5/21/05: FCST KS

Cstok

EF4
Ok.. I am fairly new at this, but here goes:

I am kind of liking the setup for Sat evening across North East Kansas.

00Z Sun. Eta is showing nice 3000+ CAPE for North East KS. Also moisture shouldn't be a problem as 60+ dew points are fcst. Helicity values are high as well looking at the 00Z Sun Eta. Looks like a cold front pushes through Sat. evening through Sun. morning for that area.

Ok... let the tomatos fly.
 
I am kind of liking this little setup(and perhaps Friday). The 850 temps are VERY warm and may be too much but who knows. I like a strong cap and strong heating, with nice turning. The real cold front should still be up in the Dakotas. If that second sfc low forms in KS there might be enough convergence and heating to get something up in that. Anymore all I want to see is nice turning and instability...and of course a boundary. The cap can do what it will do. I'm excited for at least Saturday and maybe Friday.
 
I am also liking what I am seeing for the day on Saturday for the area of Kansas from say Manhattan, through Topeka, to Fort Scott. Sure the strong cap is there and evident in the 850mb temps and CIN maps, but like last Tuesday, this may pave the way for a nice isolated supercell that will be able to drop a few tornadoes.

Looks like if anything can form and break the cap, the cell would have some rocking instability with SBCAPE of over 4000 J/Kg to work with, along with a plentiful supply of moisture with Td's running near 75 degrees. With pretty decent upper level support, potential is there for long-lived cells. While the GFS is not even showing anything for Saturday, this is something worth watching for a potential local chase.
 
Oh me, oh my, a northwesterly (actually west-northwesterly) flow event, yet again! 0Z NAM is showing a secondary upper level system developing in the Sunflower State during the day on Saturday, as a spawn off of a main upper level system that will be moving through southern Canada. This upper level system, progged at 1001mb, is to be centered in southern Kansas at 0Z Sunday. Ahead, to the north and east of the upper level system, dewpoints will be skyrocketing into the 70's as surface temperatures in eastern Kansas will heat up into the upper 80s, flirting with the 90 degree mark. Upper level support will be modest, compared to a bunch of other days this week that could have resulted in severe weather, with progged readings at 500mb of higher than 40 knots (WNW) to the north of Interstate 70. 850mb temps will be near 25 degrees celsius, which may mean that we will have a nice CAP to work with, but with surface temperatures reaching into the 90s in central Kansas, we may break that CAP. Instability is showing up very good, and the NAM model has been pretty consistent with placing an instability bullseye of maximum instability in east central Kansas. With minimum Convective Inhibitive Energy and maximum Convective Availble Potential Energy, areas of Junction City and Manhattan may stand a good chance of seeing some severe weather development on Saturday. Though the NAM model does not break any precip out in the cities, this area will continued to be monitored by future model changes. Shear will be very good, with helicity readings of 300-400 m2/s2 expected in areas south of Interstate 70 and east of Interstate 135 in Kansas. In the Junction City and Manhattan areas, helicity will be modest to good, with readings up to 300 m2/s2.

Overall, this looks like a pretty good pattern to work with, but with a CAP looming overhead, we could see a repeat of May 10th, with initiation for storms holding off until late in the afternoon (if at all), but anything that can get fired up could be like the Audubon, IA supercell.

Graphic can be found in the "My Chase Forecasts" link below.
 
Saturday looks like a real break-or-bust kind of day for NE Kansas/SE Nebraska; strong cap (that NAM erodes by 0Z), fairly strong instability, tons of shear. SFC low detaching from trough and sitting in central Kansas; not sure if it's trying to render up an attached warm front in E KS or not. NAM breaks precip out in NE KS and SE NE at 0Z, so my hopes are up. It would be interesting to try chasing NW flow storms for a change.

Winds, 850 on up are turnin' like mad (bulk shear of around 50kts), with a good LLJ and a shortwave showing up on the 500 and 700. Hell, there's even some diffluence in the 250 right along the NE KS/SE NE border.

TD's nearing 70-75, if the NAM is to be trusted. And the juice goes all the way up to 500mb.

