7/19/06 NOW: MN / IA / WI / IL

[Jeff Snyder]

Ongoing severe, forward-propagating bow echo racing across southern Minnesota, with current ARX 88D velocitiy indicating widespread winds above 71kt on the lowest tilt. For whatever reason, the reflectivity looks considerably higher on ARX than on MPX... I know there's more attenuation loss with MPX given the heavy rain between the leading convection and the actual radar site, but that doesn't appear to be significant enough to account for the large difference in reflectivity. Regardless, I wouldn't be surprised to see significant wind damage north of Rochester any time.

Edit: MPX did a blanket svr warning, covering 11 counties! It actually looks more like it was intended to be a watch watch notification product, but it was filed under a svr thunderstorm warning (with text to indicate that).

Anyone have LII data up from ARX? I'm interested to see what the highest velocities are (LIII maxes out at 71kts IIRC). From the looks of it, I wouldn't be surprised to see some gusts above 80mph.

EDIT2: From the looks of the warning polygon for that very large warning, it looks like the warning met on duty accidentally clicked the point SE of Eau Claire, WI, which may explain why the warning text went out for 11 counties.

EDIT3: Looking at the RUC/SPC Mesonalysis fields, it appears as though these storms may not be entirely surface-based. MUCAPE is near 3000-4000 j/kg, but for a parcel near 1000m. The strongest winds, as indicated on nearby radars, may not be penetrating to the surface, which agrees with the observations of "only" 40-55mph winds in those storms. Lapse rates may be low enough to allow for positive buoyancy for "downdraft" parcels, which acts to accelerate the downdrafts near the surface back upward, thereby decreasing the intensity of the winds at the surface.

 

[Danny Neal]

looks like there is further development starting to the south of the MCS in east central iowa, while the northern end of is losing some of its punch! maybe the SPC will issue something else for eastern iowa and northern illinois? im thinking bout heading out, its been too long for me and chasing anything nowadays seems like a treat to me

 

[Tony Lyza]

I haven't seen the latest RUC, but I have seen the latest WRF run. It shows very little CINH progged over nrn IL, with SBCAPEs of 4000J/kg. The helicities progged are not great (100-150m**2/s**2), but I too am anxious and thinking of heading out west towards the LaSalle/Peru area this afternoon.

 

[David Draun]

KLOT is holding off on convective chances until after midnight so far for today, even with that bow echo/MCS racing southeast at speeds up to 70 mph! Right now there's lots of grungy low-based cumulus floating around out there. LCL's are around 800m. Thunderstorms are mere hours away, and KLOT says after midnight? I guess those storms are expected to fall apart fast. I'm thinking of heading out, but gas prices will probably keep me grounded.

I wonder how high the tropopause is today. Storms on monday had tops of up to 65Kft, according to SPC watch statements.

 

[Danny Neal]

if those storms hold together they will be at a milwaukee to chicago line by about 330 pm, spc thinks restrengthening is in line for the initial mcs with the strongest most damaging weather to arrive later tonight....storms in iowa and minn are moving east at 80 mph according to the weather channel so doing the math 80 miles an hour with storms 300 miles away i would say i head out west out of the city and meet the mcs at about 3-330 just west of aurora illinois

"KLOT is holding off on convective chances until after midnight so far for today, even with that bow echo/MCS racing southeast at speeds up to 70 mph!"

im on the southside of chicago and the forecast as per LOT is sunny all day and then storms after 3 AM.......: /

anyone know why the KLOT radar isnt working, the last image i got was 754 AM maybe its just my cpu not updating???? hmmmm

 

[David Draun]

To make matters worse, the KLOT radar has been down since about 8am CDT. I would hope they get that fixed soon. The Milwaukee and Quad Cities radars will show the action otherwise

The convection is now entering far NW IL. The southern flanks of the system are still quite intense. And even if the storms do fall apart, the outflow boundary that the MCS lays down will definitely explode later.

EDIT: Moderate risk area extended all the way south and east to Chicago! LOT still holding off on storms until at least evening, but have upgraded the local HWO.

 

[Danny Neal]

Svr t storm watch issued til 8 pm, i guess the spc and i thought the same about the strengthening Storms out of Iowa, although i have a feeling it will all stay west and south of my area, my target would be la salle-peru

 

[David Draun]

Svr t storm watch issued til 8 pm, i guess the spc and i thought the same about the strengthening Storms out of Iowa, although i have a feeling it will all stay west and south of my area, my target would be la salle-peru
[/b]

And storms remain out of the forecast until late tonight. Latest mesoanalysis shows the cap weakening especially toward Chicago. And look at all the CAPE advecting into the area from the SW! Broad areas of 4500+ and now pockets of 5000-5500 showing up! Potentially explosive situation developing. :blink:

 

[Danny Neal]

And storms remain out of the forecast until late tonight. Latest mesoanalysis shows the cap weakening especially toward Chicago. And look at all the CAPE advecting into the area from the SW! Broad areas of 4500+ and now pockets of 5000-5500 showing up! Potentially explosive situation developing. :blink:
[/b]

even the weather channel, although hardly ever reliable anymore, says today plenty of sunshine high 94 and then tonight late night chance of thunderstorms, some storms may contain large hail.......i would think especially KLOT would be on top of things maybe they are that busy that they cannot update their forecast??

