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6/7/09 FCST: NE/IA/KS/OK

  • Thread starter Thread starter Michael O'Keeffe
  • Start date Start date
I still consider myself a newbie, but I don't recall ever seeing a -15 LI before. The RUC draws a small circle of -15 in the vicinity of Hiawatha, KS at 22z. Can the cap beat that?
 
I still consider myself a newbie, but I don't recall ever seeing a -15 LI before. The RUC draws a small circle of -15 in the vicinity of Hiawatha, KS at 22z. Can the cap beat that?

Well, instability alone is not going to break the cap. We're going to need some lift. The RUC is also more than likely over doing the instability. Its plotting dewpoints up to 74, which is going to skyrocket the cape/LI values. The WRF is a little more modest with Cape values over 3000.

That said, I think we have the lift along the stationary boundaries and upper level dynamics. The cap is forecast to erode enough, and even with the overestimated dewpoints on the RUC we still have strong instability in place. As others have pointed out, the RUC develops a nice little surface low in NE KS at 0z to create a triple point play. I'm looking at a 21z-0z initiation here. Good luck all
 
I still consider myself a newbie, but I don't recall ever seeing a -15 LI before. The RUC draws a small circle of -15 in the vicinity of Hiawatha, KS at 22z. Can the cap beat that?

Yes. The lifted index product is calculated at 500mb. Most capping inversions are around 700mb or lower. They are generally independent of each other, as you can have a really good lifted index but lots of warm air just above the surface that doesn't affect the sounding all the way up to 500mb.

As for today though, I do not think that there is as much of a cap to worry about. Lots more instability and the boundaries of the system look to be more defined to me.
 
The cap does not worry me near as much as LCL's do. I think we will see supercells develop today, but my hope is that we get a couple to develop along Interstate 70 near the warm front where LCL's will be closer to tornado production levels. Anywhere south of that and storm bases are going to get scary high for tornado production. If skies can clear, and a supercell can form in SE Nebraska where winds are ESE and low level shear is very high it has the potential to go nuts.

Can already see a mesolow on the surface readings west of Manhattan, KS. I'd like to stay just ahead of that, and along the warm front. Will be heading towards Holton, Kansas shortly. The earlier stuff can go, the better because it's only going to progressively move towards worse terrain.
 
First glance this morning clearly has me thinking NE/KS border for my usual 4-county target zone. In NE: Gage, Jefferson. In KS: Washington, Marshall. This area appears to be along the SW side of the most favorable 0-1 km EHI axis per 12z RUC and closest to steeper low level lapse rates/heat axis poking in from the south. With storm motion to the NE at 30-40 mph I am a bit hesitant to set up farther south at this point. Still looking things over and after a late start to the day should be on the road within a few hours.

Sure doesn't feel like a June chase day here in Hastings this morning...55 degrees with a cool northeast breeze and overcast 300 feet.
 
Jeremy Ludin and I just passed through Corning Iowa. This was our initial target area, but we've decided to push on westward. We're eyeing far southeast Nebraska or northeast Kansas now. Probably towards the Marysville Kansas area. We're gonna play the northern edge of the best instability and best wind shear. Should be less of a cap bust potential up here in theory. If it looks as if the cap can break further south we can head that way.

Overall I don't see too much change in the new models. Definitely like the leftover boundaries from the earlier convection. Sure would like to see stronger low-level winds, but I think we have just enough to get the job done.

Good luck everyone!
 
A couple of Canadian chasers, Justin Hobson and Rob McDonald, will be out there too. They're initially targeting Holton, although that may be a bit too far south (although it's a lot easier to chase from the south and east than from the north and west) and I'll reposition them as needed--too bad I couldn't go today but work is one of those commitments.

That being said, I would like them to go to Marysville and wait, but they're driving, not me.
 
I wasn't going to go out today following my far-too-late 1:00 wakeup after a stressful and sad night last night, but I'm beginning to change my mind looking at:

(a) the satellite, which shows a definite area of interest for us Northerners out around the river by OAX;

(b) the feeling like there's a little more patchwork clearing here in IA than expected by the RUC, meaning there could be something interesting in the Western IA I80 corridor (and south - and possibly north! of that as well) due to more CAPE than projected. Probably gonna capbust it because that's the kinda thing someone leaving this late will get, but it is better than not trying at all, and it helps relieve all that's on my mind.

P.S. If anyone can call me for nowcasting, I'd appreciate it. Please send me a private message for my cell, and I will pull to a rest stop to check my PM's for a reply here soon.
 
Looks like a mini-mess of convection is arising just a hair south of Beatrice. If I'm not confusing it with the crappo behind it, it may be time to begin a NOW thread given that it lasts. Looks like stuff in NW MO might be making infant attempts at something as well.
 
Sitting in Holton, KS, (Taco Bell) with a nice CAPE bullseye right over us. Still in clear air but noticing cirrus invading from the West. Still to the south and west skies are clear but I am not liking the T/Td spreads down that way. A favorable spread is further North toward the NE/KS border however cloud cover is invading. I think we are in a decent spot for convection to fire, but I have a feeling it is going to fire almost directly over us and then move to the ENE into unfavorable terrain. We will see what happens I guess. I like that 4500 CAPE bullseye though, with the cap weakening I believe this area is prime
 
Initiation prospects look pretty good over the next couple of hours from ~Topeka to Holton:

- Current analysis shows CIN eroding over NE Kansas

- Loop of the RUC precip forecast shows persistent build of convection over the area and then progressing further NE in the coming 2-6 hours

- Topeka radar indicates a boundary from roughly Manhattan towards Alma and points further SE, moving slowly east.

Environment over expected initation and subsequent storm motions looks quite favorable; not only the impressive instability but the nicely backed low level winds out ahead of the surface mesolow. Very adequate deep layer shear also in place. The LCL's, of some concern earlier, don't look too bad at all at 1,000 - 1,200 meters.
 
Discussion (2:30 PM CDT)

Earlier convection has made somewhat of a mess out of the surface map and has increased uncertainty as to location and timing of storms later today and tonight. Further complicating the forecast is a band of CI spreading form NEB into KS and IA, which will slow heating in these areas. An outflow-enhanced warm front, analyzed between I-80 and US-30 in eastern IA with visible satellite and radar, was moving northward at 15 mph. In association with this feature was an area of enhanced CU over Benton and Linn counties, however capping should suppress convection in this area during the afternoon hours.

Further S and W, satellite imagery clearly indicates a boundary between US-34 and I-80 from central through western IA. Here, strong instability has developed as dewpoints have climbed from the mid-60’s to nearly 70. Over the last 30 minutes, elevated convection has fired in east and northeast NEB. This will probably continue to build south and east towards the stronger instability – the 19Z SPC MLCAPE indicates that the cap is rapidly eroding from southcentral IA through northeastern KS. In northeast NEB and southeast KS, parameters suggest that deep convection may be imminent, however things may hold off for a few hours until the thick band of jet stream CI moves E of the area. TOP radar clearly shows a north/south-oriented boundary bisecting the radar site and moving slowly eastward. Once storms fire, all modes of severe weather are likely given the degree of instability, shear, and favorably low dewpoint spreads.

- Bill
KD0DJG
www.twistertoursusa.com
2:46 PM CDT, 06/07/09
 
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