Re: Very Unusual Convection
Posted by cypresstx on 10/24/2015, 10:18 pm



MESOSCALE PRECIPITATION DISCUSSION 0610
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
922 PM EDT SAT OCT 24 2015

AREAS AFFECTED...MIDDLE AND UPPER TX COAST...

CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY

VALID 250130Z - 250600Z

SUMMARY...VERY EFFICIENT WARM RAIN PROCESSES WILL CONTINUE TO POSE
THE THREAT FOR FLASH FLOODING ALONG THE MIDDLE AND UPPER TX COASTS
THROUGH THE EARLY MORNING HOURS.

DISCUSSION...REGIONAL RADARS INDICATED A GROWING AREA OF
CONVECTION OFF THE MIDDLE TX COAST...IN AN AREA OF IR TOPS HAVE
COOLED TO -75 C OR BELOW. THE CONVECTION IS DEVELOPING IN A 25 TO
35 KNOT LOW LEVEL SOUTHEAST INFLOW...WHERE PRECIPITABLE WATER
VALUES ARE ABOUT 2.50 INCHES (PER THE TOTAL BLENDED PRECIPITABLE
WATER PRODUCTS AND GPS READINGS). INSTABILITY HAS BEEN LIMITED TO
THE IMMEDIATE SOUTHEAST AND MIDDLE TX COAST AHEAD OF A COLD
FRONT...AS WELL AS OVER THE WESTERN GULF OF MEXICO.

THE MRMS PRECIPITATION RATE PRODUCT SHOWED HOURLY RAINFALL RATES
AS HIGH AS 3-4 INCHES WITH THE CONVECTION OFF THE MIDDLE TX
COAST...CLOSE TO THE COLDEST IR TOPS. CLOSER TO THE COAST...KCRP
RADAR INDICATED HOURLY RAINFALL RATES CLOSER TO 2 INCHES...WHERE
THE INSTABILITY IS NOT QUITE AS ROBUST. THE NEAR TERM MOTION
SHOWED THAT THE DEEPER CONVECTION (WITH THE HIGHER RAINFALL RATES)
CROSSING THE MIDDLE TX COAST BEFORE 25/03Z.

SURFACE LOW PRESSURE DEVELOPING OFF THE SOUTHEAST TX COAST WILL
FOCUS THE DEEP MOISTURE AND AVAILABLE INSTABILITY ON THE MIDDLE
AND UPPER TX COAST THROUGH 25/06Z...AS THE LOW LEVEL INFLOW
INCREASES TO 30 TO 40 KNOTS. THERE IS A STRONG HIGH RESOLUTION
GUIDANCE SOLUTION CONSENSUS TO PLACE 3-5 INCHES OF RAINFALL
BETWEEN KCRP AND KGLS...WITH BOTH THE 22Z HRRR AND THE 12Z WRF-ARW
SHOWING LOCAL 9 INCH RAINFALL AMOUNTS THROUGH 25/06Z. A
SIGNIFICANT FLASH FLOOD EVENT IS POSSIBLE...ESPECIALLY IF THE
HIGHER RAINFALL AMOUNTS END UP IN METRO AREAS.

INSTABILITY COULD END UP BEING THE LIMITING FACTOR FOR RAINFALL
TOTALS THAT HIGH. GIVEN THE DEPTH OF MOISTURE AND STRONG INFLOW
NORTH OF THE SURFACE LOW (AS WELL AS ONGOING MRMS RAINFALL
RATES)...LOCAL 6+ INCH RAINFALL AMOUNTS SEEM PLAUSIBLE.
OBVIOUSLY...RAINFALL AMOUNTS THIS HIGH WILL RESULT IN FLASH
FLOODING.

HAYES

ATTN...WFO...CRP...EWX...FWD...HGX...LCH...

ATTN...RFC...WGRFC...

LAT...LON   30959635 30929588 30759538 30519502 30279465
           30059447 29719419 29409423 29389438 29209455
           28509539 28059615 27229722 28059742 29379738
           29409739 30019790 30519768 30579757 30729709
           30869654
170
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Patricia is now a remnant low, but heavy rain threat continues - Chris in Tampa, 10/24/2015, 4:46 pm
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