Area Forecast Discussion
Issued by NWS San Juan, PR

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FXCA62 TJSJ 180114 AAA
AFDSJU

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
914 PM AST WED SEP 17 2014

.UPDATE...VERY FEW SHOWERS HAVE APPEARED IN THE SOUTHERN CARIBBEAN
WATERS IN OUR FORECAST AREA...THE REST OF THE AREA INCLUDING ALL
LAND AREAS REMAINS RAIN-FREE ALTHOUGH RADAR HINTS AT A FEW
SPRINKLES IN THE HUMACAO AND NAGUABO AREA.

&&

.DISCUSSION...FORECAST THROUGH NEXT 48 HOURS LOOKS TO BE ON TRACK.
UPPER LEVELS MAY NOT BE VERY SUPPORTIVE OF HEAVY RAINS AND STRONG
CONVECTION THURSDAY AS THE UPPER LEVEL TROUGH WILL HAVE PASSED TO
THE EAST OF THE FORECAST AREA BY 18/18Z BUT RAIN CHANCES AND
COVERAGE WILL DEFINITELY INCREASE AFTER THURSDAY NOON AND THROUGH FRIDAY.
REMNANTS OF THE UPPER LEVEL TROUGH RETURN TO WESTERN PUERTO RICO
BY SATURDAY NIGHT HOWEVER AFTER A VERY BRIEF DECREASE IN MOISTURE
AND SOME SHOWER ACTIVITY MAY BE ASSOCIATED WITH THIS SINCE
MOISTURE RETURNS RAPIDLY AFTER 20/06Z AND PUERTO RICO WILL AGAIN
BE ON THE DIVERGENT SIDE OF THE TROUGH. LITTLE ACTIVITY OCCURRED
TODAY DESPITE GOOD DIVERGENCE ALOFT BECAUSE OF THE DRY SLOT. THAT
IS NOT LIKELY TO BE THE CASE LATE SATURDAY INTO SUNDAY. WILL NEED
TO MONITOR THE SITUATION FOR EARLY ARRIVAL OF WAVES AND MOISTURE
POCKETS EN ROUTE IN THE EASTERLIES SUNDAY OR MONDAY.

&&

.AVIATION...VFR CONDS THRU 18/12Z...EXCEPT AT TNCM AND TKPK WHERE
BRIEF MVFR CIGS ARE POSSIBLE. CONDS WILL GRADUALLY DETERIORATE AS
A TROP WAVE MOVES OVER AREA THU. SHRA/ISOLD WITH THE WAVE WILL
SPREAD OVER USVI AFT 18/12Z AND OVER PR BTWN 18 /15Z- 21Z. MVFR/IFR
CONDS AND MTN OBSCURATIONS EXPECTED IN SHRA/TSRA. E TO SE WINDS OF
10-20 KT BLO FL200... WITH HIR GUSTS ARND 30 KT NEAR TSRA.

&&

.MARINE...CONDITIONS TO REMAIN BETWEEN 3 TO 5 FEET IN EXPOSED
WATERS THROUGH NEXT 7 TO 10 DAYS WITH WEAK SWELL FROM HURRICANE
EDOUARD GRADUALLY DIMINISHING. WIND WAVES WITH TROPICAL WAVES WILL
INCREASE FRIDAY AND SATURDAY AND AGAIN SUNDAY AND MONDAY WITH
PERIODS AS LOW AS 6 SECONDS.

&&

.PREV DISCUSSION... /ISSUED 315 PM AST WED SEP 17 2014/

SYNOPSIS...TUTT ACROSS THE WESTERN ATLANTIC INTO THE GREATER
ANTILLES WILL WEAKEN OVER THE NEXT FEW DAYS AS A DEEPER TROUGH
AMPLIFIES OVER THE EASTERN COAST OF USA. TROUGHINESS ALOFT WILL
RETURN ONCE AGAIN EARLY NEXT WEEK AS ANOTHER TUTT DEVELOPS ACROSS
THE CENTRAL ATLANTIC INTO THE EASTERN CARIBBEAN. NEXT TROPICAL
WAVE PASSAGE EXPECTED LATE THURSDAY INTO FRIDAY.

DISCUSSION...TUTT LOW NORTHWEST OF THE AREA WILL WEAKEN AS DEEP
POLAR TROUGH ESTABLISHES ACROSS THE EASTERN USA. MEANWHILE AT MID
LEVELS...WEAKENING OF MID LEVEL RIDGE PATTERN CONTINUES TONIGHT
AND TOMORROW. MID LEVEL RIDGE PATTERN IS SUSTAINING A WEAK CAP
ACROSS THE LOCAL ISLANDS. THE AFOREMENTIONED CAP AND LIMITED LOW
LEVEL MOISTURE ACROSS THE AREA ARE HELPING TO SUPPRESS SIGNIFICANT
SHOWER AND THUNDERSTORM ACTIVITY THIS AFTERNOON. ALTHOUGH...AFTERNOON
CONVECTION CANT BE RULED OUT LATER THIS AFTERNOON.

MOISTURE ASSOCIATED WITH APPROACHING TROPICAL WAVE...NOW LOCATED
NEAR 59W...WILL REACH THE LOCAL ISLANDS AS SOON AS THURSDAY
AFTERNOON. MODEL GUIDANCE CONTINUES TO SUGGEST MOST ACTIVE WX
THURSDAY NIGHT AND EARLY FRIDAY MORNING OVER EASTERN PUERTO RICO
AND USVI SPREADING ACROSS WESTERN PUERTO RICO FRIDAY AFTERNOON.
A DRIER AIR MASS IS EXPECTED TO MOVE IN FROM THE EAST FRIDAY NIGHT
AND SATURDAY AS THE WAVE MOVES FURTHER WEST INTO THE MONA PASSAGE
AND DOMINICAN REPUBLIC. ANOTHER WAVE CURRENTLY LOCALIZED NEAR 39W
WILL APPROACH THE AREA LATE SUNDAY/EARLY MON WITH RISK OF SHOWERS
INCREASING AGAIN.

AVIATION...VFR CONDS EXPECTED FOR ALL TAF SITES EXCEPT FOR POSSIBLE
BRIEF SHRA THAT COULD AFFECT TJMZ BY MID-AFTERNOON. ISOLD VCSH
POSSIBLE FOR LOCAL ISLANDS THRU THE NIGHT. WIND BLO FL070 E 6-14 KTS
BECOMING SE ABV FL080 AT 5-10 KTS.

MARINE...SEAS MAINLY 2-5 FT. NE SWELLS WILL BEGIN TO SUBSIDE
TONIGHT. A SLIGHT INCREASE IN WINDS EXPECTED SAT. OTHERWISE...
WINDS GENERALLY BELOW 17 KT MOST OF THE 5-DAY PERIOD.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  80  89  80  88 /  20  20  60  60
STT  78  89  78  89 /  20  30  60  60

&&

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

$$

11/12







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