3/7/06 FCST: Central / Southern Plains

[Jonathan Whitehead]

Originally posted by Storm Prediction Center
THERE IS SOME CONCERN THAT DENSE HIGH-LEVEL CIRRUS CANOPY MAY TEND TO RETARD DIABATIC HEATING ALONG DRYLINE WITH AIR MASS REMAINING CAPPED...ESPECIALLY WITH SWD EXTENT. LATEST MODEL GUIDANCE DOES SUGGEST A GENERAL NW-SE DECREASE IN THIS HIGH CLOUDINESS TODAY.

Those of you that live in the Southern Plains may have noticed the amount of dense high level cirrus in the skies the last several warm and pleasant days. I think this may be a by product of the ridge, but if this trend continues, which could easily occur then everybodys hosed. Im not sure what causes cirrus to develop on warm and windy days but I do know they are quite commonly associated with hot, dry climates ala Arizona in summer. But do look out for this in the morning.

 

[Nic Wilson]

Originally posted by BrandonWhittington
I'm still amazed on how fast and far west the moisture is returning. Dew points are now higher in the Texas panhandle than in North-central oklahoma. If moisture keeps increasing here in the panhandles, I will have to change my target area for the 3rd time. I still feel that Shattuck will be a good area, but, now I'm leaning closer to the Texas-Oklahoma State line. Dew points are now in the low to mid 40s in the eastern Texas Panhandle. I will be anxious to see how the SPC handles this.

Brandon -- What you're seeing is a pretty well defined warm front that is sneaking its way northeast through the overnight hours. Its location in 12 hours will largely define how tomorrow will pan out, as it will create a fairly dense stratus shield and the overriding Pacific moisture advection aloft will stream high cirrus into Oklahoma as well, which will negate some of the impressive >2000 Jkg-1 CAPE forecasts by the NAM.

Tonight's 00z NAM is quite consistent with its 12z counterpart from this morning, so not much else to add that hasn't been said. The FSL's experimental 13 km WRF/RUC 03z run breaks out precip. between 21z and 00z tomorrow afternoon in the Perry, OK region - once again well in line with the NAM. GFS also initiates convection between 21 and 00z near the Enid region. Pretty surprising to see such continuity between the main NWP guidance. IF convection is able to initiate, estimated storm motion will be ENE at ~ 30 kts. Wet bulb zero heights ~ 8000 ft and unstable lapse rates above -10C will be conducive toward large hail production in the vicinity of the most potent updrafts.

I will be taking my brother who is in town for his spring break on his first chase ever tomorrow, which will make it fun no matter if its a bust or not. Our target will be north up the I-35 corridor and westward to meet the dryline where the cloud cover is most minimal 12 hours from now. Best of luck to everyone that is able to head out.

P.S. Aaron - put your seminar presentation online and I'll download it while I'm baking in the sun waiting for the cap to break.

 

[Scott Olson]

Originally posted by Aaron Kennedy
I'd be very skeptical of 2500j/kg CAPE being realized in this type of early season event... just a little bit of a negative (be it clouds, slightly less dp, etc.) can absolutely kill these sorts of numbers. That said, I'd be chasing if I didn't have to give a seminar about supercells :shock:

Aaron

I wouldn't be suprised if it was less due to cloud cover, mixing, etc. With the Therodynamics tommorow we could probably count on a supercell even with half that much instability (which is consistent with current RUC, GFS, NMM WRF).

 

[Chad Ringley]

The WRF-NMM 4.5 km that the DT Center produces for the SPC (which I would assume has no Cp scheme) shows convection at 14 UTC (over Central OK), 23 UTC (SC KS), and ~04 UTC 08 March (SW OK)....Which is consistent with the current fcst thinking...i.e... early morning elevated convection, some deep sfc based convection (assuming the cirrus canopy doesn't win), and so on.

These graphics are available at:
http://wwwt.emc.ncep.noaa.gov/mmb/mmbpll/cent4km/v2/

Didn't see a link so I thought I'd post it. Looks like the Spring/Summer 4 km explicit runs for the CONUS using the WRF-ARW core will start again on April 18th.

Good luck to those out tomorrow!

