645
FXPQ50 PGUM 260819
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
619 PM CHST WED AUG 26 2026
MARIANAS SYNOPSIS
LEFTOVER STRATIFORM CLOUDS FROM THIS MORNINGS HEAVY RAINS AS WELL AS
SOME ISOLATED SHOWERS ARE VISIBLE OVER THE MARIANAS THIS EVENING.
LIGHT WINDS ARE FROM THE WEST AND NORTH AS THE COL CONTINUES TO
PERSIST OVER THE REGION. MODELS INDICATE COMBINED SEAS ARE 4 TO 5
FEET.
DISCUSSION
SHOWERS ARE EXPECTED TO BECOME SCATTERED WITH ISOLATED THUNDERSTORMS
TONIGHT. SHOWER COVERAGE MAY INCREASE BY MORNING FOR GUAM AND ROTA
WITH LOCALLY HEAVY SHOWERS POSSIBLE. MEANWHILE, TINIAN AND SAIPAN
LOOK TO HAVE ISOLATED SHOWERS IN THE MORNING, WITH SCATTERED ISLAND
EFFECT SHOWERS POSSIBLE AND DRIFTING EAST OR NORTHEAST. THE GRADIENT
OF HIGHER MOISTURE OVER GUAM AND ROTA WILL LIKELY REMAIN THURSDAY
NIGHT BEFORE PUSHING NORTH FRIDAY AND BRINGING THE POTENTIAL FOR
SCATTERED, LOCALLY HEAVY SHOWERS AND ISOLATED THUNDERSTORMS TO ALL
ISLANDS. WINDS WILL ALSO LIKELY INCREASE TO GENTLE TO MODERATE AS THE
MONSOON FLOW SHIFTS NORTH. THIS WET PATTERN MAY CONTINUE INTO THE
WEEKEND AND NEXT WEEK DEPENDING ON THE TRACK AND INTENSITY OF NEARBY
INVEST 90W. THIS WILL BE MONITORED CLOSELY THROUGHOUT THE NEXT WEEK.
MARINE
COMBINED SEAS HAVE BECOME MELLOW AT 4 TO 5 FEET AND ARE EXPECTED
TO PERSIST UNTIL ABOUT FRIDAY NIGHT AS A NEW MONSOON SURGE DEVELOPS
TO THE WEST, POSSIBLY CO-LOCATED WITH A TROPICAL DISTURBANCE. THIS
MAY ALLOW FOR SEAS TO REACH NEAR HAZARDOUS CONDITIONS FOR SMALL CRAFT
BY THE END OF THE FORECAST PERIOD, HOWEVER THIS REMAINS HIGHLY
UNCERTAIN. CURRENTLY, THERE A MODERATE RISK OF RIP CURRENTS ALONG
NORTH, SOUTH, AND WEST FACING REEFS CONTINUES OVER THE NEXT FEW DAYS,
POSSIBLY BECOMING LOW FOR SOUTH FACING REEFS SOMETIME THURSDAY.
THERE IS ALSO A MODERATE RISK OF LIGHTNING FOR THE NEXT SEVERAL DAYS.
LIGHT WESTERLY WINDS WILL START TO VERY GRADUALLY INCREASE TONIGHT
THROUGH FRIDAY. AN UNSETTLED, BUT DISORGANIZED MONSOON PATTERN IS
EXPECTED TO CONTINUE TO BRING PERIODS OF SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS THIS WEEK WITH LOCALLY HEAVY SHOWERS POSSIBLE
BY LATE TONIGHT THROUGH AT LEAST FRIDAY. HOWEVER, THE LOCALLY HEAVY
SHOWERS WILL LIKELY REMAIN ISOLATED TO GUAM AND ROTA THROUGH THURSDAY
NIGHT.
TROPICAL SYSTEMS
INVEST 99W WAS UPGRADED TO TROPICAL DEPRESSION 20W BY THE JOINT
TYPHOON WARNING CENTER (JTWC) THIS AFTERNOON, TD 20W WILL NOT IMPACT
THE MARIANAS OR MICRONESIA AS IT MOVES NORTHWARD WELL WEST OF WAKE
ISLAND OVER THE COMING DAYS. THE OVERALL ENVIRONMENT REMAINS
FAVORABLE FOR INTENSIFICATION OVER THE NEXT FEW DAYS. FOR MORE
INFORMATION ON 20W, PLEASE REFER TO BULLETINS FROM JTWC UNDER WMO
HEADERS WTPN21 PGTW AND ABPW10 PGTW.
