981
FXCA62 TJSJ 151354
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
954 AM AST FRI AUG 15 2025
UPDATE
ACCORDING TO THE LATEST TRAJECTORY AND INTENSITY FORECAST, ERIN WILL REMAIN
NORTHEAST AND NORTH OF THE LOCAL ISLANDS. HOWEVER, INDIRECT IMPACTS FROM ERIN’S
OUTER BANDS WILL AFFECT THE REGION FROM TONIGHT THROUGH EARLY NEXT WEEK. THE
MOVEMENT OF THESE BANDS WILL BE ERRATIC, BUT WILL INCREASE SHOWER AND
THUNDERSTORM COVERAGE ACROSS THE ISLANDS. THE HEAVIEST RAINFALL IS EXPECTED
SATURDAY AND SUNDAY, WITH LINGERING IMPACTS INTO MONDAY. RAINFALL ACCUMULATIONS
OF 2 TO 4 INCHES ARE EXPECTED, WITH ISOLATED TOTALS UP TO 6 INCHES,
PARTICULARLY OVER THE U.S. VIRGIN ISLANDS AND SOUTHERN AND EASTERN PUERTO RICO.
ELSEWHERE, 1 TO 2 INCHES ARE LIKELY, WITH ISOLATED AMOUNTS UP TO 4 INCHES. THIS
RAINFALL COULD LEAD TO FLOODING OF URBAN AREAS, SMALL STREAMS, AND RIVERS, AS
WELL AS LOCALIZED LANDSLIDES IN STEEP TERRAIN. A FLOOD WATCH IS IN EFFECT FOR
ALL ISLANDS FROM LATE TONIGHT THROUGH MONDAY EVENING.
MARINE
THE FORECAST REMAINS ON TRACK, ALTHOUGH SMALL CRAFT ADVISORIES HAVE BEEN
REISSUED NOW STARTING SATURDAY MORNING, WITH THE INCLUSION OF THE OFFSHORE
CARIBBEAN WATERS. THERE IS AN INCREASED POTENTIAL FOR STRONG SHOWERS AND
THUNDERSTORMS, ALONG WITH GUSTY WINDS, AS OUTER BANDS FROM ERIN MOVE OVER THE
EASTERN AND NORTHERN WATERS. WINDS OF 25–30 KNOTS, OR EVEN HIGHER, ARE
POSSIBLE, PARTICULARLY ACROSS THE OFFSHORE ATLANTIC WATERS.
BEACH FORECAST
SWELL ACTION FROM ERIN WILL RESULT IN LARGE BREAKING WAVES, CREATING DANGEROUS
SWIMMING CONDITIONS AND POTENTIAL MINOR BEACH EROSION, PARTICULARLY ALONG
NORTHERN AND EASTERN EXPOSED BEACHES. AS A RESULT, HIGH RIP CURRENT RISK AND
HIGH SURF ADVISORIES WILL BE IN EFFECT FROM SATURDAY THROUGH AT LEAST THURSDAY
NIGHT. IN ADDITION, OUTER BANDS FROM ERIN WILL BRING PERIODS OF HEAVY SHOWERS,
FREQUENT LIGHTNING, AND GUSTY WINDS, MAKING OUTDOOR ACTIVITIES POTENTIALLY
HAZARDOUS WITH CONDITIONS DETERIORATING QUICKLY.
PREV DISCUSSION
/ISSUED 443 AM AST FRI AUG 15 2025/
KEY MESSAGES...
* RESIDENTS AND VISITORS IN PUERTO RICO (PR) AND THE US VIRGIN
ISLANDS (USVI) ARE ENCOURAGED TO CLOSELY MONITOR THE DEVELOPMENT
OF ERIN, AS THE NATIONAL HURRICANE CENTER (NHC) FORECASTS ITS
TRAJECTORY TO MOVE NORTHEAST OF THE ISLANDS ACROSS THE ATLANTIC
OCEAN.
* ADDITIONALLY, WAVE ACTIONS ASSOCIATED WITH ERIN WILL LEAD TO
DETERIORATING MARINE AND COASTAL CONDITIONS ACROSS THE USVI AND PR
FROM SATURDAY EVENING THROUGH AT LEAST EARLY NEXT WEEK.
