Chase Case #4

[Bob Hartig]

Scott, I readjusted to Davenport.

Thanks for taking the time and effort to provide this case!

 

[Dennis Sherrod]

Well as usual, I am fairly well south of many others. But I am heading for a short 400 mile trip up toward mid AR for this one as of now. At this point, I sort of like the possibilities.

 

[Scott Weberpal]

18-20z data will be provided sometime between 5 and 7pm. Get your initial forecast area in before then if you wish to be included on the map. Thanks!

 

[Danny Neal]

To elaborate on other post.....

I chose Northern into Central Illinois for the chance of severe weather. (La Salle) At the time I think the main threats will be clusters of strong to severe thunderstorms traveling ESE along the cold front with the main threat being damaging winds. The DVN sounding isn't to conducive for rotating storms at the current time but I do expect a rotating storm or two based on amount of deep layer shear and strengthening of the low. Plus not to mention this convection may throw down a rogue boundary or two.

What drew me to this area was being on the edge of the jet, where lift normally occurs, and a hint of diverging winds over S WI and N IL (again where lift normally occurs) There is decent moisture and I would expect that to improve....however the only question mark in my mind. Will there be sufficient instability during the hours of peak heating, or will the leftover convection leave an area of subsidence or stratus. I see the back end of the cloud cover to be out of the area by 11-12 PM. We will see.

Least I got my fishin' pole

On an unscientific note: Never underestimate IL weather in a NW flow. Some of our strongest tornadoes have come on a NW flow, huge CAPE type day. So we will see.

 

[Verne Carlson]

I don't see much in the way of chaseable storms. Maybe a slight risk with a few large hail reports in se KS/w MO. I'm not a big fan of nw flow aloft so I'd be staying home on this one.

 

[Adam Lucio]

To elaborate why I chose peru. This setup to me doesnt look too spectacular. I also hate NW flow despite their reputation here in northern IL [I wont name the events but Danny is correct, two of our most notorious tornaodoes were on NW flow days] If it were real life it would be one of those situations where I dart out the door and go after what/if anything develops. I can come home happy with some nice shelf pictures and a run in with some hail/wind and good lightning.

In this case I think a linear mess or clusters would be the name of the game. Any chance for discrete activity would be early on, and thats IF the airmass can recover and not get worked over by the crapvection...which is a common scenario in these parts. The timing of the wave along with the best available instibility will be crucial. The crapvection could providoe some evaportranspiration, and with the spread already not too significant I dont see moisture being a huge issue today.

With the parameters being somewhat marginal and no area really striking me as a bullseye, I can see a renagade storm potential over a wide area, so I chose my location based on road network.

Further updates may change this though.

 

[David Wolfson]

My starting point target is Sidney, NE. The short wave powering southeast from upper MN/MI is hard to miss and to my eyes has derecho written all over it. And the tail-end of the afternoon's squall line has enough to work with for a rotating storm or two, but where??? And if you're 50 miles off you might as well have stayed home.

Meanwhile there's decent moisture sloshing around the central and northern high Plains. And the right entrance of the impulse could reflect itself as a trough line moving down from eastern WY/western SD in the late afternoon heating period. Winds aren't too good, so photogenic hailers are more likely than tornadoes IMO.

Lastly, I'll end up "following" whatever happens up there down toward the CO/KS border and southern high Plains. To my eyes that's where the action will be in a few days with moisture return and the wave now in the Pacific Northwest rolls along. Beats the long drive from the Midwest.

 

[Tom Dulong]

I generally agree with the 13z convective outlook discussion. I would expect mainly linear convection late in the day over southern/central/eastern Missouri where the low-level thermal and moisture ridges intersect a warm front. Shear is marginal for supercells, but perhaps a few might get going in that area after 5 pm. 12Z SRH value at SGF was fairly impressive. So..I would paint a 5 percent risk of tornadoes there.

The second area of interest would indeed be the central high plains,with morning sfc dewpoints already in the 50s. They should mix down into the 40s in the afternoon, but still be at or above the climatological threshold for severe storms. There are several mitigating factors, such as the +15 degree cap at 700 mb and rather weak low-level shear. Storm mode should be discreet non-supercell convection late in the day with possibly an isolated land spout tornado (2 percent risk).

Finally, the third and best chance for severe thunderstorms and tornadoes would be over Idaho. Fairly impressive shear, low-level moisture, potential instability, and an approaching short wave.

I'm in Oklahoma City. If I could hop in a transporter, I would be in Pocatello. However, my decision is to hop in my car and head up the turnpike toward my inital target of Springfield, MO (poor chase country).