 

[Chris C Sanner]

Maybe its the insomnia in me, but this event is relatively similar in many ways to the March 27, 2004 event which produced a couple of nice looking supercells. On that day, you had similar winds with around 1000 cape and I remember there being some really nice supercells that day. Just a thought to throw out there.

It looks like we'll have around 55-59 tds to deal with for sure, as I don't see us getting above 60 in many places tommorow. Things should be interesting no doubt. Regardless, we're in for a decent 48 hour event that will ge that SDS out of the window for most here in the Southern Plains..

MORNING EDIT: RUC this morning painting a much different picture than the NAM. If you look at the forecasted soundings for Southern or Central Oklahoma just east of the dryline in the forecasted 60tds you get a very favorable supercell/tornadic environment in my mind. However, the NAM is still very consistent in its previous runs and LCLs are still quite high across the region. Plus neither breaks out widespread precip in their 12z runs. I think we're gonna get one to break the cap today at least somewhere in stronger localized forcing and less cin. Still going to be an interesting event...

 

[Simon Brewer]

Unseasonably strong CAP, weak upper-level support, and narrow swath of instability are quite a few important indications that I will have a clear-sky-bust today. I'm still going out, but I'm pretty sure I'll be watching some struggling towers for a few hours, maybe one will actually give me hope and appear to break the CAP, but it doesn't look good.

I am, however, going out anyways, because if a storm could hold its own for at least an hour it has incredible tornado potential; the shear is unbelievable!

 

[Gabe Garfield]

Ya'll should check out the latest RUC, when you have the op. Several isolated storms (presumably supes) break out by 00z in NC OK and SC KS. The sfc winds are backed considerably more on the RUC output as compared with the ETA, resulting in strong ll shear. The only problem from the RUC is a relatively narrow plume of BL moisture.

Gabe

 

[Bill Schintler]

Chase target for today, March 7

Chase target:
20 miles SSW of Wichita, KS.

Timing:
Storm initiation 5:30 PM CST.

Comments:
An isolated supercell storm or two may form shortly before sunset in the target area. Providing that this occurs, hail along with impressive storm structure and an isolated tornado will be possible. A negative today for chasing is that any convective initiation may hold off until shortly after sunset when the low-level jet veers back to the west.

Discussion:
A somewhat complicated synoptic and mesoscale setup today, with several features embedded within SWRLY UA flow, and a lack of significant SFC features or boundaries. Of particular note are numerous ripples within a vorticity ribbon that will stretch from the TX panhandle through SRN KS and into ERN IA by 00Z today. One vort max within this feature, which will be lifting into NWRN OK, will be juxtaposed with both a narrow axis of low-level moisture with resulting instability, and decent shear as a dryline approaches I-35 in KS/OK. This max may provide the necessary local assent to overcome 50-100J/kg of CIN. Moisture return is underway as 12Z sounding data shows a 200mb deep moist layer at OUN, along with shallow moisture layers at AMA and DDC. Deep layer shear of 50kts will support storm organization, while SRHs(0-3km) will be locally enhanced to 300 m^2/s^2 by SFC backing in response to the approach of the aforementioned mid-level wave.

- bill

 

[Gabe Garfield]

Justin Walker and I will be headed out to Wellington, KS where we will base for today. I believe the best juxtaposition of CAPE/shear/low LCLs will be in this area, with options to go further north or south if need be. If ya'll are in the area, be sure to give me a holler via pm. Godspeed to all chasing today.

Gabe

 

[Chris C Sanner]

Things are looking progressively worse for initiation in Oklahoma right now. Seeing as how I can't get to Kansas before dark because of class, I'm now losing hope in the day. I'm still planning on going out, but I'm afraid I might be sitting under a cirrus filled sky all afternoon, kind of like 75% of last year's chases. This is a new year though, so who knows if our luck has changed right?

 

[matt patterson]

Ok im new to the forum, but i'm starting to notice 2 different types of forecasts here:
1. People who are actually contributing to the scenario at hand, regardless of whether or not the can chase.
2. People who a doing nothing but being pessimistic because they cant make it in time or at all. Is this actually helpful information??
This is a forecast thread and not one of "i'll play it down because i cant go"
With that said, i see some real promise in today pending moisture convergence along the dryline. winds are slightly backing more with time, instability is there with about 1500-2000j/kg. The area around 412 north and west of Enid looks really good, this is also the area where LCL's will be lowest as mentioned earlier...