* THE OUTER BANDS OF ERIN ARE EXPECTED TO BRING SHOWERS AND
THUNDERSTORMS WITH GUSTY WINDS TO THE ISLANDS, STARTING AS EARLY
AS LATE TONIGHT OR EARLY SATURDAY MORNING, WITH THE MOST
SIGNIFICANT IMPACTS LIKELY OCCURRING AROUND SATURDAY EVENING.
* WE ANTICIPATE RAINFALL TOTALS OF BETWEEN 2 AND 4 INCHES, WITH
ISOLATED HIGHER AMOUNTS POSSIBLE, PARTICULARLY ACROSS THE
SOUTHERN, SOUTHEASTERN, EASTERN INTERIOR, AND NORTHEASTERN AREAS
OF PUERTO RICO, AS WELL AS THROUGHOUT THE US VIRGIN ISLANDS DUE TO
ERIN.
SHORT TERM...TODAY THROUGH SUNDAY...
AN INDUCED SURFACE TROUGH MOVED ACROSS THE USVI AND PR OVERNIGHT,
PRODUCING SHOWERS AND ISOLATED THUNDERSTORMS. WE OBSERVED BETWEEN 1
AND 2.5 INCHES OF RAIN, MAINLY ACROSS THE NORTHERN HALF OF PR, WHILE
THE NORTHERN US VIRGIN ISLANDS OBTAINED LESS THAN A QUARTER OF AN
INCH. WINDS WERE PRIMARILY FROM THE EAST TO EAST-NORTHEAST AT 10 MPH
OR LESS, BUT WITH STRONG GUSTY WINDS NEAR THE SHOWER AND
THUNDERSTORM ACTIVITY, WHILE THE LEEWARD SIDE OF PR WAS UNDER THE
EFFECTS OF THE LAND BREEZE. ADDITIONALLY, LOW TEMPERATURES WERE IN
THE LOW 80S AND UPPER 70S ALONG THE COASTAL AREAS TO THE MID-60S IN
THE MOUNTAINS.
THE LINGERING MOISTURE OF THE INDUCED SURFACE TROUGH WILL SLOWLY
EXIT THE ISLANDS, PROMOTING THE FORMATION OF SOME SHOWERS ACROSS THE
REGIONAL WATERS AND THE WINDWARD LOCATIONS IN THE US VIRGIN ISLANDS
AND PR. RAIN ACTIVITY WILL DIMINISH SOMEWHAT DURING THE DAY, AS AN
AREA OF SUBSIDENCE IN FRONT OF ERIN MOVES FROM THE EAST. HOWEVER,
LOCAL EFFECTS AND SEA BREEZES WILL AID IN THE FORMATION OF SHOWERS
AND THUNDERSTORMS ACROSS THE INTERIOR AND WESTERN PR THIS AFTERNOON,
AS WELL AS DOWNWIND FROM THE USVI. THE STRONGEST THUNDERSTORMS COULD
PRODUCE HEAVY RAINFALL, PROMOTING AN ELEVATED FLOODING RISK.
THE EXTERNAL RAIN BANDS OF ERIN WILL MOVE ACROSS THE ISLANDS AS
EARLY AS LATE TONIGHT OR EARLY SATURDAY MORNING, AFFECTING THE
ATLANTIC OFFSHORE WATERS, ANEGADA PASSAGE, THE US VIRGIN ISLANDS,
AND THE NORTH AND EAST OF PR. THESE RAIN BANDS WILL ARRIVE
OCCASIONALLY, RESULTING IN SQUALLY WEATHER WITH THUNDERSTORMS, HEAVY
RAIN, AND GUSTY WINDS (WITH SPEEDS BETWEEN 30 AND 40 MPH, OR EVEN
GREATER). THE FREQUENCY OF THIS ACTIVITY WILL INCREASE AS ERIN
APPROACHES THE ISLANDS BY EARLY SUNDAY MORNING.
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. THE BRIGHT SIDE IS THAT MODEL
CONSENSUS STILL AGREES WITH THIS FORECAST. THUS, DUE TO THE
PROXIMITY OF ERIN, WINDS WILL SHIFT FROM THE SOUTH TO SOUTHWEST
AROUND SUNDAY AFTERNOON, POOLING PLENTY OF TROPICAL MOISTURE OVER
THE ISLANDS, INCREASING THE POTENTIAL TO OBSERVE URBAN FLOODING,
LANDSLIDES ALONG STEEP TERRAINS, AND RIVER FLOODING.
