8/26/04 NOW: Plains, Midwest

[Mike Peregrine]

MCD #2118 issued for Iowa prompts this NOW thread.

http://www.spc.noaa.gov/products/md/md2118.html

In addition, radar reflectivities indicate initiation has occurred in north central Iowa.

Satellite observations include CU pockets extending in linear formation along boundary throughout Northwest to Northcentral Iowa southwestard into Nebraska. Additional CU is noted along Nebraska-Kansas state line in an area more highly capped.

It's time to assist field chasers with realtime satellite and radar observations that may prove helpful during the remainder of this event (if one should actually happen to occur). Targeting and forecast discussions should remain in the forecast thread.

 

[Jeff Snyder]

LOL again for my commentary, you can see some disconnect between forecasts at SPC... The MCD wording of "perhaps a couple of tornadoes" doesn't seem to support the 15% tornado probability that is outlined in the Day1. Heck, I've seen that same wording used for low-end slight (2-5%) probabilities.... This just goes to show that even at the "professional" level, there's still plenty difference-of-opinion...

To get my post on-topic... There is an isolated cell that has developed rapidly in northcentral IA in the past 15 minutes. Sfc plots would put this storm right on the boundary (confirmed by radar fine-line of sorts also). If this storm can organize sufficiently, it looks as though it could be the first good supercell of the "event"... T-Td depressions are generally in the 10-15 degree range, yielding (at that elevation) sufficiently-low LCLs for us to check that of the list of favorable ingredients for tornadogenesis... Additionally, winds are very backed (to the SE) east of the storm along the boundary. I'd expect to see a tornado watch issued at any time now (3:40pm).

EDIT: Indeed.... The storm northwest of Fort Dodge now has a tornado warning with it.. There are a couple other storms on that same boundary... TCU extend back to the southwest, but I think it's going to be difficult to break the cap when considering the CINH on the 18z Omaha sounding.

 

[Mike Peregrine]

* SEVERE THUNDERSTORM WARNING FOR...
HANCOCK COUNTY IN NORTH CENTRAL IOWA.

* UNTIL 445 PM CDT.

* AT 349 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING GOLF BALL SIZE HAIL...AND DAMAGING WINDS IN EXCESS OF 60 MPH. THIS STORM WAS LOCATED 13 MILES SOUTHWEST OF BRITT...OR 32 MILES NORTHEAST OF FORT DODGE... AND MOVING NORTHEAST AT 25 MPH.

---------------------------------------

Additional initiation is now noted to the southwest of the storm noted above ... looks like we may have a line of supes pretty shortly -

 

[mikegeukes]

Just issued:
WW 788 TORNADO IA MN MO NE WI 262105Z - 270300Z
http://www.spc.noaa.gov/products/watch/ww0788.html

Profiler: Slater IA
http://weather.cod.edu/mcprofiler/SLAI4.6min.gif

Radar Images: Des Moines IA and Omaha NE
http://weather.cod.edu/analysis/paulradar.pl?DMX
http://weather.cod.edu/analysis/paulradar.pl?OAX
http://www.wunderground.com/radar/radblast.asp?ID=DMX
http://www.wunderground.com/radar/radblast.asp?ID=OAX

SPC Mesoanalysis:
http://www.spc.noaa.gov/exper/mesoanalysis.../s2/index2.html

Satellite: Visible Image Centered on Des Moines IA:
http://vortex.plymouth.edu/cgi-bin/gen_mci...1&size=768x1024

Mike

 

[Glen Romine]

Originally posted by mikegeukes
WW 788 TORNADO IA MN MO NE WI 262105Z - 270300Z

Mike

Check out the size of that sucker! Hill City KS to Milwaukee, wow. Not sure what to make of the Pocahontas cell - sure it looks good in reflectivity - but the velocity images are not that great. A svr was issued for the downstream county - so maybe they are backing off now. Cloud field over extreme se NE still toughening up.

Glen

 

[Mike Hollingshead]

Dang those became supercellular so fast...two with hooks near Ft. Dodge. Something needs to happen sw down that line or I'm going to be PISSED.

 

[Mike Peregrine]

* TORNADO WARNING FOR...
EASTERN POCAHONTAS COUNTY IN NORTHWEST IOWA.

* UNTIL 445 PM CDT.

* AT 353 PM CDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO. THIS DANGEROUS STORM WAS LOCATED 7 MILES SOUTHEAST OF POCAHONTAS...OR 23 MILES NORTHWEST OF FORT DODGE...AND MOVING NORTHEAST AT 25 MPH

 

[Jeff Snyder]

Both those cells have nice reflectivity structures above Tilt 1... I especially like Tilts 3-4, where you can see very nice flying-eagle / V structures... I'd think we'd get more development to the southwest of those cells, but LCLs tend to get high the farther southwest you get...

Whatever the case, those couple of supercells on the front/boundary in northern IA should begin to turn right soon (and move to the east or southeast) as their radar presentation indicates supercell characteristics.

 

[Glen Romine]

Originally posted by Mike Hollingshead
Dang those became supercellular so fast...two with hooks near Ft. Dodge. Something needs to happen sw down that line or I'm going to be PISSED.

Maybe you are in luck. I see something trying to get going midway between Lincoln and Falls city.

Glen

 

[mikegeukes]

Severe Weather Events:

IOWA:
419 PM CDY 2.75 inch hail Gilmore City in Pocahontas County
427 PM CDT 3.00 inch hail Kanawha in Hancock County

Mike

 

[Mike Peregrine]

Even with the higher LCLs further southwest, it is pretty dang tempting down there! ... Anything that develops in that pocket has access to tons of moisture ... and will develop out ahead of the line in front of the boundary - possibly maintaining better isolation.

Core intensity of the Iowa storms have now reached 70DBz.

 

[Mike Hollingshead]

Yeah I see that and am wonding if I should move or not. That line trials straight sw and is north of me and that thing between Lincoln and Beatrice is south of this front the sups are on. I feel like I need to go somewhere but don't want to leave the front just north of me. Though last scan and yellow dbz on whatever is forming down there........ If that forms and goes east I have little chance at catching it. Crap crap.

 

[Glen Romine]

Originally posted by Mike Hollingshead
Yeah I see that and am wonding if I should move or not. That line trials straight sw and is north of me and that thing between Lincoln and Beatrice is south of this front the sups are on. I feel like I need to go somewhere but don't want to leave the front just north of me. Though last scan and yellow dbz on whatever is forming down there........ If that forms and goes east I have little chance at catching it. Crap crap.

It shouldn't move too fast - but looking at its environment, relative to the hailers in IA - it should have a MUCH better chance of producing. Good luck!

Glen

 

[Mike Peregrine]

That cell is rapidly beginning to intensify ... looks to possibly run the core through Neb City and head east toward Shenandoah - or maybe just north of Shen -

I'm still thinking that pocket near Andrew Co. Missouri (north of STJ) may be about to break out as well -

 

[mikegeukes]

IOWA
AT 442 PM CDT...SPOTTERS REPORTED A FUNNEL CLOUD NEAR HUMBOLDT.

Storm that recently popped up.
Severe Thunderstorm Warning for Otoe County NE and Fremont County IA

Tornado Warning for Humboldt County IA until 530 PM CDT
Tornado Warning for Wright County IA until 545 CDT

Mike