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622
FXCA62 TJSJ 201359 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
959 AM AST WED AUG 20 2014

.UPDATE...IMMEDIATE PICTURE SHOWS DECREASING WATER VAPOR UNTIL
EARLY TOMORROW MORNING THEN PRECIPITABLE WATER RAMPS UP FOR STRONG
TROPICAL WAVE PASSAGE ON FRIDAY. CURRENT INDICATIONS FRIDAY ARE
FOR STRONG GUSTY WINDS ACCOMPANIED BY HEAVY RAINFALL AND A STRONG
POTENTIAL FOR FLOODING IN MOUNTAINS AND WINDWARD SLOPES OF PUERTO
RICO. CURRENT MODELS ARE IN CLOSE AGREEMENT WITH STRENGTH AND
CHARACTER OF THIS WAVE ALTHOUGH THERE IS SOME POSSIBILITY THAT
HEAVIER RAIN COULD ARRIVE A LITTLE EARLIER ON FRIDAY THAN CURRENT
THINKING.


&&

.DISCUSSION...CURRENT MODELS SHOW CONTINUED SHOWERS AND HEAVIER
RAINFALL THROUGHOUT THE NEXT 5 DAYS WITH POTENTIAL FOR URBAN AND
SMALL STREAM FLOODING TODAY AND THURSDAY AND FLASH FLOODING ON FRIDAY.


&&

.AVIATION...NO CHANGE.


&&

.MARINE...RAPIDLY DETERIORATING CONDITIONS WITH STRONG GUSTY WINDS
AND HIGHER SEAS EXPECTED BEGINNING THURSDAY NIGHT. GUSTS EXCEEDING
35 KNOTS POSSIBLE THEN.


&&

.PREV DISCUSSION... /ISSUED 550 AM AST WED AUG 20 2014/

SYNOPSIS...TUTT LOW TO THE NORTHEAST OF THE AREA WILL CONTINUE
RETROGRESSING TODAY UNTIL IT IS TO THE NORTHWEST OF THE LOCAL AREA
BY LATE TONIGHT. AN UPPER HIGH PRESSURE WILL MOVE IN AS THE
SURFACE LOW WITH ITS ASSOCIATED WAVE STARTS MOVING CLOSER TO THE
LEEWARD ISLANDS ON THURSDAY...REACHING THE CARIBBEAN WATERS LATE
ON THURSDAY INTO FRIDAY. THIS SURFACE LOW AND ASSOCIATED WAVE IS
EXPECTED TO BRING NUMEROUS SHOWERS TO THE LOCAL AREA.

DISCUSSION...SHOWERS AND THUNDERSTORMS PERSISTED ACROSS THE LOCAL
WATERS...THE USVI...AS WELL AS NORTHERN AND EASTERN PR DURING THE
OVERNIGHT HOURS. SOME OF THESE THUNDERSTORMS HAD FREQUENT
LIGHTNING AND STRONG GUSTY WINDS. THIS ACTIVITY OF SHOWERS AND
THUNDERSTORMS IS EXPECTED TO CONTINUE THROUGH THE MORNING HOURS.
THERE WILL BE ENOUGH AVAILABLE MOISTURE THAT WHEN COMBINED WITH
THE LOCAL EFFECTS AND THE TUTT LOW WILL CAUSE SHOWERS AND
THUNDERSTORMS ACROSS THE INTERIOR AND WESTERN SECTIONS OF PR THIS
AFTERNOON. ELSEWHERE YOU CAN EXPECT PASSING SHOWERS WITH ISOLATED
THUNDERSTORMS.

AN ELONGATED AREA OF LOW PRESSURE IS LOCATED EAST OF THE WINDWARD
ISLANDS IS EXPECTED TO GRADUALLY CONTINUE DEVELOPING THROUGH THE
NEXT FEW DAYS. THIS LOW PRESSURE IS FORECAST TO REACH THE
CARIBBEAN WATERS LATE THURSDAY AND CONTINUE ON THROUGH FRIDAY.
HOWEVER THE DEEP TROPICAL MOISTURE THAT THIS FEATURE WILL BRING
WILL PROBABLY LINGER THROUGH THE WEEKEND AND INTO EARLY MONDAY.
GFS MODEL HAS PRECIPITABLE WATER VALUES CLOSE TO 2 INCHES STARTING
LATE THURSDAY...BUT INCREASING EVEN MORE TO OVER 2.2 INCHES LATE
FRIDAY THROUGH SUNDAY. SOME HEAVY RAINFALL AND STRONG GUSTY WINDS
ARE POSSIBLE WITH THIS LOW PRESSURE.

AT THIS TIME THE NATIONAL HURRICANE CENTER GIVES THE LOW PRESSURE
EAST OF THE WINDWARD ISLANDS A 30 PERCENT CHANCE OF DEVELOPMENT
INTO A TROPICAL CYCLONE WITHIN THE NEXT 48 HOURS. PLEASE REFER TO
THE TROPICAL WEATHER OUTLOOKS FROM NATIONAL HURRICANE CENTER FOR
THE LATEST INFORMATION ABOUT THIS LOW PRESSURE SYSTEM.

AVIATION...MOSTLY VFR CONDITIONS EXPECTED AT ALL TERMINALS THROUGH
THE FCST PERIOD. HOWEVER...VCSH STILL EXPECTED EARLY THIS MORNING AT
PR AND USVI TERMINALS. AFT 20/16 TSRA/SHRA DEVELOPMENT OVER THE
WESTERN INTERIOR/WESTERN OF PR MAY RESULT IN BRIEF MVFR CONDS AND
MTN TOP OBSCURATIONS AT JMZ AND JBQ. LOW LEVEL WINDS FROM THE E AT
5-20 KTS.

MARINE...WINDS 15-21KT THRU THU MORNING. WINDS STRENGTHENING THU
AFTERNOON WITH THE LOW PRESSURE THU NIGHT THROUGH EARLY SAT MORNING.
WINDS 20-25 KT POSSIBLE AND SEAS 6-8 FT DURING THIS PERIOD.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  89  79  89  77 /  40  40  60  60
STT  89  79  90  79 /  40  40  50  60

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...NONE.
&&

$$

72/12










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