Flood in Puerto Rico, May 23, 2004

PUERTO RICO AND U.S. VIRGIN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1130 PM AST SAT MAY 22 2004

THE ELONGATED LOW LEVEL TROUGH ACROSS CENTRAL AMERICA AND EXTENDING
NORTHEASTWARD INTO THE NORTHEAST CARIBBEAN CONTINUES TO GENERATE
CONVECTION EXTENDING INTO THE LOCAL REGION. THE LATEST GFS GUIDANCE
INDICATES A DISTINCT LOW LEVEL VORTICITY PATCH CENTERED ROUGHLY NEAR
16 NORTH AND 70 WEST. THE SATELLITE IMAGERY INDICATES SOME
CIRCULATION IN THE LOW LEVEL CLOUD IN THAT VICINITY AND ALSO
CONVECTION FLARING UP IN THAT SAME AREA. THIS FEATURE IS FORECAST
TO SLOWLY DRIFT TO THE NORTHEAST THE NEXT 24 TO 36 HOURS. THIS WILL
HELP TO ADD SYNOPTIC SCALE LIFT ACROSS THE NORTHEAST CARIBBEAN
TONIGHT THROUGH AT LEAST SUNDAY NIGHT...IN ADDITION TO COPIOUS LOW
LEVEL MOISTURE...WITH LOW LEVEL THETA-E VALUES NEAR 340 K. IN
ADDITION THE LOW LEVEL WIND FLOW IS EXPECTED TO TURN TO THE SOUTH
SOUTHEAST WHICH WILL ADVECT EVEN MORE LOW LEVEL MOISTURE ACROSS THE
REGION. LASTLY...WITH A LOW LEVEL RIDGE ACROSS THE SE U.S AND
EXTENDING INTO THE WESTERN ATLANTIC...THE LOW LEVEL SOUTHEAST
STEERING FLOW WILL BE BLOCKED FROM PUSHING THE VORTICITY PATCH TOO
FAST TO THE NORTHWEST AND AWAY FROM THE REGION. SO THE LOW LEVEL
MOISTURE...SYNOPTIC SCALE DYNAMICS AND POTENTIAL FOR HEAVY RAINFALL
WILL LIKELY PERSIST THROUGH AT LEAST MONDAY.

FOR NOW THE RAINFALL RATES HAVE TAPERED OFF...BUT WITH THE DAY TIME
HEATING SUNDAY AND DYNAMICS WITH THE LOW LEVEL TROUGH BEING MORE
FAVORABLE AT THAT TIME ALSO...THE POTENTIAL FOR HEAVY RAINFALL
SHOULD EXIST FOR MOST OF SUNDAY. AS USUAL...WILL HAVE TO WAIT AND
SEE HOW IT ALL PANS OUT.

DIEHL

...PREVIOUS SHORT TERM UPDATE...

DECIDED TO UPDATE THE FLASH FLOOD WATCH TO INCLUDE ALL PUERTO RICO.
ALTHOUGH
PRECIPITATION AMOUNTS ESTIMATED BY DOPPLER RADAR ARE MAINLY LIGHT TO
MODERATE...RADAR MAY BE UNDERESTIMATING THIS STRATIFIED
PRECIPITATION. ANY THESE RAIN AND CLOUDS COVER MOST OF THE AREA WITH
MORE SIGNIFICANT AMOUNTS SO FAR IN THE NEIGHBORHOOD OF ST CROIX. THE
POTENTIAL FOR MORE RAINFALL REMAINS TONIGHT AND SUNDAY.

RIVERA

.SYNOPSIS...
COMPLEX SYNOPTIC SCENARIO WITH SURFACE TROUGH EXTENDING EAST TO WEST
ACROSS THE CARIBBEAN...WITH SIGNIFICANT CONVECTION SOUTH OF PUERTO
RICO AND THE MONA PASSAGE...AND SOUTH AND SOUTHWEST OF HAITI. IN
ADDITION...A TROPICAL WAVE ALONG 61 WEST WILL ALSO PROVIDE SURFACE
CONVERGENCE AND MID LEVEL INSTABILITY TO THE LOCAL REGION. FRESH TO
MODERATE EASTERLY WINDS TODAY WILL GRADUALLY WEAKEN AND TURN
SOUTHEAST ON SUNDAY...CONTINUING WEAKENING AND BECOME SOUTH MONDAY
AND TUESDAY.

