484
FXPQ50 PGUM 310754
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
554 PM CHST MON AUG 31 2026
MARIANAS SYNOPSIS
ISOLATED TO SCATTERED SHOWERS ARE VISIBLE OVER THE MARIANAS THIS
EVENING. WINDS ARE LIGHT AND VARIABLE FOR TINIAN AND SAIPAN. LIGHT TO
GENTLE WEST WINDS HAVE JUST STARTED MOVING OVER ROTA, DISRUPTING SOME
LIGHT ISLAND EFFECT SHOWERS. GENTLE WESTERLIES ARE ALSO VISIBLE OVER
GUAM. MODELS AND OBSERVATIONS INDICATE COMBINED SEAS OF AROUND 4
FEET.
DISCUSSION
A RELATIVELY CALM PERIOD OF ISOLATED TO SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS WILL PERSIST THROUGH WEDNESDAY WITH COVERAGE
HIGHER OVER GUAM. VERY LIGHT WINDS MAY ALLOW ISLAND EFFECT SHOWERS
AND ISOLATED THUNDERSTORMS TO DEVELOP FOR ALL ISLANDS, THOUGH LIKELY
NOT TOO INTENSE DUE TO LOW LEVEL DIVERGENCE AND ONLY MODERATE
PRECIPITABLE WATER VALUES. WESTERLIES OVER GUAM MAY LIMIT DEVELOPMENT
OR PUSH ANY SHOWERS THAT DEVELOP OFFSHORE AS WAS SEEN TODAY. BY
WEDNESDAY, MOIST AND UNSTABLE AIR FROM INVEST 95W MAY ALLOW FOR
HEAVIER ISLAND EFFECT SHOWERS AND ISOLATED THUNDERSTORMS DEPENDING ON
UPPER LEVEL CLOUD COVERAGE. WEDNESDAY NIGHT THROUGH SOMETIME
THURSDAY, THE MONSOON TAIL OF 95W MAY BRING NUMEROUS LOCALLY HEAVY
SHOWERS AND ISOLATED THUNDERSTORMS TO THE MARIANAS, WITH MODELS
INDICATING HIGHER CHANCES CURRENTLY OVER GUAM AND ROTA. MODELS
CURRENTLY SHOW WIDESPREAD 1 TO 2 INCHES FOR THIS EVENT BUT HIGHER
TOTALS WILL BE POSSIBLE IN HEAVIER, TRAINING SHOWERS. THIS WILL BE
MONITORED CLOSELY OVER THE NEXT DAY IN CASE A HYDROLOGIC OUTLOOK OR
FLASH FLOOD WATCH NEEDS TO BE ISSUED. GUSTY WINDS WILL ALSO BE
EXPECTED WITH ANY THUNDERSTORMS. BY LATE THURSDAY, DRY CONDITIONS MAY
RETURN BEFORE A NEW MONSOON SURGE POTENTIALLY MOVES INTO THE REGION
OVER THE WEEKEND.
MARINE
COMBINED SEAS AROUND 4 FEET WILL GRADUALLY INCREASE THROUGH THE
WEEK, REACHING AS HIGH AS 8 TO 9 FEET DUE TO AN INCREASE IN
WESTERLY SWELL. LIGHT TO GENTLE NORTHWESTERLIES WILL BECOME
SOUTHWESTERLY AROUND MIDWEEK, INCREASING TO MODERATE TO FRESH FOR
THE LAST HALF OF THE WEEK. AN UNSETTLED, BUT DISORGANIZED MONSOON
PATTERN CONTINUES TO BRING PERIODS OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS MAINLY TO GUAM OVER THE NEXT COUPLE OF
DAYS, POTENTIALLY BECOMING NUMEROUS WITH LOCALLY HEAVY SHOWERS
POSSIBLE SOMETIME WEDNESDAY.
