CHASE CASE (#3): Should I cross the river?

[nickgrillo]

A very brief discussion... All of the ongoing convection around the strengthening warm front will slowly diminish as the LLJ weakens through the late morning. This will lead to widespread insolation, with a very warm and moist boundary layer contributing to widespread extreme instability across the warm sector by the mid afternoon. Skies have already cleared south and east of the surface low in northwest OK (which should lift well northeast by the afternoon). Clouds should also mix out across the upper Mississippi valley in the afternoon and the area could hold some potential later in the day.

12z surface observations:
<img src=http://midwestchase.com/chasecase/051229072907u.gif>

12z upper-air charts:
925mb
700mb
500mb
250mb

12z observation soundings:
DTX
ILN
ILX
SGF
DVN
OUN
OAX
TOP

 

[Joel Wright]

I could be wrong, but this looks like a pretty interesting situation for my area. I would take an initial stab at the tri-state of IA, MO, IL. The warm front will likely build north into southeast IA, and with backing winds I would guess the best place to setup would be southeast IA, or west-central IL near Quincy.

 

[Darin Brunin]

Hmmmm....If the surface low is going end up where I think it is then it's going to be a MS River Valley show. Let's try Northeastern Missouri for starters right along the Mississippi River. A city would be Hannibal, MO. The hazy conditions were a good indicator of what month and year we are dealing with in this situation and probably the one thing that stuck out at me the most when I looked at this 12z surface chart.

 

[Dan Cook]

I know what day it is. I'm starting from Hannibal too.

 

[Dan Cook]

I know what day it is. I'm starting from Hannibal too.

 

[Michael P. Morris]

I guess the 850 chart shows nothing of consequence? I have only seen two tornadoes in my life but I still think that MAY be useful in determining a target area (though not nearly as useful or meteorologically sound as ogling the ETA for CAPE and helicity bullseyes)

I prefer a target farther south in the warm sector. The Springfiled sounding shows the strongest cyclonic curvature in the hodograph, and the cap strength of 2 C is just right for limiting convection until the 500 hPa impulse arrives later in the day and overspreads the region with decent synoptic scale lift. Moisture pooling in central Missouri just to the south of the warm front, not effectively sampled by SGF which has a T-Td of 4 degrees, should enhance instability.

I'll say Jefferson City as a reasonalbe starting point.

 

[Mike Peregrine]

I think that warm front is going to start moving north just a tad, and even though I hate Missouri chasing and it looks socked-in for the time being, I'm still going to drive across highway 36 and hit Monroe City, where I will follow a tornado between there and Hannibal and likely be forced to cross the river and head into Illinois before this is done. And this time, unlike last time, I'm going to stick with it instead of giving up just before the tornado.

 

[David Wolfson]

Darn, Michael and Mike, you beat me to it (except I don't remember the actual day). The warm front is going to mark the stage, and the lower level flow suggests it only makes a little progress northward. Meanwhile the surface low will move east-northeast of KC during the afternoon.

The Topeka sounding is the environment just north of the front -- above 925 like SGF, except a little more CAPE. It all comes together for me in Paris, MO, (about 20 miles southwest of Monroe City) and prepare to ride storms crossing the river along the front.

 

[Mike Peregrine]

I could be wrong of course, but this is definitely what the surface map looked like on May 10, 2003.

 

[Kurt Hulst]

I would either Start out in Brook Field or Macon, MO. Both are descent terrrained areas as i have seen 3 tornadoes on a streatch from Chillicothe to Macon May 24, 2004. I would be leary of terrain in the NE corner of MO and directly SE corner of IA. Not the greatest veiwing but still it is doable. The 925MB helps me get a feel of what the 850's will look like. i dont picture them to backed but not entirely veerd But if you are looking for the 850s go to the Skew-T's look at the wind profile.

But from those towns I would ride east twoards Quincy and Hannible. Anything along the river will be pretty non veiwable. So i would try not to waste time crossing it. So i would either drive north off of 36 on 24 and hop over at Quincy or i would continue on 36 and head to Hannible. I feel the convection will start near North Central MO. So I wouldn't start in IL.

 

[Alex Lamers]

Well...trying to ignore all the people who say they know what day this is and ruin my fun :lol: 8) ...this seemed like a pretty obvious decision for me.

This is a very dynamic setup...and you can even tell this from the surface chart. Just look at the boundaries. You have a 36 sfc dewpoint and 56 sfc temp in W OK and mid to upper 70s dewpoints and temeperatures in E OK. The dryline is very pronounced. Then you have the warm front east of the low and the airmass differences are marked but then you can also consider the cloud shield and stratiformy precip that will probably end up enhancing the difference once diurnal heating can take place south of the front.

Zone of high baroclinicity looks to set up and maintain relatively along the Iowa/Missouri border region and then into Northern Illinois. Strong differential advection should allow strong instability to develop. Looks like a good setup for clusters of highly-organized, tornadic supercells. I'd setup around Kirksville, MO along my expected track of best tornado potential when supercells should become mature and intense by late afternoon. Then I'd probably follow them off to the east-northeast into Illinois.

...Alex Lamers...

 

[Shane Adams]

I was trying to forecast this for real, but after scrolling through and reading all the posts, it seems that once again everyone is deadset on what event this was. Because I didn't chase this event, I never saw the data for that day. So if this is that event, my forecast would be a waste of time. Instead of trying to figure it our on my own, I'm just going to take the advice of everyone else and drive straight to Lima, IL, where I'll get the prize of the day and win the contest.

This would be more fun if folks just posted a target and general thoughts :wink:

 

[Alex Lamers]

This would be more fun if folks just posted a target and general thoughts :wink:

Exxxaaacccctttlllyyy Especially with SPC Storm Reports archive and the data available nowadays.

...Alex Lamers...

 

[Karen Politte]

Yes I have to second Shane's comments here. Rather than have it "competition" style to see who can "get it" first, it would be far more interesting and there would be much more incentive for me to participate if it was just a "see how you do and I'll post the answer tomorrow" style exercise. That's what used to happen when Jason Politte did these "Chase Cases" - and I preferred that style.

I usually don't get around to reading a thread like this until someone has already posted (with many winks :wink: :wink: ) their starting target town for the day - and also state that they know what date it is already.

KR

 

[Mike Peregrine]

or ... what you could do ... is simply read the forecast discussion, avoid reading the supplementary posts and post your own thoughts instead. Basically what it boils down to on actual chase day, since everyone else is usually out there eagerly posting their thoughts. That doesn't mean that you are going to go by what everyone else is saying to determine your own forecast, does it? Lots of chasers don't even read SPC outlook language, and prefer to forecast on their own without the influence of the thoughts of others ...

to each his own ... it's a great exercise regardless whether you recognize the pattern and setup from a previous event, or work through the forecast details on your own and post your thinking as Alex has done. Whatever trips your trigger - there are no gold medals being handed out so it's really a matter of what you personally would like to get out of it.

Plus ... who's to say that this is actually the day everyone is thinking it is? Could easily be a wrong conclusion on anyone's part -