Chase Case #11

[James McCormick]

Here's my best shot. My web design savvy leaves something to be desired, so I created a simple point-and-drag type web page for this event. Included:

12 Z UA maps
12 Z Surface maps
12 Z Soundings from a broad area of the northern United States (area of interest is within given maps).

http://www.openprarieexperiences.com/Storm...eStudyHome.html

Severe Weather/Tornadoes may or may not have occurred on this occasion.

Please let me know if there are other maps that should be included, or if any data needs clarification. I will put up some 18 Z data, and later 21 Z data, when I get off in the afternoon.

*UA and surface maps from Plymouth State; soundings from SPC Archives.

 

[Joel Wright]

Man, this one is kind of tough. Almost got me wondering about a bust...

I do like the area around Lamoni IA as a starting point. Stronger winds aloft just to the north. Decent moisture in the lower levels available. This looks like sometime in June to me. There seems to be a boundary just to the north.

I guess I'll take my chances with the high gas prices and head to Lamoni after stopping at Hardees for some biscuits and gravy.. :wink:

 

[David Wolfson]

Yecch. Since this is virtual chasing, I'm going to Union, MI (right about in the middle, west of Midland). The atmospheric ingredients are ok up there, and there's something passing for a cold front on the way.

If for real, I'd be going somewhere northeast of the last case (where I busted) -- Sioux Falls, IA. Enough moisture oozing up during the day, instability, and winds to feed a storm or two if forced, and I haven't burned up five tanks of gas getting to Michigan and back.

 

[Robert Dewey]

The 12Z data shows good moisture pooling across the Ohio Valley northward into southwestern lower MI. Winds in southern lower MI, eastern IN, and western OH have backed to the SE ahead of a weak SFC trough which extends from Lake Superior ESE along lake MI into western IN.

The 500MB map shows a relatively zonal flow across the north... And there appears to be a nice shortwave embedded in the flow located across northern MN SSW into western IA.

As of now, my threat region is relatively large... I would say areas of southern lower MI into IN and IL are at the highest risk. I am unsure as to what the actual trigger (if any) for convection will be... It might either be the weak SFC trough, or the shortwave impulse (depending on how fast it's moving).

Other regions of the US have less than favorable wind profiles and weak upper level support and/or a lack of significant SFC based moisture...

 

[brody_clifton]

Looks like a summer type morning ob pattern, with a decent north-south oriented surface cold front somewhere western Michican and points south to SSW. 70+ dews buldging up the southwestern side of Michican just ahead of the front at 12Z, with points east in southeast (but kinda weak at 5 and 10 kts) surface flow and clear skies. I couldn't find a 15+ kt southerly barb anywhere. And I don't really see any good upper level divergence or find any shortwaves at 500 to support any wide area upward forcing. Looks like maybe a line pattern type complex may form up by early afternoon in the clear sector of central and eastern Michican, with a greater risk for isolated supercells with any convection that fires out ahead of the line in eastern MI. I guess for a target I'd go to South Central MI, near Lansing, and be prepared to move east towards Flint or Ann Arbor at lunch if the cold front is moving east faster than I expect.

 

[nickgrillo]

Looks pretty decent to me... A cold front extends from the surface low in northeast WI and curves southwest into Oklahoma. A second frontal boundary extends from the low as a warm front and is spread across the northern U.P./Canada. There does indeed appear to be a sfc trof extending from the low and is currently moving into western MI (with backed / nearly backed sfc flow ahead of the trof). Soundings from WI/MI show a rather deep low-level moist layer -- despite very crappy lapse rates (the DTX and GRB soundings show both low-level and mid-level lapse rates nearly moist adiabatic) although the shortwave to the west could help steepen lapse rates as it approaches, later (along with afternoon insolation) enhancing instability.

As for now, I will play the area ahead of the sfc trof... In Jackson, MI... Oh boy, another MI day :lol:

 

[Nick Bender]

I took at look at this early this morning, and finally got some time inbetween my own forecasting duties to name a target.

I agree with rdewey's and nick's analysis of the situation as of the 12Z data. The only thing the soundings in the east have going for them is that deep low-level moist layer, the wind profiles don't exactly scream severe at this point. Hopefully we can advect those colder 500mb temperatures eastward, curtesy of upper level stearing/shortwave - as well as burn that cloud shield off which is present over much of the midwest; start running that CAPE up.

Thing to notice - most of the east soundings are not capped, a few have a nocturnal inversion, but the majority pretty follow a moist adiabatic profile from the surface up. With any clearing, advection of colder temperatures aloft from the east, and some luck, it may be easier to destablize the atm and promote convection - will have to see what the 18Z obs hold.

Target as of 12Z data: Toledo, OH - want to keep my option open to go northward into MI, or south/southwest into OH, IN, and ID.

 

[Charles Kuster]

I'll start in Lansing, Michigan.

