06/13/05 TALK: Midwest through Oklahoma

[Mike Johnston]

Guys, be careful out there today chasing. Storm motion on cells developing is ENE to NNE from 25 to 40 mph, but some individual cells have shown movement even over 50 mph. Alot of the activity is fairly linear, so getting in position to intercept a cell may easily place you in the path of another one coming from behind at fairly fast speed.

 

[David Wagener]

North Norman getting hit pretty decently right now. Cells starting to fire all the way back through Lawton. They may need to nudge the watch down here west and south a tad. Other stuff firing in North Texas as well in Throckmorton and Shackelford counties.

 

[Bart_Comstock]

This also is probably old news but the Mod. Risk has been extended further south into the most western parts of tor. watch #0473 in south central Oklahoma.

http://www.spc.noaa.gov/products/outlook/d...k.html#topimage

 

[Brad Emel]

Classic flying eagle near Jerseyville, Illinois. Tornado warning just issued for this cell. It's really increased in intensity over the last 15 minutes.

Moving 248 @ 25.
Meso shear 17 m/s

http://www.brademel.com/stormtrack/flyingeagle.jpg

Linked to save bandwidth for you mobile people.

 

[Nic Wilson]

If you have a chance take a look at the visible satellite loop in northern TX. There are large scale gravity waves propagating westward against the mean flow...should be interesting to see how they interact with the front to the west.

 

[David Wagener]

Looks like the tornadic potential is increasing a bit on the southern OK storms. KWTV has a rotating wall cloud on the storm just east of Duncan.

 

[Bart_Comstock]

Mesoscale Discussion 1333 has been posted in nc tx, sc/ne ok, nw ark and, sw mo. Also in effect for that area is tor. watch #0473.

 

[Bart_Comstock]

Newton and Laurence County in Sw Mo have gone tor. war. The cell is just south of Joplin currently crossing over US-71.

 

[Mike Johnston]

On the phone w/ my dad, who lives in Nixa, MO - just S of Springfield. Sirens going off, sees wall cloud to the immediate west.

 

[beaudodson]

Tornadic cells continue to race across Southern Missouri. Tornadoes have been reported on the ground during the past few minutes (Texas County). Looks like the atmosphere has not been touched across most of Southeast Missouri and Southern Illinois and then into Western Kentucky. Should be a new watch shortly. Here in Western Kentucky temps are still near 80 degrees. Looks like the storms may still be severe for the next several hours.

 

[Chris Sokol]

While today was no comparison to yesterday, it was still a fun chase. Followed the Shawnee-Seminole cell, then reversed to pick up a cell just north of Prague. Home in time for supper...unlike last night (actually, it was 3 AM).

Total gas used: $5.00

 

[Joel Wright]

Wow, what a let down in the state of IA. Things just didn't come together very well at all. This storm almost looked like an early spring type system at first glance, the kind that produce low topped mini sups. I guess it ended up behaving quite similarily to one as well.

 

[Bill Schintler]

RE: Poor performance in IA on 6/13

Wow, what a let down in the state of IA. Things just didn't come together very well at all. This storm almost looked like an early spring type system at first glance, the kind that produce low topped mini sups. I guess it ended up behaving quite similarily to one as well.

Several negatives in IA yesterday...
1) Morning guidance suggested that the first of a couple of shortwaves would affect the central part of the state by early afternoon. As the day played on, the mid/upper-level support arrived much later then predicted by the models, which left all but the western portions of IA in subsidence until the evening. This was visually evidenced by a CU field that developed in CNRTL IA early in the period which then did very little from the late morning on, despite decent insolation that was in progress.
2) A surface reflection of the advertised shortwave was predicted to develop across central IA by early afternoon in the form of a pressure trough/confluence line with surface moisture convergence along it and slightly backing winds to the east. This feature never developed, and most of the state continued with S to SWRLY surface winds during the afternoon and evening.
3) Once storms did get organized in the western part of the state and move eastward into the increased instability, the storm organization was primarily linear with a few “tail-end Charley’sâ€￾ down towards the south end, one of which did produce a few TOR reports in SCNTRL IA. Overall, the storm organization relative to inflow from the surface through 850mb was poor because of the SWRLY component of inflow into a N/S-oriented storm line moving east.
4) Finally, instability was actually quite poor. The 18Z KDVN sounding was pathetic. Despite good moisture (surface dews AOA 65F), poor lapse rates made for terrible CAPE’s. This did improve slightly in the afternoon into the evening with cooling at 500mb with the approach of the upper trough. However, with cooler temperatures also advecting in at 700mb the lapse rates in the 700mb to 500mb layer didn’t improve much. If I recall correctly, the 00Z KDVN sounding only showed an MLCAPE of 425J/kg along with little or no inhibition.

- bill

 

[Glen Romine]

Re: RE: Poor performance in IA on 6/13

Several negatives in IA yesterday...
... As the day played on, the mid/upper-level support arrived much later then predicted by the models, which left all but the western portions of IA in subsidence until the evening. .... Finally, instability was actually quite poor.

- bill

I think these are some good points Bill - but I think you could also construct an argument that the primary killer for yesterday in that area was strong midlevel subsidence. While there was a warm advection pattern below 850 mb (south-southwest surface wind veering to westerly at 850 mb), the flow was strongly backing with height from 850-500 mb (from westerly to southerly again), which is a signature for cold air advection in the layer, with a warm air advection pattern again above this. What that spells for atmospheric profile evolution is a tendency for building a strong subsidence inversion at mid levels, which is clearly growing in strength in the time series of soundings from DVN yesterday. Eventually upper level divergence started to erode the mid-level inversion and allowed for late development of storms.

Unidirectional shear from 850-500 is often tolerable, but sustained backing is typically a bad sign.

Glen

 

[Jeff Snyder]

I agree that, storms aside, the environment itself just wasn't any good, especially not for a 15% hatched tornado, moderate risk assessment. The 18z soundings from Omaha and Davenport were just horrible in terms of thermodynamics. As Bill said, lapse rates were very poor, as contributed by subsidence that Glen noted. This seemed like a CYA event for many given the strong shear aloft and fast storm motions expected, resulting in the possiblity of a longer-track tornado, though the lack of instability would likely preclude a long-lived tornado IMO. This type of outlook tends to come with early spring systems when instability is poor but shear is strong (we've had this several times in OK/TX earlier this year -- e.g. 4-25-05 in northern TX and extreme southern OK with a MDT risk in poor instability). High FAR, but pretty high POD as well.