3/25/07 NOW: IA/WI/MN/IL

[Jarrod Cook]

Portage Co. WI storm appears to be a low topped supercell. It's exhibited strong shear for quite some time now (sometimes gate to gate). I'm surprised there is not a TOR for it. Maybe they have ground truth though...

 

[rdale]

Not needed - as we've been discussing above, the low levels (winds, humidity, LCL) aren't conducive to tornado formation. About 5-10% of all rotating storms drop a tornado. Combine those two, and there is no reason to issue a warning.

 

[Mark Sefried]

Based upon the surface obs, I think that the low levels are condusive attm with the cell that is now entering Waupaca county WI. Surface obs are reporting SSE winds at 10 knots currently and 72/59 so the lcl's are definantly low enough. I am really surprised that this cell has not been tornado warned.

 

[rdale]

Rotation is very weak, winds are light, it's not moving towards a boundary...

 

[HAltschule]

Storm in Langdale County, WI just got a TOR Warning and for good reason. TVS signature with good to excellent gate 2 gate shear with it. Also 2.25" hail with the supercell. Seems like one of the best cells today as a tornado producer?!

EDIT: Look out White Lake, WI. Poss. Tornado on your doorstep.

 

[HAltschule]

FYI: SPC also just issued a MCD discussing the heightened tornadic threat in this area as there is an enhanced moisture boundary and an area of backed S/SSE winds creating more favorable shear for tornadoes.

EDIT #1: Radar presentation suggests that this tornado, assuming there is one on the ground, is rain-wrapped.

 

[Jarrod Cook]

Saying conditions aren't conducive to tornado formation is not correct. SPC put an MD out specifically saying the two cells of interest were entering a more favorable environment (e.g. backed winds as Mark suggested) and higher dewpoints.

And with a tornado warning on the norther cell, when the shear couplet looks equally (if not, less) impressive...I think the southern cell could have produced as well when it was mature.

 

[Brett Adair]

Where the cell was an hour ago wasn't very conducive......now the cell is actually moving towards the retreating warm front/moisture axis and seems to be rotating much stronger. I believe Rob was just trying to state that the severe was a better pull earlier given the less lift/shear away from the boundary. Effective SRH is MUCH higher near the boundary itself....hence the rotational couplet tightening and becoming more organized with the NE motion. That's all.

 

[rdale]

Saying conditions aren't conducive to tornado formation is not correct.

What I'm saying is that I disagree with SPC... I don't see that as an environment that is any better for tornadoes other than the fact it is closer to the boundary. If you look at the southern cell, it's barely even recognizable as a storm at this point so obviously conditions aren't good for a tornado where the moisture was better.

Not saying there won't be a tor on the Oconto Co storm, just saying I'd be surprised given the setup and I would have a hard time issuing a TOR warning. I find it more likely this storm will die.

Although that is one BIG advantage of TV - I can be on air and saying that there's a small chance of a tornado, for NWS it's black & white.

 

[afischer]

Haven't really been following the event, but the 00Z GRB sounding certainly looks supportive of tornadic supercells to me. 150mb deep BL moisture; very weak MLCINH with MLLFC around 1700m; MLLCL around 1100m; and a cute lil' sr-hodograph with 1km SRH over 200 m2/s2 for 35kt ENE movers. The temperatures in eastcentral WI have only dropped 2 degrees F since the sounding was launched, so the low-level thermodynamic envorinment should not have changed appreciably. As for why the southern storms are struggling... perhaps it is a lack of mesoscale or synoptic scale lift? Is the better DPVA farther west with the bulk of the convection? Dunno, but it doesn't seem to be because the environment invof GRB is bad...

 

[HAltschule]

FWIW, the current SPC Mesoanalyses do show an area of even more backed winds in and to the north of the immediate Green Bay area. In this same area, the current tornado warnings have been issued. It seems like a very logical, mesoscale reason as to why the the Oconto County cell had a TVS and very good g2g shear earlier whereas some of the other cells that are not in this enhanced zone have not.

EDIT: PS, that said, it looks like the TOR show is ending as the couplets have disappeared.

 

[HAltschule]

Funnel Cloud spotted 10 Miles NNW of Neopit with the Tornado Warned cell.

 

[Brett Adair]

Hmmm....I can see a slight cap still remaining.

Looks like SFC forcing isn't all that strong and the convective temp wasn't reached. I think if those dewpoints had been a little better the storms may have rooted and more tornadoes would have took place.

 

[Brandon Sullivan]

I simply meant, that the threat didn't appear to be as high as originally thought.. SPC had no fault in this and I am not criticizing them at all. Just saying a severe watch may have done the trick, but SPC was smart in putting out the tor simply to be in the right if something would become a problem.. End of Arguement.. Im sorry if anyone took my post wrong. But Im not going to lose any sleep over it.. This is a serious thread so Im going to end the arguement

 

[Jesse Risley]

Hmmm....I can see a slight cap still remaining.
Looks like SFC forcing isn't all that strong and the convective temp wasn't reached. I think if those dewpoints had been a little better the storms may have rooted and more tornadoes would have took place.

Brett, I have to agree with that analysis on dew points, which is why I sat this one out. All of this aside, I still would not rule out a few brief tornadoes in NE Wisconsin in the next few hours. I would expect things to go more linear in the next few hours.