 

[Dennis Dennison]

Ok, I have studied the maps, and place myself in Gary, Indiana.
I feel there will be some 1" hail in Colorado, I feel there will be tornado's today in Ohio, Lower Michigan, and Indiana. So I am in a position to move in any direction based on later data and observations. I think there will be at least 1 EF4 and maybe an EF5 today. I base my choice upon -go ahead and chuckle-Surface map and Satellite pic-with my thoughts that the low in OK/KS will ride out east and north on the front line, resulting in a surge of moist warm air into ILL/IN/OH later in the day, combined with daytime heating and the cold front will set up a large squall line.

 

[Josh Richardson]

As many have said things are not looking that spectacular so I may end up not chasing at all, for that reason Im not committing that far east yet until I see more data. For the mean time I've headed to Clinton IA, my in-laws live there so I guess I can hang out there if things dont look too good...lol. I'm kind of sitting sitting in the same boat as Bob here, ready to move east into IL and take 30 if I like but am not committing just yet. Not too optimistic, hopefully we somehow end up with something over here in E IA.

 

[Nathan Edwards]

In both years I've been across the pond chasing in the US, I've never chased in a North Westerly flow situation so this is kinda new to me. I'm heading to southern Wisconsin - likely the Madison area for staging. Not holding out much hope for classic supercells. I think we'lll be dealing with a bow echo before too long, but soundings from Davenport, the nearest one given to me shows some good shear so embedded tornados are likely and hopefully, I'm wrong and things stay somewhat discrete . I wouldn't be surprised to be playing catchup as storms move south so I'll stick close to the interstate for an easy south road option should I need to fly into Illinois!

 

[Shane Adams]

I see a lot of people are just throwing out targets missing some of the main questions I was looking to be answered in my original post...

"It is up to you to determine whether or not there will actually be chaseable storms (there will be storms somewhere), their severity, storm mode, whether or not you believe there will be tornadoes or if it's a non-tornado event. Large hail? Straight line winds?"

It's easy to just throw out a target, but putting some thought into what type of potential chase day it might be takes a little bit of work.

I've never been a fan of "show your work" type answers. I hated it in math when I was in 8th grade, and I still hate it as a chaser on a forecast thread. To be honest I base everything on these virtual things on surface maps and if I think I can guess the date. When it's for real, I have a strict ritual I follow that is not applicable on these exercises; i.e. I like particular models, sources, and the order and timing of which I look at everything. These virtual things are fun mainly because there's nothing to lose but face (and I lose face all the time trying to hang with forecasting chasers) when you bomb it. But what it comes down to for me is being asked to give a chase startegy/target based on another person's template. For me personally, the method by which I reach a chase/target decision is far more important than just having data thrust at me.

But to comply, I chose SE Kansas because that area looked best from 700-GL to my eyes. I'm an instability nut so I naturally gravitate towards heavy dewpoints and sweet spreads (again, SE Kansas per that map). Overall the setup looks screwy to me because I'm assuming it's a central/northern Midwest type of day, as opposed to a classic S Plains event based on thermals not just shear (which we've yet to have). I've rarely had the means to chase these type events in reality, and if I'm not chasing I don't even look at data for a given day....hence my severe lack of experience tackling these shear-dirven Midwest setups. You can add cold-core to the list of setups I know little about as well.

If this was the way I had to really pick targets, I doubt I'd ever see anything.

 

[Marc Austin]

My initial thoughts after reviewing the first batch of forecast products is that a squall line/derecho event may unfold across the upper midwest during the late afternoon hours. I don't like the idea of chasing linear stuff, although shelf clouds can be very impressive at times and provide incredible lightning displays! I could play further south along the cold front into northern MO/Eastern IA/Western IL, but I still don't like the idea of a possible line of storms. The chance for discrete cells just ahead of the front seems somewhat marginal. The weather discussion mentions possible isolated sups in eastern Colorado/western KS later in the day. I've had great luck in this area in the past, so I think initially I would start the day in Goodland, KS and wait for more data. If isolated sups do form over the plains of Colorado, I can easily hop on 70 and head west. I won't be counting on tornadoes, but looking more for some nice structure and large hail. I do believe there will be a few tornadoes in the Upper Midwest, but I'd rather take my chances on some slow-moving discrete storms. This is only after looking at the first set of data. I'll update this shortly to reflect my thoughts on any new data that has been posted.