 

[James McCormick]

I have added 18 Z Surface Data, visible sat images from around 18 Z, and I threw some profiler data from 17 Z up as well even though it is limited to the central and eastern plains. I will add 21 Z data tomorrow.

 

[Robert Dewey]

Wow, I'm not liking the sfc plot over MI... It has veered strongly to the WSW since 12z. Moisture has certainly pooled, but the unidirectional profile would lead me to believe that convection would most likely be linear. There does appear to be a nice Cu field in place, which might indicate very little (or no) cap in place, and with the sfc trof now located a bit further east - initiation of convection might commence very soon over SW lower MI (in some form or another).

I do notice some TCu's in central IL, and the sfc data does show some backed winds there - that could be a possible boundary of some sort... But profiler data shows an overall weak wind profile. But, directional shear can really make a big difference, especially on high instability days (or so it seems). In addition, the rest of southern IL, IN, and OH appear to be capped off given the lack of any Cu.

So for now, I will remain in Goshen, IN... This could very well end up being one of those high instability / no shear days - and the Cu field in MO is making me nervous.

 

[Shane Adams]

Scottsbluff, NE.

 

[Alex Lamers]

Hmmm well lets see here. Just got a look at this for the first time. At 12Z it looks like there's a shortwave headed east out of the Central Plains (NE/KS). Faster upper level flow within jet stream core is located across the North-Central US and more specifically the Dakotas, Minnesota, Wisconsin and the UP. What is really concerting is the dry air punch obvious on the 850 and 700 mb plots clearly mixing down through the lower levels in Minnesota. At 850mb the dewpoint ob goes from 5ºC in MSP to 14ºC in GRB. We shoot up to 15ºC in Davenport. Not much of an LLJ but it is the morning hours and there is a feed from Deep South Texas up into the Great Lakes. Clearly there is sufficient available moisture. I don't want to head too far north based on GRB sounding showing the hydrolapse right around 700mb and based on upstream obs the dry air will probably continue to mix down and produce a sort of capping effect.

With not much else left to work on there's a lot to ponder here. ILX sounding intrigues me because once the boundary layer becomes mixy (assuming sun and diabatic heating) the thermodynamic profile is looking great and the CAPE should be through the roof. Then looking at the 18z satellite it appears this happened...but no cu field in C IL yet so probably still workin off the -300 j/kg CINH from the AM sounding. Where the sun is out the sfc temps are pushin 90ºF and under the stratus and low clouds to the north they are generally under 80ºF which should set up a great deal of baroclinicity along the cloud line. Not much advective process due to 850 mb winds paralleling the boundary...but this could be key later in focusing some strong vorticity and potentially tornado spinups. Winds revved up on 18z profilers in MN/IA/WI so that has me thinking my dry-air theory was confirmed. I'm more interested in RRQ jet streak dynamics that could aid vertical motions over Nrn/Ctrl IL.

Analyzing the satellite there are some cu/tcu popping in MO and far S IL but it also appears that cu are going up along the cloud line, they are hard to make out under the shadowing effects of the mid-level clouds though. I would say get as close to the cloud line as possible in order to be closest to baroclinic zone and stronger upper level winds. Storms to the south should be poorly organized and of the pulse variety. If this isn't a bust my best opportunity is where I said. So I would target Peoria, IL and be prepared to move in whatever direction. There's some cu beginning to go right overhead which I can hop in the interstate and take east if I want. Otherwise I can wait on this stuff in MO and see what happens. Looks like a C IL/N IN event if at all.

...Alex Lamers...

 

[David Wolfson]

*Sigh* Since I'm already virtually way east in Michigan I might as well zip over to Canandaigua, NY (east of Buffalo). Have to keep ahead of the impulse approaching Detroit at 18Z in the decent winds and moisture. Looks like some possible early development southwest of there on the NY - PA border around Allegany. How did I get sucked into this fool's chase? :roll:

 

[Joe Zemek]

I don't see why y'all wanna go chasing in Great Lakes and Trees country when we have a good recipe for post-frontal upslope High Plains magic in CO/WY/NE. I may not be cranking King's X with Shane in Scottsbluff, but perhaps I'm in a Sterling position to see some supercellular action.

 

[Joel Wright]

Well, based on the latest trends I've decided to leave Lamoni IA and blast south on I35. Had lunch with Mike Peregrine in KC, then set up just west of KC in Lawrence KS to see what's up. Td depressions are kind of high just to the south, but there seems to be some moisture pooling along the east west boundary just to the north. Sitting here getting a nice sun tan watching the cumulus bubble up a bit, but nothing too interesting yet. I'm kind of wondering if there's enough time to sneak in a quick 9 holes of golf in..


I figure even if I don't get to see any tornadoes today, at least I'll get a nice suntan, and should at least see some storms later on, tornadic or not....


8)