WPC Met Watch |
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Mesoscale Precipitation Discussion: #0430 (2014) |
(Issued at 1038 PM EST TUE NOV 04 2014
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MPD Selection |
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MESOSCALE PRECIPITATION DISCUSSION 0430
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
1038 PM EST TUE NOV 04 2014
AREAS AFFECTED...SOUTH-CENTRAL TX
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY
VALID 050320Z - 050730Z
SUMMARY...PERSISTENT HEAVY RAINFALL IS EXPECTED TO DRIVE CONCERNS
FOR AT LEAST LOCALIZED FLASH FLOODING OVER THE NEXT SEVERAL HOURS.
DISCUSSION...IR SAT IMAGERY SHOWS AN IMPRESSIVE PLUME OF MID AND
HIGH LEVEL TROPICAL MOISTURE EMANATING OUT OF THE EASTERN PACIFIC
OCEAN AND ACROSS MAINLAND MEXICO IN ASSOC WITH TROPICAL STORM
VANCE. THE MOISTURE PLUME IS SURGING NORTHEASTWARD INTO THE RIO
GRANDE VALLEY AND HILL COUNTRY OF TX AHEAD OF AN UPPER TROUGH THAT
IS SEEN IN WV IMAGERY DIGGING INTO NORTHWEST MEXICO.
MEANWHILE...A STRONG COLD FRONT IS SLOWLY SINKING SOUTHEASTWARD
ACROSS SOUTHERN AND EASTERN TX...AND THIS FRONT IS INTERACTING
WITH THIS DEEP MOISTURE PLUME. ALREADY THERE IS AN EXPANSIVE AREA
OF MDT TO HVY RAIN IMPACTING MUCH OF SOUTH-CENTRAL TX...BUT OVER
THE LAST COUPLE OF HOURS...SOME STRONGER CONVECTIVE ELEMENTS HAVE
BEEN DEVELOPING AND PERSISTING ALONG AND JUST BEHIND THE COLD
FRONT IN AN ELEVATED FASHION FROM NEAR KSAT NORTHEAST TO KCLL. THE
ACTIVITY APPEARS TO BE GETTING ENHANCED BY A GRADUAL INCREASE IN
LOW LEVEL JET ENERGY OVER THE LOWER RIO GRANDE VALLEY AND WESTERN
GULF OF MEXICO...WITH H85 FLOW INCREASING TO OVER 30 KTS AND
YIELDING STRONGER SPEED CONVERGENCE INTO THE FRONTAL ZONE.
MEANWHILE...FAIRLY DIVERGENT FLOW ALOFT IS PROVIDING STRONGER DEEP
LAYER ASCENT AND IS COMPENSATING FOR THE OTHERWISE PATHETIC
INSTABILITY ENVIRONMENT AS MUCAPE VALUES NEAR THE FRONT AT BEST
ARE AROUND 500 J/KG.
THE LATEST HIRES MODELS INCLUDING THE 18Z NAM-CONEST AND 12Z ARW
DO NOT EXACTLY HAVE A GOOD HANDLE ON SOME OF THE HEAVIER RAINFALL
RATES THAT ARE BEING REALIZED ALONG AND JUST BEHIND THE
FRONT...BUT THE LAST COUPLE OF RUNS OF THE HRRR DO...AND IT
APPEARS AS IF THERE SHOULD BE A SEVERAL HOUR PERIOD OF HEAVIER
RAINFALL RATES REACHING UP TO 1.5 INCHES/HR OR LOCALLY HIGHER.
RAINFALL TOTALS OF 3 TO 6 INCHES WITH ISOLATED HEAVIER AMOUNTS ARE
EXPECTED WHICH WILL FAVOR AT LEAST LOCALIZED FLASH FLOODING. WILL
CONTINUE TO MONITOR.
ORRISON
ATTN...WFO...CRP...EWX...FWD...HGX...
ATTN...RFC...WGRFC...
LAT...LON 30969609 30629538 29879561 29319646 28849743
28379885 28250012 28530086 29220113 29630072
29899947 30149849 30629740
Last Updated: 1038 PM EST TUE NOV 04 2014
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