8/18/05: NOW: Great Lakes Area

[nickgrillo]

Current SPC Mesoscale analysis at 18z indicates that continuous clearing is occuring invof of the warm front/OFB draped over IL/WI, with insolation/instability increasing - with CAPEs now >2000J/KG spread across the region. Cloudcover along/near the WF has prevented stronger instability to develop most of the afternoon so far. Effective bulk shear continues to be very strong across eastern IA/northern IL/southern WI, ranging from 50-65kts in the warm sector along/south of the WF. Backing SFC winds invof of the WF is contributing to strong low-level shear as well (helicity >250 M2/S2). I think the rest of the clouds that are still lingering in northern IL will quickly burn off within the next hour or two, allowing for more ample instability to develop -- when this occurs, I'd expect strong supercells to develop.

 

[Andy Wehrle]

I'm becoming quite concerned about this new cloud deck that has advected/formed overhead. We had sunshine from about 12:00-2:00, but it is now fully overcast once again with the temperature starting to fall. The wf must be very close to here.

Edit: No sooner did I post, (the sky was as dark as it was at 6 AM this morning 10 seconds ago), then the sky began to lighten and we had a few moments of full sunshine. We're moving in the right direction.

Post-event edit: Uncanny.

 

[Jarrod Cook]

Any chasers in SW WI might be interested in Richland County, WI. There is a storm entering that county that is taking on supercellular characteristics (hook echo, meso). No TOR's yet.

Tornado Warning just issued for Richland County. Very strong rotation couplet near Viola moving to the ESE.

 

[Jeremy Lemanski]

This storm has produced damage, both to trees and homes, winds were est. to be 90mph.

Also, the Warning statement says the storm is moving east at 15, however it appers to be moving SE at around 30mph for those who are chasing the storm. There also is new development on the south side of this storm, moving toward the tornadic cell, which could lead to reduced vis. from the southern side of the storm.

EDIT, storm still appers to be heading SE or ESE, not east as the severe statement states. Speed 35-40mph.

 

[nickgrillo]

Well, it appears that the TOR-warned storm is rooted right on the warm front -- and has definitely taken on a supercellular appearance... Instability is >3000 j/kg (SB) invof of the storm -- with deep-layer shear >45kts as well... I'd see no problem with this storm producing more tornadoes (it's already produced at least one) and given the storm low-level flow (yielding particularly strong 0-1km SRH), a few tornadoes could be pretty strong... I hope somebody is on this storm...

 

[Jarrod Cook]

I hope somebody is on this storm...

This area of WI is not fun to chase in, as goes for most of SW wisconsin. Its all rolling hills and the roads can get crazy at times. Unless you're lucky, your best bet is to find a high spot and watch it if you could.

 

[nickgrillo]

Not at all surprised to see all these reports of tornadoes so far... There has been at least a 8-12 tornado reports from the pair of supercells in southern WI. Latest SPC mesoanalysis still showing a tornado-friendly envirement, with very strong deep-layer shear and >300 0-3km SRH (locally higher), with instability >2000J/KG across most of the region, which is yielding supercell composite params in the >12 range invof of the main supercells. Rotation appeared to have died down (the Madison-area supercells) a tad on radar earlier, which led to the expiration of the earlier warnings -- but spotters/hams reported multiple tornadoes on the ground, which led to another TOR for this storm.

 

[Sam Sagnella]

Damage has been reported in the city of Stoughton (pop ~12k) just to the southeast of Madison. There is a MAJOR velocity couplet northeast of Stoughton just N of US-51 and just W of I-90. Any motorists on the interstate are gonna have to deal with a potentially VERY large tornado emerging from the rain. :!:

Edit: Gr Level 3's LLDV is showing a value of 137kts. If windspeeds on the ground are anywhere near that, then this is definitely a significant tornado.

 

[Alex Lamers]

Just to let you all know, Andy Wehrle who posts often on this board, was in the path of a dangerous supercell thunderstorm at 6:37 when I told him that a tornado was turning right toward him as the supercell started to become a right mover. His IM box indicated a "log off" at 6:41 PM.

Milwaukee/Sullivan is going on the air now LIVE with a tornado message with a dangerous tornado with considerable damage in SE Dane County.

Please everyone pray that Andy is ok and that his house did not sustain damage. However the reports of the torandoes and house damage near his location are not good.

Thanks...

Alex Lamers

 

[Alex Lamers]

Andy is OK but they are still going Live on NWR and stressing the serious nature of the storm!

Stay safe out there if you live in SE WI particularly S Jefferson county. This sounds like it could be F3 or higher.

...Alex Lamers...

 

[Alex Lamers]

Apparently debris has been falling out of the sky in portions of Jefferson County. Still a classic signature with good couplets and gate to gate.

...Alex Lamers...

 

[Sam Sagnella]

It is absolutely incredible to watch the velocities from this storm; it appears that the meso that produced the Stoughton tornado has now weakened, but that another one is forming about 5 miles to the east. Fort Atkinson (pop 12k) is in the immediate path of this developing tornado.

DEBRIS WAS FALLING OUT OF THE PARENT THUNDERSTORM AS FAR EAST AS THE NWS WEATHER OFFICE IN EAST-CENTRAL JEFFERSON COUNTY.

W O W.

 

[Alex Lamers]

I don't like the looks of these mergers. If this heads even a few degrees north of east I am in trouble.

They are still live on the air here on NWR, saying this is the most serious storm of the summer and giving very detailed information on where the tornado is. They are doing an excellent job and the service they are providing seems similar to Moore, OK tornado.

...Alex Lamers...

 

[nickgrillo]

Based on the reports of the tornadoes/damages... I'd think the NWS would have considered issuing a Tornado Emergency -- considering there are a few populated cities in the path of these strong/violent tornadoes (Fort Atkinson, Jefferson, Whitewater...)!

 

[Sam Sagnella]

New velocity couplet and associated TVS are JUST west of Fort Atkinson at this time, and anyone chasing this needs to realize that this tornado is probably wrapped in rediculous rains so be careful.

Edit. Just as I was writing this, a new LSR - AT 735 PM CDT...TRAINED WEATHER SPOTTERS REPORTED A TORNADO LOCATED JUST WEST OF FORT ATKINSON.