INVEST 90W REMAINS RATED SUB-LOW BY JWTC LATE THIS AFTERNOON, MEANING
NO DEVELOPMENT IS EXPECTED OVER THE NEXT FEW DAYS. THE DISTURBANCE IS
LOCATED AROUND 15N153E AND ERRATIC MOVEMENT IN THIS GENERAL LOCATION
IS EXPECTED OVER THE NEXT FEW DAYS. 90W WILL CONTINUE TO BE
MONITORED FOR FURTHER DEVELOPMENT.
EASTERN MICRONESIA
MOSTLY DRY CONDITIONS ARE EXPECTED TO PERSIST ACROSS THE FORECAST
SITES THROUGH FRIDAY WITH SHOWER CHANCES TOPPING OUT AROUND 30
PERCENT. GENTLE TO MODERATE WEST TO SOUTHWEST WINDS WILL CONTINUE AT
POHNPEI FOR THE NEXT SEVERAL DAYS WHILE LIGHT TO GENTLE WINDS PERSIST
AT KOSRAE AND MAJURO. COMBINED SEAS AROUND 4 TO 6 FEET WILL PREVAIL
FOR THE REST OF THE WEEK WITH SEAS CONSISTING OF A SOUTH TO SOUTHEAST
SWELL AND A NORTHEAST SWELL. OTHERWISE, THE SOUTH TO SOUTHEAST SWELL
WILL CONTINUE TO PROMOTE ELEVATED SURF ALONG SOUTH-FACING REEFS AT
KOSRAE.
WESTERN MICRONESIA
SATELLITE IMAGERY SHOWS NUMEROUS TO WIDESPREAD SHOWERS AND ISOLATED
THUNDERSTORMS ACROSS YAP STATE AND SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ACROSS CHUUK STATE. ISOLATED SHOWERS ARE SEEN ACROSS
PALAU. ALTIMETRY SHOW COMBINED SEAS BETWEEN 4 AND 7 FEET ACROSS
THE REGION.
AN ACTIVE MONSOON PATTERN WILL CONTINUE TO BRING SCATTERED TO
NUMEROUS, LOCALLY HEAVY, SHOWERS AND ISOLATED TO SCATTERED
THUNDERSTORMS ACROSS PORTIONS OF YAP STATE THROUGH THURSDAY NIGHT.
SEVERAL INCHES OF RAIN HAVE ALREADY FALLEN WITH THIS EVENT, WHICH IS
ON TOP OF THE FOOT OF RAIN YAP SAW LAST WEEK. DUE TO SATURATED
CONDITIONS, FLASH FLOODING AND MUDSLIDES ARE EXPECTED WHERE THE
HEAVIEST RAIN OCCURS. PLEASE SEE THE SPECIAL WEATHER STATEMENT FOR
YAP FOR MORE DETAILS. ONCE THE ACTIVE MONSOON PATTERN LIFTS
NORTHWARD, DRIER CONDITIONS WILL RETURN TO YAP WITH ISOLATED LIGHT
SHOWERS POSSIBLE LATE THIS WEEK AND INTO THE WEEKEND. THIS DRY
STRETCH WILL ALSO EXTEND DOWN TO PALAU WHERE LITTLE RAINFALL IS
EXPECTED OVER THE NEXT WEEK OR SO.
FOR CHUUK, ISOLATED TO SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
WILL BE IN THE FORECAST THROUGH SATURDAY. BY SUNDAY AND INTO MONDAY,
THE MONSOON PATTERN LOOKS TO REORIENT ITSELF BRINGING THE ACTIVE
PHASE OVER CHUUK STATE. SHOWER CHANCES LOOK TO INCREASE TO 50 POPS
ON SUNDAY, AND 60 POPS ON MONDAY. THE ACTIVE PATTERN LOOKS TO
CONTINUE UNTIL THE MIDDLE OF NEXT WEEK.
MARINE CONDITIONS WILL REMAIN CHOPPY ACROSS YAP STATE THROUGH
THURSDAY NIGHT. WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS WILL
BE ACCOMPANIED BY FREQUENT LIGHTNING AND WIND GUSTS TO 25 KT. ONCE
THIS ACTIVE PATTERN SHIFTS NORTHWARD, COMBINED SEAS ARE EXPECTED TO
BE BENIGN. BENIGN SEAS ARE SEEN ACROSS PALAU AND CHUUK. SEA
CONDITIONS MAY BECOME CHOPPY LATE THIS WEEK FOR CHUUK AS SHOWERS AND
THUNDERSTORMS INCREASE IN COVERAGE.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA: WILLIAMS
WEST MICRONESIA: WHISNANT
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