378
FXPQ50 PGUM 220757
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
557 PM CHST TUE SEP 22 2026
MARIANAS SYNOPSIS
SATELLITE IMAGERY SHOWS MOSTLY CLOUDY TO CLOUDY SKIES OVER THE
MARIANAS, WHILE RADAR IMAGERY SHOW ISOLATED SHOWERS NEAR SAIPAN, AND
SCATTERED SHOWERS NEAR GUAM. ALTIMETRY SHOWS ABOUT 4 TO 6 FEET.
DISCUSSION
THE TRADE-WIND INFLOW OF INVEST 91W IS PRODUCING SCATTERED SHOWER
OVER THE REGION. THESE SHOWERS ARE ACCOMPANIED BY 10 TO 15 MPH
SOUTHERLY WINDS. RAIN TOTAL ARE EXPECTED TO BE AROUND 0.5 INCHES A
DAY THROUGH WEDNESDAY NIGHT. WITH 91W MOVING NORTHWESTWARD INTO THE
PHILIPPINE SEA, CONDITIONS ARE EXPECTED TO IMPROVE THURSDAY. DRIER
CONDITIONS ARE EXPECTED FOR THE LATTER HALF OF THE WEEK.
MARINE
GENTLE TO MODERATE WINDS WILL PREVAIL THROUGH MIDWEEK, THEN COULD
BECOME LIGHT TO GENTLE FROM MIDWEEK THROUGH THE SECOND HALF OF
THE WEEK. SEAS OF 4 TO 6 FEET WILL SLOWLY SUBSIDE, DROPPING A FOOT
OR SO BY MIDWEEK. DEEP SOUTHWESTERLY MONSOON FLOW WILL KEEP THE
RISK OF SCATTERED AND ISOLATED THUNDERSTORMS IN THE FORECAST FOR
THE NEXT DAY, WITH THE HIGHEST POTENTIAL ON WEDNESDAY. ISOLATED
THUNDERSTORMS WILL REMAIN A RISK THROUGH AT LEAST THE WEEKEND. THERE
WILL BE A MODERATE RISK OF RIP CURRENTS ALONG NORTH AND EAST FACING
REEFS OF THE MARIANAS THROUGH AT LEAST THURSDAY. A MODERATE RISK OF
LIGHTNING WILL CONTINUE THROUGH THE WEEKEND.
TROPICAL SYSTEMS
INVEST 91W IS LOCATED NEAR 12.5N 141.9E, (BETWEEN GUAM AND YAP) AND
HEADING IN A NORTHWESTWARD DIRECTION. THIS SYSTEM IS CURRENTLY RATED
AS HIGH, TROPICAL CYCLONE FORMATION ALERT (TCFA), MEANING THIS SYSTEM
IS LIKELY TO DEVELOP WITHIN 24 HOURS. THIS FEATURE IS PRODUCING
WIDESPREAD, LOCALLY HEAVY SHOWERS AND ISOLATED THUNDERSTORMS. THIS
SYSTEM IS EXPECTED TO STRENGTHEN OVER THE NEXT FEW DAYS AS IT MOVES
DEEPER INTO THE PHILIPPINE SEAS.
FOR MORE INFORMATION ON INVEST 91W, SEE BULLETINS ISSUED BY JTWC
UNDER WMO HEADERS WTPN21 PGTW AND ABPW10 PGTW.
EASTERN MICRONESIA
SATELLITE IMAGERY SHOWS SCATTERED SHOWERS ACROSS MAJURO AND ISOLATED
SHOWERS ACROSS POHNPEI AND KOSRAE. ALTIMETRY SHOWS COMBINED SEAS
BETWEEN 4 AND 7 FEET ACROSS THE REGION.
POHNPEI AND KOSRAE: THE MONSOON-LIKE TROUGH THAT HAS BEEN SITUATED
ACROSS EASTERN MICRONESIA WILL GENERALLY REMAIN NORTH OF POHNPEI AND
KOSRAE. THIS WILL PLACE POHNPEI AND KOSRAE ON THE EDGE OF THE
STRONGER MONSOON CONVECTION TO THE NORTH AND THE SURFACE RIDGE TO
THE SOUTH. THE CURRENT FORECAST CALLS FOR GENTLE TO MODERATE WINDS
WITH ISOLATED TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS OVER
THE NEXT SEVERAL DAYS. SOME UNCERTAINTY IN THE PLACEMENT OF THE
MONSOON TROUGH REMAINS THOUGH. IF THE MONSOON-LIKE TROUGH SETS UP
FURTHER SOUTH, POHNPEI AND KOSRAE WOULD SEE LOCALLY HEAVY SHOWERS AND
GUSTY WINDS TOWARDS THE LATTER HALF OF THE WEEK. ON THE FLIP SIDE,
IF THE MONSOON-LIKE TROUGH SETS UP FURTHER NORTH, THEN SHOWER
COVERAGE WOULD REDUCE TO ISOLATED LATER THIS WEEK. CURRENTLY,
GUIDANCE HAS POHNPEI AND KOSRAE JUST SOUTH OF THE HEAVIER SHOWERS AND
STRONGER WINDS.
