8/9/2004 FCST: MIDWEST/GREAT LAKES/NORTHERN OHIO VALLEY

[Robert Dewey]

Still kind of early, but there appears to be a threat of severe weather Monday, as an unseasonably strong trough swings through a warm/humid and possibly unstable airmass. Not going to get into real details since its a few days away (and things can change in a matter of a day, like the busted forecast a few days ago), but I am starting a thread just to discuss any future model runs or opinions...

 

[rdale]

I've been watching it on the GFS and now the 12Z Eta looks good as well... Fortunately this is not even close to the same set-up (bust-up) of the past week, it's a "real" storm system (but still not one that looks like Mid-August!)

- Rob

 

[Jeremy Lemanski]

Looks interesting to say the least. Something to keep an eye on over the next couple of days.

 

[Amos Magliocco]

I noticed both Monday and Sunday have some prospects. Guess I should open a forecast topic for the 8th but seeing how little success chasers have had in the Upper Midwest here lately, I'm inclined to wait for another run or two.

 

[Robert Dewey]

Latest 00Z ETA is starting to roll in, and its 00Z analysis is stronger with the 500MB low over the northwest (now that is ashore) compared to the 12Z 12HR ETA. Still quite a ways out, but as Rob said, this will be an actual "storm", not a developing SFC reflection along a cold front, so models should have somewhat of a better handle on it.

Still too early in my book to determine instability/cloud cover/etc., but the potential is still there for some decent storms Monday afternoon.

BTW Rob: The LDM is pretty much back up, I had to bypass the router (that was the ultimate problem, the router kept crashing - couldn't handle the data load). So, I now have the direct IP address into the server. There maybe a few restarts here and there, since I am switching from CONDUIT back to my old FTP scripts (they seemed to do better, and have more grids), on a seperate machine. Please PM me as to whether or not Garry replied to your L2 request...

 

[Robert Dewey]

Still an evolving situation for the beginning of this upcoming week. Am a little concerned about SFC moisture return, but looking at the lastest METAR data, there are widespread >65F Td's all the way into northern SD.

Another concern is the timing of the front. From the 12Z models, it looks like a late afternoon or evening event (at least to me), along the pre-frontal trough.

DTX:

A NIGHTTIME PASSAGE WILL REDUCE THE SEVERE POTENTIAL ON THE FRONT...

Seems like the NWSFO are not too concerned with a severe weather, at least as of now...

ETA has been lowering low and mid level wind speeds with each run, as well as back instability off somewhat (CAPE was originally forecasted to be >2500J/KG, now AFD from GRR says 1500J/KG, which doesn't thrill me). Latest 18Z ETA is coming in, and its analysis is yet again stronger than the previous 6HR/12HR, so we shall see...

 

[rdale]

I don't see anything terribly anti-severe quite yet... While winds are weaker on the 12Z they still easily support a nice line, and the CAPE values range from 1500-2100 depending on what sort of warming we get in the day. Not bad for a 48hr event just yet.

- Rob

 

[Robert Dewey]

Originally posted by rdale
I don't see anything terribly anti-severe quite yet... While winds are weaker on the 12Z they still easily support a nice line, and the CAPE values range from 1500-2100 depending on what sort of warming we get in the day. Not bad for a 48hr event just yet.

- Rob

Okay, good... Just need some re-assurance

 

[rdale]

SPC ensembles seem to be on-board still as well...

- Rob

 

[Jason Hetzel]

well i guess it all depends on sundays overnight activity then huh?

 

[nickgrillo]

I think the winds are too weak for good stuff. Does anybody else agree?

 

[Robert Dewey]

Originally posted by Jason Hetzel
well i guess it all depends on sundays overnight activity then huh?

Yep... Right now, it looks like its going to be a squall line event, but that all depends on the exact "shape" of the low and associated SFC wind fields...

I decided to bring up some forecast soundings in NSHARP (using the 18Z ETA), and by 21Z, a parcel of 83/66F would yield close to 2500J/KG or greater...

 

[Robert Dewey]

Originally posted by nickgrillo
I think the winds are too weak for good stuff. Does anybody else agree?

I have been watching the shortwave on the WV loop, and it looks like is spinning pretty fast, perhaps its going to be a bit stronger than forecast? Anyway, I am not too excited about the wind fields either, but if we were to ramp up CAPEs to >2500-3000J/KG, then we may get some good action (squall line at the moment)...

 

[Robert Dewey]

Latest 00Z ETA is in, and I have more confidence that a severe weather scenario may pan out. Latest data shows the 500mb shortwave fo be stronger than what the 18Z ETA had predicted, and looking at the WV loop, this looks probable. Low and mid level winds are also slightly better this go around, probably due to the stronger shortwave, with 30-40knts at 700mb. Given the better wind field, shear is better, with 0-3KM shear of 35knts, and effective SRH of 170M2/S2 (at LAN). Moisture return is still my main concern... However, modifying the ETA sounding for LAN with a parcel of 81F/63F creates just over 2500J/KG, and if the dewpoints can really get pooled to 65F (wow!), CAPE jumps to 3200J/KG - Which would certainly support severe thunderstorms.

Expect the main storm type to be a squall line given the strong forcing along the pre-frontal trough, but with BRN numbers in the mid 20's and effective SRH of 170M2/S2, I could imagine a few supercells popping up...

The severe weather season so far across MI has really been weak, with most forecasts becoming busts. At this point, I will take any form of severe weather I can get - Be it an outflow dominate squall line or a pulse severe storm...

 

[nickgrillo]

Are you crazy Rob? LOL. :lol:

MI had over 25 tornadoes so far this year! :lol:

My perspective on chasing:
Supercells/Rotating Storm: YES.
Anything Outflow Dominant: NO