9/21/05 NOW: WI/MI/MN

Few severe thunderstorms now ongoing across in ne WI near the warm front. Obvious supercell to the north of Heshena... With large hail likely associated with it (>60 VILS) and given the favorable low-level and deep-layer shear across the area, I'd definitely wouldn't rule out a tornado or two associated with these storms...
 
With dew points only in the mid-50's, the LCL is nearly 7000ft and that'd be quite a tube to get down to the surface! Nice convergent rotation in some of those cells but I can't imagine there's going to be much TOR threat as the spin doesn't look very strong at all.

I want to know what sort of whopper of a fire is going on northwest of Milwaukee - the GRB radar shows what looks to be a massive smoke plume extending nearly 60 miles but I can't find anything on sat.

- Rob
 
Pretty strong convection in MN right now. Tornado and severe thunderstorm warnings active. I see rotation very clearly, and haail is absolutely there, with a VIL of 78, what can you expect. This is a very thin storm, almost a line segment. WI did indeed get hail, but nothing to worry about, tops being .50 in.
 
I'd think even thou the LCLs are high invof the Sterns county storm... It's pretty much right on the warm front, therefore - I'd see it becoming more SFC based. Boundary layer is pretty unstable along/south of the front - with widespread 2000-3000 SBCAPE.

EDIT: Storm to the southwest of Sterns county has just been TOR-warned too... Very nice couplet/low-level mesocyclone apparent right between Willmar and Kandiyohi. Nice and isolated, too!
 
It's amazing to see how fast these storms can evolve. The storm that was far away, is now tornado warned. And the cell at the SW side, now has a meso-rotation with very high dBZ values. I think I am beginning to see a hook echo in Stearns county! Yes, I'm sure now it is! It has two meso rings on it, and a TVS. Nick, do you see the Hook?
 
Watching this one on radar. No reason for me to leave as it appears I will probably be in the middle of this one. Just as I write this, I'm hearing the tornado sirens going off. I'll report anything this happens here of course.
 
Four Tornado warnings currently active in MN, rotation is increasing, and is quite strong. I wonder if this will drop a tornado or two. There is a rotation-segment, thats tight it is 8.0 nm in diameter.
 
* AT 610 PM CDT...RADAR INDICATED A STORM CAPABLE OF PRODUCING A
TORNADO...13 MILES WEST OF LITCHFIELD...OR ABOUT 12 MILES EAST OF
WILLMAR...MOVING EAST AT 30 MPH. THIS STORM HAS PRODUCE FUNNEL
CLOUDS NEAR ATWATER IN KANDIYOHI COUNTY.

I definitely would pay attention to the Kandiyohi-Meeker county storm... Nice strong, tight low-level mesocyclone near Grove City. I'd have to bet the funnel cloud reports from this thing are authentic...
 
Yes Nick, the Kandiyohi-Meeker county storm, is even developing a Hook Echo. How are you able to see a tight low-level mesocyclone?
 
Very clearly a strong storm up there. Looks a little too close to what I assume would be suburban areas. Latest radar showed some weakening. Hope whatever tor happens to drop that it finds an uninhabited space and tears up only a field or two.

Doubtful that any other storms will get as strong and this one seems to be weakening. So maybe not today.

>edit<
One tor report so far so I guess my assumption above was not on target. Wonder if Chris got near that cell in time.

--
Tom Hanlon
 
Wow, this was very intense. Probably the most intense I've ever been in. I recorded 1 inch of rain but I'm guessing we got more. Just writing this my power has flashed twice but I'm on battery backup. Winds had to be at least 75MPH. I have some minor water damage for the first time ever. My sliding glass door couldn't take the wind and rain and water starting coming up out of my floor. This is only a 2 year old house. Some minor street flooding and tree damage. I haven't gotten out to survery my house but wouldn't be surprised to have some roofing missing. I could go on forever but just keep an eye on this one.
 
Wow, what a severe weather mess thi sis. This is a very very powerful storm system, and has dropped numerous funnels and has reports of a tornado on the ground, and, could still possibly be. It will be heading towards the twin cities if it is in fact on the ground. Rotation is EXTREMELY strong, and is generating new meso's/TVS' every second practically. Can we classify this as a Supercell? Wow, a hail report of 2.75 in, that's pretty big. There has also been some wind reports from this storm. I'd say this is a pretty dangerous situation. I hope someone will have pictures of this!
 
