722
FXPQ50 PGUM 140739
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
539 PM CHST SUN SEP 14 2025
MARIANAS SYNOPSIS
SATELLITE IMAGERY SHOWS MOSTLY CLOUDY SKIES, WHILE RADAR IMAGERY
SHOWER ISOLATED TO SCATTERED SHOWERS WITHIN THE MARIANAS AND
ADJACENT COASTAL WATERS. ALTIMETRY SHOWS COMBINED SEAS OF 3 TO 4
FEET AND RITIDIAN AND IPAN BUOYS SHOW AROUND 4 FEET.
DISCUSSION
THROUGH THE FIRST HALF OF THE WEEK, PASSING SURFACE TROUGHS WILL BE
INTERACTING WITH A TROPICAL UPPER-TROPOSPHERIC TROUGH (TUTT). THIS
COMBINATION IS EXPECTED TO PRODUCE PERIODIC SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS FOR THE MARIANAS AND ADJACENT COASTAL WATERS.
WHEN THIS INTERACTION IS AT A LULL, ISLAND-EFFECT SHOWERS ARE
POSSIBLE IN THE LATE MORNING AND AFTERNOON HOURS, ESPECIALLY ON
LIGHTER WIND DAYS. ONCE THESE TROUGHS PASS, DRIER WEATHER MAY
RETURN.
MARINE
BENIGN MARINE CONDITIONS CONTINUE THROUGH THE MIDDLE OF THE WEEK
WITH COMBINED SEAS AROUND 3 TO 5 FEET EXPECTED. THE EASTERLY TRADE
SWELL CONTINUING THROUGH THE WEEK. WINDS ARE EXPECTED TO LIGHT TO
MODERATE TONIGHT, AND DIMINISH TO LIGHT TO GENTLE THROUGH THE
BEGINNING OF THE WEEK. THEN AROUND WEDNESDAY, WINDS ARE ANTICIPATED
TO PICK BACK UP TO LIGHT TO MODERATE BEFORE FALLING AGAIN FOR THE
WEEKEND. THERE WILL BE A MODERATE RISK OF RIP CURRENTS ALONG EAST
FACING REEFS OF THE MARIANAS THROUGH MONDAY. THEN, THE RISK WILL
BECOME LOW ALONG ALL REEFS THROUGH THURSDAY DUE TO THE EAST SWELL
WEAKENING. THERE WILL BE A MODERATE RISK OF LIGHTNING ALL THIS WEEK.
EASTERN MICRONESIA...
A BROAD, SOUTHWEST TO NORTHEAST ORIENTED TROUGH IS GENERATING AN AREA
OF UNSETTLED WEATHER BETWEEN POHNPEI AND KOSRAE THIS EVENING.
SCATTEROMETRY DATA REVEALS A BIT OF SPEED CONVERGENCE BEHIND THIS
TROUGH, AS WELL AS POCKETS OF MODERATE TO FRESH GUSTS NEAR LOCALLY
HEAVY SHOWERS AND THUNDERSTORMS NEAR KOSRAE. MODEL GUIDANCE DOES SHOW
THE BULK OF CONVECTION MOVING WEST OF KOSRAE AND REORGANIZING NEAR
AND TO THE SOUTH OF POHNPEI LATER TONIGHT. HOWEVER, LOCALLY HEAVY
SHOWERS ARE EXPECTED TO LINGER NEAR KOSRAE FOR THE FIRST HALF OF THE
EVENING, TRENDING DOWN TO LOW-END SCATTERED OVERNIGHT. RELATIVELY
QUIET WEATHER IS EXPECTED AT MAJURO TONIGHT, ALTHOUGH THE
INTERTROPICAL CONVERGENCE ZONE (ITCZ) IS EXPECTED TO BUILD BACK INTO
THE REGION THIS WEEK, BRINGING SCATTERED SHOWERS TO THE MAJURO
STARTING MONDAY AFTERNOON AND STRETCHING FURTHER INTO CENTRAL
MICRONESIA AROUND MIDWEEK. IN THE LATTER HALF OF THE WEEK, THE ITCZ
MAY BECOME MORE DEVELOPED, BRINGING MORE OF AN UNSETTLED WEATHER
PATTERN FOR THE REGION.
OVERALL, BENIGN MARINE CONDITIONS CONTINUE, WITH LIGHT TO MODERATE
WINDS EXPECTED THIS WEEK. BUOY AND ALTIMETRY REVEAL 3 TO 5 FOOT
COMBINED SEAS NEAR POHNPEI AND KOSRAE AND UP TO 6 FEET EAST OF
MAJURO, COMPRISED MOSTLY OF EAST TO SOUTHEASTERLY SWELL. THERE IS
WEAKER, LONG-PERIOD SWELL EMANATING FROM THE SOUTHERN HEMISPHERE OVER
THE NEXT SEVERAL DAYS, HOWEVER MAGNITUDES ARE NOT SIGNIFICANT ENOUGH
TO IMPACT SEAS OR SURF AT THIS TIME.
