193
FXPQ50 PGUM 220857
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
657 PM CHST MON DEC 22 2025
MARIANAS SYNOPSIS
A SMALL CRAFT ADVISORY, A HIGH SURF ADVISORY AND A HIGH RISK OF RIP
CURRENTS STATEMENT REMAIN IN EFFECT.
SATELLITE IMAGERY SHOWS CLOUDY SKIES, WHILE RADAR SHOWS SCATTERED TO
NUMEROUS SHOWERS OVER THE REGION. ALTIMETRY SHOWS 9 TO 12 FEET TO THE
NORTHWEST OF THE MARIANAS AND BUOY DATA SHOWS SEA HEIGHTS AROUND 9 TO
10 FEET AT RITIDIAN POINT. AS OF 4 PM CHST, 1.41 INCHES OF RAIN HAVE
FALLEN AT THE AIRPORT.
DISCUSSION
WET AND GUSTY CONDITIONS PREVAILED TODAY, DUE TO A ROBUST TRADE-WIND
TROUGH ALONG THE EDGE OF A FRAGMENTED SHEAR LINE AND TRADE-WIND SURGE
JUST TO THE EAST OF THE MARIANAS. TOGETHER, THESE FEATURES COMBINED
TO PRODUCE NUMEROUS SHOWERS AND SCATTERED THUNDERSTORMS OVER GUAM
TODAY. THE SURFACE TROUGH WILL CONTINUE TO MOVE WESTWARD AND AWAY
FROM THE AREA TONIGHT, WHILE THE TRADE-WIND SURGE DIMINISHES IN
STRENGTH AND AREAL COVERAGE JUST EAST OF THE ISLANDS, WHICH SHOULD
ALLOW FOR A BRIEF PERIOD OF RELATIVELY DRIER WEATHER TOMORROW.
FOR GUAM AND ROTA, A FEW ROUNDS OF SCATTERED SHOWERS ARE EXPECTED
THROUGH CHRISTMAS DAY, MAINLY FROM PASSING TRADE-WIND TROUGHS AND
INCREASED TRADE-WIND CONVERGENCE, AS THE SUBTROPICAL RIDGE BUILDS
JUST NORTHEAST OF THE CNMI AND INCREASES THE PRESSURE GRADIENT
NEARBY. CURRENT MODEL GUIDANCE POINTS TO RELATIVELY DRIER WEATHER
TOWARD THE END OF THE WEEK, BUT STILL HINTS AT THE POSSIBILITY OF
SOME SHEARLINE FRAGMENT-INDUCED SHOWERS AROUND FRIDAY AND SATURDAY.
MARINE/SURF
THIS IS WHERE THE MAIN CONCERNS ARE AT. SEAS ARE EXPECTED TO REMAIN
ELEVATED AND MAY EXCEED 11 FEET AT TIMES OVER THE NEXT DAY OR SO.
WINDS HAVE DIMINISHED TO MODERATE TO FRESH. SURF ALONG NORTH FACING
REEFS REMAINS ELEVATED AND MAY REACH UP TO 12 FEET AT TIMES TONIGHT
AND EARLY TUESDAY. SURF ALONG EAST FACING REEFS HAS FALLEN BELOW THE
12 FOOT THRESHOLD FOR HAZARDOUS SURF CONDITIONS, AND THE HIGH SURF
ADVISORY HAS BEEN DROPPED FOR EAST REEFS. THE HIGH SURF ADVISORY FOR
NORTH FACING REEFS, AND THE HIGH RIP CURRENT RISK FOR NORTH AND EAST
FACING REEFS WERE EXTENDED THROUGH EARLY WEDNESDAY MORNING. THE SMALL
CRAFT ADVISORY WAS EXTENDED THROUGH TUESDAY AFTERNOON, AFTER WHICH
COMBINED SEAS ARE EXPECTED TO DIMINISH TO 7 TO 9 FEET OVER COASTAL
WATERS, BELOW LEVELS HAZARDOUS TO SMALL CRAFT. REGARDLESS, WHETHER
YOU ARE A BOATER, SURFER OR BEACH GOER, THE SEAS AND SURF ARE NOT
EXPECTED TO BE KIND FOR THE NEXT FEW DAYS. SEAS LOOK TO INCREASE ONCE
MORE IN THE LATTER HALF OF THE WEEK AS ANOTHER SIGNIFICANT NORTH TO
NORTHEAST SWELL ENTERS THE AREA, AND WILL BE MONITORED CLOSELY FOR
THE ISSUANCE OF ADDITIONAL SEA AND SURF HAZARDS.
