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000
FXCA62 TJSJ 180920
AFDSJU

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
520 AM AST TUE JUN 18 2013

.SYNOPSIS...AT UPPER LEVELS...LOW PRESSURE IS ABOUT 290 MILES
NORTH OF SAINT THOMAS AND WILL MOVE NORTH AND SLIGHTLY WEST DURING
THE NEXT 48 HOURS WITH TROUGHING EXTENDING OVER HISPANIOLA. THIS
LOW WILL MOVE EAST OVER THE WEEKEND WHILE HIGH PRESSURE RIDGES
INTO THE SOUTHEASTERN CARIBBEAN. BY MID WEEK NEXT WEEK A RIDGE
WILL HAVE BUILT INTO THE WESTERN CARIBBEAN AND EXTEND NORTH TO
FLORIDA.

AT MID LEVELS...A WEAK TROUGH OVER AND NORTH OF THE AREA WILL MOVE
SLOWLY WEST AND WEAKEN ONLY TO RE-FORM OVER THE WEEKEND NORTH OF
THE AREA. LOWER PRESSURE WILL REMAIN ENSCONCED TO THE NORTHEAST OF
PUERTO RICO THROUGH THE END OF NEXT WEEK.

AT LOWER LEVELS...HIGH PRESSURE WILL CONTINUE OVER THE CENTRAL
ATLANTIC THROUGH MID WEEK NEXT WEEK WHILE LOW PRESSURE REMAINS IN
THE SOUTHWESTERN CARIBBEAN. THIS WILL KEEP MODERATE TO FRESH TRADE
WINDS OVER THE LOCAL AREA THROUGH THE ENTIRE FORECAST PERIOD. A
TROPICAL WAVE WILL MOVE THROUGH THE AREA WEDNESDAY AND WEDNESDAY
NIGHT WITH SOME RAIN...AND THUNDERSTORMS WITH VERY GUSTY WINDS.

&&

.DISCUSSION...AGAIN VERY FEW SHOWERS WERE SEEN OVERNIGHT IN
RELATIVELY BRISK EASTERLY TRADE WIND FLOW. DUST FROM THE SAHARA
WILL PERSIST TODAY AND TONIGHT...BUT WITH THE COMING TROPICAL WAVE
SURFACE VISIBILITIES WILL IMPROVE SOMEWHAT. MOISTURE OVER THE
LOCAL AREA REACHED A MINIMUM OVERNIGHT AND WILL BEGIN TO
RECOVER...TO AS MUCH AS 2 INCHES BY 19/18Z. MOISTURE OVER SAINT
CROIX IS ALREADY APPROACHING 1.7 INCHES. THIS HERALDS THE TROPICAL
WAVE THAT WILL APPROACH ON WEDNESDAY WITH A DOUBLE TROUGH AT 700
MB. THE FIRST TROUGH WILL PASS OVER PUERTO RICO AT ABOUT 19/12Z
WHILE THE SECOND AND STRONGER TROUGH WILL MOVE THROUGH BETWEEN
20/06 AND 20/12Z. THIS WAVE IS ACCOMPANIED BY A VERY STRONG
SOUTHEAST WIND SURGE OF BETWEEN 925 AND 700 MB...WHICH ON WEDNESDAY
NIGHT WILL REACH 40 KNOTS ACCORDING TO THE GFS AND CONFIRMED BY
THE WRF AND NMM MODELS IN BOTH THE 17/18Z AND 18/00Z GFS RUNS. ANY
THUNDERSTORMS THAT FORM IN THIS ENVIRONMENT WILL BE LIKELY TO HAVE
VERY STRONG GUSTS WHICH COULD...IN A FEW PLACES...EXCEED SEVERE
LIMITS...ESPECIALLY IN THE CARIBBEAN WATERS. BECAUSE MOISTURE IN
THE LOWER LEVELS IS LIMITED AND FOLLOWED IMMEDIATELY BY MORE
SAHARAN AIR...HEAVY RAIN WILL LIKELY BE LIMITED IN COVERAGE...AND
FLOODING...EXCEPT FOR LOCAL DRAINAGE PROBLEMS...IS NOT EXPECTED WITH
THIS WAVE. MOISTURE REACHES A MINIMUM ON FRIDAY EVENING AFTER THE
WAVE PASSES SIMILAR TO THE ONE THAT JUST OCCURRED. AT THAT TIME
WINDS WILL ABATE AND SHOWERS WILL DIMINISH CONSIDERABLY. A SECOND
PULSE OF MOISTURE DEVELOPS EAST OF THE LEEWARD ISLANDS THURSDAY
NIGHT AND MOVES ACROSS THE LOCAL AREA SATURDAY NIGHT.

&&

.AVIATION...VFR COND WILL CONTINUE XCP ON TUE AFTERNOON WHERE ISOLD/SCT
SHRA AND ISOLD TSRA OVR INTERIOR/WEST PR WI MTN OBSC ARE POSSIBLE.
WIND SFC TO 2K FT GENERALLY FROM EAST AT 10-20 KT. SAHARAN DUST AT
TIMES TO CAUSE SLIGHTLY LWR VSBY.

&&

.MARINE...WINDS OF 16 TO 20 KNOTS HAVE ALREADY BROUGHT SEAS OF 4
TO 6 FEET ACROSS THE LOCAL EXPOSED WATERS. WINDS WILL BEGIN TO
INCREASE ON WEDNESDAY AHEAD OF A TROPICAL WAVE. SUSTAINED WINDS
WILL LIKELY REACH 20 TO 25 KNOTS...LOCALLY 30 KNOTS...WEDNESDAY
AFTERNOON BEGINNING IN THE SOUTHEAST CORNER OF THE FORECAST AREA.
GUSTS IN AND NEAR THUNDERSTORMS HAVE THE POTENTIAL TO REACH 45
KNOTS IN A FEW PLACES WEDNESDAY AFTERNOON AND EVENING.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  87  75  85  76 /  10  50  50  60
STT  88  77  85  76 /  10  50  50  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...NONE.
VI...NONE.
COASTAL WATERS...SMALL CRAFT ADVISORY FROM 6 AM WEDNESDAY TO 6 PM AST THURSDAY
     FOR ANEGADA PASSAGE SOUTHWARD TO 17N-ATLC WATERS OF PUERTO
     RICO AND USVI FROM 10NM TO 19.5N-CARIBBEAN WATERS OF PUERTO
     RICO FROM 10 NM TO 17N.

     SMALL CRAFT ADVISORY FROM NOON WEDNESDAY TO 6 AM AST THURSDAY
     FOR COASTAL WATERS OF NORTHERN USVI AND CULEBRA OUT 10 NM-
     COASTAL WATERS OF SOUTHERN USVI VIEQUES AND EASTERN PUERTO
     RICO OUT 10 NM.

     SMALL CRAFT ADVISORY FROM MIDNIGHT WEDNESDAY NIGHT TO 6 PM AST
     THURSDAY FOR MONA PASSAGE SOUTHWARD TO 17N.

&&

$$

10/12