3/19/06 FCST: S-CTRL US

[Tom Dulong]

The 3/15/12 UTC GFS is consisent with the previous run in advertising the digging of a major upper level trough into the western U.S. early this weekend and then ejecting it into the south central states as a closed low by Monday. The SPC has circled this area for a threat of severe in its latest 4-8 day outlook. This forecast pattern looks similar, albeit about 200 miles farther south, than the March 21st system last year:

http://www.spc.noaa.gov/exper/archive/even...0321/index.html

Happy chase dreams

 

[Jason McKittrick]

Past 5 GFS runs forecasting a whopper for SE Nebraska. Last nights GFS gave Omaha about 2.1" QPF all snow. This mornings GFS suggesting a little less about 1.6" QPF all snow. Of coarse its a little early to try and pin down amounts but it definitely looks like we will have our biggest storm of the year early next week.

A little equation I learned in synoptic meteorology....

The Snow you get = The Snow forecast * e^-t

with that in mind I don't think I will get too excited just yet.

 

[Jonathan Whitehead]

I must admit, It did catch my attention to find my area under a slight risk on the new Day 2 as I am presently at my home in W. Ft. Worth for spring break. But unfortunately for this event there will be a cold stable layer at the surface so it will be primarily a wind/hail event. Though if we could just get tonights cold front to retreat back just a little as a warm front after it stalls this afternoon, that would add a little spice to the mix, esp if the dryline were to take shape.

 

[brody_clifton]

Right now all the all the models show the closed upper low ejecting out of southern CA later this weekend,
with a surface low developing east of the Rockies Sunday and pulling up decent maritime moisure into central and southeast TX by late Sunday. Looking at the 84 hr NAM for Sunday afternoon, things look good from central TX around the austin areas NW towards Wichita Falls and NE towards DFW. NAM has the dryling running pretty much north south through these areas at 00Z Mon, with the stronger upper level winds in west TX and the 850mb LLJ in east TX at the same time. So even though the jets may not necessarily intersect, Sunday is shaping to be a chase day for you Texans and Okies.

ECMWF and GFS have similar solutions for overnight Sunday into Monday. Both have the upper low centered near NE at 00Z 3/21 and both indicate a 90+ kt 500mb jet will round the east side of the base into east TX, northwest LA, and AR. The GFS has consistenly been showing a sharp baroclinic boundary along the the warm front from central LA into AL for Tuesday, with surface dewpoints in the mid 60s pooling south of the warm front here Tuesday. I'm thinking the central of southern sections of these states will be about the only areas with enough instability for a supercell risk Tursday, but given the forecasted dynamics any that do form and manage to root at the surface could be whoppers.

 

[matt patterson]

The 18z NAM is painting an even better picture for sunday in the wichita falls/childress area. There is a beautiful Dryline Bulge, with winds backing all along the dryline. 500 spds look to be near 65-80knts with 700 spds around 40-50knts, which means one thing slower storm speeds in good chase terrain. storm motion should be ENE so getting a storm off the Dryline into the better helicity's(>300m2/s2) should not be a problem. CAPE looks to be fairly nice along the nose of the Higher TDs(60-65) yeilding greater than 2000 J/Kg.

Only time will tell but right now im planning on chasing.

Cant wait to see what 00z says. i also would like to see some agreement between the GooFuS and the others.

Later

 

[Adam Atkins]

If the 12z NAM paints the same picture as reality on Sunday, I'll kick off the 2006 season in NW TX. Cross-isobaric surface winds, backing 850 mb flow beneath a strong SW mid-level jet. If clearing occurs, there could be an isolated supercell that forms at the triple point and rides the warm front across the Red River valley, sounds good to me (and the rest of Oklahoma chasers). So far this season has looked phenomenal if you are able to keep up with storms.

Adam

 

[Justin Walker]

0z Nam still in good agreement with the earlier posts, I won't rehash. Still a question in my mind with this setup, the cap. 850mb temps running 16-17C, pretty warm. I hope low 60's Td's will be enough, but hey...it's march and low 60's Td's...I'm chasing! B)

 

[brody_clifton]

Forecast area here is for far S Central/SWern OK and northwest/northcentral TX. The GFS, the NAM, and myself all disagree on the timing of the ejecting shortwave crossing north of the region, but agree on the fact that it will happen sometime between Sunday 3/19 and Monday 3/20.