This looks like a pretty awesome-sauce kind of day. Hey, if nothing happens, at least I'll get to explore another side of Kansas. I've seen enough of the west in the past month. :)
 
There are alot of positives when looking at the 00Z NAM model for Saturday over eastern KS. I do expect supercell thunderstorms to develop late afternoon in eastern KS.....the combination of instability and shear do look pretty darn good. I would like to see the LCL heights a little lower...right now they appear on the marginal side. The LFC heights are also rather high at 18Z....but the do trend lower by 00Z over northeast KS and southeast NE. (less than 2000 m). I suppose if no one wanted to chase outside of the country on Saturday (southeast Manitoba looks pretty hot ahead of the deepening surface low) then east central and northeast KS and southeast NE look like pretty good to me.
 
Definetly looks like a good chase day on tap for Saturday in the Central Plains. Hopefully the CAP will erode early enough so we can get some chaseable convection going. I just read the SPC day 2 outlook...looks like NE KS, NW MO, SE NE, and SW IA are going to be the hot spots if development does occur.
 
The new 12Z NAM model data shifts CAPE bullseye northward and 25 degree celsius isotherm at the 850mb level westward.

Center of instability looks like it has gotten into the Cornhusker State, just to the south of Lincoln, closer to the Kansas border. A more smaller swath of 70+ degree Td's still exist, from Omaha, southward to Tulsa. Surface temps still looks the same from Nebraska, southward into Kansas. It appears now that a weaker CAP could be in place for most of SC/SE Nebraska running into NC/NE Kansas. Initiation looks like it might be a couple of hours earlier than on previous runs of the NAM model, but when is still a good question.

Though the instability bullseye may be in Nebraska, I think the better ingredients for more isolated supercells with a slightly stronger cap and better shear may be located in North Central and Northeast Kansas. NAM shows precip in SE Nebraska/NC-NE Kansas, so it's anybody's game. Nebraska for more guaranteed action and possibly earlier initation, or Kansas for something discrete and stronger with the risk of maybe nighttime initation, though the Kansas action may be higher-based than Nebraska action.

Website down at the moment, but will have updated forecast graphic on "My Chase Forecasts" in a bit.
 
I'm somewhat less enthusiastic after reviewing the 12z NAM run, as it appears the westward shift of instability axis is de-coupling from the stronger kinematics/upper level support. I was hopeful the secondary surface low progged to develop in Kansas would play a meaningful role in this setup. Instead, the center is now shown over far SW KS and appears to exert a lesser influence over surface wind field and moisture convergence. With the instability and surface lifting mechanism out in the 90 degree temps, further removed from better helicity and lower LCL's to the east, chase day may involve one of those "either, or" target decisions, with south central Nebraska perhaps being the compromise.
 
Well, the 00z NAM thankfully shifts the axis of highest instability back towards the east, so it looks like we may not have as much of an east/west targeting dilemna as previously feared. I'll take the combination of 70td/88t in eastern Nebraska over the 64td/96t in south central Nebraska.

Mention has been made of Iowa as possible target, where 0-3km SRH values reach over 500 r2s2. However, much of Iowa is expected to have significant cloud cover during the day, along with precip accumulations. Rather, I see a reasonable strategy to remain as far south under clearer skies as possible - but still within a realistic shot of convective initiation during time of highest instability.

Along these lines, I'm initially targeting an area from Beatrice to Auburn to Nebraska City, NE based on the following:

1. Good crossover of winds with height: S at surface, SW at 850mb, and W at 500mb.

2. Closest to area of lower 20t at 850mb without going into Iowa.

3. Although not ideal, 1,200 - 1,400 m LCL's much preferable to anything west of this location, and moving further north brings no improvement.

4. Southernmost band of best surface moisture convergence.

5. Best area of 0-3km shear and 0-3km helicity in the state.

6. With SE storm motions, I would rather be positioned south of metro Omaha and metro Lincoln.

7. Upside kicker: bullseye of 0.6 vorticity generation parameter, indicative of high rate of estimated tilting and stretching of horizontal vorticity by a thunderstorm updraft. Don't know much about the physics of this - but it sure sounds good!
 
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