602
FXCA62 TJSJ 171435
AFDSJU
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAN JUAN PR
1035 AM AST SUN AUG 17 2025
UPDATE
RAINBANDS FROM ERIN CONTINUE TO PRODUCE SHOWERS AND THUNDERSTORMS
ACROSS MOST OF THE EASTERN AND SOUTHERN HALF OF PUERTO RICO, AND
ACROSS ST. THOMAS AND ST. JOHN. GUSTY WINDS WERE OBSERVED ACROSS
THESE AREAS WITH GUSTS UP TO 53 MPH IN CULEBRA AND 49 MPH IN
CHARLOTTE AMALIE, ST. THOMAS. ACROSS SOUTHEASTERN PR, A GUST UP TO
42 MPH WAS REPORTED IN LAS MAREAS, GUAYAMA PR. IN TERMS OF
PRECIPITATION DURING THE PAST 6 HOURS, A STATION IN GUAYAMA
REPORTED 3.57 INCHES AND ANOTHER IN CAGUAS REPORTED 1.55 INCHES.
IN ST. JOHN, A STATION REPORTED 1.91 INCHES DURING THE PAST 12
HOURS.
FOR THE REST OF THE DAY, MORE SHOWERS AND THUNDERSTORMS ARE
EXPECTED TO DEVELOP OVER THE ISLANDS, AND AS ERIN PULLS FURTHER
NORTH-NORTHWEST OF THE REGION, MOST OF THE ACTIVITY WILL MOVE OVER
THE INTERIOR AND WESTERN PR. ANOTHER FEEDER BAND IS EXPECTED TO
MOVE OVER THE USVI AND EAST/SOUTHEAST SECTIONS OF PR DURING THE
NIGHT. THEREFORE, THE THREAT FOR FLASH FLOODING REMAINS HIGH
ACROSS ALL THE ISLANDS, AND A FLASH FLOOD WATCH IS IN EFFECT
THROUGH AT LEAST LATE MONDAY.
AVIATION
(12Z TAFS)
TEMPO MVFR TO IFR CONDITIONS ARE EXPECTED AT TIMES DURING THE
NEXT 12-24 HOURS ACROSS THE PR TERMINALS, AS INTERMITTENT RAINBANDS
FROM TC ERIN MOVE FROM EAST TO WEST ACROSS THE REGION. THE 17/12Z
TJSJ SOUNDING INDICATED SW WINDS UP TO 40 KT BLO 4000 FT.
PREV DISCUSSION
/ISSUED 500 AM AST SUN AUG 17 2025/
KEY MESSAGES...
* ERIN, MOVING WEST-NORTHWEST ACROSS THE ATLANTIC OCEAN, WILL
CONTINUE TO MOVE AWAY FROM THE US VIRGIN ISLANDS AND PUERTO RICO
TODAY.
* A FLOOD WATCH IS IN EFFECT FOR THE US VIRGIN ISLANDS AND PUERTO
RICO THROUGH AT LEAST MONDAY.
* ERIN'S FEEDING BANDS OR TRAILING MOISTURE WILL PROMOTE FAVORABLE
CONDITIONS FOR THE FORMATION OF PERIODS OF MODERATE TO LOCALLY
HEAVY RAIN AND GUSTY WINDS ACROSS THE US VIRGIN ISLANDS AND PUERTO
RICO TODAY.
* HAZARDOUS MARINE AND COASTAL CONDITIONS WILL CONTINUE ACROSS THE
ATLANTIC AND CARIBBEAN PASSAGES.
SHORT TERM...TODAY THROUGH TUESDAY...
THE CENTER OF MAJOR HURRICANE ERIN MOVED SLOWLY NEAR THE LOCAL
WATERS OF PUERTO RICO AND THE US VIRGIN ISLANDS WITH ITS EXTERNAL
RAINBANDS PRODUCING STRONG THUNDERSTORMS, GUSTY WINDS, AND FLOODING
RAINS ACROSS THE ISLANDS OVERNIGHT. WE ISSUED FLASH FLOOD WARNINGS
FOR ST. THOMAS, ST. JOHN, AND ST. CROIX OVERNIGHT. WINDS WERE SLOWLY
BECOMING FROM THE SOUTHWEST WITH GUSTY WINDS AT 30 TO 40 MPH IN PR
AND BETWEEN 40 AND 55 MPH IN THE USVI NEAR THUNDERSTORM ACTIVITY.
THE FLOOD WATCH WAS EXTENDED THROUGH MONDAY, AS THE SOUTHERLY WINDS
WILL POOL PLENTY OF TROPICAL MOISTURE FOLLOWING ERIN'S TRACK. ERIN'S
TRAILING MOISTURE WILL RESULT IN PERIODS OF HEAVY RAIN AND
THUNDERSTORMS ACROSS PORTIONS OF PR AND THE US VIRGIN ISLANDS,
CREATING A HIGH CHANCE FOR LOCALLY CONSIDERABLE FLASH AND URBAN
FLOODING, ALONG WITH LANDSLIDES OR MUDSLIDES.
