217
FXCA62 TJSJ 161817
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
217 PM AST SAT AUG 16 2025
KEY MESSAGES
* A FLOOD WATCH IS IN EFFECT FOR THE US VIRGIN ISLANDS AND PUERTO
RICO THROUGH AT LEAST MONDAY.
* THE RAINBANDS OF MAJOR HURRICANE ERIN WILL BRING SHOWERS AND
THUNDERSTORMS, PRODUCING PERIODS OF MODERATE TO LOCALLY HEAVY
RAIN AND GUSTY WINDS ACROSS THE US VIRGIN ISLANDS AND PUERTO
RICO THROUGH THE REST OF THE WEEKEND. PROMOTING AN UNSETTLED
WEATHER PATTERN, AND CONTINUING THE RISK OF URBAN, RIVER, AND
FLASH FLOODING, AS WELL AS ISOLATED LANDSLIDES ACROSS PUERTO
RICO AND THE U.S. VIRGIN ISLANDS.
* SWELLS FROM ERIN WILL DETERIORATE SEAS ACROSS THE ATLANTIC
WATERS AND CARIBBEAN PASSAGES THROUGH LATE SUNDAY. IN ADDITION,
DANGEROUS SWIMMING CONDITIONS, LIFE-THREATING RIP CURRENTS ALONG
WITH ROUGH SURF CONDTIONS WILL PERSIST ACROSS THE WEST, NORTH,
AND EAST FACING BEACHES OF THE ISLANDS THROUGH THE REST OF THE
WEEKEND.
* WEST TO NORTHWEST WINDS TODAY WILL SHIFT FROM THE SOUTH TO
SOUTHWEST ON SUNDAY AND MONDAY, PROMOTING HOT TEMPERATURES
ACROSS THE NORTHERN AND WESTERN PORTIONS OF PR.
SHORT TERM...THIS AFTERNOON THROUGH MONDAY
AS OF 2 PM, RAINBANDS ASSOCIATED TO MAJOR HURRICANE ERIN LEFT IN
GENERAL BETWEEN 1 AND 2 INCHES OF RAINFALL ACROSS PORTIONS OF
NORTHWESTERN AND EASTERN PUERTO RICO, AND UP TO THREE QUARTERS OF
AN INCH IN THE NORTHERN U.S. VIRGIN ISLANDS. MAX WIND GUSTS
REPORTED SO FAR WERE UP TO 29 MPH IN ST. THOMAS. MAXIMUM
TEMPERATURES WERE FROM THE UPPER 80S TO LOW 90S ACROSS COASTAL
AREAS OF PR, AND IN THE MID-80S ACROSS THE USVI.
ERIN IS NOW TRACKING WEST-NORTHWEST, AND IT IS EXPECTED TO
CONTINUE ON THIS TRACK THROUGH THE REST OF THE SHORT-TERM PERIOD.
THEREFORE, RAINBANDS FROM ERIN WILL CONTINUE TO MOVE AT TIMES
ACROSS PORTIONS OF THE ISLANDS AND LOCAL WATERS DURING THE NEXT
FEW DAYS. WESTERLY WINDS WILL GRADUALLY TURN MORE SOUTHERLY ON
SUNDAY, AND FEEDING BANDS SHOULD FAVOR THE SOUTHERN AND EASTERN
SECTIONS OF PR AND THE USVI FROM TONIGHT THROUGH SUNDAY MORNING.
THE RAINFALL FORECAST REMAINS ON TRACK, WITH EXPECTED RAINFALL
TOTALS OF 2 TO 4 INCHES, WITH ISOLATED AMOUNTS UP TO 6 INCHES
THROUGH AT LEAST MONDAY. LOCALLY CONSIDERABLE FLASH AND URBAN
FLOODING, ALONG WITH LANDSLIDES OR MUDSLIDES, ARE POSSIBLE.
THE STRONGEST WINDS ASSOCIATED TO ERIN WILL REMAIN ACROSS THE
OFFSHORE ATLANTIC AND OVER PORTIONS OF THE ANEGADA PASSAGE, MAINLY
TONIGHT. HOWEVER, STRONG GUSTY WINDS ARE EXPECTED WITH THE
RAINBANDS. IN TERMS OF TEMPERATURES, THE COMBINATION OF SOUTHERLY
WINDS AND HIGHER MOISTURE CONTENT WILL PROMOTE HOT TEMPERATURES ON
SUNDAY AND MONDAY, WITH HEAT INDICES LIKELY REACHING HEAT ADVISORY
CRITERIA ACROSS PORTIONS OF THE URBAN AND LOWER-ELEVATIONS OF
NORTHERN AND WESTERN PR.