 

[Chad Cowan]

I'm sitting with Adam Lucio in his new chasemobile in Peru, IL. Today doesn't look too great with the large area of early morning precip, but if that can move out soon we could see some decent instability. Tough to tell without any loops though. If I had to guess, I would say the time of year is late summer / early Fall. The thing that really narrowed down my target area is the Davenport, IA sounding which shows the best wind profile of all the soundings. I can't for the life of me figure out why the LL winds are southerly in this area but I think it may have something to do with the secondary low over SErn KS. Regarding storm mode, I believe there may be an isolated supercell and tornado threat in a brief window after initiation and transition to a widespread wind event.

 

[Scott Weberpal]

18z UPDATE

Final targets (or at least close) will have to be determined soon, as storms began to develop on this day by around 21z. Do you stay where or are or blast somewher else fast? 18z data was limited as this case is old enough that many archives don't cover it. I have included surface maps, satellite for 18z and 20z, radar, surface fronts, profiler data, and the 1630z Day 1 SPC Outlook.

Surface

Upper Midwest
Central Plains/Ozarks
Central High Plains
Surface Fronts

Satellite

1815z
2045z

Profiler and Radar Data

18z Profiler Data
20z National Radar

1630z SPC Day 1 Outlook

...NRN INTERMOUNTAIN REGION...

ONGOING ACTIVE THUNDERSTORMS MOVING INTO SWRN ID AHEAD OF THE
VIGOROUS S/WV TROUGH REFLECTS THE AVAILABLE MOISTURE/INSTABILITY
COUPLED WITH LARGE SCALE ASCENT. ISOLATED SEVERE STORMS CURRENTLY
INTO SWRN ID...EXPECTED TO INCREASE IN NUMBER AND INTENSIFY FURTHER
WITH AFTERNOON HEATING EWD ACROSS SRN ID INTO SWRN MT/WRN WY. WITH
MUCAPES CLIMBING TO 1500 J/KG AND 50 KT DEEP LAYER
SHEAR...SUPERCELLS LIKELY WHICH WILL ENHANCE LARGE HAIL AND
DAMAGING WIND THREAT ALONG WITH POTENTIAL FOR ISOLATED TORNADOES
VICINITY SNAKE RIVER VALLEY.

...MIDWEST/GREAT LAKES...

THE STRONG DIGGING TROUGH NRN MN VALLEY WILL PROVIDE VIGOROUS
UPWARD MOTION AHEAD OF THE RATHER DEEP SURFACE LOW WHICH IS
CURRENTLY MOVING SEWD FROM NRN MN INTO WI. INSTABILITY AND
MOISTURE INITIALLY AHEAD OF THIS SYSTEM IS MARGINAL...HOWEVER BY
LATER THIS AFTERNOON...THE SYSTEM WILL BE ENCOUNTERING INCREASINGLY
MOIST/UNSTABLE AIR AS IT MOVES SEWD INTO WRN PORTIONS OF OH VALLEY.

12Z ETA BY LATE THIS AFTERNOON HAS A STRONG CONVECTIVE SIGNAL AS
COLD FRONT MOVES ACROSS SRN WI INTO SWRN MI AND NRN IN. GIVEN THE
STRONG DEEP LAYER SHEAR AS 80-90 KT NWLY WIND MAX DROPS SEWD
ACROSS IA INTO WRN OH VALLEY...ORGANIZED THUNDERSTORMS WITH
POTENTIAL FOR PRIMARILY WIND DAMAGE AND LARGE HAIL WILL INCREASE
INTO THE EVENING HOURS. SEVERE POTENTIAL SHOULD CONTINUE WELL AFTER
DARK EWD ACROSS OH VALLEY GIVEN THE VIGOROUS UPPER SUPPORT AND
CONTINUED INTENSIFICATION OF SURFACE LOW.

...CENTRAL HIGH PLAINS...

SURFACE RIDGE PUSHES SWD THRU NRN PLAINS IN WAKE OF THE UPPER MS
VALLEY SYSTEM. RESULT WILL BE INCREASING UPSLOPE FLOW INTO ERN
WY/NERN CO DURING AFTERNOON WITH DEWPOINTS INTO LOW 50S PUSHING WWD
TO E SLOPES OF MOUNTAINS.

STRONG HEATING WILL INITIATE THUNDERSTORMS VICINITY HIGHER TERRAIN
ERN WY/NRN CO THIS AFTERNOON. WITH SURFACE CAPES TO 1500
J/KG...AND VEERING SHEAR PROFILES...A FEW SUPERCELLS ARE LIKELY.
PRIMARY THREAT WILL BE LARGE HAIL AS STORMS DEVELOP E/SEWD INTO
HIGH PLAINS. POTENTIAL EXISTS FOR OVERNIGHT MCS INTO WRN KS WITH
SEVERE THREAT DECREASING A FEW HOURS AFTER SS.

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