HAZARDOUS MARINE AND COASTAL CONDITIONS WILL PERSIST TODAY WITH
DANGEROUS BREAKING WAVES AND LIFE-THREATENING RIP CURRENTS ALONG THE
NORTH AND EAST-FACING BEACHES IN PR AND THE USVI.
RAIN ACTIVITY SHOULD DIMINISH SOMEWHAT AROUND SUNDAY EVENING AND
EARLY MONDAY MORNING. HOWEVER, UNDER THE SOUTHERLY WIND FLOW AND AS
CLOUD COVER DECREASES, WE EXPECT ABOVE-NORMAL HEAT INDICES DURING
THE AFTERNOON, DUE TO THE AVAILABLE MOISTURE COMBINED WITH MAXIMUM
AFTERNOON TEMPERATURES. ALTHOUGH WE EXPECT A MIXTURE OF SUNSHINE AND
CLOUDS DURING THE DAY, THE RAINFALL ACCUMULATIONS ALREADY OBSERVED,
MIXED WITH SUNDAY'S RAIN ACTIVITY, WILL CONTINUE TO SATURATE SOILS
AND INCREASE RIVER LEVELS, CREATING FAVORABLE CONDITIONS TO OBSERVE
ANOTHER DAY WITH A HIGH FLOODING THREAT WITH THE EXPECTED RAIN
ACTIVITY.
PLEASE ENCOURAGE EVERYONE IN PUERTO RICO AND THE US VIRGIN ISLANDS
TO STAY INFORMED ABOUT COMMUNITY VULNERABILITIES TO REDUCE WEATHER
IMPACTS FOR THEMSELVES AND THEIR FAMILIES.
THE WARM AND HOT HEAT INDICES WILL RETURN BY TUESDAY AS THE EAST-
SOUTHEAST WIND FLOW RETURNS ACROSS THE ISLANDS, AS WELL AS THE
TYPICAL HYDROLOGICAL PATTERN, CONSISTING OF SHOWERS EMBEDDED IN THE
WINDS ACROSS THE WINDWARD SECTIONS IN THE USVI AND PR, FOLLOWED BY
AFTERNOON CONVECTION ACROSS THE INTERIOR AND NORTHWEST QUADRANT OF
PR.
LONG TERM...WEDNESDAY THROUGH SUNDAY...
SOME CHANGES WERE INTRODUCED TO THE LONG-TERM FORECAST, PARTICULARLY
FOR THE UPCOMING WEEKEND. WINDS WILL MOSTLY REMAIN FROM THE
SOUTHEAST DUE TO A SURFACE HIGH PRESSURE LINGERING NORTHEAST OF THE
CWA. MODEL GUIDANCE SUGGESTS AN UPPER-LEVEL LOW APPROACHING THE
LOCAL AREA BY WEDNESDAY MORNING, ALTHOUGH THE LATEST SOLUTIONS AGREE
THAT THIS FEATURE SHOULD MOVE NORTH OF THE REGION. LOOKING AT THE
MID-LEVEL TEMPERATURES, 500 MB TEMPERATURES DROP TO BELOW
CLIMATOLOGICAL NORMAL ON WEDNESDAY, ENHANCING DEEP CONVECTION
ACTIVITY. DUE TO PWAT VALUES (1.6 - 1.8 INCHES), THE LIKELIEST
SCENARIO WOULD BE AN ADVECTIVE PATTERN WITH SHOWERS MOVING OVER THE
U.S. VIRGIN ISLANDS, VIEQUES, CULEBRA, AND SOUTHEASTERN PUERTO RICO
DURING THE MORNING, WHILE AFTERNOON CONVECTION COULD DEVELOP OVER
INTERIOR AND NORTHWESTERN PUERTO RICO. RAINFALL ACCUMULATIONS COULD
LEAD TO PONDING OF WATER OVER ROADWAYS, URBAN, AND POORLY DRAINED
AREAS, WITH LOW CHANCE OF URBAN FLOODING ALONG INTERIOR AND
NORTHWESTERN PUERTO RICO. A DRIER AIR MASS SHOULD FILTER INTO THE
REGION BY THURSDAY, AND DUE TO THE PRESENCE OF A MID- LEVEL RIDGE,
THE SHOWER ACTIVITY MAY BE LIMITED.
