434
FXPQ50 PGUM 311956
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
556 AM CHST TUE SEP 1 2026
MARIANAS UPDATE
SCATTERED SHOWERS WILL BE POSSIBLE THIS MORNING FOR GUAM WITH SHOWER
COVERAGE REMAINING ISOLATED FOR ROTA, TINIAN, AND SAIPAN.THOUGH, AN
AREA OF SHOWERS FAR OFFSHORE TO THE EAST MAY BRING PERIODS OF
SCATTERED SHOWERS TO THE CNMI LATER THIS MORNING. WINDS SHOULD
REMAIN LIGHT ENOUGH FOR SOME ISLAND-EFFECT SHOWERS AND THUNDERSTORMS
THIS AFTERNOON FOR ISLANDS. WEDNESDAY SHOULD BE A REPEAT OF TODAY
WITH LOWER SHOWER CHANCES IN THE MORNING, FOLLOWED BY ISLAND-EFFECT
SHOWERS AND THUNDERSTORMS IN THE AFTERNOON. THOUGH, SOME LOCALLY
HEAVY RAINFALL MAY ACCOMPANY THOSE ISLAND-EFFECT SHOWERS AND
THUNDERSTORMS DUE TO MOISTURE ASSOCIATED WITH NEARBY INVEST 95W
SPREADING OVER THE MARIANAS. COMBINED SEAS OF 4 TO 5 FEET WILL
GRADUALLY INCREASE THIS WEEK, POTENTIALLY REACHING UP TO 9 FEET LATE
THIS WEEK AS A WEST SWELL BUILDS IN. LIGHT TO GENTLE WINDS WILL
BECOME SOUTH TO SOUTHWEST BY WEDNESDAY NIGHT AND INCREASE TO MODERATE
TO FRESH LATE THIS WEEK. A MODERATE RISK OF RIP CURRENTS WILL
CONTINUE ALONG EAST AND WEST-FACING REEFS FOR THE NEXT FEW DAYS,
POTENTIALLY INCLUDING NORTH AND SOUTH-FACING REEFS AS EARLY AS
WEDNESDAY. THE RIP CURRENT RISK MAY REACH HIGH RISK ALONG WEST-
FACING REEFS LATER THIS WEEK AS THE AFOREMENTIONED WEST SWELL BUILDS.
TROPICAL SYSTEMS UPDATE
INVEST 94W REMAINS THE SUBJECT OF A TROPICAL CYCLONE FORMATION ALERT
(TCFA) FROM THE JOINT TYPHOON WARNING CENTER (JTWC) THIS MORNING.
THE MONSOON DISTURBANCE IS LOCATED AROUND 22N132E AND DEVELOPMENT
INTO A SIGNIFICANT TROPICAL CYCLONE (TROPICAL DEPRESSION) IS STILL
EXPECTED WITHIN THE NEXT 24 HOURS. ENSEMBLE GUIDANCE MOVES THE
DISTURBANCE GENERALLY WESTWARD OVER THE NEXT 12 TO 24 HOURS, BEFORE
IT MAKES THE TURN TO THE NORTHWEST. 94W IS EXPECTED TO MOVE OUT OF
NWS GUAM'S AREA OF RESPONSIBILITY SOMETIME DURING THE 24 TO 36 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 DISTURBANCE, INVEST 95W, CONTINUES TO BE RATED SUB-LOW BY
JTWC AND IS LOCATED AROUND 14N150E THIS MORNING. NO DEVELOPMENT IS
EXPECTED DURING THE NEXT COUPLE OF DAYS AND ENSEMBLE GUIDANCE LIFTS
THE INVEST GENERALLY NORTHWARD OVER THE NEXT 12 TO 24 HOURS BEFORE
TURNING TO THE NORTHWEST THEREAFTER.
EASTERN MICRONESIA UPDATE
ISOLATED TO LOW-END SCATTERED SHOWERS, ALONG WITH ISOLATED
THUNDERSTORMS, ARE EXPECTED AT ALL THREE FORECAST SITES THROUGH AT
LEAST TONIGHT. MODERATE WEST TO SOUTHWEST WINDS AT POHNPEI WILL EASE
SLIGHTLY TODAY, BECOMING MOSTLY GENTLE BY TONIGHT WITH LIGHT TO
GENTLE WINDS PREVAILING AT KOSRAE AND MAJURO. COMBINED SEAS OF 5 TO
6 FEET AT POHNPEI WILL DECREASE A FOOT OR SO TONIGHT WITH COMBINED
SEAS OF 4 TO 5 FEET CONTINUING INTO WEDNESDAY FOR BOTH MAJURO AND
KOSRAE.
WESTERN MICRONESIA UPDATE
SHOWER CHANCES AT YAP WILL INCREASE TODAY AND CONTINUE INTO MIDWEEK AS
AN ACTIVE MONSOON PATTERN MOVES IN OVER PORTIONS OF YAP STATE.
LOCALLY HEAVY RAINFALL WILL BE POSSIBLE IN HEAVIER SHOWERS AND
THUNDERSTORMS. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL
CONTINUE OVER THE NEXT COUPLE DAYS AT CHUUK BUT SHOWER CHANCES HAVE
GENERALLY TRENDED DOWN COMPARED TO PREVIOUS DAYS AS THE BETTER,
MONSOONAL FORCING LIFTS TO THE NORTH AND WEST. DRIER CONDITIONS WILL
CONTINUE AT PALAU THROUGH AT LEAST WEDNESDAY. GENTLE TO MODERATE
WEST TO SOUTHWEST WINDS WILL PERSIST AT YAP AND PALAU FOR THE NEXT
COUPLE OF DAYS WHILE MODERATE TO FRESH WEST TO SOUTHWEST WINDS AT
CHUUK SLOWLY EASE TO MODERATE OVER THE NEXT COUPLE OF DAYS. THE
LATEST SCATTEROMETRY PASS FROM YESTERDAY EVENING SHOWED SUSTAINED
WINDS HAVE FALLEN BELOW ADVISORY CRITERIA OF 22 KNOTS, SO LET THE
SMALL CRAFT ADVISORY EXPIRE AT 5 AM FOR CHUUK. COMBINED SEAS OF 5 TO
7 FEET WILL CONTINUE AT CHUUK AND YAP OVER THE NEXT COUPLE OF DAYS
WHILE SEAS AROUND 3 TO 4 FEET PERSIST AT PALAU.
PREV DISCUSSION
/ISSUED 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/EAST AND WEST MICRONESIA/TROPICAL UPDATE: WHISNANT
MARIANAS: OGLE
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: WILLIAMS
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