Wow, just wow......3 tornado warnings, 7 thunderstorm warnings, and now 4 flood warnings....this thing just keeps churning.
 
Andrew,

I would say that the storm that approached and passed immediately north of the Twin Cities was an HP supercell, with a very strong, rain-filled RFD. The storms have now taken on the look of an MCS, so the tornado threat is diminishing with this cluster. Also -- it's relatively common to have meso and TVS indicators tripped for strong shear along MCS gust fronts. Such indicators do NOT usually indicate a tornado potential -- just horizontal shear along the gust front. Yes, you can get brief gustnado type activity along this area, but a TVS along the leading gust front of an MCS USUALLY doesn't represent the same hazard as a TVS in the updraft of a supercell...

Latest LSR:
0703 PM TSTM WND DMG ANDOVER 45.26N 93.33W
09/21/2005 ANOKA MN LAW ENFORCEMENT

THREE HOUSES DESTROYED...PEOPLE TRAPPED IN DAMAGED
HOUSES.
 
Media reports large steel A frame transmissions lines down, one of them square on top of a car in the northern Twin Cities metro.
 
When supercells begin there line/bow out that usually means the storm has become primarily outflow dominate. Which usally undercuts any circulation that trys to occurr below the storm. As Jeff pointed out that it is not uncommon to get gust nados or spin ups along the gust front. So andrew basically thats the case as storms line out they gust out becoing downdraft dominate pushing the energy ahead of the cell.
 
Originally posted by Andrew Khan
So it's no longer a supercell then, it's just an MCS? Why did the tornado threat die down here after?

For a number of different reasons...

Including nocturnal boundary layer cooling (although there is some SFC-based instability still spread across southern MN) and although the threat for severe thunderstorms still continues... It'll be in the form of either damaging winds (as the storms gust out) or large hail. Often, after sunset, any isolated cells will form into a line - and then progress through the rest of the night a MCS. This, of course is not always the case, but I'm just saying...
 
Thanks for explaining it, Kurt, Nick and Jeff. These storms still have a number of flood warnings and severe thunderstorm warning on them, however.
 
Looking at the reports, it appears that this supercell did more nontornadic damage damage than many tornadic supercells produce. There are 2 reports of tornadoes in MN, but there are many more rather remarkable reports of intense wind damage in the northern Twin Cities metro area. On radar, it looked like an HP beast with a very intense, rain-filled RFD, as it crossed the northern metro, before transitioning into an MCS as it crossed into WI.

The 0z MPX showed ~450 0-3km SRH with 2250-2500 CAPE (extrapolated to the equilibrium level since the sounding ends in the mid-levels). Given the rotation evident on radar, it MAY have been a tornado, but the times don't really match up well with radar imagery for me to suspect a tornado. I'd bet much of it is >90mph winds in the wet RFD.

Below are some of the more high-end reports...
http://kamala.cod.edu/offs/KMPX/0509220308.nwus53.html


0650 PM ROGERS - HENNEPIN MN: TRAINED SPOTTER
APARTMENT BUILDING WALLS BLOWN IN.

0703 PM ANDOVER - ANOKA MN: LAW ENFORCEMENT
THREE HOUSES DESTROYED...PEOPLE TRAPPED IN DAMAGED HOUSES.

0704 PM ANDOVER - ANOKA MN: TRAINED SPOTTER
3 FOOT DIAMETER TREE DOWN.

0707 PM BROOKLYN PARK - HENNEPIN MN: TRAINED SPOTTER
GODFATHERS PIZZA WALL BLOWN IN.

0707 PM BROOKLYN CENTER - HENNEPIN MN: TRAINED SPOTTER
3 FOOT DIAMETER TREE DOWN ON TOP OF HOUSE.

0708 PM RAMSEY - ANOKA MN: TRAINED SPOTTER
3 FOOT DIAMETER TREES DOWN.

0708 PM COON RAPIDS - ANOKA MN: TRAINED SPOTTER
SEVERAL 12 INCH DIAMETER TREES UPROOTED

0712 PM MOUNDS VIEW - RAMSEY MN: TRAINED SPOTTER
ROOF REMOVED FROM MOBILE HOME. MANY TREES DOWN. POWER LINES DOWN.

0712 PM MOUNDS VIEW - RAMSEY MN: TRAINED SPOTTER
ROOF OFF OF MOBILE HOME...TREES AND POWER LINES DOWN

0715 PM COON RAPIDS - ANOKA MN: STORM CHASER
LARGE PORTION OF ROOF REMOVED...TREES BROKEN IN HALF.

0720 PM BLAINE - ANOKA MN: TRAINED SPOTTER
HOUSES SEVERELY DAMAGED...ROOF TORN OFF HOME AND ON FIRE...NEAR MADISON SCHOOL.

