05/09/04 FCST: Great Lakes

[Robert Dewey]

I know this may be out on a limb considering the relatively lack of event (slight bust?) today across MI (for the most part)...But the past two runs of the ETA (18Z/00Z) show some decent potential for Sunday Afternoon. I was going to create a new topic for this event earlier, but decided to wait since I thought the ETA may be having some convective feedback problems.

Discussion...ETA develops a nice little shortware Saturday night/Sunday morning, and drives this eastward across the Lakes. Nice return flow appears to setup with dewpoints in the lower 60's by mid afternoon Sunday (ETA was actually correct today as far as SFC moisture, maybe it will be correct Sunday as well). By 00Z Monday, instability will be in place with CAPE of 2000-2500J/KG, combined with excellent shear - SFC winds are S/SW, veering to westerlies at 850mb with a jet of >50-55knts, creating for excellent low level shear/helicity (helicity values are around 250-300m2/s2, which is good for that deep into the warm sector), all as the cold front moves through. ETA also outputs some convective QPF across the region, indicating that if the ETA does indeed hold true, convection is likely.

Now that I created a new topic, all severe weather will miss the area on Sunday...

Anyone else have some thoughts?

Robert

 

[rdale]

I just hopped on to do the same... Much better wind speeds through all levels of the atmosphere combined with a nice dry punch at 700-500. Lansing helicity 325-375 Sunday afternoon with temps near 80 and dews in the mid-60's...

I spent an hour trying to find why today's 850 temps warmed up (assuming clouds) and why it wasn't caught on any model but nothing had the extent of the warming, and only the 21Z RUC even hinted at that cap. Once it broke though to our south -- OUCH.

- Rob

 

[Robert Dewey]

Yeah, today was kind of a bust for MI...Just as I typed that, I can hear a few claps of thunder, a cell has just popped up over me (about 5 miles E of NWS DTX). I decided to run the Sunday data using NSHARP (rather than data from the good old 'net)...And by 21Z Sunday, SRH are in excess of 315m2/s2, with CAPES AOA 2500J/KG...If this situation holds, could be looking at a significant event across the area...

Robert

 

[Robert Dewey]

Well, after checking the 12Z ETA today, things arn't looking as good as they were. The low is much further north, and very dry air at 700-500mb overspreads the region, which may cap things off, given the lack of significant convergence. Instability and shear are still very strong, but these parameters won't matter if storms fail to initiate.

On the other hand...The 12Z MM5 looks like the 00Z ETA. I plan on running the WS-ETA for both the ETA and GFS 12Z model run, to see what happens...I will likely report my findings later this evening after looking at the 18Z models and the 12Z WS-ETA output...

Rob Dale, whats your take on this situation?

Robert

 

[rdale]

My take is -- not even worth discussing it quite yet ;> We proved yesterday that the models can't come close to handling this pattern. A perfect storm setup resulted in nothing due to an unforecast(able?) cap at 850mb. Then storms exploded along the state line, then a new area developed north of Jackson well north of the front and dropped large hail as it passed towards DTW. Then a separate round of sevwx dropped hail near Kazoo this morning, now a pretty good MCS caused hail and wind damage across Indiana before daybreak. None of this was picked up on very well ;> So I'll say "there is a chance of svr over the weekend" and that's it for now (I'm telling viewers to pay little attention to the details of my 6-day forecast!)

 

[Robert Dewey]

Your right. I guess I will just wait till tomorrow and look at actuall analysis and then judge from there.

As far as the models being wrong yesterday, one model was right in location and timing - The DTX convective init model - http://www.crh.noaa.gov/dtx/?page=cidisplay
It forecast the event from the 12Z run, although it only had a lead time of 12-15 hours, it still outperformed the RUC.

I usually don't look at that model very much because it gets updated once in a "blue moon", so I just rely on the operational RUC...But the Convective Init model does seem to have a pretty good track record, we will see how it performs today.

Robert

 

[Tim Stoecklein]

Well, I'm glad to see we can rekindle this post. We are starting to see come clearing ahead of the storms coming from Wisconsin. Heating down state seems to be sufficient. I'm not sure we're going to see any rotating supes, but we may be in for some hail and strong winds. If that front continues to move north, we could see some substantial cells.

Tim

 

[Tom Van Kuiken]

Looking at the KGRR radar at around 6PM, you can see the outflow boundary from the line over Lake Michigan collide with the interior convection. Really explosive development.

 

[rdale]

...explosive... but not severe... So far it looks like GRR isn't going to verify more than one of the 10+ warnings they issued today (and that was with 3/4" hail.) A few were quite questionable in the first place.