FOR COASTAL SURF, THERE WILL BE A MODERATE RISK OF RIP CURRENTS
ALONG WEST-FACING REEFS FOR THE NEXT FEW DAYS. MODELS AND BUOYS
INDICATE NORTH- AND SOUTH-FACING REEFS ARE BELOW 5 FEET. THE RISK MAY
REACH HIGH ALONG WEST- FACING REEFS AROUND MIDWEEK AS A WEST SWELL
BUILDS IN. THERE WILL BE A MODERATE RISK OF LIGHTNING FOR GUAM
BEGINNING TUESDAY AND LASTING THE WHOLE WEEK.
TROPICAL SYSTEMS
A DEVELOPING MONSOON DISTURBANCE, INVEST 94W, IS CENTERED NORTHEAST
OF LUZON NEAR 21N132E AND IS CURRENTLY THE SUBJECT OF A TROPICAL
CYCLONE FORMATION ALERT BY THE JOINT TYPHOON WARNING CENTER (JTWC).
THIS MEANS THAT 94W IS EXPECTED TO BECOME A SIGNIFICANT TROPICAL
CYCLONE (TROPICAL DEPRESSION) WITHIN THE NEXT 24 HOURS. 94W IS
CURRENTLY MOVING SLOWLY NORTHWEST. LATEST SATELLITE DATA SHOWS A
BROAD, ELONGATED LOW-LEVEL CIRCULATION CENTER (LLCC) OBSCURED BY
PERSISTENT CONVECTION SOUTH THROUGH WEST OF THE CENTER. SINCE
CONDITIONS REMAIN CONDUCIVE TO DEVELOPMENT, INVEST 94W IS EXPECTED TO
SLOWLY STRENGTHEN AS IT MOVES NORTHWEST, POSSIBLY MOVING OUT OF THE
GUAM AREA OF RESPONSIBILITY (AOR) WITHIN THE NEXT 24 HOURS.
FOR MORE INFORMATION ON INVEST 94W AND THE TCFA, SEE BULLETINS
ISSUED BY JTWC UNDER WMO HEADERS ABPW10 PGTW AND WTPN21 PGTW.
A WEAK MONSOON DISTURBANCE, INVEST 95W, IS FOUND EAST-SOUTHEAST OF
GUAM, NORTHEAST OF WENO, CHUUK, NEAR 12N154E. INVEST 95W IS
CURRENTLY RATED SUB-LOW, MEANING DEVELOPMENT IS NOT EXPECTED FOR THE
NEXT FEW DAYS. LATEST ASCAT ANALYSIS SHOWS A WEAK CIRCULATION WITH
LIGHT WINDS NEAR THE CENTER AND STRONGER ENVIRONMENTAL WINDS FARTHER
SOUTH WITHIN A MONSOON SURGE ACROSS CHUUK STATE THROUGH NORTHEAST OF
POHNPEI. INVEST 95W LOOKS TO SLOWLY MOVE TOWARD THE NORTH-NORTHWEST
OVER THE NEXT FEW DAYS, WITH LITTLE DEVELOPMENT EXPECTED UNTIL AFTER
THE MIDDLE OF THE WEEK.
EASTERN MICRONESIA
THE MONSOON TROUGH IS PRODUCING A SURGE TO THE SOUTHEAST OF INVEST
95W, CENTERED NORTHWEST OF POHNPEI, AND WILL CONTINUE TO INFLUENCE
THE PATTERN FOR MAINLY POHNPEI THROUGH TUESDAY AFTERNOON. AS 95W
SLOWLY MOVES NORTH-NORTHWEST, IT WILL PULL THE MONSOON TROUGH FARTHER
NORTH, ALLOWING THE SURGE TO WEAKEN NEAR POHNPEI. THIS WILL RESULT IN
DECREASING CONVECTION FOR THE ISLAND OVER THE NEXT 24 HOURS, WITH
ONLY ISOLATED SHOWERS EXPECTED FOR POHNPEI BY TUESDAY AFTERNOON. FOR
KOSRAE, MOSTLY ISOLATED SHOWERS OVER THE NEXT FEW DAYS. HOWEVER, A
LITTLE SURGE IN CONVECTION IS EXPECTED THERE THIS EVENING, NEAR
MIDNIGHT, THAT WILL BRING LOW-END SCATTERED SHOWERS TO THE ISLAND
UNTIL EARLY TUESDAY MORNING. MAJURO LOOKS TO REMAIN DRY THROUGH AT
LEAST THE END OF THE WEEK.
