732
FXPQ50 PGUM 250921
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
721 PM CHST SUN JAN 25 2026
MARIANAS SYNOPSIS
VISIBLE SATELLITE IMAGERY AND DAYTIME SCATTEROMETRY DATA SHOW
WIDESPREAD CLOUDINESS, SCATTERED TO NUMEROUS SHOWERS, AND MODERATE TO
STRONG WINDS ACROSS THE NORTHERN CNMI TODAY, SHIFTING SOUTHWARD
ACROSS TINIAN AND SAIPAN THIS AFTERNOON. GUAM AND ROTA REMAIN SOUTH
OF THIS FEATURE, WITH LIGHT TO MODERATE WINDS AND PATCHY SHOWERS
ACROSS THE ISLANDS AND SCATTERED SHOWERS DEVELOPING ACROSS
NORTHWESTERN ROTA WATERS. ALTIMETRY DATA SHOWS 8 TO 11 FEET NEAR THE
REGION.
DISCUSSION
A SHEAR LINE IS EXPECTED TO PRODUCE UNSETTLED WEATHER FOR THE REGION
OVER THE NEXT FEW DAYS. AS THIS FEATURE DESCENDS FURTHER SOUTH OVER
THE NEXT FEW DAYS, LOCALLY HEAVY SHOWERS WITH STRONG TO NEAR-GALE
FORCE GUSTS ARE POSSIBLE THROUGH MIDWEEK, WITH NUMEROUS TO WIDESPREAD
SHOWERS DEVELOPING TONIGHT FOR TINIAN AND SAIPAN AND SCATTERED TO
NUMEROUS SHOWERS DEVELOPING MONDAY FOR GUAM AND ROTA. LATEST MODEL
GUIDANCE SHOWS THAT THE MAIN CONCERN FOR ANY FLOODING IS WITHIN THE
NEXT 24 TO 36 HOURS WHERE RAINFALL ESTIMATES CAN REACH UP TO 3 TO 6
INCHES PRIMARILY ACROSS THE CNMI, WITH LOCALLY HIGHER AMOUNTS
POSSIBLE. THEN, WINDS NORTH OF THE SHEAR LINE MAY BEGIN TO WEAKEN
SLIGHTLY TUESDAY, HOWEVER, STILL EXPECT AN UNSETTLED WEATHER PATTERN
AS THIS FEATURE CONTINUES TO BRING A STEADY SUPPLY OF SHOWERS THROUGH
WEDNESDAY.
MARINE/SURF
COMBINED SEAS OF 8 TO 11 FEET REMAIN HAZARDOUS TO SMALL CRAFT, DUE
TO A SIGNIFICANT PULSE OF NORTHERLY SWELL AND ELEVATED WIND WAVES,
ASSOCIATED WITH A SHEAR LINE. AS THIS FEATURE DESCENDS FURTHER SOUTH
OVER THE NEXT FEW DAYS, LOCALLY HEAVY SHOWERS WITH STRONG TO NEAR-
GALE FORCE GUSTS ARE POSSIBLE THROUGH MIDWEEK, STARTING TONIGHT FOR
TINIAN AND SAIPAN AND STARTING MONDAY FOR GUAM AND ROTA. A SMALL
CRAFT ADVISORY REMAINS IN EFFECT THROUGH MONDAY AFTERNOON FOR GUAM
AND ROTA AND HAS BEEN EXTENDED THROUGH EARLY TUESDAY MORNING FOR
TINIAN AND SAIPAN, SINCE MODERATE TO STRONG WINDS ARE EXPECTED TO
PERSIST ACROSS THE CNMI FOR A BIT LONGER. SEAS AND WINDS GRADUALLY
RELAX BELOW HAZARDOUS LEVELS TOWARD THE SECOND HALF OF THE WEEK.
A HIGH SURF ADVISORY AND A HIGH RISK OF RIP CURRENTS CONTINUES ALONG
WEST AND NORTH FACING REEFS THROUGH MONDAY AFTERNOON. SURF DECREASES
SLIGHTLY ALONG WEST AND NORTH FACING REEFS AS NORTHERLY SWELL
SUBSIDES AND NORTHEAST TRADE SWELL BECOMES THE PRIMARY SWELL. THIS
MAY ALLOW FOR SURF AND RIP RISK TO FALL BELOW HAZARDOUS LEVELS ALONG
WEST AND NORTH FACING REEFS BY MONDAY EVENING AND BEGIN TO INCREASE
SURF ALONG EAST FACING REEFS. HOWEVER, ANOTHER PULSE OF NORTHWEST TO
NORTH SWELL LOOKS TO ARRIVE LATE MONDAY NIGHT OR TUESDAY, POSSIBLY
CAUSING SURF AND RIP RISK TO INCREASE TO HAZARDOUS LEVELS ALONG WEST
AND NORTH FACING REEFS AROUND MIDWEEK. A MODERATE RISK OF RIP
CURRENTS CONTINUES ALONG EAST FACING REEFS THROUGH MIDWEEK.
