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AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE SAN JUAN PR
1018 PM AST MON NOV 9 2009

.UPDATE...SATELLITE PICTURE INDICATES A BAND OF DRY AIR AHEAD OF
SHOWERS THAT ARE MOVING SOUTH TOWARD WESTERN PUERTO RICO. SOUNDING
CONFIRMS AS PRECIPITABLE WATER HAS DROPPED ALMOST ONE HALF INCH IN
THE PAST 24 HOURS. EXPECT MAIN SHOWERS TO MISS THE ISLAND HOWEVER
IN ACCORDANCE WITH LATEST NAM GUIDANCE. SOME SHOWERS WILL STILL
CONTINUE...MAINLY ALONG THE NORTH COAST WHERE NAM SHOWS
CONSIDERABLE NEGATIVE SURFACE MOISTURE FLUX DIVERGENCE. SHOWERS
WILL RE-DEVELOP DURING THE AFTERNOON.


&&

.DISCUSSION...WINDS AT 850 MB OVER SAN JUAN ARE NORTHEAST AROUND
A LOW FORMING JUST NORTHEAST OF THE LEEWARD ISLANDS. THIS LOW IS
FORECAST TO DRIFT NORTHWEST WHILE DEVELOPING SOME. AS IT DOES SO
WINDS AT 850 MB WILL SHIFT TO SOUTH EVEN SOUTHWEST TUESDAY NIGHT
OVER BOTH PUERTO RICO AND THE U.S. VIRGIN ISLANDS. AFTER THE WINDS SHIFT...
PRECIPITATION WILL FALL MORE ON THE SOUTH AND EAST COAST TUESDAY
NIGHT AND OVER MUCH OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS
DURING THE DAY ON WEDNESDAY. MODEL SOLUTIONS DIVERGE SOMEWHAT
AFTER WEDNESDAY WITH THE NAM BRINGING BETTER MOISTURE OVER THE
WEST HALF OF PUERTO RICO ON THURSDAY WHILE THE GFS PLOWS IT INTO
THE DOMINICAN REPUBLIC. AT THIS TIME IT IS TOO SOON TO TELL WHICH
WILL BE RIGHT.

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
326 PM AST TUE NOV 10 2009

.SYNOPSIS...MID TO UPPER LEVEL LOW...AND A SERIES OF ASSOCIATED
SHORT WAVES...WILL CONTINUE TO AFFECT THE LOCAL AREA FOR AT LEAST
THE NEXT 24 TO 36 HOURS...AS DEEPER TROPICAL MOISTURE BEGINS TO
SURGE NORTHWEST ACROSS THE FA AND COMBINES WITH LOCAL EFFECTS...
TO PRODUCE A SIGNIFICANT INCREASE IN ACTIVE WEATHER ACROSS THE
LOCAL ISLANDS.

&&

.DISCUSSION...DEEPER MOISTURE WILL CONTINUE TO ADVECT SLOWLY
NORTHWEST ACROSS THE LOCAL AREA TONIGHT THROUGH WEDNESDAY AND WILL
THEN LINGER NEARBY FOR AT LEAST A COUPLE OF DAYS. AT THE SAME
TIME...MID TO UPPER LEVEL LOW WILL REMAIN LOCATED JUST NORTH OF
THE LOCAL AREA. AN ASSOCIATED SHORT WAVE TROUGH WILL MOVE ACROSS
THE LOCAL ISLANDS TONIGHT THROUGH WEDNESDAY AND SHOULD PROVIDE
FAVORABLE CONDITIONS FOR SIGNIFICANT AND POTENTIALLY EXPLOSIVE
CONVECTIVE DEVELOPMENT LATER TONIGHT THROUGH AT LEAST THE FIRST
PART OF WEDNESDAY...WITH PERIODS OF ACTIVE WEATHER STILL EXPECTED
TO CONTINUE LATER WEDNESDAY THROUGH THURSDAY. AT THIS POINT...
ALTHOUGH THE POTENTIAL FOR HEAVY RAIN AND EVENTUALLY SOME FLOODING
EXISTS...WE OPTED TO HOLD OFF FOR NOW ON A FLASH FLOOD WATCH.
HOWEVER...IF THIS ACTIVITY REALLY BEGINS TO EXPLODE LATE TONIGHT...
LATER SHIFTS MAY NEED TO GO WITH A WATCH. PLEASE REFER TO
ZFP AND OTHER PRODUCTS FOR FORECAST DETAILS.

&&

.AVIATION...EXPECT PREVAILING VFR CONDITIONS ACROSS MOST OF THE
LOCAL ISLANDS AND TAF SITES TONIGHT. HOWEVER...MVFR AND LOCALLY
IFR CONDITIONS AND MOUNTAIN OBSCURATIONS WILL CONTINUE THROUGH
10/21Z ACROSS SOUTH CENTRAL AND SOUTHWEST PUERTO RICO...
INCLUDING TJPS IN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS.
ACROSS THE U.S. VIRGIN ISLANDS...INCREASING SHOWERS AND
THUNDERSTORMS AND EXPANDING MVFR CONDITIONS SHOULD PREVAIL THROUGH
TONIGHT. OVER TNCM AND TKPK...INITIAL VFR CONDITIONS SHOULD ALSO
SLOWLY DETERIORATE...AS SHOWERS AND THUNDERSTORMS DEVELOP AND
BEGIN TO AFFECT THESE TAF SITES BY 10/22Z OR 10/23Z. VOLCANIC ASH
AND STEAM PLUME WILL BE TRICKY...AS SURFACE TROUGH BEGINS ITS
NORTHWEST TREK. BUT...FOR AT LEAST EARLY TONIGHT...EXPECT ASH AND
STEAM TO MOVE GENERALLY NORTH NORTHEAST OR NORTHEAST.

&&

.MARINE...HAZARDOUS MARINE CONDITIONS WILL CONTINUE THROUGH AT
LEAST WEDNESDAY EVENING AND POSSIBLY BEYOND...AS LARGE...LONG
PERIOD NORTH NORTHEAST SWELLS CONTINUE TO AFFECT THE ATLANTIC
WATERS AND THE CARIBBEAN PASSAGES. THESE SWELLS SHOULD PEAK BY MID
MORNING WEDNESDAY AND THEN SLOWLY SUBSIDE THROUGH WEDNESDAY NIGHT
AND THURSDAY. A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR MOST
OF THE LOCAL ATLANTIC AND CARIBBEAN WATERS AND THE CARIBBEAN
PASSAGES TONIGHT.