LONG TERM...TUESDAY THROUGH SATURDAY
..FROM PREV DISCUSSION ISSUED AT 502 AM AST SAT AUG 16 2025
THE LONG-TERM FORECAST REMAINS ON TRACK, WITH VARIABLE CONDITIONS
FOR MID NEXT WEEK AND HIGH UNCERTAINTY BY THE END OF THE FORECAST
PERIOD. AS HURRICANE ERIN CONTINUES ITS WAY INTO THE WESTERN
ATLANTIC, THE WIND FLOW IS EXPECTED TO REMAIN WITH A SOUTHERLY
COMPONENT, POOLING TROPICAL MOISTURE INTO THE REGION. FROM THE
LATEST MODEL GUIDANCE, PRECIPITABLE WATER (PWAT) VALUES ARE LIKELY
TO REMAIN SEASONAL TO NEAR-ABOVE-NORMAL (1.70 - 1.90 INCHES). THE
LIKELIEST SCENARIO WOULD BE AN ADVECTIVE PATTERN WITH SHOWERS
AFFECTING SOUTHERN PUERTO RICO AND THE U.S. VIRGIN ISLANDS IN THE
MORNING, AND AFTERNOON CONVECTION ACROSS THE INTERIOR AND NORTHERN
PORTIONS OF PUERTO RICO. NEVERTHELESS, PREVIOUS RAINFALL ACTIVITY
DUE TO HURRICANE ERIN AND SATURATED SOILS MAY ENHANCE THE FLOODING
RISK ACROSS THE AREA, PARTICULARLY THE INTERIOR AND NORTHERN
PORTIONS OF PUERTO RICO. THE FLOODING RISK WILL REMAIN LIMITED TO
ELEVATED FOR THE AFOREMENTIONED AREAS, WITH A LOW CHANCE OF ISOLATED
FLASH FLOODING.
THE SURFACE HIGH PRESSURE OVER THE CENTRAL ATLANTIC SHOULD MIGRATE
WESTWARD, PROMOTING SE WINDS THROUGH THURSDAY. GLOBAL MODELS
CONTINUE SUGGESTING THE ARRIVAL OF AN UPPER-LEVEL LOW BY WEDNESDAY,
REMAINING SOUTH OF THE CWA. THE PRESENCE OF THIS FEATURE MIGHT
INCREASE INSTABILITY ACROSS THE AREA, BUT A DRIER AIR MASS FILTERING
INTO THE REGION IS LIKELY. DUE TO THE COMBINATION OF DIURNAL
HEATING, LOCAL EFFECTS, AND AVAILABLE LOW-LEVEL MOISTURE, AFTERNOON
CONVECTION COULD BRING SHOWERS AND ISOLATED THUNDERSTORMS MAINLY
OVER WESTERN PUERTO RICO. RAINFALL ACCUMULATIONS ARE LIKELY TO
ENHANCE PONDING OF WATER OVER ROADWAYS, URBAN AREAS, AND POORLY
DRAINED AREAS, WITH A LOW CHANCE OF URBAN FLOODING.
AS MENTIONED IN THE PREVIOUS DISCUSSION, THERE WAS HIGH VARIABILITY
BETWEEN THE DETERMINISTIC GUIDANCE OF THE GFS AND THE ECMWF DUE TO
THE POTENTIAL OF ANOTHER DISTURBANCE, LIKELY TO BECOME A TROPICAL
CYCLONE, APPROACHING THE CWA. THE LATEST GUIDANCE INDICATES AN
INCREASE IN PWAT VALUES TO ABOVE-NORMAL LEVELS (MEAN AROUND 2.0 -
2.2 INCHES), BUT THERE’S STILL HIGH VARIABILITY DUE TO A LACK OF
CONSENSUS AMONG MODELS. HENCE, CITIZENS AND VISITORS SHOULD CONTINUE
MONITORING HURRICANE ERIN AND WAIT A FEW DAYS FOR MODELS TO REACH AN
AGREEMENT.
DUE TO A SOUTHERLY COMPONENT IN THE WIND FLOW, WARMER THAN NORMAL
TEMPERATURES, AND AVAILABLE MOISTURE, HEAT INDEXES ARE VERY LIKELY
TO EXCEED 100 DEGREES FAHRENHEIT, AND EVEN MEET HEAT ADVISORY
CRITERIA. HENCE, THE HEAT RISK WILL REMAIN LIMITED TO ELEVATED FOR
THE URBAN AND COASTAL AREAS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS, WITH A MEDIUM CHANCE OF ELEVATED TO SIGNIFICANT RISK ON
WEDNESDAY.
