Chase 2009 Day 31 Discussion

[Nick F]

We are currently heading SE from Childress, TX to get in position for storms to fire in N central Texas later ahead of SE moving cold front dropping down from the High Plains ... sfc charts pick out an outflow boundary from overnight storms we saw flashing to the north moving east across Oklahoma. The outflow boundary lies roughly SW-NE from Big Spring, TX through Witchita Falls, TX up to Ardmore, OK area - we are heading towards Witchita Falls and we can already see cu line towards this OFB.

Alot of the NSSL circus on the road SE too with their probe vehicles and dopplers on wheels after staying over the road in Childress ... were on the livestream just now with all their equipment on their roofs.

[nsrobins]

OK Nick. Great to see some green back on the SPC convective discussions.

Today is probably all about 'sniffing the dirt', with weak OFBs and convergence and topography and Uncle Tom and all thrown into the mix as to when and where you might get something to fire.

Watch the skies (and the radar of course!), but if I were to stick a pin I'd say the River crossing north of W Falls and up to Lawton might be a good place to start. Good luck.

[Nick F]

Wooah - SPC have upgraded from text to SLIGHT risk for today's outlook. Last year we wouldn't have got so excited - bu this year with such a crap pattern and with no SLIGHT since last Wednesday it is very welcome.

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1127 AM CDT TUE MAY 26 2009

VALID 261630Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS OVER PARTS OF SOUTHERN OK AND

NORTH-CENTRAL TX...

...SOUTHERN PLAINS...

LATEST SURFACE ANALYSIS SHOWS A COLD FRONT DROPPING SOUTHWARD ACROSS

WESTERN KS AND THE OK/TX PANHANDLES. AHEAD OF THE FRONT...SCATTERED

OVERNIGHT THUNDERSTORMS HAVE RESULTED IN SEVERAL DIFFUSE SURFACE

BOUNDARIES OVER SOUTHERN/EASTERN OK AND NORTH TX. STRONG HEATING

AND DRYING WILL OCCUR FROM THE WEST ACROSS TX...YIELDING AFTERNOON

MLCAPE VALUES OVER 3000 J/KG ROUGHLY FROM MWL/SPS EASTWARD INTO

SOUTHWEST AR. WEAK FORCING ALOFT SUGGESTS THAT LOCALIZED

CONVERGENCE ALONG SURFACE BOUNDARIES WILL LIKELY BE THE MAIN FOCUS

FOR THUNDERSTORM INITIATION. FULL SUNSHINE SHOULD ALLOW AIRMASS TO

REACH CONVECTIVE TEMPERATURE /LOWER 90S F ON 12Z FWD RAOB/ AND LEAD

TO A FEW INTENSE MULTICELL CLUSTERS. STEEP LOW AND MID LEVEL LAPSE

RATES AND WEAK BUT SUFFICIENT DEEP LAYER VERTICAL SHEAR INDICATE A

RISK OF LARGE HAIL AND DAMAGING WINDS.

LATER THIS EVENING AND TONIGHT...A SHORTWAVE TROUGH OVER SOUTHERN NM

WILL EMERGE INTO THE SOUTHERN HIGH PLAINS AND LIKELY PROMOTE

SCATTERED HIGH-BASED THUNDERSTORMS ACROSS WESTERN AND CENTRAL TX.

THESE STORMS WILL SPREAD EASTWARD INTO CENTRAL TX OVERNIGHT WITH A

RISK OF LOCALLY DAMAGING WINDS AND HAIL.

[NL]

Yahooo..!!! Paul.S did mention yesterday that he'd expect a slight risk to be issued, no doubt alot of chasers could be out today in the hope of seeing something decent...hoping for a surprise or two for you lads today.. good luck.!!

[Nick F]

We have vortex 2 convoy behind us with Josh Werman et al, we will let them roll in front of us for you to see on the streaming, lol.

[Roger J Smith]

The weak frontal boundary appears to be just north of Mineral Wells to around Ardmore OK ... would suggest Jacksboro southeast of Wichita Falls as possible convective zone in about 2-3 hours.

