Chase 2011 - Day 2 Discussion

[Nick F]

Looking like another good chase opportunity today in a very similar area to yesterday due to a stalled front running NE from The Great Bend in west Texas through DFW on up through Arkansas and upto the Great Lakes, the severe risk along this front being where the greatest moisture pool is from central Texas on up through Arkansas to western Tennessee.

Text forecast: http://www.spc.noaa.gov/products/outlook/day1otlk.html

VERTICAL SHEAR WILL BE MORE THAN SUFFICIENT TO SUPPORT SUPERCELLS AS

SRN FRINGE OF 65 KT SWLY MID-LVL FLOW TOPS A SLY LLJ OF 35-40 KTS.

STORM MODE WILL PROBABLY FEATURE A MESSY MIX OF ROTATING STRUCTURES

AND LINE SEGMENTS WITH LONGER-LIVED DISCRETE ENTITIES ACROSS

CNTRL/ERN TX. THE STRONGEST LOW-LEVEL SHEAR WILL EXIST ACROSS THE

ARKLATEX REGION NEWD TOWARD MEMPHIS WHERE A COUPLE TORNADOES CANNOT

BE RULED OUT. OTHERWISE...LARGE HAIL AND DMGG WINDS CAN BE

EXPECTED.

NAM and GFS show precip breaking along CF out by 00z UTC (6pm CDT) from central Texas NE through DFW area and on up through Arkansas:

NAM CAPE and SR Helicity overlap pretty good for supercells points NE, E and SE of DFW:

So east of DFW in NE Texas up into AR looks reasonable for rotating storms and thus tornado potential, though given storms will fire along cold front, it could turn messy quickly - so ideally need to get on storms in early stages while they remain discrete. Don't think the team need to move far from their current overnight stay. I would target the triangle between Tyler, Longview and Mount Pleasant in NE Texas.

[Paul]

Stream now live:

http://www.netweather.tv/index.cgi?action=chaselive;sess=

[Nick F]

I see the team are headed NE through western Arkansas on the I-30, certainly a good choice, given SPC have upgraded the tornado risk to 10% up the I-30 corridor in AR towards Memphis, TN on the 1630z day 1 outlook update:

DAY 1 CONVECTIVE OUTLOOK

NWS STORM PREDICTION CENTER NORMAN OK

1106 AM CDT SUN MAY 01 2011

VALID 011630Z - 021200Z

...THERE IS A SLGT RISK OF SVR TSTMS FROM CNTRL TX NEWD INTO PARTS

OF THE LWR MS AND LWR TN VLYS...

...CNTRL TX NEWD INTO PARTS OF THE LWR MS AND LWR TN VLYS...

WITH TROUGH/UPPER LOW OVER SRN ROCKIES MAKING SLOW PROGRESS EWD THRU

THE PERIOD...STRONG SWLY MID/UPR JET WILL REMAIN ACROSS SRN PLAINS.

THE SURFACE COLD FRONT WITH REINFORCEMENT FROM THE DEVELOPMENT OF

THIS MORNINGS ACTIVE POST FRONTAL CONVECTION HAS PUSHED SEWD ACROSS

NCENTRAL TX.

THE WARM SECTOR ACROSS TX EWD TO THE MS RIVER IS PRIMED FOR A SEVERE

THUNDERSTORM THREAT WITH VERY MOIST LOW LEVELS...ATOP WHICH RESIDES

A PRONOUNCED EML WITH LAPSE RATES IN EXCESS OF 8C/KM. THUS FAR THE

MOST ACTIVE STORMS...INCLUDING SEVERE...HAVE BEEN ELEVATED TO THE N

OF FRONTAL ZONE.

AS WARM SECTOR TEMPS RISE TO THE MID 80S IN E TX TO MS RIVER...CINH

WILL DISSIPATE...LEADING TO DEVELOPMENT OF SURFACE BASED SEVERE

THUNDERSTORMS IN THE AREA OF BEST CONVERGENCE ALONG THE FRONTAL

ZONE. AMPLE DEEP SHEAR WILL EXIST FOR SUSTAINED STORMS/SUPERCELLS AS

SRN FRINGE OF 50-60 KT SWLY MID LVL FLOW TOPS 35-40 KT SSWLY

CONFLUENT LLJ. STORM MODE WILL RANGE FROM SEMI-DISCRETE SUPERCELLS

TO COMPLEX ROTATING STRUCTURES/BROKEN LINE SEGMENTS. THE STRONGEST

LOW LVL SHEAR SHOULD EXIST FROM NE TX AND THE ARKLATEX NEWD TO NEAR

MEMPHIS...WHERE A FEW TORNADOES MAY OCCUR. OTHERWISE...LARGE HAIL

AND BOWING SEGMENTS WITH DMGG WIND SHOULD BE THE MAIN SVR THREATS.

