11/12/05 FCST: Upper Midwest through Southern Plains

[Mike Hollingshead]

If it got it from the NAM it was then certainly going in a better direction. The mm5 on Earl's site had a better handle on this before the nam.

 

[Ronnie Bradley]

It depends on which model you look at...... 12 run of NAM is neutral/slightly positive... 12Z run of GFS is negative tilt.

NMC is favoring the GFS solution. Based on BUFKIT forecast soundings from the latest run, eastern OK/northeast TX/Arkansas/northwest LA have the best chances for supercells...mainly Saturday night into Sunday. Unfortunately, it looks like the "best chase" opportunity will be in the trees at night .

As usual, it has to strike at night . I've also been following the models (mostly GFS) at the cod.edu site. From the looks of things, dewpoints better come up quick. Dews are in the mid / high 30's F over much of Arkansas. That LLJ better get its act together if anything is to materialize within 12 / 24 hours!
Right now (11:00 pm CST) KLZK's VWP is showing a slight veering wind profile (SSE surface winds; SW winds around 4,000 ft. All the winds are low level and not anything above 12-13K ft, according to the radar.

To my eyes, the GFS is indicating a negative (albeit slight) trough during the Saturday evening / Sunday morning timeframe.
Anyway, I'm prepared . GRLevel 2 is waiting...

 

[Dan Dawson]

Interesting the GFS has shown pretty much what the eta has now come to, for several runs. Chalk one up for the GFS....or at least to this point. The MM5 was also similar to the latest ETA for a few runs.

I'm thinking of a Lincoln to Nebraska City line and then into southern IA...early At least it seems to be the place the models think the dews will reach.

For what it's worth, depending on what MM5 you are using it could be getting it's IBC (Initial Boundary Conditions) from the NAM... I think the GFS is initializing things better, and is leading to better performance (up until now, at least).

Just to clarify, I think you mean Initial *and* Boundary Conditions. They are technically two different things. The initial conditions are applied to the entire grid domain of the model (i.e. MM5 in this case) at the initial time of the forecast, usually by direct interpolation from, say, the NAM, or GFS, or some other large® scale model, while the boundary conditions (derived from the forecast fields from the large-scale model) are applied at regular intervals during the forecast only at the boundaries of the model grid, so that the MM5 or whatever model is being run "nested" inside the NAM knows where to get evolving atmospheric information from outside of it's domain. I don't want to sound picky or anything, as I'm sure you knew the distinction, but just thought I'd clarify it for others here who may not know how these things are done.

 

[Bill Tabor]

Ok reviewed some more now with the latest NAM out. I like the set up less for my southern area. Shortwave is showing slight neg tilt now, but appears to 'congeal' / pull sfc low further north and east a tad faster than previous run leaving less for those of us down south. If the overcast forecast verifies then it could be tough for instability. Latest NAM is showing less Cape than earlier run and better shear moves off further north and east faster. This gives even less chance for Tx and even eastern OK may only catch severe a bit. Looks like MO will be the main center of action on the southern end IMO. I'd keep north Tx in a slight but not sure if I'd give them any torn probability. Eastern Ok for 2% torns. MO maybe 5% with nw AR catching a tad as well. If lucky maybe a small squall line later in Tx. It would be nice to see a small shower pass through Austin during the evening. Looks like a 'yawner' to me IMO at least for Tx and possibly Ok. Perhaps as this system moves further east in the next day or so there could be some potential for those areas.

 

[Scott Lincoln]

Of course we can't forget to mention Iowa, which will be closer to the surface low and closer to the dynamics of the system. If this scenario is similar to what we had last week, it will be more dynamically driven and not driven by the normal parameters we look for in the spring like instability and moisture. It also looks to me like the best forcing will be just south of the low pressure center, which moves through NW Iowa during the day.

Regardless of what happens, I never imagined seeing bufkit profiles like I am looking at now in mid-november....

 

[Mike Peregrine]

Iowa is the place for me - within 200 mi. of the low, in the narrow intersection closest to the boundaries intersecting a triple point. With lower dewpoints and total CAPE than what we normally consider acceptable, this system has a few earmarks for the development of low-topped supercells to develop by afternoon closer to the pool of very cold air aloft. Just a thought, but I'd say extreme SW Iowa will be a great target today, so get close to the TP. It will be cool and grungy, with lots of elevated crud just to the east, so most chasers will wonder why they are there ... but the day still has the potential to end up like a dynamic, early spring system.