MAJURO: AN ACTIVE WEATHER PATTERN CONTINUES ACROSS MAJURO. SCATTERED
SHOWERS ARE ONGOING ACROSS MAJURO AND ARNO ATOLLS. GUIDANCE SHOWS A
SLIGHT TAPERING DOWN OF SHOWERS AND THUNDERSTORMS OVER THE COMING
DAYS AS THE FOCUS SHIFTS TO THE WEST. SOME LOCALLY HEAVY RAINFALL
AND GUSTY WINDS WILL BE POSSIBLE TONIGHT.
ACROSS THE FAR NORTHERN MARSHALL ISLANDS, WIDESPREAD VERY HEAVY
RAINFALL AND SCATTERED THUNDERSTORMS HAVE BEEN SEEN ACROSS BIKINI
ATOLL. STRONG GUSTY WINDS OF 35 TO 40 KT HAVE BEEN SEEN WITHIN THIS
AREA OF CONVECTION. THIS FEATURE IS EXPECTED TO REMAIN NORTH OF
POHNPEI AND KOSRAE OVER THE COMING DAYS, BUT WILL CONTINUE TO BE
MONITORED UNTIL IT EXITS THE REGION.
COMBINED SEAS ARE BETWEEN 4 AND 7 FEET ACROSS EASTERN MICRONESIA.
COMBINED SEAS WILL SEE MINOR FLUCTUATIONS OVER THE NEXT FEW DAYS,
BUT WILL GENERALLY REMAIN WITHIN THE 4 AND 7 FOOT RANGE. SOME CHOPPY
SEAS WILL BE POSSIBLE NEAR HEAVIER SHOWERS, BUT SEAS HAZARDOUS TO
SMALL CRAFT ARE NOT EXPECTED THROUGH THE PERIOD.
WESTERN MICRONESIA
INVEST 91W IS NOW THE SUBJECT OF A TROPICAL CYCLONE FORMATION ALERT
FROM THE JOINT TYPHOON WARNING CENTER. NO DIRECT IMPACTS FROM 91W ARE
EXPECTED ACROSS WESTERN MICRONESIA AS THE DISTURBANCE LIFTS TO THE
NORTHWEST INTO THE PHILIPPINE SEA OVER THE COMING DAYS. THOUGH, A
MONSOON SURGE TO THE SOUTHWEST OF THE DEVELOPING TROPICAL CYCLONE
WILL BRING HIGH-END SCATTERED TO WIDESPREAD SHOWERS, LOCALLY HEAVY AT
TIMES, AND ISOLATED THUNDERSTORMS, TO PORTIONS OF YAP STATE AND
PALAU THROUGH AT LEAST WEDNESDAY. THE HIGHEST SHOWER COVERAGE AND
THUNDERSTORM CHANCES WILL BE AT YAP. PLEASE SEE THE SPECIAL WEATHER
STATEMENT THAT WAS ISSUED FOR YAP STATE AND PALAU FOR ADDITIONAL
INFORMATION. SHOWER AND THUNDERSTORM CHANCES WILL BEGIN FALL BACK TO
MOSTLY SCATTERED STARTING THURSDAY NIGHT AS THE MONSOON SURGE LIFTS
NORTHWARD AS INVEST 91W CONTINUES TO PULL AWAY FROM THE REGION.
MOSTLY GENTLE TO MODERATE WEST TO SOUTHWEST WINDS ARE EXPECTED TO
CONTINUE AT BOTH PALAU AND YAP THROUGH FRIDAY WITH OCCASIONAL GUSTS
UP TO 30 MPH POSSIBLE AT YAP, ESPECIALLY NEAR HEAVIER SHOWERS AND
THUNDERSTORMS. COMBINED SEAS OF 4 TO 6 FEET WILL CONTINUE OVER THE
NEXT COUPLE OF DAYS AT YAP AND PALAU, WITH LOCALLY CHOPPY SEAS
POSSIBLE THROUGHOUT THE COASTAL WATERS OF YAP. SEAS HAZARDOUS TO
SMALL CRAFT ARE NOT EXPECTED THROUGH THE PERIOD, BUT MAY BE LOCALLY
HAZARDOUS NEAR HEAVIER SHOWERS AND THUNDERSTORMS. BE AWARE OF THE
LATEST WEATHER CONDITIONS AND TRENDS BEFORE TRAVELING BETWEEN
ISLANDS.
DRIER CONDITIONS ARE EXPECTED TO PREVAIL AT CHUUK FOR THE NEXT
COUPLE OF DAYS WITH SHOWER CHANCES TOPPING OUT AROUND 30 PERCENT.
SHOWER CHANCES WILL INCREASE STARTING ON FRIDAY AND HIGHER
PRECIPITATION CHANCES WILL LIKELY CONTINUE INTO THE WEEKEND. LIGHT
TO GENTLE WEST TO SOUTHWEST WINDS WILL CONTINUE THROUGH SATURDAY AT
CHUUK. COMBINED SEAS AROUND 4 FEET WILL PERSIST THROUGH THE REST OF
THE WEEK AND MAY DROP A FOOT OR SO AS WE HEAD INTO THE WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: BOWSHER
EAST MICRONESIA: WILLIAMS
WEST MICRONESIA: WHISNANT
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