Analysis of NAM 60 hour output valid 00Z 03/20 (6 PM CST):
From the NAM, I'm liking this area for Sunday - just northeast of the Wichita Falls area encompassing a few counties along, north and south of the Red River. With a weakening 850mb jet forecasted during the afternoon, due to a flattening upper trough blasting east, it may become more difficult to push higher thetae air that far north. But I think the idea of juicy air pooling somewhere up in nw Texas during the late afternoon is believeable. NAM shows a 60-65 kt jet max over the same area all day Sunday. Bad thing is, the NAM, as of 12Z0317, doesn't have the real shortwave cutting across north Texas until Monday afternoon, and along with it a 90kt 500mb jet max over SW Texas by midday Monday as a result of the shortwave centered over northeast NM becoming negatively tilted during the afternoon. My opinion is, this system won't hang around that long, and will have already ejected east by early AM Monday due to a digging upstream shortwave approaching northern California. A compromise would mean things happen overnight, so hopefully me or the NAM one are right on the timing.

This morning's 78hr NAM output for 18Z Monday:
It actually paints a hevkuva picture for a region just southeast of Lawton, OK east to I35, and south along I35 to Fort worth. 1500+ J/kg in both SBCAPE and MLCAPE, 330+K thetae, -6 LI, and the nose of a 65kt southwesterly jet streak crossing at about a 45 degree angle an east/west oriented warm front draped right across the area. And a very large dryline bulge just south of the area. That kinda setup would allow for tornado factory type supercells around that warm front. But, Monday is a right good ways off still to pinpoint any specific area with any confidence.

The GFS is more inline with my thinking on the timing of the upper system pushing east, and has the nose of the upper jet max about 500 miles to the east/NE by 18Z monday.

 

[Gabe Garfield]

Sunday looks to be a reasonably good chase day if insolation can establish itself in west Texas. I'm impressed by the strong low-level shear along the warm front and the backing of surface winds ahead of the dryline (according to the 12Z Eta). I suppose the main caveat will be whether or not the rather impressive cirrus deck will thin or not. If it does, I imagine that supercells and tornadoes would be likely (especially along the warm front).

A little excerpt from WFO San Angelo's afternoon AFD:

MAIN UPPER LEVEL LONGWAVE TROF LIFTS TO FOUR CORNERS REGION BY SUNDAY
EVENING...WITH DEEP SURFACE CYCLOGENESIS PROGGED BY THE GFS AND
ETA OVER SOUTHWEST TX. THIS WILL HOLD THE SURFACE DRYLINE TO OUR
WEST UNTIL A LEAD SHORTWAVE EJECTS INTO THE PANHANDLE BY MIDNIGHT
SUNDAY NIGHT. AT THIS TIME...EXPECT THE DRYLINE TO BEGIN ITS
EASTWARD PUSH THROUGH WEST CENTRAL TX...WITH A POSSIBLE WARM FRONT/
DRYLINE TRIPLE POINT NEAR SWEETWATER AT MIDNIGHT. ETA PROGS MID
LEVEL LAPSE RATES OVER WEST CENTRAL TX AT 8 TO 9C/KM AND 0 TO 3KM
HELICITY VALUES OF 250 TO 400 MS/S2 AT MIDNIGHT. SUNDAY EVENING
COULD HOLD IN STORE A SIGNIFICANT SEVERE WEATHER EVENT FOR WEST
CENTRAL TX...WITH DESTRUCTIVE TORNADOES LARGE HAIL AND DAMAGING
WINDS POSSIBLE.[/b]

Gabe

 

[Kyle Frisbie]

I like what you posted there Gabe. My personal quandary at the moment is deciding if I want to drive most of the way across Texas tomorrow morning for a chance at this. Of course, all that I can think about is driving a few hundred miles to be under some thick cirrus, very limited instability, only to find a few marginal hailers. I've been watching this for awhile, because of the weekend chase opportunity, I have had a tendency to try too hard to find good things about setups in March that fit my schedule...lol...But I wouldn't mind starting the new chase year tomorrow. Here are my main concerns (Limited daytime heating & Timing: Best action too close to dark). This setup always seems to start with a few weak hail storms in the afternoon and then gets going after dark with a big messy MCS that sweeps across the state. Any of you have a differing perspective?

