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

I was reading about this in the KOAX Afd as well... looks like a warmfront drapped from an area of low pressure will be drapped across Southern Nebraska late Saturday afternoon. With temps forecast in the low 90's and associated dewpoints forecast to be in the low 70's *ahem* overdone, instability values should sore into the 4-5000 j/kg range. Right now I'd like to be right along that warmfront where low level shear will be maximized.

Preliminary target: just south of York, NE
 
Thanks for the "heads up", Tim.

I've noticed a trend of people linking directly to the "so-many-hours-out" images. These sorts of links are only useful (at least relevant) to the posting for a limited time. When the next model run occurs (in 3 or 6 hours) the link will then point to a time frame different than the one your post was referencing. This especially limits the "lifespan" of usefulness for a thread. Someone going back and looking at older conversations to learn will only be confused by the images or image links provided, because they no longer match what was being discussed.

Would I be out of line in suggesting that posts can be useful longer if one saves the image to a web server or blog and then links to it there? Renaming the images will make them easy to identify. For example, instead of
CONUS_ETA212_ML_CAPE_60HR.gif
name it ML_CAPE_00z_05212006.gif (with the time and valid date as part of the filename).
This will make it easier for you to identify and pick out the image you want from your local images folder.

NOTE: If you wish to discuss my suggestion (above) the FORECAST thread is not the place to do it. I've created a separate thread here. Please post any comments you have regarding my suggestion to that thread and save this one for FORECAST-related stuff.

With that in mind, here are permanent links to the images that I believe Tim was referring to:

http://144.216.1.212/models/ML_CAPE_18z_05202006.gif
http://144.216.1.212/models/ML_CAPE_00z_05212006.gif
http://144.216.1.212/models/EnergyHelicity...8z_05202006.gif
http://144.216.1.212/models/EnergyHelicity...0z_05212006.gif
http://144.216.1.212/models/SRHelicity_18z_05202006.gif
http://144.216.1.212/models/SRHelicity_00z_05212006.gif
http://144.216.1.212/models/LiftedIndex_18z_05202006.gif
http://144.216.1.212/models/LiftedIndex_00z_05212006.gif
http://144.216.1.212/models/STP_21z_05202006.gif
http://144.216.1.212/models/STP_00z_05212006.gif

Darren Addy
Kearney, NE
 
I was also looking at this area for possible chase, the biggy problem
I see is the very warm 700mb temp progged to be around 10 to 13C
and may be too capped. Also the NAM tends to overdue the dewpoints
and this will affect the progged CAPE.

So the eastern edge of the cap in eastern MO, IA, or IL may be still a good
area and this is where the mid level and upper level winds will be stronger.
 
Good tip Tim,

Just had a peek at the 12Z ETA run, most of the ingredients appear to be there but the 500 and 850 mb winds ( > 30 knots) appear to favour MO vs the other States of the forecast area. NWS is forcasting a stong CAP for the region, however temps colder than -10 at 500 mb over MO should support vigorous convection if any moisture can break through the warm-dry layer. Event is still quite a few hours out, but I would tend to think that this will play out in upper MO and into IA or IL as well.
 
This Saturday?

Hmmm.....

I guess it depends on what you're chasing.

If you're into huge mesoscale bombs, mondo ice machines and great lightning....terrific!

But if you're looking for tornadoes....chances are pretty slim(not out of the question, however...).

As you can tell...I'm not a big fan of northwesterly flow...

For those of you that are looking for tornadoes.....save your gas money for next week!

Tim
 
I think Tim has captured the essence for Saturday, but...
northwest flow events can be great for tornados. I know
Tim knows that, but he is not a big fan of NW flow.

I am just looking at that area for more of a virtual chase, than
a real chase, because I don't care to drive that far from
western Kansas, so I am also looking more forward to next
week for the ridge to break and better flow to come over the
rock pile.

That being said, the atmosphere could produce a tornado on
Saturday in the forecast area, if the dewpoints and low level
flow can increase ahead of the cold front. I see now the NAM
is showing cooler 700 Temps, and lower dewpoints, so just
based on this like Tim says, not all that probable, but the
atmosphere has a way of adjusting in ways the models can't
resolve that far out. With northwest flow the shear profile
is not all that bad as progged. If the surface pressure can fall
locally and the surface winds pick up then the convergence
and shear for the storms increases. I know this is a bunch
of ifs and buts, but it is May and one cannot let down their
guard totally.

I think this Saturday will be a wait and see where the real
atmosphere will be and take a hard look at it on Saturday
morning before venturing hundreds of miles, but hey if you
are out in that area anyway and on chase vacation you should
at least see some good storms and possibly take home a prize.
 
I don't see anything that would point to a major tornado day tomorrow -- what are you looking at?
 
Tomorrow looks like the kind of day when you're the only person who sees the tornado.
 
Tomorrow looks like the kind of day when you're the only person who sees the tornado.
[/b]

Things arent looking that great tommorow, from what I can tell. Especially when it comes to the cap and shallow moisture, but I plan on chasing. Target right now is between Wichita and Enid. I'll be happy seeing some structure :)
 
Taking my chances on tomorrow for a variety of reasons, mainly cause I want the heck out of Denver on my vacation! :lol:

Moisture looks meager and the flow not so great, but as my good buddy Verne proved back on May 7, strange stuff happens out this far west.

