Troy Kimmel Weather

Forecasting Austin and South Central Texas Weather Since 1984

TK’s Special Briefing…. (855am CT-Wed/13May2015)

Austin / Travis County and South Central Texas Weather Update #14
Prepared by UT University/Incident Meteorologist Troy Kimmel
855am CT – Wednesday / 13  May 2015

…. NWS/Weather Prediction Center Issues Heavy Rainfall
Mesoscale Discussion for Our Area ….

LINK: http://www.wpc.ncep.noaa.gov/metwatch/metwatch_mpd_multi.php?md=0082&yr=2015

TEXT:
MESOSCALE PRECIPITATION DISCUSSION 0082
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
948 AM EDT WED MAY 13 2015

AREAS AFFECTED…SOUTHEAST TEXAS

CONCERNING…HEAVY RAINFALL…FLASH FLOODING LIKELY

VALID 131340Z – 131900Z

SUMMARY…MERGING CLUSTERS OF INTENSE CONVECTION ARE EXPECTED LATE
THIS MORNING THROUGH MID-AFTERNOON. VERY INTENSE RAINFALL RATES
WILL RESULT IN FLASH FLOODING.

DISCUSSION…A WELL-DEFINED SOUTHERN STREAM UPPER LEVEL TROUGH
EJECTING ACROSS THE UPPER RIO GRANDE VALLEY THIS MORNING WILL
EJECT EAST THROUGH MID-AFTERNOON AND DRIVE A WELL-DEFINED AXIS OF
CONVECTION TOWARD PORTIONS OF SOUTHERN AND SOUTHEAST TEXAS. THE
ACTIVITY ALREADY OCCURRING ALONG A LINE FROM KERV TO WEST OF KCOT
HAS BEEN CHARACTERIZED BY VERY COLD CONVECTIVE TOPS THE LAST
COUPLE OF HOURS AS STRONGLY DIVERGENT FLOW ALOFT INTERACTS WITH A
VERY MOIST AND MODESTLY UNSTABLE S/SE LOW LEVEL JET WHICH BASED ON
12Z RAOB DATA IS ON THE ORDER OF ABOUT 30 KTS.

THE MODELS SUGGEST SOME ADDITIONAL UPTICK IN THE LOW LEVEL JET
AIMED INTO THE SOUTHERN FLANK OF THE UPPER TROUGH AND ASSOCIATED
CONVECTION TODAY. THIS COUPLED WITH INCREASED DIURNAL HEATING
THROUGH THE DAY WILL ALSO SUPPORT A MODERATELY UNSTABLE AIRMASS
OUT AHEAD OF THE CURRENT ACTIVITY. SO…WILL BE EXPECTING ONGOING
CONVECTION TO SUSTAIN ITSELF AND EXPAND A BIT IN COVERAGE AND
ORGANIZATION THROUGH MIDDAY.

COMPLICATING MATTERS FURTHER IS THE ONGOING COLD-TOPPED CONVECTION
NEAR A WEAK INVERTED TROUGH IN BETWEEN KALI AND KCRP AND NORTH TO
NEAR KVCT. UPSTREAM CONVECTION IS LIKELY TO MERGE WITH THIS
ACTIVITY TOWARD MIDDAY OR EARLY AFTERNOON. THE RESULT WILL BE
EXTREMELY HEAVY RAINFALL POTENTIAL…WITH RATES OF OVER 3
INCHES/HR POSSIBLE. THE LATEST HRRR FAVORS ADDITIONAL RAINFALL
AMOUNTS OF 3 TO 6 INCHES WITH ISOLATED HEAVIER AMOUNTS.

THIS WILL SUPPORT FLASH FLOODING AND WILL EXACERBATE ONGOING
RUNOFF PROBLEMS FROM EARLIER HEAVY RAINS.

ORRISON

ATTN…WFO…CRP…EWX…FWD…HGX…