.DISCUSSION...
DOPPLER RADAR INDICATED A BROAD BAND OF MODERATE TO HEAVY RAIN
EXTENDING FROM SOUTHERN PUERTO RICO...EAST SOUTHEAST THROUGH ST
CROIX. THIS BAND IS EXPECTED TO CONTINUE DRIFTING NORTH TO AFFECT
THE LOCAL ISLANDS THROUGH AT LEAST MIDNIGHT. THE HEAVIEST ACTIVITY
IS EXPECTED ACROSS THE EASTERN TWO THIRDS OF PUERTO RICO...INCLUDING
THE ISLANDS OF VIEQUES AND CULEBRA...AND EXTENDING EAST THROUGH THE
U.S. VIRGIN ISLANDS.

GFE MODEL CONTINUE SHOWING VERY WET AND UNSTABLE ATMOSPHERE TONIGHT
THROUGH SUNDAY. STRONG MID LEVEL RISING MOTION...STRONG UPPER LEVEL
DIVERGENCE...AND A SIGNIFICANT RIDGE OF LOW LEVEL THETA-E ARE THE
PRINCIPAL INGREDIENTS TO PRODUCE SUSTAIN CONVECTION ACROSS THE LOCAL
REGION. A FLASH FLOOD WATCH WILL BE BE CONFIGURED TO INCLUDE THE
EASTERN TWO THIRDS OF PUERTO RICO...VIEQUES...CULEBRA...AND THE U.S.
VIRGIN ISLANDS THROUGH 10 PM.

&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  72  83  71  86 /  90  90  70  70
STT  71  82  71  84 /  50  90  80  80

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...FFA  PRZ001>006-012-013 TIL 6 AM.
VI...FFA  VIZ001-002 TIL 6 AM.

&&

ROCHE

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JUAN PR
600 AM AST FRI MAY 22 2004

PRZ001>013-AMZ710>750-231000-
630 AM AST FRI MAY 22 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO.

.TODAY...THE INFLUENCE OF AN ELONGATED AREA OF LOW PRESSURE ACROSS
THE CARIBBEAN...AND THE MOIST SOUTHERLY FLOW AROUND IT IN OUR LOCAL
AREA...COUPLED WITH STILL FAVORABLE UPPER LEVEL WINDS...AND AMPLE
AMOUNTS OF LOW TO MID LEVEL MOISTURE WILL SET THE STAGE FOR
CONTINUED PERIODS OF CLOUDY SKIES AND RAINY CONDITIONS OVER PUERTO
RICO. WHILE THE HEAVIEST RAINS ARE EXPECTED TO REMAIN OVER MUCH OF
THE LOCAL CARIBBEAN WATERS...CONDITIONS ARE SUCH THAT SCATTERED TO
NUMEROUS SHOWERS WITH ISOLATED THUNDERSTORMS WILL AFFECT MOST OF THE
ISLAND DURING THE DAY. THE HEAVIEST CONCENTRATION WILL BE DURING THE
AFTERNOON AND EVENING HOURS. DUE TO THE PROLONGED PERIOD OF
INTERMITTENT...HEAVY RAIN...THE RISK FOR FLASH FLOODING AND RIVER
FLOODING WILL CONTINUE ACROSS PORTIONS OF THE ISLAND WITH POSSIBLE
MUDSLIDES OVER MOUNTAIN TERRAIN. THE RISK WILL INCREASE TONIGHT AS
THE AREA OF GREATEST MOISTURE MOVES NORTH ONTO THE ISLANDS.

A MODERATE TO OCCASIONALLY STRONG TRADE WIND FLOW OVER THE REGION
WILL MAINTAIN ROUGH AND CHOPPY SEAS...WITH THE STRONGEST WINDS
AND HIGHEST SEAS OVER THE ATLANTIC OFFSHORE WATERS.

.SPOTTER CALL TO ACTION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED.

.DAYS TWO THROUGH SEVEN...

