Flash Flood Watch 15, NWS JSJ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE SAN JUAN PR
851 PM AST THU DEC 24 2009

.UPDATE...LINE SO FAR HAS MAINTAINED STRENGTH AND INTEGRITY WITH
SOME ELECTRICAL ACTIVITY STRETCHING FROM 10 NM NORTHWEST OF
AGUADILLA TO WELL OUT INTO THE MONA CHANNEL WEST OF CABO ROJO. BUT
HEAVY SHOWER ACTIVITY HAS ALSO CONTINUED FROM GUAYANILLA AND JUANA
DIAZ TO SAN LORENZO AND FAJARDO. SUFFICIENT RAIN IS ON THE WAY
SUCH THAT A FLASH FLOOD WARNING HAS BEEN DEEMED PRUDENT FOR
NORTHEAST PUERTO RICO. AND WILL ISSUE A FLASH FLOOD WATCH BUT HAVE
NOT DECIDED HOW MUCH OF PUERTO RICO IT WILL INVOLVE.

&&

.DISCUSSION...WRF MODEL STILL DOING BEST. NAM HAS NOT EVEN GOTTEN THE
LINES POSITION RIGHT AND SO MUST COMPLETELY DISCOUNT IT. GFS DOING
OK WITH LOW PRESSURE FORMING OR DEEPENING NORTHEAST OF LOCAL AREA
DURING NEXT 24 HOURS THEN DRIFTING EAST NORTHEAST. WRF HAD
CONSIDERABLE RAIN REMAINING ON THE NORTHEAST COAST FOR MUCH OF THE
NIGHT. EXPECT SIGNIFICANT RAIN AMOUNTS BUT...AT LEAST FOR THE TIME
BEING...HEAVY RAIN AND FLOODING SHOULD BE VERY LOCALIZED IN THE
EAST. STILL WATCHING TO SEE HOW WELL THE WRF WILL VERIFY. ITS
FORECAST IS UNIQUE AND CALLS FOR THE LINE TO SPLIT TO THE NORTH AND
SOUTH SOUTHEAST. ITS SOLUTION KEEPS THE RAIN OFF OF WESTERN PUERTO
RICO EXCEPT FOR AMOUNTS LESS THAN .25 INCHES. THIS SEEMS
REASONABLE FOR THE MOMENT AND THUNDERSTORMS HAVE REMAINED
OFFSHORE...BUT THUNDERSTORMS SUGGEST IT MAY BE ABLE TO SPREAD RAIN
GREATER THAN FORECAST...SO WILL MONITOR CLOSELY.

&&

.AVIATION...
HEAVY RAIN ONGOING THIS EVENING TO PRODUCE TEMPO IFR
CONDS IN +TSRA TJPS...TJSJ AND TJBQ THROUGH 06 TO 08Z AND OVER THE
USVI SITES 10 TO 12Z.

&&

.PREV DISCUSSION... /ISSUED 645 PM AST THU DEC 24 2009/

UPDATE...HAVE UPDATED FORECAST TO TAKE DOWN MANY SMALL CRAFT
ADVISORIES THAT EXPIRED AT 6 PM AST....AND ALSO TO INCREASE POPS
ACROSS WEST AND SOUTH PUERTO RICO IN THE NEAR TERM. THE BAND
MOVING ACROSS THE MONA CHANNEL IS HOLDING ITS STRENGTH IF NOT
STRENGTHENING AND WILL BEGIN TO AFFECT PUERTO RICO BEFORE 8 PM
AST. AN AREA OF VERTICAL MOTION AHEAD OF IT IS ALREADY BEGINNING
TO MANIFEST ITSELF IN THE INCREASING FREQUENCY OF SHOWERS IN THE
CARIBBEAN AND SOUTHERN PUERTO RICO. THE BAND ITSELF HAS SHOWN
CONSIDERABLE ELECTRICAL ACTIVITY SO FEEL CONFIDENT THAT WE WILL
HAVE AT LEAST SOME THUNDERSTORMS.

AVIATION...NO CHANGE FROM BELOW.

