06/23/10: NOW: IA/IL/MI/IN/OH

[nickgrillo]

Deep, moist convection has already initiated along the boundary in southeast IA -- in deference to a region of lowered sbLFC heights / eroded sbCINH (induced by strong sfc diabatic heating and moisture pooling along and south of the OFB). This convection should rapidly intensify as continued surface heating will erode any potential static stability within the inflow sector (allowing convection to feed off boundary layer parcels). Extremely favorable 0-6km deep-layer shear profiles (i.e. 45-55kts) and extremely large CAPE (i.e. SB parcel CAPE 3500-4500j/kg) will likely support a couple of cyclic supercells across southeastern IA and northern IL within the next few hours. Later, this could become a rather damaging wind event. I'm happy to see the insolation across southern MI... Favorable kinematic and thermodynamic profiles across the entire warm sector could possibly yield a derecho event this evening into tonight as initial supercells congeal into a synoptic-scale line.

 

[Dean Baron]

The convection in IA is still fighting some sort of inhibition. They're almost ready to explode, but for now something is holding them back. Not exactly sure what is keeping them from completely going, my guess is that whatever inhibition it is will be gone shortly. I dont like all the convection going up in that area though, hopefully one or two become dominant quickly and kills off the rest of the crapvection trying to go up right now.

 

[Scott Lasker]

CUrrently 30 miles west of Mendota. Nice cu building nicely just off to the west.

 

[Rob Gardner]

First Tornado Warning issued... Looks like the back ends of these crap lines will be the most producing until / if this thing goes cellular.. Looks like it might be more linear though :/

 

[nickgrillo]

I really hate the SW sfc flow (which will hinder much of the tornado potential with supercells). Nonetheless, the confirmed (by the public) tornadic storm to the west of Davenport doesn't look too bad, and I'd expect it to hold it's strength as it progresses into slightly more favorable low-level shear. Quite obviously surface-based, the convection moving into northern IL should continue to intensify as updrafts interact with the extremely unstable (i.e. 3500-5000j/kg sbCAPE) and sheared (>50kts of 0-6km deep-layer shear) background environment.

 

[Jonathan Eakins]

The DeKalb county supercell is showing some strong low level rotation on SRV.

 

[Skip Talbot]

Its like chasing a monsoon out there. The storms are very wet, copious amounts of rain, very little hail (at least that I could find). Super hazy, low contrast structure and generally poorly organized structure. The Davenport/Muscatine storm exhibited a big whale's mouth and rainy core with no apparent rain free base. It probably had a better looking base a half hour before I got there. The best structre I saw was on an unwarned storm that had a half assed attempt at a wall cloud west of Davenport before the line consumed it. Looks like everything has congealed into an ugly line now with just the Dekalb storm clinging to what little rotation it has left, although it looks like its morphing into the blob of a line too.

 

[MikeWeingand]

I agree with skip. I was just on the lee county tornado warned cell in northern il. Couldn't see a thing until it was basically right over me. There was some weak rotation and a lot of scud lifting up towards the base and pretty strong winds but that's about it.

 

[Robert Dewey]

My hopes still aren't too high for MI... Looks like "best" activity will probably stay south of I96/I69, and even that looks isolated as of right now. I also noticed dewpoints have mixed out a bit over SE MI -- Tds in the mid 60's as opposed to the low-mid 70's further south and west. This is leading to lower CAPE / higher CIN values. As seen on the radar, the northern cells near the IL/WI border are really struggling.

However, HRRR does show sfc moisture advecting back into southern MI by 03z, with SBCAPE reaching 1500-2000j/kg. It also breaks out convection beginning around 01-02z across far SW MI, and moves this eastward.

 

[J West]

Currently a cell is TOR warned in NE Wisconsin, which came up out of nowhere.

I'm at work and can't look at much but it seems the sun has been out up there all afternoon, so whatever cap may have existed is able to be punched through. I think the storms are lined up along the cold front...?

 

[Ian Contreras]

Rain rain rain rain and more rain. A pair of trucks (one nb and one sb) were on their side on I-57 between Chicago Heights and Frankfort. Tons of lightning too.

 

[nickgrillo]

Agreed on the topic of CINH (which is much stronger when using a mean 100mb mixed-layer parcel, indicative of the convective mixing). However, RUC does forecast an increase in surface-based instability -- mainly along and south of I-94 -- in the next several hours (i.e. sbCAPE 2000-3000j/kg) which could maintain (and possibly strengthen) the convective band pushing into the GRR / IWX CWA's (which has a long history of significant wind damage).

EDIT: Small convective cluster in central Jackson Co. has prompted TOR-warnings for Jackson and Washtenaw counties. Looking at SRV scans out of DTX, it does appear to have some decent low-level cyclonic rotation.

My hopes still aren't too high for MI... Looks like "best" activity will probably stay south of I96/I69, and even that looks isolated as of right now. I also noticed dewpoints have mixed out a bit over SE MI -- Tds in the mid 60's as opposed to the low-mid 70's further south and west. This is leading to lower CAPE / higher CIN values. As seen on the radar, the northern cells near the IL/WI border are really struggling.

However, HRRR does show sfc moisture advecting back into southern MI by 03z, with SBCAPE reaching 1500-2000j/kg. It also breaks out convection beginning around 01-02z across far SW MI, and moves this eastward.

 

[Robert Dewey]

Just reposting this because it's something you'll rarely see:

THE NATIONAL WEATHER SERVICE IN NORTHERN INDIANA HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
CASS COUNTY IN SOUTHWEST MICHIGAN...
ST. JOSEPH COUNTY IN SOUTHWEST MICHIGAN...
NORTHWESTERN KOSCIUSKO COUNTY IN NORTH CENTRAL INDIANA...
MARSHALL COUNTY IN NORTH CENTRAL INDIANA...
WESTERN LAGRANGE COUNTY IN NORTHEAST INDIANA...
SOUTHEASTERN ST. JOSEPH COUNTY IN NORTH CENTRAL INDIANA...
ELKHART COUNTY IN NORTH CENTRAL INDIANA...
EASTERN STARKE COUNTY IN NORTHWEST INDIANA...

* UNTIL 930 PM EDT/830 PM CDT/

* AT 824 PM EDT/724 PM CDT/...NATIONAL WEATHER SERVICE DOPPLER RADAR
INDICATED A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING
EXTREME DAMAGING WINDS IN EXCESS OF 90 MPH. THESE SEVERE STORMS
WERE LOCATED ALONG A LINE EXTENDING FROM 10 MILES WEST OF DOWAGIAC
TO 7 MILES NORTHWEST OF NORTH LIBERTY TO 11 MILES WEST OF KNOX...
AND MOVING EAST AT 55 MPH.

Storm does exhibit perfect bow echo qualities... and low level velocity scans are in excess of 70knts.

 

[Jason Bolt]

Now several TOR warnings have gone up along this line in kind of a catch all warning for these extremely high winds and spinups associated with the line.

 

[Chip Redmond]

By far the biggest tornado warnings I have ever seen. Will be interesting to see how it evolves over the next several hours.

Chip