AVIATION
(18Z TAFS)
MAJOR HURRICANE ERIN WILL CONTINUE TO BRING ADDITIONAL RAINBANDS
WITH ISO TSRA ACROSS THE LOCAL AREA DURING THE REST OF THE
WEEKEND. MOSTLY TEMPO MVFR TO BRIEF IFR CONDS EXPECTED WITH THESE
INTERMITTENT BANDS. WINDS HAVE ACQUIRE A WESTERLY COMPONENT WITH
WIND SPEEDS BTW 10-20 KT, AND A SOUTHERLY COMPONENT IS EXPECTED
BY THIS EVENING AND THROUGH SUNDAY. LOCALLY HIGHER WINDS ARE
EXPECTED AT TIST THROUGH THE PERIOD.
MARINE
THE EXTERNAL BANDS OF HURRICANE ERIN, PRODUCING SQUALLY WEATHER,
WILL CONTINUE TO INCREASE ACROSS THE LOCAL WATERS AND PASSAGES
THROUGH SUNDAY. BASED ON THE LATEST NATIONAL HURRICANE CENTER TRACK
FORECAST, THE SOUTHERN PORTION OF ERIN EYEWALL IS EXPECTED TO PASS
CLOSE TO THE NORTHEAST CORNER OF OUR CWA OF THE MARINE ZONE AMZ711
(OFFSHORE ATLANTIC WATERS) FROM LATE THIS AFTERNOON THROUGH
TONIGHT, AND IT SHOULD MOVE OFF TO THE NORTH AND AWAY FROM OUR
ATLANTIC WATERS ON SUNDAY.
ERIN IS EXPECTED TO PRODUCE HAZARDOUS SWELL ACTION THAT WILL
IMPACT THE ATLANTIC AND CARIBBEAN PASSAGES THROUGH AT LEAST EARLY
NEXT WEEK. MARINERS AND VISITORS ARE URGED TO REMAIN IN PORT
THROUGH THE WEEKEND.
PLEASE REFER TO THE LATEST COASTAL WATERS FORECAST (CWFSJU) AND
MARINE WEATHER MESSAGE (MWWSJU) FOR MORE INFORMATION.
BEACH FORECAST
LIFE-THREATENING RIP CURRENTS AND HIGH SURF CONDITIONS ARE
EXPECTED ACROSS THE EAST, NORTH, AND WESTERN FACING BEACHES OF THE
U.S. VIRGIN ISLANDS AND PUERTO RICO THROUGH THE REST OF THE
WEEKEND. HOWEVER, SWELLS GENERATED FROM HURRICANE ERIN WILL
CONTINUE TO IMPACT THE NORTHERN COASTLINE OF THE ISLANDS THROUGH
NEXT WEEK. MINOR BEACH EROSION IS POSSIBLE IN THE MOST VULNERABLE
COASTAL AREAS. DANGEROUS SWIMMING CONDITIONS WILL PERSIST ACROSS
ALL COASTLINES THROUGH THE WEEKEND. UNEXPERIENCED SURFERS AND
SWIMMERS ARE URGED TO AVOID GOING INTO THE WATER.
PLEASE REFER TO THE LATEST COASTAL HAZARDS MESSAGE (CFWSJU) AND
SURF ZONE FORECAST (SRFSJU) FOR MORE INFORMATION.
SJU WATCHES/WARNINGS/ADVISORIES
PR...FLOOD WATCH THROUGH MONDAY EVENING FOR PRZ001>013.
HIGH RIP CURRENT RISK THROUGH LATE SUNDAY NIGHT FOR PRZ001-002-
005-008-010-012-013.
HIGH SURF ADVISORY UNTIL 6 AM AST MONDAY FOR PRZ001-002-005-008-
012-013.
VI...FLOOD WATCH THROUGH MONDAY EVENING FOR VIZ001-002.
HIGH RIP CURRENT RISK THROUGH LATE SUNDAY NIGHT FOR VIZ001-002.
HIGH SURF ADVISORY UNTIL 6 AM AST MONDAY FOR VIZ001-002.
AM...TROPICAL STORM WARNING FOR AMZ711.
SMALL CRAFT ADVISORY FROM 6 AM SUNDAY TO 6 AM AST MONDAY FOR
AMZ711.
SMALL CRAFT ADVISORY FROM 4 PM THIS AFTERNOON TO 6 AM AST MONDAY
FOR AMZ712-716-726-733-741.
SMALL CRAFT ADVISORY UNTIL 6 AM AST MONDAY FOR AMZ723.
SHORT TERM...DSR
LONG TERM...MNG
AVIATION...DSR
MARINE/BEACH...DSR
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