Flash Flood Warning 144, NWS JSJ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1130 PM AST SUN OCT 2 2005

.11 PM UPDATE...UPPER LOW THAT APPEARED TO BE WEAKENING ACROSS THE
AREA THIS AFTERNOON WAS JUST REORGANIZING...AND HAS SUNKEN
SOUTHWESTWARD WITH LOW CENTERED NOW AS A TRIPLE POINT CONNECTING
TUTT SEGMENTS. THIS HAS COMBINED THIS EVENING WITH A PASSING LOW TO
MID LEVEL VORT CENTER TRAVERSING WNW ACROSS THE LOCAL AREA FOR A
VERY ACTIVE EVENING. A QUIKSCAT PASS THIS EVENING HAS VERIFIED WHAT
STLT IMAGERY SUGGESTED LATE THIS AFTERNOON...AND MY BINOCULAR AIDED
VIEW AT THE BEACH SUGGESTED THIS AFTERNOON...THAT A FRESH ESE WIND
FLOW IS DOMINATING THE LOCAL OFFSHORE ATLANTIC WATERS...AND IS EVEN
STRONGER WELL OFF SHORE DUE TO THE BUILDING HIGH PRESSURE ACROSS THE
WEST CENTRAL ATLANTIC. THIS HAS PRODUCED A PRONOUNCED DIFFERENCE IN
LOCAL WINDS AND SEAS...BEING SLIGHT ACROSS THE CARIBBEAN AND
INCREASING SHARPLY SOUTH TO NORTH ACROSS THE LOCAL ATLANTIC. HAVE
THUS ISSUED A SCA FOR OFF SHORE ATLANTIC...AND FOR A CHANGE HAD TO
INCREASE WINDS ABOVE THE GFS FORECAST.

SHOWERS AND THUNDERSTORMS...SOME INTENSE...WILL CONTINUE TO MOVE WNW
OVERNIGHT AND INTERMITTENTLY AFFECT THE EAST AND NORTH LOCAL
WATERS...THE BRITISH...SPANISH...AND U.S. VIRGIN ISLANDS (DID I
FORGET ANYBODY?)...AND THE EAST HALF OF PUERTO RICO...TO PRODUCE
PERIODS OF STRONG GUSTY WINDS...VERY HEAVY RAINFALL AT 3-5 INCH PER
HOUR RATES...AND FREQUENT LIGHTNING. A FLASH FLOOD WATCH IS NOW IN
EFFECT FOR EAST...SOUTHEAST...AND EASTERN INTERIOR P.R. AND ST CROIX
DUE TO CURRENT PRECIP FREQUENCY AND RECENT RAINS OF THE PAST 12
HOURS. THE EAST AND SOUTHEAST HALVES OF P.R. MAY SEE SIGNIFICANT
RIVER FLOODING AND ISOLATED MUDSLIDES BY SUNRISE. 70

&&

.4 PM SYNOPSIS...AT UPPER LEVELS..THE STRONG UPPER LOW THAT HAS BEEN
CREATING THE RING OF CONVECTION TO OUR NORTHEAST MOVED SOUTH
SOUTHWEST TOWARD THE VIRGIN ISLANDS AND WEAKENED. IT WILL FORM A
BRIDGE OF LOW PRESSURE BETWEEN THE NEXT TWO LOWS MENTIONED. A
STRONGER LOW NEAR 33 NORTH 43 WEST WILL PUSH SOUTHWEST THROUGH
THURSDAY MORNING...BUT WILL ONLY SERVE TO BRING A NORTHWESTERLY
UPPER LEVEL JET DOWN TO 20 NORTH 60 WEST AND NO CLOSER. LOW PRESSURE
EAST OF FLORIDA WILL MOVE ACROSS FLORIDA AND INTO THE GULF OF MEXICO
BY MID WEEK...LEAVING A RIDGE OVER THE LOCAL AREA THAT WILL PERSIST
THROUGH SATURDAY.

AT MID LEVELS...LOW PRESSURE JUST NORTH OF PUERTO RICO WILL MOVE TO
CUBA AS HIGH PRESSURE RIDGES IN OVER THE AREA FROM THE NORTH ON
TUESDAY. HIGH PRESSURE CONTINUES BUILDING SOUTH PREEMPTING A TROUGH
FROM THE NORTHEAST THROUGH SATURDAY...POSSIBLY SPUN DOWN FROM THE
UPPER LEVEL LOW IN THE SAME PLACE. HIGH PRESSURE THEN MOVES
NORTHWEST.

