Mesoscale Discussion 8

Issued

Jan 9, 2012, 5:59 AM CST (11:59 UTC)

Expired

Jan 9, 2012, 8:30 AM CST

In force

3 hr

Issued by

the Storm Prediction Center

The Houston radar (KHGX), 100 km from the middle of the area, began a volume at 12:01 UTC, the scan nearest the moment this went out.

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627 
ACUS11 KWNS 091200
SWOMCD
SPC MCD 091159
LAZ000-TXZ000-091430-

MESOSCALE DISCUSSION 0008
NWS STORM PREDICTION CENTER NORMAN OK
0559 AM CST MON JAN 09 2012

AREAS AFFECTED...PORTIONS S-CENTRAL TX...MIDDLE-UPPER TX COASTAL
PLAIN...SWRN LA.

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 091159Z - 091430Z

CONVECTIVE REGIME DISCUSSED IN EARLIER MESOSCALE DISCUSSION 7 IS
UNDERGOING EWD AND COASTWARD SHIFTS IN GEOGRAPHY AND AMIDST GEN
INCREASE IN TSTM COVERAGE...HOWEVER OVERALL SVR THREAT APPEARS TOO
MRGL/ISOLATED FOR WW ATTM.  STILL...THREAT FOR A TORNADO AND/OR
ISOLATED DAMAGING GUST IS NONZERO...AND EXPECTED TO CONTINUE THROUGH
REMAINDER EARLY-MID MORNING WITH SLOW SHIFT EWD OVER AREA.

FURTHERMORE...MID-UPPER LEVEL CYCLONE OVER NRN CHIHUAHUA APPEARS TO
HAVE BEGUN ITS EWD TURN AS PROGGED.  AS RELATED FIELDS OF MID-LEVEL
DESTABILIZATION SHIFT EWD...LAPSE RATES AWAY FROM ANTECEDENT TSTMS
SHOULD INCREASE THROUGH REMAINDER MORNING...FROM W-E...WHILE
FAVORABLE DEEP-LAYER SHEAR IS MAINTAINED.  AS SUCH...HAIL WILL
BECOME MORE PROBABLE ON EITHER SIDE OF SFC FRONT...SIZES BEING
PRIMARILY SUBSEVERE TO ISOLATED MRGL-SVR BASED ON SOUNDING ANALOGS
AND OUTPUT FROM 2-D HAIL MODEL.

1130Z SFC MESOANALYSIS SHOWED QUASISTATIONARY FRONTAL ZONE FROM
CENTRAL/NRN LA SWWD THROUGH INFLECTION POINT OVER HOUSTON/WALKER
COUNTIES TX...CORRESPONDING CLOSELY TO MESOCYCLONE OF POTENTIALLY
SVR TSTM THERE.  FRONT EFFECTIVELY HAS BEEN SHUNTED SOUTHWARD BY
CUMULATIVE OUTFLOW FARTHER SW...PRODUCED BY INCREASINGLY DENSE BAND
OF TSTMS...AND WAS EVIDENT ACROSS PORTIONS GRIMES/COLORADO/KARNES
COUNTIES.  FRONT THEN ARCHED THROUGH WAVE LOW THAT HAS MOVED ENEWD
FROM MEX...TO NEAR COT.  EXPECT MOST OF FRONT TO SHIFT SEWD THROUGH
REMAINDER MORNING TOWARD COAST...AIDED ON MESOBETA SCALE BY TSTM
OUTFLOW.  THIS WILL SHRINK THAT PORTION OF WARM SECTOR CONTAINING
EFFECTIVELY SFC-BASED PARCELS...WITH MLCAPE RANGING FROM AROUND 250
J/KG OVER SWRN LA TO AROUND 1000 J/KG ALONG MIDDLE TX COAST.
PROFILER/VWP DATA INDICATE EFFECTIVE SHEAR AND SRH EACH HAVE
DECREASED SOMEWHAT SINCE 07Z IN RESPONSE TO SOME WEAKENING/VEERING
OF LOW-LEVEL FLOW...BUT STILL REMAIN FAVORABLE FOR OCNL SUPERCELL
ORGANIZATION.  STRONGEST LOW-LEVEL MESOCYCLONES AND POTENTIAL FOR A
TORNADO SHOULD BE INVOF FRONT.  WITH WEAK CINH...EXPECT OVERALL
INCREASE IN TSTM COVERAGE TO CONTINUE.  WITH TIME...THIS WILL
FURTHER COMPLICATE CONVECTIVE MODES...WITH CLUSTERED AND
QUASI-LINEAR STRUCTURES BECOMING MORE PREVALENT.

..EDWARDS.. 01/09/2012

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...LCH...SHV...HGX...CRP...EWX...

LAT...LON   28209705 28379755 28999920 29789965 30309899 30379742
            31009546 31199315 30919238 29989336 29509449 29359475
            29269476 28899534 28389635 28319638 28199666 28209705

Mesoscale Discussions in Texas, 2012Mesoscale Discussions in Louisiana, 2012Every mesoscale discussion in 2012

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.