EASTERN MICRONESIA
A MOSTLY DIFFUSIVE AND DRY TRADE-WIND REGIME INDUCED BY A COMBINATION
OF A REGION-WIDE NEAR-EQUATORIAL TROUGH (NET) AND AN EXTENSIVE
EAST-WEST ORIENTED SUBTROPICAL RIDGE ACROSS WAKE ISLAND, IS EXPECTED
TO CONTINUE ACROSS MUCH OF EASTERN MICRONESIA THE NEXT SEVERAL DAYS.
MOSTLY ISOLATED SHOWERS ARE EXPECTED FOR MUCH OF THE WEEK, EXCEPT
FOR A SMALL UPTICK IN SHOWER COVERAGE OVER KOSRAE TUESDAY AND TUESDAY
NIGHT AS A MINOR SURFACE TROUGH FORMS UPSTREAM. SIGNIFICANT SHOWER
POTENTIALS ARE NOT EXPECTED TO DEVELOP UNTIL NEXT WEEK, WHEN A MORE
PRONOUNCED ITCZ MAY DEVELOP.
COMBINED SEAS OF 5 TO 6 FEET ARE EXPECTED TO INCREASE A FEW FEET IN
THE SECOND HALF OF THE WEEK, AS NORTHEASTERLY SWELL AND LOCALIZED
WIND WAVES CONTINUE TO INCREASE.
WESTERN MICRONESIA
LATEST SATELLITE IMAGERY SHOWS MOSTLY CLEAR SKIES ACROSS THE REGION
THIS EVENING, WITH ONLY ONE THUNDERSTORMS SEEN SOUTH OF GUAM NEAR
10N. ALTIMETRY SHOWS SEAS OF 9 TO 11 FEET WEST OF PALAU AND WEST
THROUGH NORTHWEST OF YAP PROPER. SEAS ARE BETWEEN 6 AND 8 FEET WEST
OF WENO, CHUUK, AND 4 TO 5 FEET EAST.
A DRY PATTERN CONTINUES ACROSS WESTERN MICRONESIA, WILL POPS
(PROBABILITY OF PRECIPITATION) REMAINING IN THE 10 TO 20 PERCENT
RANGE THROUGH THE END OF THE WEEK FOR PALAU AND YAP, AND THROUGH
MIDWEEK FOR CHUUK. AROUND THURSDAY, A TRADE-WIND TROUGH IS EXPECTED
TO APPROACH CHUUK FROM EASTERN MICRONESIA, BRINGING INCREASED
SHOWERS TO WENO FOR THE LAST HALF OF THE WORK WEEK.
A STRONG SHEAR LINE REMAINS NORTH OF 10N THIS EVENING. THIS SHEAR
LINE CONTINUES TO GENERATE A LARGE NORTHWEST TO NORTH SWELL THAT IS
PRODUCING SEAS UP TO 11 FEET OVER PALAU AND YAP WATERS. MODELS KEEP
TRYING TO BRING THE SEAS DOWN OVER BOTH LOCATIONS, HOWEVER,
ALTIMETRY SUPPORTS MAINTAINING A SMALL CRAFT ADVISORY (SCA) AT BOTH
PALAU AND YAP. THE SCA FOR BOTH LOCATIONS WAS EXTENDED ANOTHER 12
HOURS BASED ON ALTIMETRY WEST OF PALAU AND WEST THROUGH NORTHWEST OF
YAP, AND A SOFAR BUOY WELL WEST-NORTHWEST OF PALAU. ALTIMETRY SHOWS
SEAS OF 9 TO 11 FEET FOR BOTH YAP AND PALAU, WHILE THE SOFAR BUOY
SHOWS SEAS REMAIN ELEVATED WELL WEST-NORTHWEST OF PALAU. SEAS ARE
EXPECTED TO SUBSIDE BY MONDAY MORNING FOR PALAU AND BY TUESDAY
MORNING FOR YAP. HOWEVER, IF ALTIMETRY CONTINUES TO SHOW ELEVATED
SEAS, THE SCAS MAY NEED TO BE EXTENDED AGAIN. FOR WINDS, YAP WILL SEE
LIGHT TO GENTLE WINDS BECOMING GENTLE TO MODERATE LATE IN THE WEEK.
MEANWHILE, PALAU WILL MAINTAIN LIGHT TO GENTLE WINDS THROUGH THE
WEEK. FOR CHUUK, COMBINED SEAS OF 5 TO 7 FEET WILL BUILD TO BETWEEN 6
AND 8 FEET AS EARLY AS TUESDAY. AS THE NORTH SWELL, CURRENTLY
AFFECTING PALAU, YAP AND THE MARIANAS, MOVES INTO THE REGION, IT
COULD RESULT IN HAZARDOUS SURF ALONG NORTH FACING REEFS TUESDAY OR
WEDNESDAY. WINDS WILL BE GENTLE TO MODERATE THROUGH THE WEEK FOR
WENO.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR GUZ001.
HIGH SURF ADVISORY UNTIL 6 PM CHST MONDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 6 PM CHST MONDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 6 PM CHST MONDAY FOR
PMZ151-152.
SMALL CRAFT ADVISORY UNTIL 6 AM CHST TUESDAY FOR PMZ153-154.
MARIANAS: CRUZ
EAST MICRONESIA: MONTVILA
WEST MICRONESIA: KLEESCHULTE
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