2/28/07 FCST: TX / OK / KS / NE

[Brandon Sullivan]

Sure Everyone noted the moderate risk across southern Mo and northern AR. That looks to be a good chase target.. Im thinking Springfield? The only thing stopping this from being a massive outbreak would be the timing. But im impressed no matter what.. Im possibly even pondering Columbia MO.. More central of the state. based on the CAPE progs. Helicity values also upped drastically.. If this is going to be the first big one in this area. Im onto going to miss it.

 

[Karen Politte]

I see the first caveat of relying solely on models and getting carried away with them. The ETA/NAM did NOT initialize well on this latest run. It had the moisture shunted south and west of AR with ZERO Tds throughout the state.

In real life - there is a broad area of bonafide 50+Tds across the southern half of AR and 40s elsewhere in the state.

This being said - I don't know how much we can rely on the ETA. My internet at work has stopped working and so I can't look at any other models. In fact it'll be a miracle if I manage to get this post off. Moisture for this system seems in better supply than the previous one, though. I can't chase either days so I am not doing much forecasting. I'll be watching this from home overnight.

KL

 

[rdale]

The ETA/NAM did NOT initialize well on this latest run. It had the moisture shunted south and west of AR with ZERO Tds throughout the state.

You may be looking at a bad website... All looks pretty good on my download, and even COD shows 12Z dew points in the upper-30's / lower-40's which is pretty much dead on with obs at 12Z.

http://weather.cod.edu/forecast/ETA/SP/etaSP_2_dewp_0.gif

By 18Z the NAM has plenty of low-level moisture over AR which given the current DP's in the upper-40's to mid-50's matches well too...

http://weather.cod.edu/forecast/ETA/SP/etaSP_2_dewp_6.gif

PS Don't use the name "Eta" anymore, that model is completely gone on a national level...

 

[Kenny Drake]

PS Don't use the name "Eta" anymore, that model is completely gone on a national level...

Good point, the only problem is websites have been very very slow to update. The RAP/NCAR site still uses ETA, COD still uses ETA. At this point its probably best to think NAM but still recognize that ETA is the same model.

Now as for current obs, OK mesonet show veering winds across central OK which is definitely not good for convergence along the dryline. However, I'm expecting these to back going into the afternoon after cyclogenesis occurs somewhere across NW Oklahoma. This should back the winds at the 850 level too, bringing some moisture back in. Initiation across C OK still looks very questionable. The 11am hourly RUC analysis forecast sounding (from Storm Machine) still shows ankle deep moisture extending only to about 900mb. However, the 3hr RUC sounding shows the depth increasing to about 850mb. The 9hr RUC forecast sounding (valid 00Z) shows a nearly adiabatic temperature profile up to 800mb and a moistening environment. LCLs still look a little high, around 815mb. Winds are progged to back nicely across with SSE at the surface veering to SW around 800mb. Daytime heating looks to be a sure bet from central OK northwards after looking at the current visible sattelite imagery. Low 60 Tds are now evident across southern OK per the Mesonet, and if the winds do back across central OK during the afternoon hours then the chance of seeing an isolated cell somewhere over central OK looks good. The vertical profile is definitely supportive of supercells, but LCLs may be too high to support tornadoes before things move east after sunset. The dryline Td gradient is still very shallow but will sharpen as the day progresses and cyclogenesis occurs. Once this happens, winds should back and convergence should increase ahead of the dryline eroding the CAP. Hopefully the convective instability will take care of the dry air problem near 800mb.

All in all, if initiation can occur over central OK we could see a rogue cell go up before dark. LCLs are probably too high before sunset, but if the winds can back sufficiently from the surface to 800mb then there is a chance (if your looking for a daylight nader). Large hail will not be a problem until eastern OK per the SPC Mesoanalysis hail params as -10 to -30C CAPE is relatively weak.

 

[Adam Atkins]

First evidence of surface convergenc SE of Norman in Grady county. Subtle veering just west of the dryline has provided a bit of enhancement and a tiny Cumulus field just popped up. This is probably going to become more widespread as the winds east of the DL begin to back as the surface pressure falls continue ahead of the upper level trough/associated jet streak. LCL's pretty high, upper 70's temps and mid-to upper 50's Tds.

EDIT: Purcell profiler showing the latest 900 mb wind obs backing from WSW to more of a SWerly vector, needs to continue because fairly uniderectional winds above surface ATTM.

 

[Melissa Moon]

Comparing the 12 and the 20z OUN soundings, it appears that the moisture situation above the surface has improved somewhat, while it seems to be about the same (albeit warmer now) at the surface. The LCL has lowered quite a bit, from around 700 mb to down closer to 850 mb. And seeing those Td’s in Central-to-Eastern OK approaching 60 most certainly cannot hurt…

 

[Donald Giuliano]

It seems the situation for this afternoon is looking pretty ugly for chasers. BL moisture is lacking with a discouraging OUN afternoon sounding and mid-upper 50s dewpoints throughout the warm sector...we need the dewpoints to go up 5F into the low 60s, which I view as unlikely at this time, with only 3 hours until sunset and the 60+ dewpoints down near DFW. I'm not excited about the possibility of getting the moisture up here in time for anything significant before dark.

 

[Jim Bishop]

It seems the situation for this afternoon is looking pretty ugly for chasers. BL moisture is lacking with a discouraging OUN afternoon sounding and mid-upper 50s dewpoints throughout the warm sector...we need the dewpoints to go up 5F into the low 60s, which I view as unlikely at this time, with only 3 hours until sunset and the 60+ dewpoints down near DFW. I'm not excited about the possibility of getting the moisture up here in time for anything significant before dark.

I agree the surface moisture is lacking somewhat from what was forecast this morning (i.e. low to mid 50s currently instead of upper 50s to near 60). But the BL moisture is has recovered quite nicely. Now OUN's got a 8C Td @ 850mb. The BL looks good for lp supercells. I agree that the tornado threat will hold off until after dark, once the higher surface dewpoints are advected further north.

I'm impressed with the RUC's persitence of indicating convective initiation along the dryline. Satellite imagery suggests it could be correct with towers developing over Central & North Central Oklahoma at this time.

 

[Jeff Snyder]

Gabe G., Kim K., Dan D. and I are heading north up I-35 and then taking 44 up NE a bit and then north to around the Stillwater area and hope for initiation on the dryline. This area will likely see surface winds backing soon and seems to be the area where the best juxtaposition of CAPE and hopefully improving low-level shear in the next couple of hours will be.

 

[Mike Peregrine]

I've been watching the warm front up here come tantalizingly close, along with dewpoints that continue to inch their way northward. RUC just loves to break out the precip right around 7:00 p.m. in a line moving from just SE of KC down through eastern Kansas. Judging from satellite, there's nothing but blue skies (and now some Cu in Oklahoma, I see). My plan tonight is to head south to the Butler area. Thinking about doing some night spotting anywhere from Butler to Warrensburg.

 

[Andrew Francis]

here in stillwater winds still out of the south with cu towers trying to go up here and there, looks like east of here is where the towes are more persistant