PLEASE BE ADVISED THAT WE ENCOURAGE EVERYONE IN PUERTO RICO AND THE
US VIRGIN ISLANDS TO KEEP AN EYE ON ERIN OVER THE NEXT FEW DAYS, AS
OUR WEATHER CONDITIONS DEPEND ON ITS PROGRESS.
LONG TERM...MONDAY THROUGH FRIDAY...
SOME CHANGES WERE INTRODUCED TO THE LONG-TERM FORECAST, INCREASING
UNCERTAINTY FOR THE SECOND PART OF THE NEXT WORKWEEK. THE LATEST
PROBABILISTIC GUIDANCE OF THE GFS AND ECMWF SHOWS AGREEMENT OF
PRECIPITABLE WATER VALUES REMAINING ABOVE THE 75TH PERCENTILE (2.0 -
2.2 INCHES), DUE TO POSSIBLE TROPICAL MOISTURE POOLED BY TROPICAL
STORM ERIN. AS MENTIONED IN THE PREVIOUS DISCUSSION, THE MAIN AREAS
OF CONCERN ARE THE INTERIOR AND NORTHERN PORTION OF PUERTO RICO AND
THE U.S. VIRGIN ISLANDS DUE TO S-SE WIND FLOW COMBINED WITH DIURNAL
HEATING AND LOCAL EFFECTS. ADDITIONALLY, PREVIOUS RAINFALL ACTIVITY
AND SATURATED SOILS COULD ENHANCE THE POTENTIAL OF URBAN FLOODING,
LANDSLIDES, AND RIVER RISES OVER THE AFOREMENTIONED AREAS. ONCE
AGAIN, THE FLOODING RISK WILL REMAIN LIMITED TO ELEVATED FOR MOST
PORTIONS OF PUERTO RICO AND THE U.S. VIRGIN ISLANDS. RESIDENTS AND
VISITORS SHOULD CONTINUE TO MONITOR THE SYSTEM AND STAY TUNED FOR
FURTHER UPDATES.
MOISTURE CONTENT IS EXPECTED TO GRADUALLY DECREASE BY WEDNESDAY AS
ERIN MIGRATES NORTHEASTWARD INTO THE WESTERN CARIBBEAN BASED ON THE
LATEST NHC ADVISORY. A SURFACE HIGH PRESSURE SHOULD SETTLE JUST
NORTHEAST OF THE CWA AND LINGER FOR THE NEXT FEW DAYS, PROMOTING
WINDS FROM THE SOUTHEAST. AN UPPER-LEVEL TROUGH SHOULD APPROACH THE
LOCAL AREA, INCREASING MOISTURE CONTENT, COOLING 500 MB TEMPERATURES
AND INCREASING INSTABILITY ALOFT. NEVERTHELESS, THERE’S SOME
UNCERTAINTY INTRODUCED TO THE FORECAST, MAINLY FOR FRIDAY, DUE TO
ANOTHER TROPICAL WAVE APPROACHING THE CARIBBEAN BASIN, ALTHOUGH
THERE ARE SOME DISCREPANCIES. THE GFS 06Z SOLUTION SHOWS A POTENTIAL
TROPICAL CYCLONE MOVING ACROSS THE CENTRAL ATLANTIC, TURNING NORTH
BEFORE APPROACHING THE CWA , WHILE THE ECMWF 00Z SOLUTION SHOWS
THIS DISTURBANCE APPROACHING THE LOCAL AREA. BASED ON THE
DETERMINISTIC GUIDANCE, THE GRAND ENSEMBLE SHOWS A GRADUAL
INCREASE IN MOISTURE CONTENT, BUT THERE IS HIGH VARIABILITY IN
PWAT VALUES DURING THAT TIME PERIOD. SINCE THESE CONDITIONS ARE
EXPECTED AT THE END OF THE FORECAST PERIOD, UNCERTAINTY REMAINS
HIGH, AND CHANGES TO THE FORECAST WILL CONTINUE FOR THE NEXT FEW
DAYS.
IF THE WIND FLOW REMAINS WITH A SOUTHERLY COMPONENT, ABUNDANT
MOISTURE CONTENT, AND ABOVE CLIMATOLOGICAL NORMAL 925 MB
TEMPERATURES, THE HEAT RISK WILL LIKELY CONTINUE LIMITED TO ELEVATED
ACROSS URBAN AND COASTAL AREAS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS DURING THE LONG-TERM FORECAST. TUESDAY AND WEDNESDAY ARE
LIKELY TO BE THE HOTTEST DAYS OF THE PERIOD, WITH HEAT INDEXES
MEETING HEAT ADVISORY CRITERIA.