FOR THE MARINE ENVIRONMENT, LIGHT TO GENTLE WINDS ARE EXPECTED FOR
KOSRAE AND MAJURO THROUGH THE PERIOD, WITH SEAS OF 3 TO 4 FEET. AT
POHNPEI, GENTLE TO MODERATE WINDS ARE EXPECTED TO WEAKEN, BECOMING
LIGHT TO GENTLE TUESDAY AFTERNOON. COMBINED SEAS OF 4 TO 6 FEET WILL
SUBSIDE TO BETWEEN 3 AND 4 FEET AROUND THURSDAY.
WESTERN MICRONESIA
SATELLITE IMAGERY SHOWS ISOLATED SHOWERS ACROSS PALAU AND YAP.
SCATTERED SHOWERS ARE SEEN OVER WENO, BUT NUMEROUS SHOWERS ARE SEEN
ACROSS PORTIONS OF CHUUK STATE TO THE NORTH AND WEST OF WENO.
ALTIMETRY SHOWS THAT COMBINED SEAS ARE BETWEEN 6 AND 8 FEET ACROSS
CHUUK STATE AND 3 TO 6 FEET ELSEWHERE.
QUIET CONDITIONS CONTINUE ACROSS PALAU AND YAP WITH THE DRY PORTION
OF THE MONSOON ANCHORED OVER FAR WESTERN MICRONESIA. SHOWERS CHANCES
WILL INCREASE FOR YAP THROUGH THE WEEK AS THE ACTIVE PHASE OF THE
MONSOON PATTERN SHIFTS WEST ACROSS YAP STATE. SCATTERED TO NUMEROUS
SHOWERS WILL PERSIST THROUGH THURSDAY NIGHT FOR YAP BEFORE A DRIER
STRETCH RETURNS FRIDAY AND INTO THE WEEKEND.
CHUUK WILL SEE SCATTERED SHOWERS AND GUSTY WINDS THROUGH WEDNESDAY
NIGHT. THE RISK FOR LOCALLY HEAVY RAINFALL HAS DECREASED FOR WENO AS
THE HEAVIER BAND OF SHOWERS AND THUNDERSTORMS HAS SHIFTED TO THE
NORTHWEST. CHUUK WILL TREND DRIER THIS WEEK AS THE ACTIVE MONSOON
PATTERN LIFTS NORTHWEST. SHOWERS LOOK TO BECOME ISOLATED BY THURSDAY
WITH DRIER CONDITIONS PERSISTING INTO THE WEEKEND.
COMBINED SEAS ARE CURRENTLY BETWEEN 6 AND 8 FEET ACROSS CHUUK AND 3
TO 6 FEET ACROSS YAP AND PALAU. A SMALL CRAFT ADVISORY WAS EXTENDED
THROUGH TONIGHT FOR CHUUK FOR WINDS UP TO 25 KT AND GUSTS TO 30 KT.
SEAS LOOK TO REMAIN ELEVATED THROUGH WEDNESDAY NIGHT AS SOUTHWEST
SWELLS INCREASE TO 6 FEET. CHOPPY SEAS WILL MAKE INTER-ISLAND TRAVEL
DIFFICULT AT TIMES. BENIGN MARINE CONDITIONS WILL PREVAIL ACROSS YAP
AND PALAU THROUGH THE PERIOD.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: WILLIAMS
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