Chase Case #7

[Pat Lawrence]

Feel free to state the date and/or location -- first person to give the correct date wins

Tornadoes did occur..

Here are the 12Z maps and soundings:

SFC:

500mb

All upper charts use temperature, dewpoint depression, and heights in the station plots. The 300mb map has wind shading at ~ 50, 70 and 90 kts, and includes divergence.

850mb
700mb
300mb

Soundings:
Midland TX
Shreveport LA
Norman OK
N Little Rock AR
Topeka KS
Salem-Lecrone IL
Peoria IL
St Cloud MN
Green Bay WI

I'll add 15Z and 18Z surface analyses later.


Pat

All maps were generated by Digital Atmosphere

 

[samuel stone]

I dont know the date but it is similar to may 13th, 2005.

 

[Mike Peregrine]

At first I thought this might be April 7, 2002 (Throckmorton), just because of the surface data out of Texas, but this looks too warm to the north to be that day, since it stayed cool and murky north of the warm front. My eyes are still drawn to Texas, though ... the sounding out of Midland is looking good, showing instability and good curvature, so I'm going to go with somewhere in central Texas for this. Probably another Throckmorton day other than 04/07/02, since tornadoes seem to love that town.

 

[Charles Kuster]

I will start at Duncan, Oklahoma and wait for the next set of data. I will definitely be prepared to move further south depending on what the 18Z data shows, but for now I am going to stay at Duncan.

 

[Scott Olson]

I'll go for the southern setup as well, I just can't ignore how dry a lot of the northern soundings are. Im also not a big fan of the wind profiles for these areas. However, If I did chase the northern target I would chase Stevens Point, moisture is not ridiclously shallow and should increase, winds should back more and increase in speed and would create quite a good amount of low level wind shear. Most important the OFB from Madison should find its way there for some interaction and may further create enough rotation to ignore other factors.

I prefer the southern target for outbreak potiental. The low isn't very deep but the directional shear looks more classic, wish there was more speed shear but that could change. It looks as though the northern cyclone could deepen more with some help from the left exit region. The fog is okay with me, keeping the LCL's low and creating some differential heating boundaries.

Im not overly sure but I'll goto Dallas and wait for my data...

 

[Mike Hollingshead]

Boy -19c at 500mb with morning obs of of 60/54 and a nice sfc boundary pushing east under strong sw flow aloft. Give me the lfq of that upper jet and the deeper sfc low with those dews. A 996 in the north or a 1011 in the south. I'll take the north target, but a bit south on the sfc trough up there. I'm going to the quad cities in se IA.

 

[mikegeukes]

Hint Peoria IL, Salem IL and St Cloud MN, no longer have soundings

Mike

 

[Mike Hollingshead]

Hint Peoria IL, Salem IL and St Cloud MN, no longer have soundings

Hmmmm, it isn't 1974.

 

[Pat Lawrence]

Hint Peoria IL, Salem IL and St Cloud MN, no longer have soundings

Mike

Yes, but when did they stop launching balloons...that is the key...kinda, sorta

Stop giving hints, Mike

Pat

 

[Mike Peregrine]

wow - interesting ... it's not May 4, 1977 is it -

Cool that you used Digital Atmospheres for this, by the way ... this makes me want to get it again -

 

[Scott Olson]

Okay before more data I will go with more northern Target listed in previous post, I like the moisture/instability/shear of the southern setup more. But I got a *feeling about the deeper northern cyclone, OFB, and backed surface winds...

 

[Mike Umscheid]

wow - interesting ... it's not May 4, 1977 is it -

Cool that you used Digital Atmospheres for this, by the way ... this makes me want to get it again -

I don't know the date on this one... but looks like a west TX or western-Central TX day to me. My early aftn data stop is ABI.. H7 cold front coming out of NM and mid-teens 850mb dews at MAF, can't beat that..

 

[Robert Dewey]

I like Central / Eastern TX... Good moisture, nice backed SFC flow, 700MB thermal axis should be pushing east of the region late afternoon (allowing for a weakening CAP), and the shortwave over the SW... Decent shear is present too, so I could imagine this being a day that produces a strong tornadoes.

 

[Gabe Garfield]

On a day like this where there isn't a good juxtaposition of shear/instability on the large scale, it's a good idea to target where there is large CAPE and sufficient shear. With this in mind, west Texas looks to be a very good target based on the Midland sounding. I think the surface low or any outflow boundaries were likely the biggest players in the events of this day. Since the flow isn't that strong at 500 mb, it is likely that the surface low near Abilene didn't move too much later in the day.

Target: Aspermont, TX

Gabe

 

[Pat Lawrence]

15Z SFC Maps:

This is really fun! A couple of people are REALLY close to the answer. Just remember I want to know the exact date Just to give a small hint, a person narrowed down the area of most concern fairly early on...they were a bit off on the area they chose to focus on, sort of, but they basically pinpointed the main chase area

Thanks for taking the time to consider the question I posed to the Stormtrack members!

18Z sfc charts will be posted tomorrow.

Pat