0721 PM BLAINE - ANOKA MN: TRAINED SPOTTER
ROOF OFF OF TWO HOMES NEAR JACKSON AND 104TH COURT

0730 PM FRIDLEY - ANOKA MN: TRAINED SPOTTER
SHED COMPLETELY DESTROYED

0730 PM FRIDLEY - ANOKA MN: TRAINED SPOTTER
15 INCH TREE DOWN

0737 PM NORTH ST PAUL - RAMSEY MN: TRAINED SPOTTER
4 FOOT DIAMETER TREE DOWN.

0732 PM MINNEAPOLIS - HENNEPIN MN: LAW ENFORCEMENT
*** 1 FATAL *** LARGE TREE BRANCH FELL ON TOP OF VICTIM.
 
Jeff, are you saying that there could have been a possible tornado, in the break between where the radar sounding end and begin? How can you tell what a HP/LP/Classic Supercell looks like on radar? I have occasionally been able to identify, them, but sometimes it becomes more difficult. I am interested to see if anyone has any pictures of this thing. BTW, there is still two flood warnings and one thunderstorm warning still in MN.
 
After watching all the local news reports, the damage is fairly bad in several urban areas. From what I saw, it did not appear to be damage from a tornado. Several homes have been destroyed, several roads have been shut down, many reports and pictures of golf ball and even what appeared to be near baseball size hail, it seems nearly every road is flooded to some point, and at last count 160,000 homes were without power.
 
Originally posted by Andrew Khan
Jeff, are you saying that there could have been a possible tornado, in the break between where the radar sounding end and begin? How can you tell what a HP/LP/Classic Supercell looks like on radar? I have occasionally been able to identify, them, but sometimes it becomes more difficult. I am interested to see if anyone has any pictures of this thing. BTW, there is still two flood warnings and one thunderstorm warning still in MN.

"Radar sounding"? :lol: :wink:

The 0Z sounding, as Jeff mentioned, showed strong low-level shear/instability... Then, radar coinsided that with rotation on the storms where the tornadoes were reported. For the Atwater report, I'd have to say it's authentic... As radar was showing a nice low-level mesocyclone at the time of the report(s). Now, the report near the Twin Cities is certainly questionable.

You'll often notice that Classics have that "flying-V" shape to them on radar (of course, not always present)... While HPs are more grungy looking, and sometimes take on the "kidney bean" shape on radar. LPs often show very low DBZ associated with them... In turn with the 6/7/05 Kadoka, SD LP... Which was producing a tornado - And had a 40 DBZ reflectivity at the time!
 
Sorry about the 'Radar Sounding' lol. I thought he was saying that. Anyway, this will help me to identify supercells on radar. I need to keep studying how they look and variate.
 
> I was sitting at 10 and 65 near Mounds View around 7pm. I watched the storm coming in and saw what could have been a tornado in the distance, but I think it was just low scud, and blowing dust. As it got right on top of me, the south side of the notch REALLY wrapped up. Beautiful, low meso, mothership with striations on the bottom. Just below the cloud base, was an arced line of scud, that was dancing around the edge of the meso like a merry go round. It was breath taking. Within the minute, the sirens went off. It was to my south, (Near Brooklyn Park) I headed south on 35w to 694, where I saw MANY power flashes to my southwest. (Fridley, New Brighton) Fruther south on 694, between 35e and 35w, I saw a bunch more power flashes and a 3 foot long branch, about a half inch in diameter, landed on my back window, while I was driving 40 mph. At that point I got very nervous. I inched my way to Maplewood where I was supposed to take pictures of a concert, only to find the whole area without power and the show postponed till thursday night.

Doug Raflik
[email protected]
 
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