AT LOWER LEVELS...THE ACTIVITY FROM THE UPPER LEVEL LOW IS BEGINNING
TO DISSIPATE...BUT WILL LEAVE AN AREA OF MOIST AND UNSTABLE AIR THAT
IS LOOSELY CONNECTED WITH A MASS OF MOISTURE JUST EAST OF THE
BAHAMAS AND THE REMNANTS OF THE WEAKENING TROPICAL DEPRESSION 19.
THAT BAND...WHICH STRETCHES FROM ABOUT 10 NORTH AND 52 WEST TO 26
NORTH 72 WEST TONIGHT...CONTINUES TO BE TRACEABLE IN THE MODELS
SOLUTIONS THROUGH THURSDAY AND SLOWLY DRIFTS ACROSS PUERTO RICO AND
THE U.S. VIRGIN ISLANDS ON WEDNESDAY. TOWARD THE END OF THE SOLUTION
THE GFS BRINGS A TROPICAL CYCLONE TO JUST EAST OF THE WINDWARD
ISLANDS ON SUNDAY NEXT AND THEN MOVES IT NORTH.

&&

.DISCUSSION...THE SOUNDING CONTAINED MORE MOISTURE IN THE COLUMN
THAN YESTERDAY AND STRONG ACTIVITY WAS ALREADY IN PROGRESS WHEN THE
SUN ROSE THIS MORNING. WITH NORTH UPPER LEVEL FLOW AROUND THE UPPER
LEVEL LOW TO THE NORTHEAST...ANVIL BLOW OFF WAS ALREADY BLOCKING
MOST OF THE SUN FROM REACHING PUERTO RICO AND THE U.S. VIRGIN
ISLANDS BY MID MORNING. SOME THUNDERSTORMS DID CONTINUE IN THE AREA
SOUTH OF THE LOW AND SOME BROKE AWAY AND MOVED SOUTHWEST ACROSS THE
ISLANDS. SHOWERS CONTINUED TO MOVE OFF THE CARIBBEAN SEA AND ONTO
EASTERN PUERTO RICO DURING THE AFTERNOON. THE SOURCE OF PUERTO RICOS
ACTIVITY DURING THE AFTERNOON WAS FROM THE ONE AREA THAT RECEIVED
THE MOST SUNSHINE...THE SOUTHWEST CORNER. WITH MOIST FLOW IN PLACE
AND WEAK NORTHEASTERLY SURFACE FLOW...THUNDERSTORMS FORMED OVER THE
SOUTHWEST COASTAL STRIP OF PUERTO RICO BETWEEN THE BEACHES AND THE
CORDILLERA CENTRAL...AND ONE PLACE IN PENUELAS RECEIVED OVER 5
INCHES OF RAIN. RAIN WILL CONTINUE IN THESE TWO AREAS UNTIL SUNSET.

THE LOW PRESSURE ALOFT IS BEGINNING TO WEAKEN CONSIDERABLY AND THE
CONVECTION THAT RESULTED IS BEGINNING TO DISPERSE. THIS WILL LEAVE
SCATTERED SHOWERS OVERNIGHT. THE BAND OF MOISTURE WILL REMAIN TO OUR
NORTHEAST UNTIL TUESDAY NIGHT WHEN WE SHOULD AGAIN EXPERIENCE HIGHER
THAN USUAL SHOWER AND THUNDERSTORMS ACTIVITY. THIS WILL LAST THROUGH
THURSDAY AND THEN WE RETURN TO TYPICAL AFTERNOON PATTERNS THAT ARE
MORE DEPENDENT ON SURFACE WINDS.

WORTH MENTIONING...BUT STILL LOW ON THE SCALE OF PROBABILITY...IS
THE SWIRL OF CONVECTION THAT MOVED OFF OF AFRICA A WHILE AGO AND IS
NOW NEAR 23 WEST SOUTH OF 16 NORTH. THE GFS PICKS UP ON
THIS...DEVELOPS A CIRCULATION...AND BRINGS IT TO 8 NORTH AND 40 WEST
BY THURSDAY MORNING AND TO 13 NORTH 54 WEST BY SUNDAY MORNING. AT
THAT POINT IT IS PRESUMABLY A TROPICAL STORM OR BETTER AND IT DRIVES
TOWARD A WEAKNESS IN THE PRESSURE FIELD TO THE NORTH NORTHWEST. IN
THIS WAY IT APPEARS TO MISS THE LOCAL AREA ALTOGETHER. THIS SCENARIO
LOOKS FINE...IF IT CAN GET TOGETHER IN THE FIRST PLACE...WHICH FEW
OTHER SYSTEMS HAVE BEEN ABLE TO DO IN THE LAST 4 WEEKS OR SO. SO FOR
NOW WE WILL LEAVE IT ON THE OUTSIDE-CHANCE TO-BE-WATCHED LIST.

&&

.MARINE...THE CONVECTION THAT FORMED A RING AROUND THE UPPER LEVEL
LOW TO OUR NORTHEAST HAS SUFFICIENTLY RILED THE SEAS WITH SHORT
PERIOD WAVES SUCH AS TO BE NOTABLE EVEN ON THE NORTHERN SHORES OF
PUERTO RICO...AND THEREFORE HAVE RAISED THE FORECAST FOR THE SEAS IN
THE ATLANTIC BY ABOUT 1 FOOT. THIS SHOULD DISSIPATE BACK TO OR BELOW
THE LEVELS THAT THE MODEL HAS BEEN ANTICIPATING DURING THE NEXT 24
TO 36 HOURS. SEAS THEN REMAIN RELATIVELY TRANQUIL FOR THE NEXT 7
DAYS WITH LITTLE IN THE ATLANTIC OVER 4 FEET...AND NOTHING IN THE
CARIBBEAN OVER 3 FEET.