AS FOR THE UPCOMING WEEKEND, THE NATIONAL HURRICANE CENTER IS
CURRENTLY MONITORING AN AREA OF LOW PRESSURE WITH A 0 % CHANCE OF
FORMATION FOR THE NEXT 48 HOURS AND A 20 % CHANCE IN THE NEXT 7
DAYS. AS MENTIONED IN PREVIOUS DISCUSSIONS, GLOBAL MODEL GUIDANCE
HAS BEEN SUGGESTING THE POTENTIAL FOR A VIGOROUS TROPICAL WAVE TO
DEVELOP INTO A POTENTIAL TROPICAL CYCLONE APPROACHING THE CARIBBEAN
BASIN. NEVERTHELESS, VARIABILITY CONTINUES HIGH, PARTICULARLY ON
FRIDAY. ALTHOUGH THE DETERMINISTIC GUIDANCE FROM THE GFS AND ECMWF
AGREES ON AN INCREASE IN MOISTURE CONTENT, UNCERTAINTY REMAINS HIGH
REGARDING TRAJECTORY AND INTENSITY. HENCE, THE FLOODING RISK WILL
REMAIN LIMITED FOR MOST PORTIONS OF PUERTO RICO AND THE U.S. VIRGIN
ISLANDS, ALTHOUGH IT MAY CHANGE DUE TO HIGH UNCERTAINTY. ONCE AGAIN,
RESIDENTS AND VISITORS SHOULD KEEP MONITORING AND STAY TUNED TO THE
LATEST ADVISORIES OF HURRICANE ERIN.
AS MENTIONED IN PREVIOUS DISCUSSIONS, THE HEAT RISK IS EXPECTED TO
REMAIN MOSTLY LIMITED TO ELEVATED ACROSS URBAN AND COASTAL AREAS OF
PUERTO RICO AND THE U.S. VIRGIN ISLANDS. NEVERTHELESS, DUE TO HOTTER
THAN NORMAL TEMPERATURES AND ABUNDANT MOISTURE, THE HEAT RISK MAY
INCREASE AND BECOME ELEVATED TO SIGNIFICANT, MEETING HEAT
ADVISORY/WARNING CRITERIA.
AVIATION...
(06Z TAFS)
INTERMITTENT PERIODS OF SHRA/TSRA ASSOCIATED WITH ERIN'S OUTER BANDS
ARE EXPECTED THROUGH THE FORECAST PERIOD. THIS WILL LEAD TO
EXTENSIVE PERIODS OF REDUCED VIS AND LOW CEILINGS, LIKELY IN THE
MVFR AND IFR CONDITIONS. WIND SPEEDS WILL BE AT 20-30 MPH, BUT GUSTS
COULD REACH 35-40 KTS AT TIMES, ESPECIALLY IN THE USVI TERMINALS.
MARINE...
ERIN'S OUTER BANDS PRODUCING THUNDERSTORMS WITH HEAVY RAIN AND GUSTY
WINDS ACROSS THE REGIONAL WATERS. BASED ON THE LATEST NATIONAL
HURRICANE CENTER TRACK FORECAST, THE SOUTHERN PORTION OF ERIN
EYEWALL WILL CONTINUE TO MOVE AWAY FROM OUR ATLANTIC WATERS THIS
MORNING. ALTHOUGH ERIN WILL CONTINUE TO PRODUCE HAZARDOUS SWELL
ACTION THAT WILL IMPACT THE ATLANTIC AND CARIBBEAN PASSAGES, WE
EXPECT LOCAL CONDITIONS TO SLOWLY IMPROVE LATER TODAY. MARINERS AND
VISITORS ARE URGED TO REMAIN IN PORT TODAY.
BEACH FORECAST...
LIFE-THREATENING RIP CURRENTS AND HIGH SURF CONDITIONS CONTINUE
ACROSS THE EAST, NORTH, AND WESTERN FACING BEACHES OF THE U.S.
VIRGIN ISLANDS AND PUERTO RICO THROUGH EARLY MONDAY. HOWEVER, SWELLS
GENERATED FROM HURRICANE ERIN ARE LIKELY TO CONTINUE TO IMPACT THE
NORTHERN COASTLINE OF THE ISLANDS THROUGH THE WEEK. MINOR BEACH
EROSION IS POSSIBLE IN THE MOST VULNERABLE COASTAL AREAS.
DANGEROUS SWIMMING CONDITIONS WILL PERSIST ACROSS ALL COASTLINES
THROUGH AT LEAST MONDAY. 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 TONIGHT 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 TONIGHT FOR VIZ001-002.
HIGH SURF ADVISORY UNTIL 6 AM AST MONDAY FOR VIZ001-002.
AM...TROPICAL STORM WARNING FOR AMZ711.
SMALL CRAFT ADVISORY FROM 5 PM THIS AFTERNOON TO 6 AM AST MONDAY
FOR AMZ711.
SMALL CRAFT ADVISORY UNTIL 6 AM AST MONDAY FOR AMZ712-716-723-
726-733-741-742.
UPDATE...DSR
LONG TERM....MNG
AVIATION...DSR
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