THE LOW LEVEL TROUGH ASSOCIATED WITH THE ELONGATED AREA OF LOW
PRESSURE OVER THE EASTERN CARIBBEAN WILL BE THE MAIN WEATHER MAKER
SUNDAY AND MONDAY AS IT DRIFTS NORTH THEN WESTWARD TO THE CENTRAL
CARIBBEAN. THE TROUGH IS THEN FORECAST TO MOVE NORTHWARD INTO THE
SUBTROPICAL ATLANTIC BY EARLY NEXT WEEK. UNSETTLED WEATHER WILL
CONTINUE OVER PUERTO RICO PUERTO RICO AT LEAST THROUGH TUESDAY...
WITH SOME IMPROVEMENT EXPECTED THEREAFTER. AS A RESULT...THERE WILL
CONTINUE TO BE THE RISK OF DANGEROUS FLASH FLOODING AND MUDSLIDES...
ESPECIALLY ON SUNDAY AND MONDAY WHEN THE RAINFALL IS EXPECTED TO BE
HEAVIEST.

A MODERATE TO FRESH TRADE WIND FLOW AND CHOPPY SEAS WILL PREVAIL
ACROSS THE LOCAL ISLANDS THROUGH AT LEAST EARLY NEXT WEEK BUT WINDS
AND SEAS WILL BEGIN TO SUBSIDE BY MID TO LATE WEEK.

VIZ001-002-AMZ710>730-231000-
630 AM AST FRI MAY 22 2004

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

.TODAY...THE INFLUENCE OF AN ELONGATED AREA OF LOW PRESSURE ACROSS
THE CARIBBEAN...AND THE MOIST SOUTHERLY FLOW AROUND IT OVER THE
LOCAL AREA...COUPLED WITH FAVORABLE UPPER LEVEL WINDS...AND AMPLE
AMOUNTS OF LOW TO MID LEVEL MOISTURE WILL MAINTAIN CLOUDY SKIES WITH
OCCASIONAL SHOWERS AND RAIN IN THE U.S. VIRGIN ISLANDS. THE HEAVIEST
AND MOST FREQUENT RAIN IS EXPECTED IN SAINT CROIX. SOME OF THESE
STORMS MAY PRODUCE INTERMITTENT HEAVY RAINS THAT MAY CAUSE LOCALIZED
FLOODING OF STREETS AND POOR DRAINAGE AREAS. TONIGHT RAIN WILL
INCREASE FOR ALL OF THE VIRGIN ISLANDS AS WILL THE CHANCE OF
SIGNIFICANT FLOODING IN GUSTS AND LOW LYING TERRAIN.

A MODERATE TO OCCASIONALLY STRONG TRADE WIND FLOW OVER THE REGION
WILL MAINTAIN ROUGH AND CHOPPY SEAS...WITH THE STRONGEST WINDS
AND HIGHEST SEAS OVER THE ATLANTIC OFFSHORE WATERS.

.SPOTTER CALL TO ACTION STATEMENT...
SPOTTER ACTIVATION MAY BE REQUIRED.

.DAYS TWO THROUGH SEVEN...CONTINUED MOISTURE TRANSPORT IN THE
EASTERLY WIND FLOW...ALONG WITH THE LOW LEVEL TROUGH AND ELONGATED
AREA OF LOW PRESSURE OVER THE EASTERN CARIBBEAN WILL BE THE MAIN
WEATHER MAKER THROUGH THE NEXT FEW DAYS AS IT DRIFTS NORTH THEN
WESTWARD TO THE CENTRAL CARIBBEAN BY SUNDAY. THE TROUGH
IS THEN FORECAST TO MOVE NORTHWARD INTO THE SUBTROPICAL ATLANTIC BY
EARLY NEXT WEEK. THIS WILL RESULT IN A CONTINUATION OF THE CLOUDY
AND UNSETTLED WEATHER PATTERN OVER THE U.S. VIRGIN ISLANDS AT LEAST
THROUGH EARLY NEXT WEEK WITH SOME IMPROVEMENT EXPECTED THEREAFTER.
CONDITIONS SIMILAR TO PREVIOUS DAYS...WITH PERIODS OF OCCASIONAL
MODERATE TO HEAVY RAINS AT LEAST THROUGH TUESDAY WILL CAUSE
LOCALIZED FLOODING OF STREETS AND POOR DRAINAGE AREAS ESPECIALLY ON
SUNDAY.

A MODERATE TO FRESH TRADE WIND FLOW AND CHOPPY SEAS WILL PREVAIL
ACROSS THE LOCAL ISLANDS THROUGH AT LEAST EARLY NEXT WEEK BUT WINDS
AND SEAS WILL BEGIN TO SUBSIDE MIDDLE AND LATE WEEK.

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.