PREV DISCUSSION... /ISSUED 258 PM AST THU DEC 24 2009/

SYNOPSIS...A LOW PRESSURE SYSTEM NORTHEAST OF HISPANIOLA WILL
CONTINUE TO TRACK EASTWARD. VARIABLY CLOUDY SKIES...WITH
OCCASIONAL SHOWERS...ARE EXPECTED FOR CHRISTMAS DAY AND THE
UPCOMING WEEKEND...AS THIS LOW PASSES JUST NORTH OF THE LOCAL
ISLANDS AND THE REMNANTS OF AN OLD FRONTAL BOUNDARY PUSH SOUTHWARD
ACROSS THE REGION.

DISCUSSION...ISOLATED TO SCATTERED SHOWERS CONTINUE TO AFFECT THE
U.S. VIRGIN ISLANDS AND THE SOUTHEAST PORTIONS OF PUERTO RICO. THE
DOPPLER RADAR IS SHOWING A BAND OF SHOWERS ASSOCIATED TO THE
BEFORE MENTIONED LOW...ALONG THE PUNTA CANA AREA. THIS BAND OF
SHOWERS AND THUNDERSTORMS IS FORECASTED TO MOVE EASTWARD ACROSS
THE MONA PASSAGE AND AFFECT THE WESTERN PORTIONS OF PUERTO RICO
LATE THIS EVENING. SCATTERED TO NUMEROUS SHOWERS ARE EXPECTED TO
SPREAD EASTWARD INCREASING THE POPS FOR MOST OF THE ISLANDS
THROUGH AT LEAST EARLY SATURDAY.

REMNANTS OF AN OLD FRONTAL BOUNDARY TO OUR NORTH IS FORECASTED TO
MOVE SOUTHWARD ACROSS THE LOCAL ISLANDS...BRINGING ANOTHER BRIEF
SURGE IN SHOWER ACTIVITY BETWEEN LATE SATURDAY AND SUNDAY.

AVIATION...SHORT WAVE OVER THE MONA CHANNEL WILL BRING TSRA
ACTIVITY TO TJBQ AND TJMZ BY 00Z...THEN OVER TJSJ BY 04Z AND THE
USVI SITES 08Z. EXPECT MVFR CIGS WITH TEMPO IFR VSBYS IN +TSRA.
WEAK REMNANT VA OVER THE AREA STILL LINGERING A BIT MAY RESULT IN
SOME HAZY SKIES AROUND FL100...BUT SHOULD HAVE NO IMPACT ON OPS.

MARINE...THE BUOY 41043 IS ALREADY SHOWING A SIGNIFICANT DECREASE
ON THE SWELL HEIGHT...THEREFORE THE HIGH SURF ADVISORY WILL BE IN
EFFECT THROUGH 6 PM TODAY. ANOTHER NORTHERLY SWELL WILL BE REACHING
OUR LOCAL WATERS ON SUNDAY WITH A LARGE PULSE BETWEEN MONDAY NIGHT
AND TUESDAY. MARINERS AND BEACH GOERS SHOULD MONITOR OUR FORECASTS
AS SMALL CRAFT AND HIGH SURF ADVISORIES WILL BE ISSUED. THERE IS
A POTENTIAL FOR COASTAL FLOODING TO OCCUR THEREFORE COASTAL FLOOD
WATCHES MAY BE ISSUE FOR THE NORTHERN PORTIONS OF THE ISLANDS AND
EXPOSED BEACHES.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  75  85  75  83 /  50  50  30  70
STT  76  83  75  84 /  40  60  40  70

&&

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

93/12

HAZARDOUS WEATHER OUTLOOK FOR PUERTO RICO AND THE U.S. VIRGIN
ISLANDS
NATIONAL WEATHER SERVICE SAN JUAN PR
519 AM AST THU DEC 24 2009

