575
FXCA62 TJSJ 141845
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
245 PM AST THU AUG 14 2025
KEY MESSAGES
* MAINLY FAIR WEATHER CONDITIONS WILL PREVAIL TODAY ACROSS THE
ISLANDS, WITH LIMITED SHOWERS AND FEW ISOLATED THUNDERSTORMS
OVER SOUTHWESTERN PUERTO RICO.
* AN INDUCED SURFACE PERTURBATION WILL BRING FREQUENT PASSING
SHOWERS ACROSS THE U.S. VIRGIN ISLANDS, VIEQUES, CULEBRA AND
EASTERN PUERTO RICO LATER TONIGHT INTO FRIDAY MORNING.
* TROPICAL STORM ERIN IS EXPECTED TO MOVE NORTHEAST OF THE REGION
BY EARLY SUNDAY. HOWEVER, THE EXTERNAL BANDS OF ERIN WILL START
TO REACH THE ISLANDS AS EARLY AS TOMORROW NIGHT.
* RESIDENTS AND VISITORS CAN EXPECT HAZARDOUS MARINE AND COASTAL
CONDITIONS FROM SATURDAY THROUGH MONDAY. PLEASE STAY TUNED FOR
FURTHER WEATHER UPDATES ON THIS TROPICAL SYSTEM AS IT MOVES
WESTWARD OVER THE CENTRAL ATLANTIC.
SHORT TERM...TONIGHT THROUGH SATURDAY
CALM WEATHER CONDITIONS WERE SEEN ACROSS THE REGION UNDER MOSTLY
SUNNY TO PARTLY CLOUDY SKIES. LATER IN THE AFTERNOON, THE CLOUD
COVERAGE BEGAN TO INCREASE ACROSS THE REGION WHERE SHOWERS AND
ISOLATED THUNDERSTORMS DEVELOPED OVER SOUTHWESTERN PUERTO RICO.
DOPPLER RADAR ESTIMATED UP TO 1 INCH OF RAIN, PARTICULARLY OVER CABO
ROJO. THE U.S. VIRGIN ISLANDS OBSERVED PASSING SHOWERS MAINLY OVER
ST. CROIX DURING THE EARLY AFTERNOON HOURS. WARM TO HOT CONDITIONS
WERE OBSERVED AS WELL, WITH HIGHS IN THE UPPER 80S TO LOW 90S ALONG
THE COASTAL AND URBAN AREAS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS. HEAT INDICES WERE SEEN REACHING THE 105 TO 110 DEGREES
FAHRENHEIT ALONG THE COASTAL AREAS OF THE ISLANDS AS WELL.
A DRIER AIR MASS CONTINUES TO DOMINATE THE LOCAL AREA, PROMOTING
STABLE CONDITIONS ALOFT AND LIMITED SHOWERS THROUGH EARLY THIS
EVENING. THEN, A INDUCED SURFACE PERTURBATION WILL REACH THE LOCAL
ISLANDS ENHANCING THE POTENTIAL TO OBSERVE FREQUENT PASSING
SHOWERS OVERNIGHT INTO FRIDAY MORNING. THIS PERTURBATION WILL
QUICKLY MOVE AWAY FROM THE REGION BY FRIDAY AFTERNOON, FOLLOWED BY
AN AREA OF SUBSIDENCE AHEAD OF TROPICAL STORM ERIN AND LIMITING
THE POTENTIAL FOR SHOWERS.
HOWEVER, THE SCENARIO WILL SLOWLY CHANGE AS THE EXTERNAL BANDS OF
ERIN STARTS TO REACH THE REGION. THESE BANDS ARE FORECAST TO
ARRIVE AS EARLY AS FRIDAY NIGHT AND SATURDAY MORNING. AS MENTIONED
IN THE PREVIOUS DISCUSSIONS, THIS PATTERN WILL RESULT IN SQUALLY
WEATHER, PRODUCING GUSTY WINDS AND HEAVY RAINFALL FROM TIME TO
TIME. RESIDENTS AND VISITORS ARE URGED TO MONITOR THE WEATHER
CONDITIONS AS THE WEEKEND PROGRESSES FOR ANY SIGNIFICANT CHANGES
IN THE CURRENT FORECAST.
LONG TERM...SUNDAY THROUGH THURSDAY
(FROM PREVIOUS FORECAST)
THE LONG-TERM FORECAST REMAINS ON TRACK, AS THE WET AND UNSETTLED
PATTERN IS EXPECTED TO CONTINUE. BASED ON THE LATEST NHC'S
TRAJECTORY AND INTENSITY FORECAST FOR ERIN, ITS CENTER SHOULD MOVE
OFF TO THE NORTHEAST OF THE NORTHEAST CARIBBEAN AROUND EARLY
SUNDAY MORNING. HOWEVER, IF THIS FORECAST VALIDATES, ERIN'S
EXTERNAL RAIN BANDS COULD TURN MORE FREQUENT AS ERIN APPROACHES
THE ISLANDS FROM A DISTANCE. NEVERTHELESS, THE PROXIMITY OF ERIN
WILL SHIFT FROM THE SOUTH TO THE SOUTHWEST AROUND SUNDAY, POOLING
PLENTY OF TROPICAL MOISTURE OVER THE ISLANDS THROUGH MONDAY. BASED
ON THE LATEST MODEL GUIDANCE, PRECIPITABLE WATER VALUES ARE
LIKELY TO EXCEED THE 75TH PERCENTILE (2.0 - 2.2 INCHES, WITH LOW
CHANCE OF REACHING 2.4 INCHES), WELL ABOVE CLIMATOLOGICAL NORMAL.