[plymouthflye]

We are currently heading SE from Childress, TX to get in position for storms to fire in N central Texas later ahead of SE moving cold front dropping down from the High Plains ... sfc charts pick out an outflow boundary from overnight storms we saw flashing to the north moving east across Oklahoma. The outflow boundary lies roughly SW-NE from Big Spring, TX through Witchita Falls, TX up to Ardmore, OK area - we are heading towards Witchita Falls and we can already see cu line towards this OFB.

Alot of the NSSL circus on the road SE too with their probe vehicles and dopplers on wheels after staying over the road in Childress ... were on the livestream just now with all their equipment on their roofs.

Well, after yesterdays busted and sea-bound storms in the E of the Uk, i for one, am looking forward to some action on here over the next few hours.

Let the show commence

[Nick F]

Well, after yesterdays busted and sea-bound storms in the E of the Uk, i for one, am looking forward to some action on here over the next few hours.

Let the show commence

Let's hope we have some action to show you. Currently at Lake Arrowhead SE of Witchita Falls, with a stunning panoramic view of lake and surrounding area. Got fairweather cu field atm above us, but it 30C and very oppressive - so should start to see Tcu in next few hours trying to break the cap.

[ANYWEATHER]

Let's hope we have some action to show you. Currently at Lake Arrowhead SE of Witchita Falls, with a stunning panoramic view of lake and surrounding area. Got fairweather cu field atm above us, but it 30C and very oppressive - so should start to see Tcu in next few hours trying to break the cap.

Yes, look forward to your pics when I get up in the morning, "HOPEFULLY" you will get something to shoot, WISH I was out there with you Guys.........! Best Wishes IAN.

[user700]

Good luck today looks good!

[Nick F]

Yes, look forward to your pics when I get up in the morning, "HOPEFULLY" you will get something to shoot, WISH I was out there with you Guys.........! Best Wishes IAN.

You coming next year though aren't you?

Currently headed along Hwy 82 to Gainesville north of DFW, wind is backed SE there and Td's higher, winds at Witchita Falls are N'erly and Td's lower wich is less ideal.

[NL]

If Vortex2 know whats best for them they'd best keep up with ya..!!

[Nick F]

SPC have updated 1939z, and now include 2% tornado risk aswell in DFW area ... very interesting discussion:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

0239 PM CDT TUE MAY 26 2009

VALID 262000Z - 271200Z

...THERE IS A SLGT RISK OF SVR TSTMS LATE THIS AFTN/EVE ACROSS PARTS

OF THE SRN PLAINS....

...20Z UPDATE...

ONLY MINOR CHANGES HAVE BEEN MADE TO THE 16Z CATEGORICAL AND

PROBABILISTIC OUTLOOKS...BASED ON APPARENT TRENDS IN OBSERVATIONAL

DATA AND LATEST MODEL GUIDANCE. SEVERE POTENTIAL...WHILE PROBABLY

NOT COMPLETELY NEGLIGIBLE IN MOST AREAS WITH A RISK FOR

THUNDERSTORMS...STILL GENERALLY APPEARS MARGINAL IN NATURE OR LIKELY

TO REMAIN HIGH LOCALIZED. AN EXCEPTION SEEMS TO EXIST ACROSS PARTS

OF NORTHERN/CENTRAL TEXAS...WHERE SURFACE HEATING BENEATH CAPPING

ELEVATED MIXED LAYER AIR EMANATING FROM THE PLATEAU REGION IS

CONTRIBUTING TO STRONG TO EXTREME INSTABILITY.

...NORTHERN/CENTRAL TEXAS...

