant ;> which can be continued in another forum, for now I'm planning on heading into IN/IL Thursday night and hanging around through Friday.

- Rob

 

[George Tincher]

Hmmmm, guys, just wondering if I should stock my storm shelter with water and get the portable power supply hooked up to the lights before Friday? Hehe. If the stuff comes through here overnight Thursday or Friday morning, I may need to use it. Staying above ground in these lousy hills during darkness...looking for a tornado could be very hazardous to ones health! Hehe. What appears to be the timing and location of Friday's storms, as I haven't been able to look at anything past Thursday at this point.

-George

 

[mrobinson]

FYI The second topic on this forum always links to the SPC graphics so there's no need to repost in each thread... Anyways I think that might be a little rushed bringing it all the way into southern MI before daybreak Friday. Just starting to get the new stuff in now and it looks like a farther west track of the low would lead to a slowing down of the sevwx threat. At least it's something worth looking forward to!

- Rob

PS Although NWS disagrees with all of us - Detroit, Grand Rapids and Northern Indiana make no mention of thunderstorms, let alone severe, for the end of the week!

reposting the full SPC is against the rules.. however discussing it and linking to portions of it are allowed. If you feel that is redundent I'd be happy to take it up with the other moderators to discuss your concerns. Please feel free to PM me or any of the other mods with them. The rules and regs are a work in progress. All imput is valued so when chase season goes into full swing all the bugs are worked out.

Melissa

 

[rdale]

GFS would bring the squall line across MI/IN/OH before daybreak, Eta holds it off til 18Z-ish.

 

[George Tincher]

Thanks for the update Rob. I suppose I'll have to wait until closer in to see which solution looks more likely. The overall severity could certainly be much different if the storms move through in the pre-dawn hours compared to mid-day or near peak heating. Depending on timing and how fast the system moves, my next concern would be whether or not there would be clearing and more heating take place prior to the passage of the front. If that were to happen, there could be a second wave of storms. But again, that's much too far into the future to plan for now. But it is something to watch. I think I'll go ahead and stock my shelter now though, just to be on the safe side! :mrgreen:

-George

 

[George Tincher]

Ok, giving this a quick once over, it appears Friday's activity will be a big ol' squally. It looks ripe for severe but the winds seem pretty much unidirectional at all levels (at least in the Ohio Valley). I would think any tornado threat would come from embedded supercells, while the bigger threat would be from damaging winds. As far as timing, it's still a wait and see situation. But as of right now, I don't see Friday as a big tornado day...although there could be plenty of severe weather. Of course this will likely all change 10 times between now and then. LOL. I am not very comfortable at times with model data 24 hours in advance of a system, so I sure won't rely too heavily on products 72-84 hours in advance. It is however fun to look at after a long, cold, boring Winter!

-George

 

[Robert Dewey]

Just got done looking at the 18Z Model runs. The 18Z ETA looks very good, GFS is still faster, but is slower than the 12Z run, ever so slightly.
Current ETA would have 2 waves of severe weather. The first wave, could be a significant squall line from southwest MO into northeast IL. Tornadoes may be possible, especially if individual cells can develop ahead of the line, where SFC winds may be more south/southeasterly, and SRH will be above 250m2/s2. SFC based CAPE in Chicago, right before the squall line moves through, is in the 500-750 range, and given the last event where CAPES were even smaller than that, this system should be able to sustain severe across that region. This line pushes east, with probably the brunt of it south of lower MI. Lower MI actually stays in the upper 30's temp wise until about 12Z FRI, then a rapid warm up is in store.

Then, the other wave of severe weather comes in, primarily for areas from southern IN into lower MI...and points east into OH. ETA 18Z run is now showing temps near 70F all the way up to Saginaw, MI by 18-21Z and this is possible, as the ETA usually has a better handle on low level temps and boundaries. I think the reason for the warm-up, is that a strong dry slot moves in after the first squall line, allowing for some sunshine/sfc heating. Dewpoints also creep up into the mid to upper 50's, so the atmosphere should be rather prime for severe weather across this region. Winds fields are excellent, to say the least. Winds at 850MB are around 65KNTS, increasing to 115KNTS at 500MB, but the ETA may actually be too strong with the upper level winds (another model bias). Strong 985MB sfc low will be slamming into this airmass, with very strong convergence, so initiating convection should not be a problem. Also of note, SRH across this area, after the initial 12Z squall line, increase to >400m2/s2, so it should be interesting to watch the storms in the afternoon. I just hope that if this whole scenario pans out, that the shear wont be too strong, and prevent storms entirely.

Robert

 

[rdale]

"SFC based CAPE in Chicago, right before the squall line moves through, is in the 500-750 range, and given the last event where CAPES were even smaller than that, this system should be able to sustain severe across that region. "

Surface based CAPEs during yesterday's event near CHI were 1000-1500, horribly underforecast by the Eta & GFS. If they stay in the hundreds like currently noted there would be no formation of cells in advance of the squall line.

- Rob

 

[Dan Cook]

If case 1 pans out, I'll be on my first chase as I got a road trip planned on Fri coming home.

 

[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