UNDER A S-SW WIND FLOW, IT IS LIKELY TO OBSERVE AN ADVECTIVE
PATTERN DURING THE MORNING HOURS, WITH SHOWERS AND THUNDERSTORMS
AFFECTING WINDWARD SECTIONS OF THE LOCAL ISLANDS, BUT THE CONCERN
REMAINS HIGH FOR THE INTERIOR AND NORTHERN PORTIONS OF PUERTO RICO
AND THE U.S. VIRGIN ISLANDS. DUE TO CONTINUOUS SHOWER ACTIVITY
AND SATURATED SOILS, THE POTENTIAL TO OBSERVE URBAN FLOODING,
LANDSLIDES ALONG STEEP TERRAINS, AND RIVER FLOODING WILL INCREASE.
WE EXPECT FUTURE ADJUSTMENTS TO THE FORECAST DUE TO THE EXISTING
ERROR ASSOCIATED WITH DAY 4 IN THE FORECAST. THUS, WE ENCOURAGE
EVERYONE IN PUERTO RICO AND THE US VIRGIN ISLANDS TO KEEP AN EYE
ON ERIN OVER THE NEXT FEW DAYS, AS THE INTENSITY AND TRACK
FORECAST WILL UNDERGO CHANGES, AND OUR WEATHER FORECAST DEPEND ON
ITS PROGRESS. STAY TUNED FOR FURTHER UPDATES.
BY TUESDAY NIGHT, A SURFACE HIGH PRESSURE OVER THE CENTRAL
ATLANTIC SHOULD STRENGTHEN, PROMOTING WINDS FROM THE SOUTHEAST.
BASED ON THE DETERMINISTIC GUIDANCE OF THE GFS AND ECMWF, PWAT
WILL LIKELY DECREASE TO SEASONAL VALUES (1.6 - 1.8 INCHES).
NEVERTHELESS, MODEL SOLUTIONS CURRENTLY AGREE THAT AN UPPER-LEVEL
TROUGH WILL LIKELY APPROACH THE CWA BY WEDNESDAY MORNING,
INCREASING MOISTURE CONTENT ONCE AGAIN.
WITH A S-SE WIND FLOW, ABUNDANT MOISTURE, AND ABOVE- NORMAL 925
MB TEMPERATURES, THE HEAT RISK IS LIKELY TO INCREASE EARLY NEXT
WEEK. THE MOST LIKELY SCENARIO WOULD BE HEAT INDEXES ACROSS URBAN
AND COASTAL AREAS REACHING HEAT ADVISORY OR HEAT WARNING CRITERIA,
BUT THIS WILL DEPEND ON THE BEHAVIOR OF ERIN DURING THAT PERIOD.
AVIATION
EXPECT VFR CONDS ACROSS ALL TERMINALS DURING THE FORECAST PERIOD.
MAINLY FAIR WEATHER CONDITIONS WILL PREVAIL, HOWEVER, SHRA/TSRA
DEVELOPING ACROSS THE INTERIOR AND WESTERN PR BY THIS AFTERNOON
AND COULD IMPACT THE VCTY OF TJPS THRU 14/23Z. ENE WINDS WILL
DECREASE AT 10 KTS OR LESS AFT 14/23Z. THEN, INCREASING BTW 12-16
KTS AFT 15/13Z WITH HIGHER GUSTS AND SEA BREEZE VARIATIONS.
MARINE
AN INDUCED EASTERLY PERTURBATION CROSSING THE LESSER ANTILLES WILL
MOVE ACROSS PR AND THE USVI TOMORROW, INCREASING SHOWER ACTIVITY,
LOCAL WINDS, AND SEAS MAINLY ACROSS THE CARIBBEAN SEA. THE EXTERNAL
BANDS OF ERIN, PRODUCING SQUALLY WEATHER, WILL ARRIVE AS EARLY AS
SATURDAY MORNING AND MOST LIKELY AROUND SATURDAY EVENING, AS ERIN'S
NHC TRAJECTORY FORECAST MOVES IT OFF TO THE NORTHEAST AWAY FROM
PR/USVI OVER THE ATLANTIC OCEAN THROUGHOUT THE WEEKEND. ERIN'S
HAZARDOUS SWELL ACTION WILL IMPACT THE ATLANTIC AND CARIBBEAN
PASSAGES FROM SATURDAY EVENING THROUGH AT LEAST EARLY NEXT WEEK.
MARINERS AND VISITORS ARE URGED TO CLOSELY MONITOR THE EVOLUTION OF
ERIN.
BEACH FORECAST
THE MODERATE RISK OF RIP CURRENTS CONTINUES ACROSS THE NORTH AND
EAST-FACING BEACHES IN PUERTO RICO AND ST. CROIX IN THE U.S. VIRGIN
ISLANDS. THUNDERSTORMS WILL DEVELOP ACROSS THE LOCAL WATERS DUE TO
AN EASTERLY PERTURBATION AND MAY APPROACH SOME COASTAL AREAS.
IMPORTANT: ERIN'S SWELL ACTION COULD DETERIORATE MARINE AND COASTAL
CONDITIONS, CREATING LIFE-THREATENING RIP CURRENTS FOR THIS UPCOMING
WEEKEND. RESIDENTS AND VISITORS ARE URGE TO AVOID THE COASTAL AREAS
FROM SATURDAY AFTERNOON TROUGH MONDAY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...HEAT ADVISORY UNTIL 5 PM AST THIS AFTERNOON FOR PRZ001>005-007-
008-010>013.
VI...HEAT ADVISORY UNTIL 5 PM AST THIS AFTERNOON FOR VIZ001-002.
AM...NONE.
CVB/GRS
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