BOUNDARY LAYER DESTABILIZATION APPEARS MAXIMIZED NEAR THE DALLAS/

FORT WORTH METROPLEX...NEAR OR JUST EAST OF A WEAK SURFACE LOW... ON

THE NOSE OF A PRE-FRONTAL LOW-LEVEL THERMAL RIDGE EXTENDING

NORTHEASTWARD OUT OF THE HIGH PLAINS. VERY STEEP LOW AND MID- LEVEL

LAPSE RATES...COUPLED WITH HIGH LOW-LEVEL MOISTURE CONTENT AIR ALONG

A CONVECTIVELY GENERATED/ENHANCED BOUNDARY EAST SOUTHEAST OF THE

LOW...HAS CONTRIBUTED TO MIXED LAYER CAPE IN EXCESS OF 3000

J/KG...ACCORDING TO THE LATEST RUC ANALYSIS. IT APPEARS THIS COULD

APPROACH 4000 J/KG WITH ADDITIONAL HEATING.

WHILE WEAK LOWER/MID TROPOSPHERIC COOLING IS ONGOING ACROSS THE

SOUTH CENTRAL HIGH PLAINS...WEST AND SOUTH OF A MID-LEVEL

CIRCULATION BEGINNING TO TURN EASTWARD ACROSS WESTERN KANSAS... THIS

PROBABLY WILL NOT BE OF MUCH IMPACT TO NORTH CENTRAL TEXAS.

BUT...HEATING TOWARD CONVECTIVE TEMPERATURES...COUPLED WITH

LOW-LEVEL WARM ADVECTION/CONVERGENCE...MAY BE SUFFICIENT TO INITIATE

CONVECTIVE DEVELOPMENT PRIOR TO 27/00Z. IF THIS OCCURS ...POTENTIAL

EXISTS FOR RAPID INTENSIFICATION TO SEVERE LEVELS... DESPITE THE

WEAK NATURE OF THE FLOW FIELDS AND SHEAR. LARGE HAIL AND DAMAGING

DOWNBURSTS LIKELY WILL BE THE MAIN THREATS WITH EAST SOUTHEASTWARD

ADVECTING/PROPAGATING STORMS. BUT...AN ISOLATED TORNADO IS NOT OUT

OF THE QUESTION.

THOUGH UPPER FORCING IS STILL WEAK/UNCERTAIN...IT IS POSSIBLE THAT

NOCTURNAL STRENGTHENING OF A SOUTH SOUTHWESTERLY LOW-LEVEL JET TO

AROUND 30 KT COULD SUPPORT UPSCALE CONVECTIVE GROWTH THIS EVENING.

THERMODYNAMIC PROFILES APPEAR VERY FAVORABLE FOR STRONG CONVECTIVELY

GENERATED COLD POOLS...WHICH SHOULD TEND TO CONSOLIDATE AND ADVANCE

WITH STRONGER NEW CONVECTIVE DEVELOPMENT ...SOUTHWARD INTO/ACROSS

CENTRAL TEXAS...ACCOMPANIED BY GUSTY WINDS AND HAIL.

[Nick F]

Can't escape the vortex2 circus, yet another doppler on wheels (DOW) ahead ... lol

[pottyprof]

I see you guys are using the heavy gear now..

[NL]

MD issued severe potential watch possible

406

ACUS11 KWNS 262049

SWOMCD

SPC MCD 262048

TXZ000-OKZ000-262215-

MESOSCALE DISCUSSION 0872

NWS STORM PREDICTION CENTER NORMAN OK

0348 PM CDT TUE MAY 26 2009

AREAS AFFECTED...PORTIONS OF N-CNTRL TX TO THE BIG COUNTRY

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 262048Z - 262215Z

UNCERTAINTY REMAINS HIGH OVER TIMING AND LOCATION OF TSTM INITIATION

INTO LATE AFTERNOON...ESPECIALLY WHERE BUOYANCY APPEARS MAXIMIZED.

BUT...AT LEAST ISOLATED TSTMS SHOULD DEVELOP BY 22Z ALONG VARIOUS

SURFACE TROUGH/OUTFLOW BOUNDARIES ACROSS W-CNTRL TX INTO THE BIG

COUNTRY. DESPITE MODEST DEEP-LAYER FLOW...STEEP LOW/MID-LEVEL LAPSE

RATES SHOULD SUPPORT POTENTIAL FOR SEVERE HAIL/WINDS. A WW DOES NOT

APPEAR IMMINENT...BUT THE AREA WILL CONTINUE TO BE MONITORED FOR A

POSSIBLE WW.