AVIATION...
(06Z TAFS)
EXPECT VFR CONDS THRU THE FCST PRD, WITH OCCASIONAL SHOWERS
ARRIVING ACROSS IST/ISX/JSJ THROUGHOUT THE DAY. SHRA/TSRA WILL
DEVELOP ACROSS THE INTERIOR AND W-PR, PROMOTING MOUNTAIN OBSC IN PR
BTWN 15/16-23Z, IMPACTING JBQ AND THE VCTY OF JPS. THE EXTERNAL
BANDS OF ERIN WILL BEGIN TO IMPACT THE LOCAL FLYING AREA AFT 15/23Z,
SLOWLY INCREASING IN FREQUENCY THROUGHOUT SATURDAY. EXPECT E-ENE
WINDS AT AROUND 10 KT THROUGH AT LEAST 15/13Z, AFTER THAT, THEY WILL
RANGE BETWEEN 15-20 KT WITH HIGHER GUSTS AND SEA BREEZE.
MARINE...
AN INDUCED EASTERLY PERTURBATION EXITING THE LOCAL AREA WILL
CONTINUE PRODUCING SHOWERS AND THUNDERSTORMS THROUGH MIDDAY,
INCREASING LOCAL WINDS, AND SEAS MAINLY ACROSS THE CARIBBEAN WATERS.
THE EXTERNAL BANDS OF ERIN, PRODUCING SQUALLY WEATHER, SHOULD ARRIVE
AS EARLY AS TONIGHT OR EARLY SATURDAY MORNING. BASED ON THE NATIONAL
HURRICANE CENTER TRAJECTORY FORECAST, ERIN SHOULD MOVE OFF TO THE
NORTHEAST AWAY FROM PUERTO RICO AND THE U.S. VIRGIN ISLANDS INTO THE
WESTERN ATLANTIC ON SUNDAY. ERIN IS EXPECTED TO PRODUCE HAZARDOUS
SWELL ACTION THAT 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...
NO MAJOR CHANGES WERE INTRODUCED TO THE BEACH FORECAST. TODAY, THE
MODERATE RISK IS EXPECTED TO CONTINUE OVER NORTH AND EAST-FACING
BEACHES OF PUERTO RICO, CULEBRA, AND ST. CROIX. NEVERTHELESS, BEACH
CONDITIONS ARE EXPECTED TO GRADUALLY DETERIORATE AS TROPICAL STORM
ERIN, EXPECTED TO UPGRADE TO HURRICANE LATER TODAY, MOVES CLOSER
TO THE REGION THIS WEEKEND. ERIN'S SWELL ACTION COULD DETERIORATE
MARINE AND COASTAL CONDITIONS, CREATING LIFE-THREATENING RIP
CURRENTS FOR THIS UPCOMING WEEKEND. RESIDENTS AND VISITORS ARE
URGED TO AVOID THE COASTAL AREAS FROM SATURDAY AFTERNOON THROUGH
MONDAY.
SJU WATCHES/WARNINGS/ADVISORIES
PR...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING FOR
PRZ001>013.
HIGH RIP CURRENT RISK FROM SATURDAY MORNING THROUGH LATE SUNDAY
NIGHT FOR PRZ001-002-005-008-010-012-013.
HIGH SURF ADVISORY FROM 8 AM SATURDAY TO 6 AM AST MONDAY FOR
PRZ001-002-005-008-012-013.
VI...FLOOD WATCH FROM LATE TONIGHT THROUGH MONDAY EVENING FOR VIZ001-
002.
HIGH RIP CURRENT RISK FROM SATURDAY MORNING THROUGH LATE SUNDAY
NIGHT FOR VIZ001-002.
HIGH SURF ADVISORY FROM 8 AM SATURDAY TO 6 AM AST MONDAY FOR
VIZ001-002.
AM...SMALL CRAFT ADVISORY FROM 8 AM SATURDAY TO 6 AM AST MONDAY FOR
AMZ711-723.
SMALL CRAFT ADVISORY FROM 6 PM SATURDAY TO 6 AM AST MONDAY FOR
AMZ712-716-726-733.
CVB/MMC/RVT
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