anywho......i decided not to go out today seems like whenever i do it always hits hardest at home so im gona try that strategy and stick it out around these parts but if i had to go out i would pick the rochelle - mendota - la salle-peru area, IMO i dont think the north or northwest side of chicago will get much of anything but the atmosphere is cooking so maybe, the northern end will flare up??? i am monitoring the skywarn network along with dupage county and will county EOC and they seem to be sending spotters out to the southern ends of their counties.........by the looks of the radar at 150 pm looks like the southern counties in KLOT area will get the majority of the severe weather..... <_<

EDIT:: "THE STRONGEST STORMS ARE EXPECTED TO MOVE SOUTH OF
THE CHICAGO METRO AREA...AND COULD REACH A LINE FROM MORRIS TO
PONTIAC AROUND 330 TO 400 PM. FOR THE CHICAGO AREA...A LARGE
AREA OF RAIN AND THUNDERSTORMS WILL REACH THE FAR WEST SUBURBS
BY AROUND 400 PM." From Nowcast KLOT

my suspicions were true that the strongest weather will not hit CHI-TOWN directly :/

 

[Danny Neal]

hmmm storms are riding the warm front, the storms from clinton are almost moving due south now....interesting to see if these storms make it all the way down to peoria and kankakee, looks like the action will flare up later tonight

 

[Mike Hollingshead]

Sitting in Pocahantas IA in a library. Car about overheated again as I drove slowly around town trying to find this place. Looking like I might be here awhile(chase related not car/radiator related as I'm fine if I keep it moving). Some pretty sick indicies on the spc meso page right now with sup composite of 46 and siggy tor of 9. 3km ehi of 11 lol. Moisture convergence max is just nw of me just south of the MN border in nw IA. I almost wish this was a smidge more east than it is as 700 temps are pretty nasty here right now at 15-16c. Hopefully that can be overcome and we can see what will happen in this environment. I sort of think it will happen today with this intense heating that was underway pretty early. CIN is slowly eroding here right now. I'd think somewhere between GTG and FRM would be the spot to go, perhaps just south of there.

Edit: I'm wondering about maybe something more to the south now. The 16c 700 temps are actually more to the north and I now see something may have just popped up to the south along that boundary(on satellite). Less CIN in that area and the bullseye of the indicies. I should go look outside I guess.

Edit: 19z ruc has stuff there by 22z. Wonder if they'll lift over the boundary east too quick or if they'll be able to turn on it.

 

[Danny Neal]

THE NATIONAL WEATHER SERVICE IN THE QUAD CITIES HAS ISSUED A

* SEVERE THUNDERSTORM WARNING FOR...
BUREAU COUNTY IN NORTH CENTRAL ILLINOIS...

SEVERE THUNDERSTORMS CAN PRODUCE TORNADOES WITH LITTLE OR NO ADVANCE
WARNING. SOME WEAK ROTATION HAS BEEN DETECTED WITH THIS STORM."

Could this be gustnadoes??? or an embedded supercell? looks to me like leading edge turbulance

EDIT: im not sure if theres a new echo popping up right south of rockford or if thats the nuclear plant causing a false radar return......the last 3 frames or so a yellow/red small echo popped up and hasnt moved much

 

[Danny Neal]

anyone chasing around moline or the quad cities? i was listening to the skywarn network and some guy reported a tornado that went thru the north side of town not to long ago, it would be interesting to see if that was true or not..... it might have briefly touched down since in the warning text they did detect weak rotation in the thunderstorm

EDIT: im listening to the spotter network from the National Weather Service, and they reported an uncomfirmed meso in northern ogle county and a downburst in moline which answers my question about the tornado

 

[Scott Lincoln]

SEVERE THUNDERSTORMS CAN PRODUCE TORNADOES WITH LITTLE OR NO ADVANCE
WARNING. SOME WEAK ROTATION HAS BEEN DETECTED WITH THIS STORM."

Could this be gustnadoes??? or an embedded supercell? looks to me like leading edge turbulance
[/b]

Gustnadoes are not associated with parent storm rotation, and form along gust fronts and outflows of storms. They are mentioning something they are seeing on radar.... probably just making note of the possibility that this storm may become tornadic later. Many times in severe thunderstorm warnings where the atmosphere makes it possible for tornadoes they will mention the possibility for tornadoes to form with little or no warning, this is normal.

 

[Danny Neal]

Gustnadoes are not associated with parent storm rotation, and form along gust fronts and outflows of storms. They are mentioning something they are seeing on radar.... probably just making note of the possibility that this storm may become tornadic later. Many times in severe thunderstorm warnings where the atmosphere makes it possible for tornadoes they will mention the possibility for tornadoes to form with little or no warning, this is normal.
[/b]

yeah i know it is normal to hear that, but KLOT and KDVN or KILX rarely says weak rotation is detected, i always see "severe thunderstorms can and occasionally do produce tornadoes" so i pieced together the report i heard from moline to the storm moving thru the county, hmmm must have misinterpreted the statement then