WESTERN MICRONESIA
A BROAD MONSOONAL PATTERN IS DEVELOPING FROM SOUTHEAST ASIA AND
ACROSS THE PHILIPPINES, CONNECTING WITH A WEAK CIRCULATION THAT
DEVELOPED NEAR 12N131E AND IS SLOWLY DRIFTING WESTWARD AND EXPECTED
TO MOVE WEST OF 130E OVERNIGHT. PALAU AND YAP ARE ON THE EASTERN
EDGE OF THIS MONSOON PATTERN WHICH IS KEEPING WINDS FAIRLY LIGHT AND
VARIABLE OVERALL. YAP IS EXPERIENCING FAIRLY DRY WEATHER THIS EVENING
AND THIS IS EXPECTED TO CONTINUE INTO MONDAY AND POSSIBLY TUESDAY.
MEANWHILE, CONVERGENT FLOW OVER PALAU IS GENERATING SCATTERED SHOWERS
AND ISOLATED THUNDESTORMS WITH SCATTEROMETER DATA EARLIER IN THE
DAY SHOWING POCKETS OF 20 KT WINDS WITH SOME OF THESE SHOWERS. OVER
THE PAST COUPLE OF HOURS, INFRARED SATELLITE IMAGERY HAS SHOWN CLOUD
TOPS WARMING AND SOME THINNING OF THE CLOUD COVER OVER PALAU,
SUGGESTING A DOWNWARD TREND IN SHOWERS IS STARTING TO OCCUR. MODEL
GUIDANCE SUPPORTS THIS TREND CONTINUING SO EXPECT SCATTERED SHOWERS
TO CONTINUE INTO THE LATE EVENING HOURS, AND THEN BECOMING ISOLATED
AFTER MIDNIGHT AS THE MAIN AREA OF CONVERGENCE SHIFTS WESTWARD. WITH
WINDS EXPECTED TO REMAIN LIGHT, ISLAND-EFFECT CONVECTION DURING THE
DAYTIME HOURS IS POSSIBLE. ALSO, WITH THE PROXIMITY OF CONVERGENT
FLOW DUE TO MONSOONAL PATTERN NEAR THE PHILIPPINES, PERIODS OF
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS CANNOT BE RULED OUT FOR
MONDAY AND MONDAY NIGHT. THE NEXT MAIN POTENTIAL FOR SHOWERS AND
THUNDESTORMS FOR BOTH YAP AND PALAU WILL BE AROUND WEDNESDAY AS THE
NEXT DISTURBANCE APPROACHES AND THEN AND SHIFTS NORTHWEST OF THE
ISLANDS LATER IN THE WEEK, POTENTIALLY LEADING TO A SIMILAR STEP UP
EXPERIENCED OVER THE PAST FEW DAYS.
FOR CHUUK, PASSING TRADE-WIND TROUGHS AND TRADE CONVERGENCE HAVE
BROUGHT PERIODS OF SCATTERED SHOWERS AS THESE FEATURES PASS THROUGH
THE STATE. AS OF THIS EVENING, THERE SOME INCREASED CLOUD COVER OVER
CHUUK LAGOON, BUT SHOWERS LOOK TO BE FAIRLY ISOLATED. NEW SHOWERS
ARE DEVELOPING EAST OF CHUUK AND EXTENDING BACK TOWARDS POHNPEI AND
KOSRAE, ALONG A BROAD TROUGH MOVING THROUGH THE REGION, WHICH IS
EXPECTED TO INCREASE SHOWERS ACROSS CHUUK AGAIN LATER TONIGHT AND
INTO MONDAY. MODEL GUIDANCE ALSO SUPPORTS THE ITCZ REDEVELOPING NEAR
THE MARSHALL ISLANDS AND THEN EXTENDING INTO CHUUK STATE AROUND THE
MIDDLE OF THE WEEK, CONTINUING THE OVERALL WET PATTERN AT CHUUK
THROUGH THE WEEK.
ALTIMETRY DATA SHOWS SEAS ARE AROUND 2 TO 3 FEET ACROSS PALAU AND
YAP AND UP TO 4 FEET ACROSS CHUUK. WINDS ARE STILL FAIRLY LIGHT
ACROSS THE REGION WITH THE PRIMARY SWELL BEING EAST-NORTHEAST. MARINE
CONDITIONS ARE NOT EXPECTED TO CHANGE MUCH AT PALAU AND YAP OVER THE
NEXT FEW DAYS BESIDES FOR MODELS SUPPORTING WINDS BECOMING MORE
SOUTHEAST TO EAST LATER THIS WEEK. SEAS MAY BUILD SLIGHTLY AT CHUUK
AROUND LATER THIS WEEK AS WINDS INCREASE SLIGHTLY AS THE ITCZ SHIFTS
INTO CHUUK FROM EASTERN MICRONESIA.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: BOWSHER
EAST MICRONESIA: CRUZ
WEST MICRONESIA: SCHANK
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