2/9/2009 FCST: KS/NE/IA

[Dick McGowan]

I'm liking this day more and more for cold-core tornadoes.

http://wxcaster4.com/nam/CONUS_ETA_0-3KM_CAPE_78HR.gif
http://www.weather.cod.edu/forecast/GFS/gfsUS_850_vvel_78.gif
http://www.weather.cod.edu/forecast/GFS/gfsUS_500_temp_78.gif
http://www.weather.cod.edu/forecast/GFS/gfsUS_500_avort_78.gif

Pretty textbook setup minus the questionable dews. If dews can make lower 50's (maybe even 49), I'd say there is a solid chance for tornadoes associated with low-topped supercells in Eastern Nebraska/Western Iowa. Storms will fire early around 18-20z, so I'll be leaving early in the morning if this verifies. IIRC Jeff Snyder and Justin Walker saw tornadoes in early March of 2006 with upper 40 dewpoints on a cold-core setup in NC OK. Still a ways out though!!!!

18z is out: http://www.wxcaster.com/CONUS_MESO-ETA_0-3KM_CAPE_72HR.gif
http://www.wxcaster2.com/CENTRAL_MESO-ETA_SFC_SLPTMPDPTWINDSBLI_72HR.gif

 

[Dustin Wilcox]

It's been flopping around, 3 runs ago the GFS looked good, then it flopped, then again last night the GFS trended a little more favorable. Now that the NAM is in reach it too hints at the possibility. Got to like that CAPE bull’s-eye in the Dry Slot, and nearly -2 LI's. I was looking back, to 2/24/07 and it looks like dews never topped 50 anywhere in the target area really, though that day, the SFC low was at least 5mb lower than currently forecast at sub 986, and the low was slightly more organized and vertically stacked. A lot of similarities though, that day yielded several near tornadoes. 18Z GFS is in excellent agreement with the NAM as well. I’m not real excited, though I can’t say I don’t have any hope, as I have been taking advantage of the nice weather to get all the electronics installed in my new car, just in case…

 

[Michael O'Keeffe]

I agree with Dick we definitely could see some good cold core action in SE NE/NE KS on Monday.

Stats are only stats things can happen and I'm not letting my guard down since there have been tornadoes in NE Kansas in January before, just ask Scott Currens.

I'm saying I am not going to not chase what looks like a CLASSIC setup just because the numbers say there haven't ever been anything before. Because there's a first for everything right?

Anyway based on the 12z & 18z NAM the position of the 500mb low in contrast to the surface low is in the right spot for cold core, and the 500mb temps are cold enough to create some SBCAPE and MLCAPE possibly reaching 500 j/kg which is plenty and the 0-3km CAPE values look to be pretty big as well with values approaching 200 j/kg. That with the incredible shear is more than enough for some tornado cold core action.

 

[Brian Stertz]

Guess the key to the whole set up is if there can be any good clearing around that cold pool. Loads of vorticity and maybe an mid/upper 50's with a upper 40's Td could possibly do it. Think I'll wait for better things down the road...no matter how badly I want/need to chase. If I were to go...that area around Beatrice looks pretty good btw. In that strato-cu deck "season" so that may be the wildcard of this event.

 

[Verne Carlson]

Only ingredient I see missing for CC on this day is a good heat axis punching in from the southwest. Cold surface temps are wrapped around the surface low spoiling the setup. Everything else looks in place.

 

[Dick McGowan]

Yeah good call Brian/Verne.......and you'll never really know till the day of. Although, there is some hinting at a dryslot developing at the surface, whether or not warmer air will make it in with it to steepen the lapse rates is questionable.


http://www.weather.cod.edu/forecast/WRF/SP/wrfSP_0_30mb_dewp_78.gif
http://www.weather.cod.edu/forecast/WRF/SP/wrfSP_850_vvel_78.gif

 

[Chad Cowan]

There is definitely potential for some mini-sups but a few things worry me. First of all this shortwave is moving along at a good clip, throw in some very weak and shallow moisture and the dryline will be screaming east. Second thing is the ongoing precip/ squall line that develops late Sunday night. This is the hardest part of the forecast, esp this far out, but I don't think there will be redevelopment behind this line. Most likely any chaseable storms would have to come from this line breaking apart and individual cells strengthening throughout the day. Although the thermodynamic profile is barely marginal, most of the CAPE will be in the lower part of the troposphere which should lend itself to short but solid updrafts.

Edit: Just looked at the 18z GFS... of course precip forecasts aren't all that reliable but this new data is stellar for chasability on Monday. Like the previous runs' precip forecasts, at 12 & 18z Monday it shows a large squall line arcing from mid-MO into TX. This new output shows deep convection developing around 18z from around KC to Omaha in the the area of highest LL instability and where I assume there will be a very strong mid-level dry punch to help with clearing. I can definitely see some similarities to 2/24/07, and even though that day didn't live up to expectations, that day was probably my best photogenic storm day: first storm near Gardner KS, 2nd storm, 3rd storm after it dropped a TOR on Holden MO.

