4/21/04 FCST: Great Lakes

[rdale]

Changes in this mornings model run... The Eta is bringing more warm air well into Mich tomorrow, getting us into the 70's and setting the stage for possible severe weather as the cold front sweeps through late afternoon / early evening. Wind profiles look good with a bit of directional shear.

My concern is that it allows us to warm up by clearing things via drying -- and that trying could be too much for any storms to pop. I'll add more with a full look later this afternoon.

 

[Robert Dewey]

I have to agree the severe weather threat is looking pretty good if we manage to get good SFC heating, and clear out any morning convection that may be lingering. Latest 12Z ETA shows quite a bit of SFC CAPE and very good wind fields (0-1KM helicity is OK in EXTREME eastern lower MI, and deep layer shear is supportive of supercells/bow echoes), the GFS shows good wind fields, but is not as unstable (GFS seems to always keep air more stable). DTX said that they were going for a more "subdued" severe weather event, rather than an "all out outbreak".

DTX:

AGAIN...AM LEANING TOWARD A SOMEWHAT SUBDUED EVENT...
AS OPPOSED TO ALL OUT OUTBREAK DUE TO ONLY MODEST SUNSHINE AND
INSTABILITY. WILL HAVE A MUCH BETTER FEEL BY MORNING THOUGH.

What I am not understanding here, is do they mean modest sunshine and instability would create an all-out outbreak? The punctuation in these discussions always seems to lack...

I will probably also right a detailed forecast, or attempt to, with the 18Z GFS, unless something signficant changes (i.e. total severe threat diminished greatly).

BTW...Rob Dale, I just started getting L2 data...

Robert

 

[Robert Dewey]

Well...The latest 00Z WED ETA is in, and its looking good for the Great Lakes. Relatviely deep low pressure will ride along lake MI, swinging a cold front through during prime heating (18Z-00Z). Excellent speed shear will exist, and depending on the exact shape of the low, I could possibly see winds backing to the southeast a bit with this event, which will determine exact helicity...Though attm helicity isn't too high. Models show plenty of instability with 18Z-FH ETA soundings off NSHARP showing anywhere between 1800j/kg-2200j/kg with a rather conservative parcel of 72F/58F (that seems odd for some reason). LCLs and LFCs will be pretty low, and that would certainly help the tornado potential, if one exists. After looking at the IR, I am worried that excess clouds will hang around, and could hinder any activity, but after todays tornado outbreak in IL/IN...I will keep my mind open. I will see what things look like in the morning, and decide if I will chase or not...

BTW... I am issuing a Tornado Watch for tomorrow across all the regions from MI to the Gulf.... :lol:

Robert

 

[Jeff Snyder]

Originally posted by rdewey

BTW... I am issuing a Tornado Watch for tomorrow across all the regions from MI to the Gulf.... :lol:

Robert

LOL :lol:

Unrelated to this thread, I'm throwing rules aside and I will begin issuing watches up to 3 weeks in advance. May 12th, 2004, Tornado watch in northcentral OK and southcentral KS...