08/09/09 NOW: IA

[Jeff Duda]

Cell bow echo currently screeching east across central Iowa. Numerous reports of large hail (up to 2.5" just reported near Eldora) and high winds associated with it. The storm appears to be taking on supercell characteristics from time to time, especially with the formation of an inflow notch midway up the front of it. A look at a vertical cross section on GR2 revealed that this storm appears to be tilted upright still, indicating that, if it is going to become a line/bow echo and not a cell, it has yet to mature.

 

[Ryan Wichman]

It looks like Waterloo is right in the path of the storm...2" hail is NOT the way I would want to start off my day. A lot of wind and hail reports are coming out of this storm, based on velocity scans I'm not sure what the actual tor threat is attm. The storms seems to exhibit supercell characteristics at times, but the very unidirectional flow through the atmosphere will make it hard to really take on a classic sup shape. I would expect this storm to start laying down a nice cold pool here soon and start shaping into a bow....we'll see.

 

[Jeff Duda]

I've been watching it for a good hour and a half now, waiting for that to happen, but so far it hasn't.

 

[Ryan Wichman]

Some just reported TEACUP sized hail...I have heard of some strange reports, but that might take the cake.

 

[Chris Nuttall]

Teacup is actually a standard measurement used, you just don't see it very often. I don't think most people know how big a teacup is, so they usually default to one size bigger or smaller, which is grapefruit, softball, and baseball. Here's a good list of the "standard" references:
http://www.spc.noaa.gov/misc/tables/hailsize.htm

 

[Ryan Wichman]

Chris, I stand corrected. A teacup is not the first thing that comes to mind when I think of hail. Nor did I really study teacups for their size, but I appreciate the correction.

 

[Kevin Walters]

Damage to farm south of Wellsburg in Grundy county. Barn and machine shed destroyed, house had part of roof removed and windows blown out. Classic hurricane hailer in progress.

 

[Mark Sefried]

South central Iowa has backed SE surface winds attm. Although they are not very strong (under 13 knots or less) they may be enough at the low levels to get things to rotate some. So it may be wise to keep an eye out for the area.

 

[John Vandehei]

Looks like Michigan is about to get into the action. Broken line is forming up from near Chicago extending NE up to Grand Rapids. A pretty good storm over Lake Michigan looks to come ashore near Muskegon in the next half an hour. I doubt I'll try and chase anything. Sitting here at home looks to be as good as place as anywhere.

 

[Ryan Wichman]

Looks like Des Moines and the southern and eastern half of Iowa is going to get rocked over the next few hours. New complex of storms developing just west of I-35 should be able to take advantage of fresh atmosphere, strongly unstable air and decent lapse rates.

 

[Jason Harris]

Between Jackson and Rives Junction looks intriguing, warning includes

DAMAGING WINDS IN EXCESS OF 75 MPH

and GR3 hail estimates have all been ranging over 2. Seems like that section of storm might be increasingly organized though nothing impressive on SV1. Perhaps enough for a little spinner? on the other hand, latest scan looks light a new cell there muddying up the structure. Anybody taking pics out there?
update: just got tornado warning.

TORNADO WILL BE NEAR...
GRASS LAKE BY 835 PM EDT...
FRANCISCO BY 840 PM EDT...
JACKSON BY 840 PM EDT...

 

[Joel Wright]

Powerful bowing line segment east of Des Moines. Two mesovorticies can clearly be made out west of Cedar Rapids, and west of Iowa City.

Looks like the I-80 corridor is in for a rough evening as these storms race eastward. Additional activity in southwest Iowa as well.

Could be some serious flash flooding issues later this evening as storms continually train over the same areas. Best threat for this look to be from southwest Iowa into east-central Iowa. Synoptic surface low is forecast by the RUC to lift into eastern Iowa by late in the night. This may keep the LLJ focusing the heavy rains over the same areas, instead of the whole area shifting southeastward as it otherwise might have. Gonna have to keep an eye on how this all plays out...

 

[David Draun]

SPC Mesoanalysis Derecho Composites are maxed from the Quad Cities to Chicago. Tons of untouched instability in excess of 4500J/kg across much of northern IL in the path of this evolving event. A nice instability gradient is along the IL/WI state line. This is where I expect the bow echo to track along. This could take aim on the Chicago Metro toward the midnight hour. Several southbound outflow boundaries have stalled over the area as well which might be a good path for an embedded circulation to track along which has happened before in these situations. New isolated storms near the Macomb, IL area drifting northeast out ahead of the developing MCS could be indicators of the LLJ firing up. Northern Illinois and especially the Metro area have been spared much of the spring and summer but it appears we will get our share of severe storms overnight.

Could the SPC issue a PDS severe watch in the next couple hours?

 

[HAltschule]

Police Scanner reports from Linn County, IA reporting measured winds of 90 MPH.

 

[John Vandehei]

SPC Mesoanalysis Derecho Composites are maxed from the Quad Cities to Chicago. Tons of untouched instability in excess of 4500J/kg across much of northern IL in the path of this evolving event. A nice instability gradient is along the IL/WI state line. This is where I expect the bow echo to track along. This could take aim on the Chicago Metro toward the midnight hour.

Yeah, I was kind of noticing that. Looks like what hit lower Michigan may not be the final wave, at lease for the southern tier of counties. After the storms you mentioned move through Chicago, they could be waking me up sometime late tonight. Then, again, there may be enough of a cold pool along the I-94 corridor from this evening's storms to steer the overnight storms along and south of the MI/IN state line.