6/8/09 FCST: IL/WI/MI/IN/OH

[Bob Hartig]

From the time that Monday came within its range, NAM-WRF has been indicating tornadic potential in the Great Lakes. A weak surface low positioned in WI/northern IL backs winds nicely, with a WF stretching east across Michigan. Everything appears to be in place. The wild card is the discrepancy between the NAM and the GFS, the latter of which has been moving the low consistently eastward and tilting it positively. Two very different pictures here, with the NAM offering plenty to like and the GFS painting nothing but horribly veered surface winds and unidirectional flow overall.

I'm not savvy enough to determine which model is the more trustworthy, but my gut tells me that the NAM has got the better handle on things. If that's the case, then we Great Lakes chasers should finally get a little action in our own backyard. MI, IN, and OH look to be the main candidates at the moment, though I've included WI and IL to make allowances for deviation in future runs.

 

[Bob Hartig]

While my droogs are out in Iowa, I'm pining away back in Caledonia, MI. Guess I'm not too surprised that no one has leaned in on this thread, since there's plenty going on between today and tomorrow (when I will be out chasing), and I suppose the Great Lakes region isn't exactly a storm chaser magnet. But for those of us who live here, the NAM continues to suggest some action on Monday. The GFS isn't as optimistic, but I'm seeing what looks like a trend toward agreement with the NAM.

The 12Z NAM was a bit disappointing, but the 18Z run doesn't look too bad. Backing winds are a bit displaced from CAPE, but there's a nice confluence of LLJ and MLJ, with dewpoints tapping into the mid-60s. Being a fan of F5 Data, I overlaid three different tornado indices (SPC sigtor, Stensrud, and APRWX), and what to my wondering eyes should appear but a bullseye right where I live. That's the second time I've gotten this from the NAM for Monday, and the EHI is right there with it.

That's the quick and dirty, and I expect it'll change. Frankly, I'd love to see the low drop south and west a bit. But it's nice to see both the NAM and GFS at least starting to coincide on the placement of that low. The GFS is rendering a more unidirectional prog than the NAM, and with both models, winds veer quickly as you move into decent CAPE. But that being said, I have hopes that when I head home after playing in Iowa tomorrow, the weather will offer something interesting right here in the 'hood (northeastern IL, northern IN, MI, and northern OH).

 

[Andy Wehrle]

I'm surprised that the trend since yesterday has been to speed the system up. Usually these things slow down with time. Figures since yesterday's NAM looked great for southern Wisconsin with a nice CAPE/THETA-E/moisture tounge nosing right into the area. Directional shear was also decent, although would have liked to see stronger winds at 500mb. Today's runs have the low/warm sector almost through the state by 00z TUE.

 

[L.B. LaForce]

Oh hay....MI chaser here haha. I'll look it over more tomorrow, but at least it looks to be somewhat decent (compared to what we have had all year-nothing!). Keep us updated on your F5 data bullseye..im curious as to what it says tomorrow. I just might have to skip a class tomorrow night. :|

 

[Jim Zandonai]

Here in N.IL we haven't had anything worth chasing either.. looks like Monday may have some storms develop in the NW-W part of the state early then trek eastward..with the best likelyhood east of I-39.. I am working on Monday but may try to get off early IF I see things develop well west of I-39 for an intercept.
Instabilty looks good with some respectable capes but it may depend on how fast the mornings activity moves out..

 

[Bill Schintler]

Chase Target for Monday, June 8

Chase target (IL, WI):
10 miles north of Rockford, IL.

Timing and storm mode:
Storms will rapidly develop in the area between 2 and 3 PM CDT. Supercells will be likely early in storm evolution, before a rapid transition to a big convective mess. Storms will move rapidly to the northeast at 35-40 mph. This has the potential to produce a number of tornadoes; however, chase conditions will be poor at best due to rapid storm movement, poor road network, and too much convection.

Chase target (CO):
Brush, CO (60 miles northeast of Denver)

Timing and storm mode:
Storms will move into the area between 5 and 6 PM MDT, with multicells the primary storm mode. A short-lived supercell or two cannot be ruled out, however.