 

[Dustin Wilcox]

FWLIW, I just quickly peeked at the 0Z NAM, just now in, it's a little more favorable on the CC setup than the previous two runs, it's got a tad more moisture 1-2 degrees, and the system overall is stronger, deeper low, and a little colder upstairs. I'm still pessimistic, but at least it didn't get any worse...

 

[nickgrillo]

FWLIW, I just quickly peeked at the 0Z NAM, just now in, it's a little more favorable on the CC setup than the previous two runs, it's got a tad more moisture 1-2 degrees, and the system overall is stronger, deeper low, and a little colder upstairs. I'm still pessimistic, but at least it didn't get any worse...

Agreed... NAM forecast soundings (for instance: here and here) show a favorable thermodynamic/kinematic profile for shallow supercells. Cold mid-level temps surrounding the 500mb low / mid-level shortwave and low-level 0-3km CAPE of > 150j/kg and relatively steep low-level lapse rates (for a CC setup) will enhance low-level parcel acceleration / stretching in convective cells. The forecast hodographs are exceptionally large and cyclonically curved -- with 0-1km SRH a widespread >250j/kg. Based on the way it looks right now, I would definitely chase this event if I lived within <200mi of the surface low.

 

[Brian Stertz]

Tonight's NAM looks all the better for the cold core setup in S.Nebraska in the Fairbury-Lincoln-Beatrice area. Very nice dry slot with super 500mb height falls and impressive vorticity, 0-1 SRH is looking good as is the 0-3km CAPE. May only need a Td of 50 on this event to get a tube or two down. Still plenty of things to look at between now and then....am more impressed though. Better activate the cold core crews...if tonights trend continues.

 

[Chris Allington]

Tonight's NAM looks all the better for the cold core setup in S.Nebraska in the Fairbury-Lincoln-Beatrice area. Very nice dry slot with super 500mb height falls and impressive vorticity, 0-1 SRH is looking good as is the 0-3km CAPE. May only need a Td of 50 on this event to get a tube or two down. Still plenty of things to look at between now and then....am more impressed though. Better activate the cold core crews...if tonights trend continues.

I was just going to post about that. The last couple runs have really started hinting at the dry slot developing and giving us some decent warming. I'm not terribly optimistic but I have to work so it would make since that something cool would happen. Things should have a motion that would let me chase them on my way into work though.

 

[jshields]

today's day 3 outlook highlights the potential of mini sup's with a broken squall line and even tornadoes if enough clearing occurs. i was really excited about this but looking at the 18Z GFS run tonight makes me a little more pessimistic, as it looks like the low is slower moving through nebraska leaving the rain and clouds throughout the whole afternoon. only time will tell i guess, but if the sun pops out on monday aft, i will be out chasing locally in se nebraska or western iowa. did anyone else see this also?! i guess i haven't looked at the nam yet tonight so hopefully that looks a little better than the gfs does to me right now!

http://www.spc.noaa.gov/products/outlook/day3otlk.html

 

[Randall Cooper]

NAM looks better for the 00Z run, I will definitely be chasing this on Monday. Even if it doesnt amount to much, its too close not to at least get out and test all the new equipment I have this year, well within 200 miles

 

[Matt Gingery]

Yeah Day 3 is shy to the fact that there may be a chase day for us on Monday. Works great for me! 3 hr drive to Topeka area for me. If the forecast holds I will head out around 1:30 SGF time and be in Topeka around 4:30. I hope the outlook is much more clear tomorrow, as I would like to slide over to Emporia, its much closer. Maybe Tuesday in the jungles around Little Rock/Memphis. I would like to keep in contact with anyone that intends on heading out. . .

http://www.spc.noaa.gov/products/outlook/day2otlk.html

Day 2 outlook still holds on forecast trends of a dry punch to take place with low topped supercells.

 

[Brian Stertz]

Looks to me like the best cold core supercell threat will occur from extreme NE Kansas into extreme SE Nebraska extreme tip of NW Missouri ,and WC/SW Iowa. Not only do the models support very strong vorticity in this area, there is also a very pronounced mid-level dry punch aimed at this area by late afternoon to assist in clearing. There is a town up there on the Missouri River on the Nebraska side...Auburn NE...that has a notorious past with cold core tornadoes. If everything comes together as it looks on the latest NAM, things could get pretty interesting near this town...or possibly not far across the river in extreme NW Missouri & SW Iowa. Not calling a dead on target off 48 hrs. NAM, but this would be my pick for the target area forecast exercise....