The higher terrain of Western Kansas offers some hope for some storms tomorrow as less moisture isn't always a bad thing. Moisture is trying to tounge its way into the area, but the ETA is obviously well overdone. But we could see a small surprise.

Focus isn't that great, either, but after the string of nothingness, rain would be a welcome change. Especially in Kansas... we'll be out!
 
I expressed my pessimism about this weeked in the long-term thread in W&C, and that sentiment hasn't changed much. Shear profiles from far northern OK into southern KS don't look too bad, with rather loopy low-level hodographs. My main concern still involves available moisture. 12z soundings from southern/eastern TX indicate that the moisture is extremely shallow, which can be expected when we deal more with modified cP air than true tropical air. For example -- BRO shows moisture about 50mb deep, decreasing to about 20-25mb deep at CRP; LCH indicates about 40-50mb deep moisture as well, with FWDjust pitiful. With a moderate LLJ tomorrow and strong insolation / diabatic heating, I'm extremely worried that the moisture that we may have may completely mix out. Models continue to handle the surface moisture fields extremely poorly as well... For example, the 12z 8km Central US WRF run indicates >65F Tds across all of eastern KS east of I35 right now (9hr forecast). Surface observations, however, show that the Tds in that area are largely in the 52-60F range. This is a little surprising, since the WRF, from my experience, tends to be much better (relative to other op models) with the handling of surface dewpoints. In addition, the same models indicate >50F Tds in northern KS right now, whereas surface obs indicate Tds are in the 30s. Ugh!

Now, moisture may mix out some tomorrow, but mixing also works to make the low-level thermal profile more homogenous (i.e. nearly dry-adiabatic low-level lapse rate), which can help mix out some cap / negative area. However, looking at, for example, the NAM forecast sounding for 21z tomorrow at PNC, if we adjust the surface dewpoint to 59-60F, the LCL becomes ~3000m (about 725mb), with CAPE about cut in half and CINH double (at least) the NAM forecast. This is quite worrisome. Again, the shear profiles look sufficient for supercells (heck, check out the WLD sounding from the 12z NAM -- awesome hodograph curvature, with 430 0-3km SRH and 45kts 0-6km shear), but marginal moisture may inhibit thunderstorm development all together (the WLD sounding valid 21z indicates -60 j/kg CINH without any adjustment to the moisture profile). If we do mix deeply tomorrow, we could get some very high-based supercells.

All this said, I may head up towards the OK/KS border. If we can get a thunderstorm or two, I think there is a good chance for a supercell given moderate CAPE and deep-layer shear. The hodograph curvature also looks pretty good, which will help enhance updraft strength as we get favorable vertical perturbation pressure gradients. Low-level shear looks pretty good from the northern tier of OK counties into southern KS, but tornado potential looks minimal given very high LCLs and tendency for strong sub-cloud evaporational cooling.

EDIT: I see this afternoon's OUN AFD indicates this line of thinking as well:
<div class='quotetop'>QUOTE("OUN AFD")</div>
SEVERAL MODEL RUNS...MOST NOTABLY THE PARALLEL NAM...HAVE DEVELOPED
CONVECTION ALONG THE FRONT IN NORTHERN OKLAHOMA SATURDAY EVENING AND
OVERNIGHT. THIS MODEL...ALONG WITH THE NAM-ETA AND GFS...ARE ALL
STRONGLY OVERESTIMATING THE DEPTH AND MAGNITUDE OF BOUNDARY LAYER
MOISTURE. PARALLEL NAM MAY BE THE CLOSEST TO REALITY...EXCEPT FOR
EXCESSIVE MOISTURE POOLED ALONG THE FRONT. USING MORE REALISTIC
DEWPOINTS IN THE NAM-ETA SOUNDINGS YIELDS LITTLE IF ANY INSTABILITY
SATURDAY...SO FORECAST WILL REMAIN DRY.

EVEN THE AIRMASS OVER THE GULF OF MEXICO IS RELATIVELY DRY...WITH
DEWPOINTS AS LOW AS MIDDLE 50S IN THE CENTRAL GULF. TROPICAL
MOISTURE IS CONFINED TO THE CARRIBEAN AND NEAR THE YUCATAN.[/b]
 
Taking a quick look at the 03z RUC and the 00z NAM I like the area in
extreme ne Kansas up near Topeka and Kansas City, to maybe extreme
eastern KS into Missouri for possible supercells.

The reason is the mid level winds continue to be forecast of 30 to 40kts
and this area is on the edge of the very warm H7 cap and in the axis
of highest dewpoints. The low to mid level shear profile has lots of
turning and convergence.

If the storms slow enough to gain enough mid level storm relative
shear for the formation of deep mesocylones, the dewpoints don't mix
out into the 50s, and the surface inflow does not relax, then I see the
possibility for a few tornados.
 
It will be very convient for me that my Family reunion is in Ingersol out side of Cherokee so if anything pops that is anywhere near my line of sight it will be hugs and kiss' to everyone and on my way.
 
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.
 
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.
 
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)
 
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!
 
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.
 
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.
 
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