FARTHER SW WHERE DEEP LAYER SHEAR IS WEAKER AND CAP A LITTLE

STRONGER...SCTD SEVERE STORMS MAY FORM A BIT LATER IN THE AFTN JUST

AHEAD OF THE FRONT/DRY LINE OVER ERN PARTS OF THE HILL COUNTRY AND

OVER E CNTRL TX. WHILE SUPERCELLS WILL BE LIKELY GIVEN MUCAPE IN

EXCESS OF 3000 J/KG...PRIMARY CONCERN WILL BE VERY LARGE HAIL WITH A

MORE ISOLATED TORNADO THREAT.

..HALES/COHEN.. 05/01/2011

Quite ominous looking skies on the live feed, already storms just to their north along the cold front ... lots of trees blocking the view though!

[NL]

MESOSCALE DISCUSSION 0682

NWS STORM PREDICTION CENTER NORMAN OK

1212 PM CDT SUN MAY 01 2011

AREAS AFFECTED...NERN TX...FAR SERN OK...SWRN/CNTRL AR...FAR WRN TN

CONCERNING...SEVERE THUNDERSTORM WATCH 261...

VALID 011712Z - 011845Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 261

CONTINUES.

LATEST SFC ANALYSIS DEPICTS A FRONTAL ZONE EXTENDING AS A COLD FRONT

FROM 15 E JBR TO 30 W PBF...AS A STATIONARY FRONT FARTHER SOUTHWEST

TO 25 NW TYR...AND AS A COLD FRONT SOUTHWEST INTO CNTRL TX. A MODEST

LLJ /SSWLY FLOW AROUND 30 KT PER FORT WORTH AND SHREVEPORT VWP DATA/

ATOP THE NWD-SLOPED FRONTAL SFC IS ALLOWING FOR CONVECTION TO

REGENERATE IN NERN SECTIONS OF WW 261...AND FARTHER NE INTO CNTRL AR

AND FAR WRN TN.

WHILE THE ACTIVITY APPEARS TO HAVE WANED ELSEWHERE TEMPORARILY...

VISIBLE SATELLITE IMAGERY DEPICTS BREAKS IN THE CLOUD COVERAGE NEAR

AND SOUTHEAST OF THE SFC BOUNDARY INTO THE WARM/UNSTABLE SECTOR.

HORIZONTAL CONVECTIVE ROLLS HAVE BEEN NOTED NEAR AND WEST OF THE

SHREVEPORT AREA. WITH CONTINUED DESTABILIZATION OWING TO

INSOLATION...AS WELL AS FRONTAL CONVERGENCE AND AMPLE LOW-LEVEL AND

DEEP-LAYER VERTICAL WIND SHEAR...AN INCREASING POTENTIAL FOR

SURFACE-BASED SEVERE THUNDERSTORMS /INCLUDING SUPERCELLS/ WITH THE

THREAT FOR TORNADOES WILL OCCUR NEAR THE FRONT AND WITHIN THE WARM

SECTOR. THUS...WW 261 WILL NEED TO BE REPLACED BY A TORNADO WATCH

WITHIN AN HOUR.

[nsrobins]

I30 primed for tornadic storms - CS AR. Somewhere Malvern area is where the boundary will be in next few hours: rich 72dps creeping north.

[NL]

SPC have issued a Tornado Watch

URGENT - IMMEDIATE BROADCAST REQUESTED

TORNADO WATCH NUMBER 262

NWS STORM PREDICTION CENTER NORMAN OK

1250 PM CDT SUN MAY 1 2011

THE NWS STORM PREDICTION CENTER HAS ISSUED A

TORNADO WATCH FOR PORTIONS OF

LARGE PART OF SOUTHERN AND EASTERN ARKANSAS

PARTS OF NORTHWEST LOUISIANA

PARTS OF NORTHWEST MISSISSIPPI

PARTS OF WESTERN TENNESSEE

PARTS OF NORTHEAST TEXAS

EFFECTIVE THIS SUNDAY AFTERNOON AND EVENING FROM 1250 PM UNTIL

900 PM CDT.

TORNADOES...HAIL TO 3 INCHES IN DIAMETER...THUNDERSTORM WIND

GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE

AREAS.