20Z SUBJECTIVE SURFACE ANALYSIS PLACED A MESOLOW AROUND 20 N MWL

WITH SEVERAL RATHER DIFFUSE TROUGHS/BOUNDARIES REMAINING EVIDENT IN

THE WAKE OF CONVECTION NOW OVER ERN TX. RECENT VISIBLE SATELLITE

IMAGERY DEPICTED CU/TCU INCREASING FROM THE PERMIAN BASIN INTO THE

BIG COUNTRY. MODIFIED 12Z MAF RAOB SUGGESTS THIS AREA IS UNCAPPED TO

MIXED-LAYER PARCELS. GIVEN TEMPERATURE/DEW POINT SPREADS AOA 40 DEG

F...DRY MICROBURSTS AND HAIL MAY OCCUR. FARTHER EAST...MIDDLE 60S TO

LOWER 70S SURFACE DEW POINTS PERSIST ACROSS NERN TX...ALTHOUGH

SHRINKING IN AREAL EXTENT AS DRIER AIR CONTINUES TO MIX NWD.

CONVECTIVE INITIATION IN THE NEAR-TERM MAY REMAIN SUPPRESSED BY

LARGER-SCALE DESCENT IN THE AFTERMATH OF MCS ALONG THE SABINE RIVER

VALLEY. OPERATIONAL AND HI-RES MODEL GUIDANCE VARY SUBSTANTIALLY

WHETHER OR NOT CONVECTIVE INITIATION WILL OCCUR INTO EARLY EVENING

ACROSS N-CNTRL TX. IF IT DOES OCCUR...THE VERY UNSTABLE AIR MASS

WOULD SUPPORT RAPID TSTM DEVELOPMENT WITH LARGE HAIL AND DAMAGING

WINDS AS THE PRIMARY THREATS.

..GRAMS.. 05/26/2009

[Nick F]

Parked up at Comfort Suites by I-35 interchange, Gainesville ... and surrounded by the National Severe Storms Laboratory circus with all their equiped vehicles. Just going to wait for initiation. 82F here with 72F dewpoints.

I see SPC have a meso discussion which has some uncertainty about initiation in the area ... but some high-end instbility loaded gun available if it does go.

[Roger J Smith]

Looks like some convection firing near Graham, still like the area Jacksboro to Bowie which is a bit to the west of the team's current location for supercell development, hopefully this will build into their vicinity. Weak upper winds should result in rather slow forward progress once supercells develop.

[Nick F]

Hi Roger, been watching those cells done near Graham - but dew points are lower down there with drier air advecting from SW in that area - cells have evaporated on latest Barons update and were probably high-based given dew point spread.

dew points somewhat better here with a SE wind vector - was 73F Td earlier though even here moisture is getting mixed out a bit from the SW. Very juicy out there though, have A/C on full - very oppressive outside the car!

[nsrobins]

90F+ surface ts and 72F dps - phew! According to windmapper the dryer air is slowly mixing from the SW agreed but surface winds show orthogonal convergence along an axis just to the West of you now.

Will the cap break in time? The clock is ticking.

[Nick F]

Could be a late initiation ... sometimes cap may not break until 7-8pm. Hopefully it will be in next 1-2 hrs.

[nsrobins]

Could be a late initiation ... sometimes cap may not break until 7-8pm. Hopefully it will be in next 1-2 hrs.

21Z RUC lifts the lid at 22Z (about now) Nick. 4000+ max CAPE available pretty much on top of you now.

I see Stu Robinson is in Wichita F and Paul Knightly is in Bowie. Amazing how a slight risk is attracting all the bison to the waterhole!

[Nick F]

We are now heading south 30 miles to Denton - storm has exploded WNW of Fort Worth on last few Barons updates with NE movement. Chase is on ...

[nsrobins]

Should take it close to Decatur.

Guys if you can have a look at the Denmark group stream on TVN. OMG, that that cell is undergoing absolutely awesome explosive convection.

[Ross B]

Good luck guys, the stream is working perfect