 

[Kiel Ortega]

Just for thought...what is the "chasability" of all this with forecasted storm motions of ~55-60 kts (so right turning supercells, if they happen, really aren't going to be all that slow)? Haven't got the time to figure out the event, but just was curious about speeds, so I took a look at the 09Z RUC soundings....I'm way past keeping an updraft intact...but is it going to be possible to chase this stuff with those kinds of speeds (don't know the road networks in the NC MO area--the 5% tornado area this morning)...IMO, I doubt it.

 

[Mike Hollingshead]

I'm way past keeping an updraft intact...but is it going to be possible to chase this stuff with those kinds of speeds (don't know the road networks in the NC MO area--the 5% tornado area this morning)...IMO, I doubt it.

Drive east on an e-w highway and catch them as they move ne. Storms in IA April 8, 1999 were moving amazingly quick and looking at Stertz and Piotrowski's tornado video from that day it certainly looked worth going out and being a chaser on, even if one can't exactly stay with one storm.

My target remains the same but with thoughts of actually moving it a smidge more west. Hopefully though Lincoln will be far enough west. It is currently 33 in North Platte, lol.

 

[Mike Peregrine]

Won't be easy to chase ... fast storm motion combined with difficult terrain/roads will make it a challenge. But we'll still have to give it a shot. Doubtful that we'll see much in the way of true right-turning in a situation like this. They'll just keep booking off to the northeast. Hopefully we'll manage to set up ahead of one or two cells to let them breeze by.

 

[Damon Scott Hynes]

Hopefully though Lincoln will be far enough west. It is currently 33 in North Platte, lol.

I'm planning on Syracuse along NE-2. At least It'll be over with quick! I don't want to get near Lincoln with all the Husker fans leaving the game early

 

[Mike Peregrine]

While my target will likely stay in extreme NW Missouri, SW Iowa, here is the 05h RUC's idea of sfc-based CAPE, which is well west of I-29.

http://www.emc.ncep.noaa.gov/mmb/rucsvrfcs...rent/cape05.gif

By 12h, instability quickly pushes well to the east as the dryline makes its fast punch, which makes me think that it would be good to be well ahead of the DL to let storms get off the ground and start moving. Still thinking about it.

http://www.emc.ncep.noaa.gov/mmb/rucsvrfcs...rent/cape08.gif

L.I. certainly starts maxing out near Bruning (hwy 81 corridor) at 05h. Hmmm ... I might have to go further west too ...

http://www.emc.ncep.noaa.gov/mmb/rucsvrfcs...rent/lift05.gif

 

[Jonathan Whitehead]

At the SPC now looking at the latest updates. Still going w/ my initial forecast of SQALL LINE. Will see everyone in E OK, headin to FSM now.

 

[Ryan Pfannkuch]

12z RUC showing good signature of convective initiation over the SW 1/4th of IA around 3pm or so. If nothing farther west gets going and organized earlier, I'm thinking the Hwy 71 corridor between Atlantic and Clarinda in SW IA is an area I'll be monitoring very closely.

No matter what, anything that fires down that way, whether it be cellular or linear, will be moving up towards me in central IA very quickly so I could easily get involved whether I actively chase or not.

 

[Cindy Simons]

Dew Point

I'm watching the dew point. At this point, the dew point in Des Moines is only 48. Some mild showers are approaching so let's see if the dew point rises over the next few hours.

 

[Ronnie Bradley]

Right now, radar is showing light to moderate showers moving NNE/NE around 40mph in Arkansas, mostly over the western 1/3rd of the state. Vertical Wind Profile out of KLZK is showing rather strong mid and upper level winds, mostly out of the SW. Surface winds are out of the S or SSW. There is a smidgen of directional shear but not much. As of now, multicellular lines of showers and storms are being favored. We'll see if any discreet cells jump out ahead of the line this evening...
Monday, another neutral trough is forecasted by GFS to cross over Arkansas. Late next week, it looks like a big ridge is going to set up shop over the western 3rd of the US and a big trough over the east. Time for those Alberta clippers! Brrr.... ?