THE TORNADO WATCH AREA IS APPROXIMATELY ALONG AND 40 STATUTE

MILES NORTH AND SOUTH OF A LINE FROM 60 MILES WEST SOUTHWEST OF

TYLER TEXAS TO 55 MILES NORTHEAST OF MEMPHIS TENNESSEE. FOR A

COMPLETE DEPICTION OF THE WATCH SEE THE ASSOCIATED WATCH OUTLINE

UPDATE (WOUS64 KWNS WOU2).

OTHER WATCH INFORMATION...CONTINUE...WW 261...

DISCUSSION...WELL DEFINED FRONTAL ZONE EXPECTED TO BE THE FOCUS FOR

SEVERE THUNDERSTORM DEVELOPMENT THIS AFTERNOON. WITH STRONG SHEAR

PROFILES IN PLACE COUPLED WITH A VERY MOIST AND MDTLY UNSTABLE AIR

MASS...SUPERCELLS ARE LIKELY. TORNADOES WILL BE POSSIBLE WITH ANY

SUPERCELL ALONG WITH VERY LARGE HAIL AND DAMAGING

WINDS...PARTICULARLY WITH ANY BOWING SEGMENT THAT DEVELOPS.

AVIATION...TORNADOES AND A FEW SEVERE THUNDERSTORMS WITH HAIL

SURFACE AND ALOFT TO 3 INCHES. EXTREME TURBULENCE AND SURFACE

WIND GUSTS TO 70 KNOTS. A FEW CUMULONIMBI WITH MAXIMUM TOPS TO

550. MEAN STORM MOTION VECTOR 24035.

TORNADO WATCH PROBABILITIES FOR WT 0262

NWS STORM PREDICTION CENTER NORMAN OK

1249 PM CDT SUN MAY 01 2011

WT 0262

PROBABILITY TABLE:

PROB OF 2 OR MORE TORNADOES : 60%

PROB OF 1 OR MORE STRONG /F2-F5/ TORNADOES : 30%

PROB OF 10 OR MORE SEVERE WIND EVENTS : 60%

PROB OF 1 OR MORE WIND EVENTS >= 65 KNOTS : 30%

PROB OF 10 OR MORE SEVERE HAIL EVENTS : 80%

PROB OF 1 OR MORE HAIL EVENTS >= 2 INCHES : 50%

PROB OF 6 OR MORE COMBINED SEVERE HAIL/WIND EVENTS : >95%

&&

ATTRIBUTE TABLE:

MAX HAIL /INCHES/ : 3.0

MAX WIND GUSTS SURFACE /KNOTS/ : 70

MAX TOPS /X 100 FEET/ : 550

MEAN STORM MOTION VECTOR /DEGREES AND KNOTS/ : 24035

PARTICULARLY DANGEROUS SITUATION : NO

[Paul]

Team back on the road now

http://www.netweather.tv/index.cgi?action=chaselive;sess=

[vortex_liam]

cool... That storms looking good... from the NW radar in the small map getting my proper radar up

[nsrobins]

Any cell MAgnolia/Camden will be ones to watch - loads of decent moisture to feed on and just south of the current boundary position.

[Paul Sherman]

Pretty much a shocker today from the weather and SPC Their 10% Tornado risk did not fire a Storm, we effectively had a Cap Bust as the Boundaries did not behave as expected, the Front was not pushed back North enough and the air was pretty capped. Our only chance now is for some elevated Storms at our overnight location in Monticelli (Arkansas). We do have an Outflow Boundary to our South West so hoping for some elevated hailers, temps are still 81f with SE Surface winds and a few storms out west rumbling towards us.

Another Slight Risk tomorrow will see us chase in Louisiana and Mississippi

[nsrobins]

I think the models had a bad day Paul. From obs I could see a defined northern WF type boundary across CS AR and RUC had the cap lifting to allow cells to fire south of the I30. Something didn't quite click and the cap stayed in place.

You win some and lose some :blush:

[Paul]

No storms, but we still have some video highlights of yesterday!