5/20/06 FCST: KS / NE / MO

[Rich Thompson]

In reference to Jeff Snyder's ealier post regarding the low-level moisture:

The big problem we have is not a modifying "continental polar" air mass, but a relatively *warm* and dry continental air mass over the Gulf basin. The sea-air temperature differences are minimal, which suggests that sensible heat fluxes will also be minimal. Why does this matter? Well, there's little to generate a deep/moist boundary layer over the ocean without the temperature difference to drive mixing. That's the big reason why there's been so little change in the moisture for the past 3-4 days at the buoys and coastal locations.

The offshore flow phase and a relatively warm air mass:
http://www.chasetolive.com/images/CRP1.gif

The onshore flow phase with a shallow marine boundary layer:
http://www.chasetolive.com/images/CRP2.gif

Until we get the old frontal zone in the Caribbean to retreat back to the NW, we'll continue to have problems with a "shallow" marine boundary layer that's susceptible to "mixing out" inland. It may seem counterintuitive, but we would be better off now if a much colder air mass had scoured the Gulf basin!

Rich T.

 

[Fritz Kruse]

Quick look at 12z soundings, show very junky low level moisture:
http://www.rap.ucar.edu/weather/upper/

The dewpoints should mix out in the afternoon like others
have been saying, unless they can pool along and just
north of the boundary.

I think I am staying home and watch the Preakness and
wait for next week.

 

[Mike Hollingshead]

Buoy 42001 5 Day Plot

Buoy 42002 5 Day Plot

Those out in the central Gulf seem to be doing well. Some of the better air that was shunted south must be making its way back. Too bad we can't launch baloons from those.

(I guess this has nothing to do with the current day and maybe doesn't belong on here)

 

[mikegeukes]

NAM Forecasts
Lowest Boundary Layer Dew Point Temperature (deg C)
http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/e...td_animate.html
http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/e...td_animate.html

Dew Points are in Celsius not Fahrenheit
10C=50F 15C=59F 20C=68 25C=77 30C=86F

Lowest Boundary Layer RH (%)
http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/e...rh_animate.html
http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/e...rh_animate.html

Mike

 

[cdcollura]

Good afternoon,

I am currently sitting in Cassville in SW MO and cap is holding strong...

Not expecting much with the 700 mb temps at near 10 deg C despite decent shear (boundary induced) and high CAPES.

Spent downtime from ridge near St Louis so I am headed back for activity hopefully in KS tomorrow (5-21) so a slight detour off I-44 didn't hurt much.

Models are all breaking down the ridge somewhat - Thank God!

 

[Mike Johnston]

Noting the discussions about quality and depth of moisture, re: today's setup it must be acknowledged that actual surface dewpoint observations seem to be tracking fairly close to the model forecasts. Quick check of the OK mesonet shows good swath of mid- to upper-60's tds across the eastern portion of the state.

Still many negatives which must be overcome - very high LFC's and LCL's, strong capping inversion, I wouldn't necessarily give up the ghost on this setup, especially on a weekend for chasers in the vicinity (of the western edge of the SPC slight risk outlook). Some hints of differential advection, and the normalized CAPE and lifted index as indicated on the current mesoanalysis are encouraging. Reading over the AFD's in the region, with deference to the pros, clearly confirms this as an "underdog" setup, but with continuing tendency of the RUC trying to break out precip past 00z just along the warm front and deepening the surface low over the panhandle, the environment, IMO, is interesting enough to continue monitoring.

 

[nickgrillo]

Yeah, there is a pretty strong inversion aloft (~10C at 700mb) with CINH being the weakest just south of the front in extreme southern MO and northern AR (where more insolation due to less cloud cover has resulted in stronger diabatic heating and resultant steeper low-level lapse rates) with SPC mesoanalysis showing high LFCs (2500-3000m) which is a product of the inversion layer. Current surface analysis shows very high dewpoint deficits across the region (i.e. northwest/northcentral AR obs showing > 25 F depressions) which is yielding high LCLs, particuarly south of the frontal zone (with smaller depressions just north of the front further into southern MO) -- e.g. 1800m AGL or higher. The RUC wants to initiate precip across the region (southwest MO) by 00z, which isn't out of the question given the persistant low-level convergence along the front (along with moisture convergence) which may aid in the initiation of deep convection within the next several hours. The background thermdynamic and kinematic setup is more than favorable for organized supercells and bow echoes (e.g. 40-50kt 0-6km shear and 2000-3000j/kg sbCAPE) should deep convection develop, which isn't a definite, but quite the possibility.