07/04/05: TALK: GREAT LAKES

[nickgrillo]

The time has come for a TALK thread...

I still am not overly impressed by todays setup in MI, but it might get somewhere. If anything really good fires... I wouldn't mind going after it, but I am not expecting much more then a line with <70MPH winds coming through by mid-evening.

 

[Robert Dewey]

I still have mixed feelings about the prospects for severe weather. It looks like the basic MCS setup, but there seems to be an overall lack in SFC moisture pooling. Generally, July MCS events feature Td's up into the mid 70's with weak to moderate shear. In this situation, we have moderate shear, but instability is the big question. I don't know what's up with the RUC spreading <55F Td's across MI as the afternoon progresses (kind of a donut shape, upper 60's all around). This could very well be the result of mixing, as the layer just above the SFC through about 600mb is bone dry. If SFC dews remain high enough, and convection does develop - that wedge of dry air would significantly increase downdraft strength. I'm gonna go to bed, and see what's happening tomorrow.

 

[Robert Dewey]

Not much has really changed. Alot more sunshine than I expected, and temps should soar to 90F or a bit higher. Td's generally in the upper 60's to near 70F across far SE lower MI, with some isolated low 70's. Td's in IN appear to be bumping up several degrees in the past couple of hours, per METAR data. But, I have noticed the dews at several stations in south central MI and northeast IN drop SEVERAL degrees in just and hour or two - Now a report of 57F about 50KM southwest of LAN.

Shear remains decent in the low levels, with 20-30knts of shear between 0-3km - quite favorable for linear convection and bow echos.

The MCV down in MO/IL is racing northeast pretty quick as well. Tracking the main band, it appears to be moving at 35-40knts to the northeast. That would put it near LAN at 00Z-ish, and would definitely be a focal point for development.

I just hope our dews don't mix out... Modifying12Z RUC2 soundings for 18Z-00Z; if we are able to keep/gain a parcel of 90F/65F, that still yields 2800J/KG of SFC based CAPE. A parcel of 90F/67F would yield over 3500J/KG, so low level moisture is the key. A parcel of 90F/70F yields pretty close to 4800J/KG of SFC based CAPE. MLCAPE is quite a bit lower, as between 900-600MB is quite dry ("inverted v" sounding). In fact, a parcel of 90F/70F only yields 1300J/KG. But, that does have a positive; it would significantly enhance downdraft potential.

 

[Jeremy Lemanski]

storms are popping rapidly over lk michigan east of chicago, just south of what once was a bow echo that moved across the northern areas of chicago with high winds. This should merge and form a good line of storms that move ENE into michigan, with many places in the upper 80s and points in the mid to upper 60s.

Storms also going severe on the windshift in central michigan, with a cell in jackson county going from nothing to warned in about 30 minutes.

 

[Robert Dewey]

As I had feared - Deep instability wasn't realized today - as Td's did in fact mix out like the RUC forecasted. Instability was better across IL and SW lower MI, where a few severe thunderstorms did occur.