Discussion(IL, WI):
The synoptic setup is impressive, however details concerning the exact location of small-scale boundaries and convection depend on earlier convection with attendant OFBs and air mass modification. SFC low pressure will track from extreme NERN IA at 18Z to central Lake Michigan at 00Z as an increasingly negatively-tilted mid-level shortwave overspreads the area. Morning convection and associated clouds will move N and E of the area by mid-morning, allowing for a period of heating. The favored location may be along a warm front along the IL/WI border by early afternoon, with the best combination of shear and instability.

Discussion(CO):
Storms should initially fire in extreme southeast WY and over the Front Range west of Denver and Colorado Springs by mid-afternoon. Lift will increase within the left-exit region of a 60kt H3 speed max and coupled jet structure, and a weak Denver cyclone should develop. Dewpoints will increase into the low-50’s just N of the Palmer Divide in an area of up-sloping flow. Jet stream CI will overspread areas E of the Front Range after 22Z, however sufficient insolation should take place to realize MLCAPEs of 500-1000J/kg. Low clouds will persist in NERN CO through 18Z, with differential heating resulting. Deep-layer shear of 35-40kts along with SFC-3km SRH of 150-200m2/s2 may be sufficient for storm organization and rotation updrafts despite the marginal moisture and instability.

- Bill
9:14 PM CDT, 06/07/09

 

[Scott Weberpal]

Chase target (IL, WI):
however, chase conditions will be poor at best due to rapid storm movement, poor road network, and too much convection.

Poor road network...are you kidding? This area is heavily populated with a very dense paved road network. That is, until you hit a big lake, then there's a bit of a network problem.

Anyway, according to the 4km WRF (all I've looked at) looks like a legit shot at low topped sups in C. WI associated with the vort max if clearing can occur after the initial wave. After an all night drive home, not sure how motivated I'll be to chase screaming low topped sups even if they are close to home.

 

[David Draun]

SPC appears to show some concern about a marginal tornado threat across NE IL in their 1630Z outlook. The WF has cleared the WI border and a strong WAA regime has taken over, complete with 65-70F dewpoints. There appears to be an outflow boundary just west of the Chicago metro area where winds are shifting from SE/S to SW. SBCAPE as of noon is already 2000 J/kg Just SW of Chicago, with higher mid-level lapse rates expected to advect eastward with time. Storms should initiate along the front out in NW IL by 2pm, any storm that can interact with a boundary will have potential to become tornadic, especially farther east. Forecast soundings show convective temperature is just a few degrees under the forecast highs. Capping, if any, appears to be weak so everything will go all at once.

I could see an MD going out for a possible severe thunderstorm watch in a couple hours. I don't think it will be a tornado watch but we will see. The I-88 corridor between Dekalb and Chicago would be a good target if traffic was not so bad.

 

[Jeremy Ludin]

Joel Wright and I are about to cross into Illinois near Hannibal MO. It looks like we'll be targeting the Peoria LaSalle area. Already CAPE approaching 2,000j/kg in much of Illinois. Really liking the strong mid-level punch coming out of Missouri. Just wish the lower-level wind fields were a bit better.

Should be a shot at a getting a few tornadoes early on before the mode becomes more linear. We're just gonna have to be on these things shortly after initiation. Lets all try to avoid that damn gorilla hail today! LOL

 

[David Draun]

I could see an MD going out for a possible severe thunderstorm watch in a couple hours. I don't think it will be a tornado watch but we will see. The I-88 corridor between Dekalb and Chicago would be a good target if traffic was not so bad.

Nailed it, LOL.

All gloating aside, cumulus are already popping across the area. There does not appear to be any CIN whatsoever as they are quickly towering up. The theta-e ridge in NW IL will likely be lighting up shortly. I'm no longer seeing the SE winds in IL though.

 

[Chris C Sanner]

CURVEBALL!

Ok maybe not, but I'm just going to throw my plan out today. I'm planning on targeting Southern parts of Oklahoma along the front where it looks like an old and weak outflow boundary resides as well. With surface winds out of the ESE along the old boundary, CAPE at 4000, decent mid level flow and enhanced surface vorticity with the boundaries, I think the potential is there for a surprise red dot or two in S. Oklahoma today, but I also think the odds of it are pretty low. Not planning on much today, but a supercell would make me happy. Anything on top of that would be gravy.