8/21/07 NOW: NE/KS/SD

[Dustin Wilcox]

Similar to yesterday, Sean and I are along 275 very near Oneill NE, explosive devlopment just in the last 5 minutes, parameters are pretty high in this area, hopefully the lack of convection to the East will allow for better results today.

 

[Jeff Miller]

Intense supercell over Lake Andes, SD has recently split in the last 10 minutes. The southern split has turned right, and is heading for a larger complex of thunderstorms over O Neill, NE which is moving due east. Expect this to conglomerate into a well organized convective system and charge east.

Believe large hail threat will transition to a wind event as it nears the Sioux City general vicinity.

EDIT: Right turner has gone TOR WARNED as it encounters greater shear.

 

[Jeff Snyder]

Intense supercell over Lake Andes, SD has recently split in the last 10 minutes.

And a gorgeous split that is! Surface observations indicate that these storms (the cyclonic and anticyclonic pair) are located very near a warm front, which may provide enhanced low-level vorticity (the FSD VWP is pretty nice). Mesoanalysis indicates strong deep-layer shear across southern SD (decreasing as one moves southward through NE), which will support strong supercells. TBSS / "hail spike" showing up on multiple elevation angles now with that southeastern SD right-mover, and velocities are on the uptick (dealiasing errors showing up on 1.5 degree SRV scan attm).

I'd give the best tornado threat with this supercell, though I'm watching the cluster of cells developing along the front near and SW of O'Neill. There's plenty of CAPE (and low-level CAPE) to, perhaps, lead to a spin-up as storms develop southwestward along this front. There's also some good seperation between the O'Neill storms as the storms down near and south of I80.

EDIT: Sweet BWERs with both the cyclonic and anticyclonic supercells in southeastern SD! That cyclonic supercell east of Lake Andes is a near textbook classic supercell (very nice BWER, awesome hook echo, TBSS/hail spike, etc).

EDIT2: I made a brief BR1 and BR3 side-by-side graphic... GORGEOUS! http://www.tornadocentral.com/now/082107_2301_FSD_BR1_BR3.png

 

[Jeff Miller]

Amazing to watch as the northern part of the O Neill storm has also undergone its own split, creating a seperate supercellular storm right between the O Neill and Lake Andes Sups.

Tornadic potential for now is greatest at this time as I anticipate the entire feature to consolidate into an intense squall line.

 

[afischer]

4.25" hail reported at 6pm with the Charles Mix co. storm.

This event is strongly reminiscient of 7-15-04 with respect to the surface pattern, T/Tds, and the locations of the tor-warned supercells... though that event had more veered steering flow.

 

[Jeff Miller]

Keeping a close eye on the Lake Andes storm... Latest scan showing quite a hook starting to develop. This could be very close to producing if it hasn't briefly already.

 

[Jason Boggs]

Here is a look at that beauty of a supercell near Dante SD:

 

[afischer]

Spotters are apparently reporting hailstones as large as 6-8" in diameter in Dante SD, per FSD's latest LSR.

 

[Dick McGowan]

Spotters are apparently reporting hailstones as large as 6-8" in diameter in Dante SD, per FSD's latest LSR.

Wow! GR3 showing tops up to 67.5 with VIL's constantly in the mid to upper 80's. It looked like Kory Hartman was going to punch through that storm, but took a different route now. He's now heading south, already in the forward flank.