Flood in Puerto Rico, April 20, 2004

FXCA62 TJSJ DDHHMM
AFDSJU

PUERTO RICO AND U.S. VIRGIN ISLANDS FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
530 AM AST TUE APR 20 2004

.DISCUSSION...
MID TO UPPER TROUGH FROM SW ATLC DIGGING SOUTHWARD INTO THE WESTERN
CARIB THIS MORNING WILL CONTINUE TO PRODUCE BROAD LIFT ACROSS THE
REGION TODAY AND ALSO CONTINUE TO DRAW TROPICAL MOISTURE FROM THE
AMAZON ACROSS THE LOCAL REGION. THIS WILL LIKELY LIMIT SUNSHINE
AGAIN TODAY AND MAINTAIN MOSTLY CLOUDY TO CLOUDY SKIES. LOW LEVEL
MOISTURE IS SUGGESTED BY RECENT GUIDANCE TO BE LIMITED TO THE AREA
OF CONVECTION MOVING ACROSS EASTERN P.R. AND THE LOCAL CARIB WATERS
WITH UPSTREAM LLVL MOISTURE EXPECTED TO BE DECREASING NEXT 48 HOURS.
CIRRUS AND AS CANOPIES WILL SPREAD PATCHY STRATOFORM PRECIP ACROSS
THE REGION AND HAVE ATTEMPTED TO INCLUDE THIS IN GRAPHICAL FORECASTS
FOR AREAS NOT DOMINATED BY NUMEROUS CONVECTION. IMPROVING SKIES AND
WEATHER WILL BE SEEN THURSDAY THROUGH THE UPCOMING WEEKEND.
&&

.MARINE...
RECENT QUIKSCAT PASSES AND NESDIS STLT DERIVED WINDS CONTINUE TO
DEPICT A BROAD TROUGH FROM THE CARIB COAST OF SOUTH AMERICA NNE
ACROSS THE LOCAL REGION AND INTO THE W CENTRAL ATLC...WITH LLVL
PERTURBATIONS MOVING WWD ACROSS THE LOCAL AREA. ESE FLOW WILL
PREVAIL ACROSS THE AREA TODAY TO THE EAST OF LLVL TROUGH AND IS
FORECAST TO DIMINISH THIS EVENING...WHICH IS A DEPARTURE FROM RECENT
GUIDANCE. SOME SIGNIFICANT CHANGES IN PAST FEW MODEL RUNS LEAD ME
WITH LOW TO MODERATE CONFIDENCE IN WIND FORECAST NEXT 36 HOURS. SEAS
TO SLOWLY SUBSIDE THROUGH WED MORNING THEN MORE QUICKLY THROUGH THE
END OF THE WEEK.
&&

.AVIATION...
THICK LAYERED MID AND UPPER CLOUDS WILL CONTINUE TO PROVIDE
CONDITIONS FOR RHYME ICING ACROSS THE REGION THROUGH TONIGHT.
ALSO...YESTERDAYS VISIBLE IMAGERY SHOWED SEVERAL ZONES OF
TRANSVERSE BANDING ACROSS THE TOP OF THIS STRATIFIED UPPER CLOUD
DECK SUGGESTING VERTICALLY INDUCED SPEED SHEAR AND TURBULENCE WHICH
SHOULD PREVAIL AGAIN TODAY...LIKELY 28-35K FT.
&&

.HYDROLOGY...
FLASH FLOOD WATCH HAS BEEN ISSUED FOR MUCH OF P.R. THIS MORNING...
ND AGAIN ISOLATED AREAS OF 5-7 INCHES ARE POSSIBLE TODAY...BUT
WIDESPREAD AREA OF CONVECTION MOVING ACROSS EASTERN P.R. ATTM COULD
LEAD TO WIDESPREAD AREA OF 2-4 INCHES AND CAUSE SOME FLOODING
PROBLEMS PRIOR TO MAX HEATING. DUE TO THIS FOCUSING OF RAINFALL
ALREADY...FLASH FLOOD POTENTIAL LOOKS HIGHER TODAY THAN YESTERDAY...
FOR AT LEAST THE EAST HALF OF P.R.
&&

.PRELIMINARY POINT TEMPS/POPS...
SJU  84  72  85  73 /  60  50  50  50
STT  83  71  84  72 /  50  40  40  40

&&

.SJU WATCHES/WARNINGS/ADVISORIES...
PR...FFA PRZ001-004-006-007-009>011.
VI...NONE.

&&

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE SAN JUAN PR
600 AM AST TUE APR 20 2004

PRZ001>013-AMZ710>750-211000-
600 AM AST TUE APR 20 2004

THIS HAZARDOUS WEATHER OUTLOOK IS FOR PUERTO RICO.

.TODAY AND TONIGHT...WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS
ASSOCIATED WITHE LOW TO UPPER LEVEL TROUGH WILL AFFECT THE ISLAND OF
PUERTO RICO TODAY. RAINFALL ACCUMULATIONS OF AROUND 3 INCHES PER
HOUR ARE POSSIBLE OVER LOCALIZED AREAS. THIS CONDITION HAS THE
POTENTIAL TO PRODUCE FLASH FLOODING...AND COULD ALSO PRODUCE SOME
RIVER FLOODING.

LONG PERIOD EAST NORTHEAST SWELLS WILL CONTINUE ACROSS THE LOCAL
ATLANTIC WATERS AND CARIBBEAN PASSAGES. SWELLS WILL BECOME NORTHEAST
AS THEY SUBSIDE SLOWLY TONIGHT.

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

.WEDNESDAY THROUGH MONDAY...UNSTABLE ATMOSPHERIC CONDITIONS AND
PLENTY OF LOW LEVEL HUMIDITY WILL CONTINUE AT LEAST WEDNESDAY AND
THURSDAY TO PRODUCE SCATTERED TO NUMEROUS SHOWERS MAINLY ACROSS THE
INTERIOR AND WEST SECTIONS OF THE ISLAND.

VIZ001-002-AMZ710>730-211000-
600 AM AST TUE APR 20 2004

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

.TODAY AND TONIGHT...RAINFALL ACTIVITY OVER THE U.S. VIRGIN ISLANDS
WILL BE LESS COMPARED WITH YESTERDAYS AS IT MOVES WEST TOWARD
PUERTO RICO. HOWEVER...HIGH CONCENTRATION OF LOW LEVEL MOISTURE WILL
CONTINUE OVER THE LOCAL AREA TODAY. SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS MAY PRODUCE URBAN AND SMALL STREAM FLOODING.

LONG PERIOD EAST NORTHEAST SWELLS WILL CONTINUE TO AFFECT THE LOCAL
ATLANTIC WATERS AND THE EASTERN CARIBBEAN PASSAGES THROUGH TODAY.

.SPOTTER CALL TO ACTION STATEMENT...
SPOTTER ACTIVATION IS NOT ANTICIPATED TODAY.

.WEDNESDAY THROUGH MONDAY...WEATHER CONDITIONS WILL CONTINUE TO
IMPROVE ON WEDNESDAY THROUGH THE WEEKEND.

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.