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

[Ben Pinette]

Supercells or not, I'm in. Time to elleviate some SDS

As has been stated here already, those chasing SE MI, stay away from Wayne County and southern Oakland and Macomb counties. Very populated and road networks are not an option unless you like stop lights every 1/4 mile. Anywhere else you should be in good shape for viewing. Monroe, Lenawee, Hillsdale, and Branch County (IN,OH border counties) are your best for flat open terrain. Not like the plains, but the best you'll get around here.

I-69, US-127, US-12, M-50, M-52, US-23, I-94, I-96 will take you absolutely anywhere you need to go.

 

[Robert Dewey]

Still looks like the event is on tap for Friday. Have done some research on past severe weather events here in MI, and the last strong tornado to tear through was an F4 in Bloomfield Hills on March 20 1976, so March severe weather outbreaks can and do occur here in MI/IN/OH. Check out http://www.spc.noaa.gov/staff/hart/outbreaks/, they have 00Z and 12Z analysis and 3 hourly SFC analysis for every significant tornado event since 1970 (including the March 20 1976 event). I was actually quite surprised when I reviewed some of these events, as I thought system strength would have been stronger (March 20 1976, April 3 1974). The system slated for Friday is actually a bit stronger than April 3rd and March 20th events, but directional shear is not as good. The exact amount of directional shear will hinge on the shape of the sfc and upper level lows (wind direction usually follows the heights/isobars), which at this point is still anyones best guess, and has been changing from run to run.

Robert

 

[Ben Pinette]

Rob and Robert, thanks for the updates and keep them coming. I won't have time to look at anything now until at least 18Z today, if not 00Z Friday.

 

[Robert Dewey]

Just got done checking all the latest data from the 06Z models. Not much has changed as far as the event is concerned. I ran some forecast soundings through BUFKIT, and things are really looking good for severe weather. ETA 06Z run indicates the best timeframe will be between 18Z-21Z FRI. Bufkit momentum transfers are showing that 60KNT wind gusts wills will be able to mix down in the afternoon, and that isn't even in the convection. I do believe this is overdone, and that non-convective wind gusts to 50KNTS will be possible (~60MPH).
One big concern for tomorrow is instability. Regardless of instability, a squall line will likely develop, with damaging winds the obvious threat. However, bufkit indicates 0-3km helicity is over 350m2/s2 between 18-21Z, with extreme speeed shear between the SFC and 700MB. The problem is, we must have a CAPE of at least 1150J/KG to get any supercells to sustain themselves. The morning forecast discussion from DTX explains this situation well. Its hard to say at this point, but if sun does break through (ETA strongly suggests it does), than temps will near 70F, and with dewpoints in the mid 50's, will help to bring more instability. The biggest factor in determining the instability though, is the 500mb cold core. If the 500mb temps are a degree or two lower, than instability will be higher...ETA has been indicating a bit colder at 500mb for the past few runs, which is why it is showing more instability.

If for some reason we do end up with less instability, below 750J/KG...Then I would expect mainly a low topped and narrow squall line, possibly thunderless...With a pretty good threat of damaging winds.

Robert

 

[rdale]

I don't see any reason this wouldn't be a low-topped event regardless of supercells / squall line... Also with the Eta allowing for afternoon sun - PWAT's also drop down to 3/4" or less during the day which isn't good for standalone long-lived storms.

 

[Robert Dewey]

Rob, I just meant low topped as in lower tops than if instability was higher. I am talking about a line of damaging winds, with showers (perhaps a couple rumbles of thunder), that do not peak above 10K or 15K feet.

When I was talking about higher instability, I was generally meaning supercells with heights of 25K feet, which is still generally low-topped. Sorry about the confusion


Robert

 

[Caleb Lawrence]

I'm definitely looking forward to tomorrow. I had a dream there was a tornado south of me lastnight.

Ah, pre-season hopes...

 

[rdale]

IWX is going dry for northern Indiana / southern MI during Friday -- that's a gutsy call! I can understand why the Eta (even 18Z) suppresses all convection in the day but would be hard pressed to go with a no-storm forecast. I've not changed my forecast at all from the earlier posts...

- Rob

 

[Robert Dewey]

Yeah, IWX dropped the mention of thunderstorms in the zone forecast for Friday afternoon, now they only mention light rain showers! DTX issued a special weather statement mentioning severe and the possibility of an isolated tornado. I just hope that mid level temps cool enough, and that there is enough convergence along the front to initiate thunderstorms. If storms do occur, they will likely be severe given winds aloft. I also noticed helicity is a bit higher with the 12Z run of the ETA, but only by around 50m2/s2, but this means nothing if there is no instability.

Robert

 

[Dan Robinson]

Further south into KY and TN may be favorable if the area gets any clearing during the day on Friday. Even without insolation, the higher surface temps should help get us at least some decent lightning - which is good enough for me at this point. I'm planning on heading southwest into central Kentucky tomorrow morning.

 

[Tim Stoecklein]

Well, what do you think fellow Michiganians? Are we still going to have a shot tomorrow or is it just going to be a significant soaking which may lead me to have to kayak to town?

I think we're going to have the moisture in place, but is the instability going to be there?

 

[rdale]

Actually I don't think the moisture will be in place tomorrow... The drying forecast to move in also caps things off. There won't be a lot of forcing with the unidirectional winds. But then again that didn't hurt things in TX where CAPEs were low and winds were strong. But I don't see how we could get a soaking tomorrow...

 

[Tim Stoecklein]

Well, that's what I get for not checking before I posted here huh? Just more snow I guess :cry:

 

[Robert Dewey]

Could be a decent soaking tonight in southern lower MI, but not tomorrow, unless your speaking for northern lower. Dewpoints currently in the upper 50's from Indianapolis south, with a few 60F reports in southern IL. Based on analysis and RUC forecasts, I believe dewpoints will likely reach the mid 50's tomorrow. If we do manage to scour out some of the clouds tomorrow afternoon, then temps should warm to 65-70F. I have two concerns for tomorrow...

1) Mid level warming - The layer between 700mb and 500mb really needs to lose about 2C, which may happen since there is a large dewpoint depression in that region, making it easier for temps to fall. If temps do not cool, then instability will remain weak.

2) Convergence along the front - Convergence along the front doesnt look so good (wind convergence/moisture convergence), making it hard to initiate thunderstorms. If we have better instability than the weak 500J/KG the ETA is showing, then I believe the actual cold front may be able to initiate convection. I do not have access to frontogenesis fields, but I am assuming that since there is a decent thermal gradient, frontogenesis should be decent.

Will have to see what the 00Z and 06Z ETA show...


Robert

 

[Blake Naftel]

Re: 3/5: FCST: Friday in the Great Lakes

Just now jumping into this forum/topic ... my brief take on the situation...

Was not extremely positive about Friday (today) as per the 00Z Thursday ETA; but with the current RUC and ETA data deepening the low; and keeping it farther W than originally anticipated.. backing E/SE surface winds across L. MI through pre-midday Friday.. coupled ample sheer at 850/700/500 points to a 50/50 shot at low topped SUPs; maybe an isolated tornado or two. Not too thrilled with forecasted Td's/moisture availability. CAPE is nearly non existent (small area of 500 J/Kg); but this may be being underforecasted by the RUC (the model Im glancing at attm). Td's reach the low-mid 50s across IN/OH/MI border by 12Z... mid 50 Tds by 15Z. Of course; flow becomes fairly unidirectional after 15Z... alas the window for rotating storms/pre frontal passage is slim, yet there.

Another other thoughts/analysis?

..Blake..