&&

.AVIATION...AVIATORS WILL HAVE TO PUT UP WITH CONTINUED
THUNDERSTORMS IN THE WESTERN/SOUTHWESTERN INTERIOR OF PUERTO RICO
FOR THE NEXT 4 AFTERNOONS. WE MAY ALSO SEE AN INCREASE IN MID-LEVEL
CLOUDINESS AS THE MOISTURE IN THE BAND BETWEEN THE TWO DISTURBANCES
STRETCHES AND MOVES SOUTH OVER THE AREA TUESDAY THROUGH THURSDAY.
OTHERWISE NO OTHER HAZARDS TO AVIATION ARE ANTICIPATED. SNELL

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...FFA PRZ002>004 TIL 10Z.
VI...FFA VIZ002 TIL 10Z.
&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JUAN PR
600 AM AST SUN OCT 2 2005

PRZ001>013-AMZ710>750-031030-
600 AM AST SUN OCT 2 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO.

.DAY ONE...TODAY AND TONIGHT

AN UPPER LEVEL TROUGH LOCATED ACROSS THE NORTHERN LEEWARD ISLANDS
AND THE EASTERN CARIBBEAN WILL CONTINUE TO ENHANCE THE SHOWER
ACTIVITY ACROSS THE LOCAL REGION TODAY. SCATTERED TO NUMEROUS
SHOWERS AND ISOLATED THUNDERSTORMS WILL OCCUR OVER PARTS OF THE
LOCAL ISLANDS... BUT MAINLY ACROSS THE INTERIOR AND WEST PORTIONS OF
PUERTO RICO DURING THE AFTERNOON HOURS. HEAVY LOCALIZED RAINFALL
WILL LEAD TO AREAS OF URBAN AND SMALL STREAM FLOODING AND RIVER
FLOODING.

.DAYS TWO THROUGH SEVEN...

THE COMBINATION OF A LINGERING UPPER LEVEL LOW OR TROUGH AND A BAND
OF MOISTURE APPROACHING THE ISLANDS FROM THE NORTHEAST WILL RESULT
IN AT LEAST SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER PARTS
OF THE LOCAL ISLANDS. AS ALWAYS...WITH SHOWER AND THUNDERSTORM
ACTIVITY COMES THE CHANCE OF LOCALLY HEAVY RAIN WHICH CAN LEAD TO
AREAS OF URBAN AND SMALL STREAM FLOODING AND RIVER FLOODING.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED.

VIZ001-002-AMZ710>730-031030-
600 AM AST SUN OCT 2 2005

THIS HAZARDOUS WEATHER OUTLOOK IS FOR THE U.S. VIRGIN ISLANDS.

.DAY ONE...TODAY AND TONIGHT

AN UPPER LEVEL TROUGH LOCATED ACROSS THE NORTHERN LEEWARD ISLANDS
AND THE EASTERN CARIBBEAN WILL CONTINUE TO ENHANCE THE SHOWER
ACTIVITY ACROSS THE LOCAL REGION TODAY. SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WILL OCCUR ACROSS PARTS OF THE LOCAL ISLANDS.
HEAVY LOCALIZED RAINFALL MAY LEAD TO URBAN AND GUT TYPE FLOODING.

MODERATE LONG PERIOD NORTH NORTHEAST SWELLS MOVING THROUGH THE
REGIONAL WATERS CONTINUE TO GRADUALLY SUBSIDE TODAY.

.DAYS TWO THROUGH SEVEN...

THE COMBINATION OF A LINGERING UPPER LEVEL LOW OR TROUGH AND A BAND
OF MOISTURE APPROACHING THE ISLANDS FROM THE NORTHEAST WILL RESULT
IN AT LEAST SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER PARTS
OF THE LOCAL ISLANDS. AS ALWAYS...WITH SHOWER AND THUNDERSTORM
ACTIVITY COMES THE CHANCE OF LOCALLY HEAVY RAIN WHICH CAN LEAD TO
AREAS OF URBAN AND GUT TYPE FLOODING.

.SPOTTER CALL TO ACTION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED.

STAY TUNED TO NOAA WEATHER RADIO AND OTHER LOCAL MEDIA FOR FURTHER
DETAILS OR UPDATES.

FOR ADDITIONAL INFORMATION...VISIT THE NATIONAL WEATHER SERVICE WEB
SITE FOR PUERTO RICO AND THE U.S. VIRGIN ISLANDS AT (ALL LOWERCASE
LETTERS): HTTP://WWW.SRH.NOAA.GOV/SJU.

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