 

[brody_clifton]

What the 3/19 00Z NAM says the atmosphere near and just to the northwest of the San Antonio, TX area will be like at 06 Z 3/20, or around 12AM Central time Monday morning:

Lifted Index: -10.1
Surface Temp: Upper 60s
Surface Dewp: Mid-60s
SBCAPE: 2700 J/kg
MLCAPE: 2500 J/kg
0-3km SR Helicity: 400 m^2/s^2
0-1km SR Helicity: 350 m^2/s^2
Position relative to dryline: Just ENE of a dryline buldge
Lower trop. winds: 10-15 kts SE at the surface, 35kt SSW at 850mb, 50kt SW at 700mb
Position relative to upper jet streak: Just southeast of the nose of an advancing 75kt jet max at 500mb.

0-1km EHI: 5

One interesting thing is, the NAM shows a very small but tight shortwave at 250mb over this area, with the southwesterly winds at that height increasing from around 100kts to over 120kts.

But all of this may be for naught due to the forecasted cinh of 150+ JKG, 850MB temps near 20 C, and 700 mb temps around 6 C in the region. However, the model output does show a small hole of sub-80 J/kg CINH opening up right under the 250mb vortmax. It's still 30 hrs out, it'll be neat to see if this feature remains in future runs. The amount of cinh the NAM has building in from 00Z to 06 Z is insane, with very little (less than 25 J/kg) at 00Z but a large swath of over 250 J/kg coming up from the gulf coast.

 

[Justin Walker]

0z NAM doesn't paint as nice of a picture as I would want to see the night before. There will be lots of ll shear and not just speed shear, but winds turning with height. Hodographs look very nice in the TA. Moisture should be sufficient, but shallow, with low to mid 60's Td's across west TX. Two big problems with this setup might be the stratus crap and the placement of the warm front. I have a tough time seeing the wf along a line e/w through throckmorton county, there is not much waa to push the wf that far north. The stratus will really limit insolation so CAPE values will be around the 1000-1500 J/kg.

It is also interesting to note that the 0z GFS has the ll shear much less with the 850 hPa winds of only 20knts unlike its counterpart the NAM with 35-40knts. If the GFS plays out, the potential for tomorrow is not so good. With all this said, I will make the decision about tomorrow in the morning. I'll be looking for the stratus to be thinning or clearing out, if that occurs, I'm gone.

 

[Mark Oerther]

After looking at both NAM and GFS guidance I have been given a glimmer of hope that there will be some clearing in the Abilene area tomorrow. The 850hPa humidity at 18z begins to show this clearing, on both models and has my interest. This will be one of the things I will look for on the satellite tomorrow before making a decision on chasing.

 

[Andrea Griffa]

I really like the zone between Aspermont and Spour where Eta paints a good convergence zone and a strengthning of the LLJ.
Good chase to all guys

Edit: the new run of Eta push down the zone richer in moisture. Better go down toward Abilene and see what happens.

 

[Kevin Walter]

Sitting in MAF at the moment, pouring over surface and satellite trend to determine if today will be feast or famine, and if it's feast, if it will be a chasable or socked in grunge. Currently in Midland we have heavy rain and some fog, but as per surface analysis we are just north of the front, so that is expected. I'm amazed at the continual forecast northward movement of this front, and the continual lack of its actual movement (over the past several days), as it still appears to still reside between MAF and Ft. Stockton. Despite being socked in grunge here, I'm encouraged by satellite trends, as it appears that the upper-level wave is finally starting its triumphant push eastward. The question remains for me, though, if it will arrive with the necessary lift (in the seemingly certain absence of surface heating with the abundant cloudiness) to initiate severe convection long enough before dark to make it chasable. If something surface-based can go, the shear should be abundant. Also, if the area between Ft. Stockton and Midland can be characterized by Midland's mid-level lapse rates and some portion of Del Rio's moisture (both as measured by 12Z soundings), thermodynamics should be favorable.

I guess we hurry up and wait.