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.