6/28/2005 TALK: North Central US MT/SD/NE, later IA/MN

Strating a thread because TORN watches are going up and there is already a tornado on the storm reports pages.

Looks like several fields of CU are starting to show up all across southern SD, so looks to start getting interesting.


Just pulled up the latest data from the SPC and the forecasts, looks like there is some strong energy and beautiful dynamics digging in from both the West and the Southeast, and a collission area for the two peaks of energy around southeastern SD.

I have no idea what that means.

Just got done reading an e-mail from the Turner County (SD) Emergency Manager, he's having a meeting with all county EMs at the FSD WFO. He said that Todd Heitkamp (WCM-in-charge) says that they are looking at two storm systems developing, one from the west-northwest, and another from the southeast. The one from the WNW looks to pack a punch of about 80 mph winds by the time it reaches FSD in a MCS/bow echo setup. Todd also said they're not sure what this field of energy will do coming up the MO river from W IA, but it looks to be interesting when they meet.

Again, I have no idea what that means.
Forgot to add - any chasers in the area need a nowcaster, drop me an email and i'll send you my cell number, I won't be able to go out tonight.
Looks like there is some good potential in extreme SW Saskatchewan today with a funnel cloud reported near Gull Lake and some nice tight cells south of Swift Current. i. I don't think the storms will get very big today but tornadoes are a definate possibility. I'm gonna save my gas money for Friday though but I will be home most of the evening watching what unfolds....

Just got off the phone with Bill at the NWS FO, he said that now they're looking at storms developing over SC SD and NC NE, moving NE, they'll hit that band of energy coming up from IA when the storms get between Chaimberlain 9V9 and Yankton YKN, explode in the major supercells, with bow characteristics, later becoming a large-scale bow echo with winds in excess of 90 mph. Ouch.
I love talking to myself in TALK thrieads...lol

Another MD just went up for SE SD, CU field is evident, supercells with "Full Range of Severe Possible"...What's that supposed to mean???? If you ask me, it means wind, hail, rain, tornados, the whole shebang. This may get interesting...

I wanna go chase :cry:
Well, a look at SPC/RUC Mesoanalysis graphics depicts a very favorable setup for tornadic supercell across northwestern and into South Dakota, where 3000-4500 j/kg MLCAPE is nicely juxtposed with 200 (central) to ~500 (northwestern) 0-3km SRH, yielding SCPs of 40 and Siggy Torn parameter values of 5-10... Surface obs show southeasterly to easterly surface flow beneath southeasterly 20-35kt 850mb flow and 30-35kt southwesterly 500mb flow.

Radar obs, however, depict a different situation. A broken line of storms developed near Rapid City and are pushing eastward. They have been unable to completely sustain themselves, however. Tilt 1 scans don't look too bad, but Tilts 2-4 show that only one or two of the cores have much strength aloft. The storm on I90 looks most promising given a recent slight right-turn and occassional couplet in the low-levels, but reflectivity is struggling and pulsing. Meanwhile, a left-split has been rocketing NNE and is about to collide with a storm in northern SD (don't have a county map in front of me attm).

It appears that the storms may be struggling to remain surface-based. RUC analysis is showing 25-75 j/kg CINH invof the storms, which, given the not-entirely-impressive surface convegence, may not be enough to allow for sustain surface-based convection. This does correspond well with radar obs, IMO.

So, the question appears to be whether these storms can become (and persist) surface-based. On one hand, nocturnal cooling is beginning to set in, which will further increase negative buoyancy and discourage surface-based convection. On the other hand, strong upper-level divergence is beginning to spread over the region, associated with divergence in the left-exit region of a nice 300mb jet streak nosing into the area.

I'd like to see a supercell be able to sustain itself in the awesomely-shear and highly unstable environment in northwestern SD, but the only storm up there now is struggling a bit.