AMZ710>745-PRZ001>013-250930-
SAN JUAN AND VICINITY-NORTHEAST-SOUTHEAST-EASTERN INTERIOR-
NORTH CENTRAL-CENTRAL INTERIOR-PONCE AND VICINITY-NORTHWEST-
WESTERN INTERIOR-MAYAGUEZ AND VICINITY-SOUTHWEST-CULEBRA-VIEQUES-
THE NEARSHORE AND OFF SHORE ATLANTIC AND CARIBBEAN COASTAL WATERS-
519 AM AST THU DEC 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO AND THE
ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT
LONG PERIOD...NORTHERLY SWELLS WILL CONTINUE TO AFFECT THE
ATLANTIC WATERS AND THE CARIBBEAN PASSAGES THROUGH AT LEAST THIS
AFTERNOON. THESE SWELLS WILL CONTINUE TO RESULT IN ROUGH AND
HAZARDOUS MARINE AND SURF CONDITIONS...INCLUDING RIP CURRENTS
ALONG THE NORTHWEST THROUGH NORTHEAST COASTS OF THE LOCAL ISLANDS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR MOST OF THE LOCAL
ATLANTIC WATERS AND THE CARIBBEAN PASSAGES. IN ADDITION...A HIGH
SURF ADVISORY WAS ISSUED UNTIL 6 PM THIS AFTERNOON FOR BREAKING
WAVES 10 TO 15 FEET ALONG SOME NORTHERN COASTS.

NO OTHER HAZARDOUS WEATHER IS EXPECTED AT THIS TIME.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY
LONG PERIOD...NORTHEASTERLY SWELLS WILL INVADE THE AREA WATERS ON
SATURDAY AND LASTING THROUGH THE BEGINNING OF THE UPCOMING WEEK. THESE
SWELLS WILL RESULT IN ROUGH AND HAZARDOUS MARINE AND HIGH SURF
CONDITIONS...INCLUDING RIP CURRENTS ALONG THE NORTHWEST THROUGH
NORTHEAST COASTS OF THE LOCAL ISLANDS.

.SPOTTER INFORMATION STATEMENT...
SPOTTER REPORTS OF HAZARDOUS SEAS OR DANGEROUS SURF WOULD BE
GREATLY APPRECIATED.

AMZ715-725-VIZ001-002-250930-
ST. THOMAS ST. JOHN ADJACENT ISLANDS-ST CROIX-
NEARSHORE ATLANTIC AND ADJACENT CARIBBEAN COASTAL WATERS-
519 AM AST THU DEC 24 2009

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS AND
THE ADJACENT COASTAL WATERS.

.DAY ONE...TODAY AND TONIGHT
LONG PERIOD...NORTHERLY SWELLS WILL CONTINUE TO AFFECT THE
ATLANTIC WATERS AND THE CARIBBEAN PASSAGES THROUGH AT LEAST THIS
AFTERNOON. THESE SWELLS WILL CONTINUE TO RESULT IN ROUGH AND
HAZARDOUS MARINE AND SURF CONDITIONS...INCLUDING RIP CURRENTS
ALONG THE NORTHWEST THROUGH NORTHEAST COASTS OF THE LOCAL ISLANDS.
A SMALL CRAFT ADVISORY REMAINS IN EFFECT FOR MOST OF THE LOCAL
ATLANTIC WATERS AND THE CARIBBEAN PASSAGES. IN ADDITION...A HIGH
SURF ADVISORY WAS ISSUED UNTIL 6 PM THIS AFTERNOON FOR BREAKING
WAVES 10 TO 15 FEET ALONG SOME NORTHERN COASTS OF SAINT
THOMAS...SAINT JOHN AND ADJACENT SMALLER ISLANDS.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY
LONG PERIOD...NORTHEASTERLY SWELLS WILL INVADE THE AREA WATERS ON
SATURDAY AND LASTING THROUGH THE BEGINNING OF THE UPCOMING WEEK. THESE
SWELLS WILL RESULT IN ROUGH AND HAZARDOUS MARINE AND HIGH SURF
CONDITIONS...INCLUDING RIP CURRENTS ALONG THE NORTHWEST THROUGH
NORTHEAST COASTS OF THE LOCAL ISLANDS.

.SPOTTER INFORMATION STATEMENT...
SPOTTER REPORTS OF HAZARDOUS SEAS OR DANGEROUS SURF WOULD BE
GREATLY APPRECIATED.