Good Luck for those heading out.

Later

 

[Chad Ringley]

Originally posted by Chris_Sanner
Things are looking progressively worse for initiation in Oklahoma right now. Seeing as how I can't get to Kansas before dark because of class, I'm now losing hope in the day. I'm still planning on going out, but I'm afraid I might be sitting under a cirrus filled sky all afternoon, kind of like 75% of last year's chases. This is a new year though, so who knows if our luck has changed right?

I agree with you Chris...flow is veering quite a bit ahead of the dryline in NC OK, and the cirrus canopy shows up quite well in the solar rad graphics from the Mesonet...about a 300-400 W/m^2 gradient between Enid and areas to the E.

EDIT: Matt, the flow does seem to be backing a bit farther E near TUL, but I think we'll need to see this happen more toward the I-35 corridor to get any show this afternoon. Don't like the sfc wind trends immeaditley ahead of the dryline right now (in the Alva, Seiling, Woodward area).

 

[Eddie Natenberg]

Hello everyone, I have come out of my cave to give an unusual forecast.

I feel that the SPC has done a good job with outlining the area of highest props of severe weather and tornado threat. This is located north of OKC to ICT along the I35 corridor. I believe based on the most recent surface data and RUC progs that convection will form in this area as a complex and propagate east with the biggest threat being hail and high winds. The problem here is that I don't think parcels will be able to rise through the boundry layer, especially since we have a nice cirrus canopy in the area. That being said I would say that there is a chance for early storms and stronger cells inbeded in a complex later tonight to become temporary surfaced based. This should keep tornado potential to about 2% - 5%.

Guess (wait I mean forecast) #2: Convection will not initiate due to increased convergence along the dryline, but more importantly to a strong area of enhanced vorticity advection at 500 and 700 mb thats enters the region around 0 - 3z tonight. This will be along and ahead of the dryline in the northern half of OK. Storms will congeal into a line fairly quickly along the KS / OK border due to a rapidly increasing LLJ leading to strong convergence for elevated cells. I am pretty impressed with the RUC foreecast for the LLJ seems propable and unseasonablly strong (40 to 50 knots). This may help maximize vorticity closer to the boundry layer, if stoms can become rooted.

Guess 3: Ok this is the forecast that will probably bust. My target is from lawton north to I40. Why? a poorly defined small area of strong winds at 700 mb will cause the possibility of isolated development of convection along the dryline in SW OK with increased vorticity advection. If convection can break the cap, then i think it should stay isolated and with dewpoints being higher in SW OK I hope low level instability will be maximized and increase tornado potential. Time for a gamble.

Eddie

 

[Karen Politte]

Broad area of upper-50 Tds stretches up to the OK/KS border at 1.10PM CDT. Welcome to March - home of the shallow moisture chase days. Those wondrous days that make you salivate with 991mb lows progged by the models (OK OK that's for tomorrow), and yet even though you could go out you know that the habitual moisture problems are an overriding negative for the whole scenario.

If you want to chase model runs - go out and wait for the RUC's promised precip to break out over western/northern/NWrn OK by 0300Z. Maybe you'll get some lightning. During daylight hours you'll be playing with 500-1000CAPE.

SPC's Mesoanalysis page shows our beloved supercell composite up to "8" along the I-35 corridor north of OKC to the KS border. Not too shabby. There's even a 1 SigTor along the same plot.

Impressive drying is through to DDC now which has a Td of 25. There are some easterly components to the southerly winds in central and north-central Oklahoma which bear watching.

Good luck to all who go out. Note - I haven't forecasted for KS at all. I'm keeping my sights - and brainpower - on Oklahoma.

Chalk me up under the pessimistic category. :wink:

It's easy when gas is 2.30/Gal and rising...

Karen

 

[Mikey Gribble]

I am targetting Medicine Lodge (or somewhere along 400 depending upon where the dryline sets up). I think we got a good shot at a tornado or two if storms can fire at a reasonable time. Not a bad setup for early March. Good luck to everyone out chasing today.