EASTERN MICRONESIA
THE TAIL-END OF A BROAD MID-LATITUDE LOW PRESSURE FRONTAL SYSTEM
EXTENDS INTO THE REGION AT AROUND 12N180 AND TRANSITIONS INTO A
WEAKENING SHEAR LINE ACROSS THE NORTHERN MARSHALLS, PASSES NEAR
KOSRAE AND POHNPEI, THEN MEETS A BROAD SURFACE TROUGH IN SOUTHERN
CHUUK AND POHNPEI STATES. A BAND OF WIDESPREAD, PATCHY CLOUDS AND
SHOWERS ARE FOUND ALONG THIS BOUNDARY, WITH CONVECTION DEEPENING
SOUTHWEST OF POHNPEI, CLOSER TO THE AFOREMENTIONED TROUGH. KOSRAE AND
MAJURO ARE SLIGHTLY SOUTH OF THE CONVECTION, SO ONLY ISOLATED
SHOWERS ARE EXPECTED TONIGHT, WITH SHOWERS STARTING TO FILL IN NEAR
MAJURO AFTER MIDNIGHT. SCATTERED SHOWERS AND A SLIGHT CHANCE OF
THUNDERSTORMS ARE EXPECTED AT POHNPEI TONIGHT, BUT AS THE TROUGH
CONTINUES TO MOVE FARTHER WESTWARD AND THE SHEAR LINE CONTINUES TO
DISSIPATE, OVERALL SHOWERS DECREASE TO ISOLATED BY TUESDAY NIGHT.
ISOLATED TO SCATTERED SHOWERS ARE EXPECTED FARTHER EAST OVER KOSRAE
AND MAJURO THIS WEEK, THEN THE INTERTROPICAL CONVERGENCE ZONE (ITCZ)
LOOKS TO BUILD BACK IN OVER THE DATE LINE LATE WEEK.
LATEST ALTIMETRY AND BUOY DATA SHOW SEAS ARE 4 TO 7 FEET AT KOSRAE
AND 6 TO 8 FEET NEAR POHNPEI AND MAJURO. HAZARDOUS SURF IS STILL
EXPECTED ALONG NORTH REEFS OF POHNPEI AND KOSRAE, BUT HAVE EXTENDED
ANOTHER 12 HOURS TO BETTER ENCOMPASS THE INCOMING PULSE OF LONG-
PERIOD NORTHERLY SWELL, EXPECTED TO ARRIVE LATE TONIGHT AND EARLY
TUESDAY MORNING. OTHERWISE, RETAINED A SIMILAR UNCERTAINTY CONVEYED
IN THE PREVIOUS FORECAST DISCUSSION, TO MONITOR THE DURATION OF LONG-
PERIOD NORTHERLY SWELL IN SUBSEQUENT MODEL RUNS BEFORE DECIDING TO
EXTEND THE ADVISORY TOO FAR OUT. WITH THIS PULSE IN NORTHERLY SWELL,
SEAS NEAR POHNPEI ARE EXPECTED TO INCREASE TO 7 TO 9 FEET ON TUESDAY,
POSSIBLY NEARING HAZARDOUS LEVELS OF 10 FEET.
WESTERN MICRONESIA
MUCH OF FAR WESTERN MICRONESIA REMAINS UNDER A RELATIVELY DRY TRADE-
WIND PATTERN, WITH ISOLATED TO SCATTERED SHOWERS LOOSELY FOCUSED
AROUND A SHALLOW TROUGH JUST WEST OF PALAU, AND A NORTHWEST-TO-
SOUTHEAST ORIENTED BAND OF WEAK TRADE-WIND CONVERGENCE JUST EAST OF
YAP. SHOWERS LOOK TO DECREASE NEAR PALAU OVERNIGHT AS THE TROUGH
MOVES AWAY, AND INCREASE SLIGHTLY NEAR YAP LATE OVERNIGHT AS A
ROBUST TRADE-WIND TROUGH, CURRENTLY LOCATED JUST WEST OF THE
MARIANAS, SHIFTS WESTWARD TOWARDS THE AREA WITH TRADE-WIND
CONVERGENCE INCREASING SLIGHTLY AHEAD OF IT. HOWEVER, MOST OF THE
UNSETTLED WEATHER IN THE REGION IS LOCATED MUCH FURTHER EAST, JUST
SOUTH OF CHUUK LAGOON. NUMEROUS TO WIDESPREAD SHOWERS AND ISOLATED
THUNDERSTORMS ARE FOCUSED ALONG A ROBUST TRADE-WIND TROUGH WHICH
EXTENDS SOUTHWEST FROM AROUND 7N154E, JUST SOUTHEAST OF CHUUK COASTAL
WATERS, INTO A BUFFER CIRCULATION CENTERED AROUND EQ145E. MODEL
GUIDANCE DEPICTS THIS TROUGH LIFTING NORTHWEST OVER THE NEXT DAY OR
SO, BRINGING NUMEROUS LOCALLY HEAVY SHOWERS AND ISOLATED
THUNDERSTORMS TO CHUUK ON TUESDAY, TAPERING DOWN TO SCATTERED
SHOWERS LATE TUESDAY NIGHT AS THE TROUGH SHIFTS WEST OF THE AREA.
THIS FEATURE WILL INCREASE SHOWERS FOR YAP AND PALAU AROUND THURSDAY
THROUGH SATURDAY AS IT TRANSITS WESTWARD THROUGH THE AREA, EXITING
WEST OF THE REGION AROUND SUNDAY.
LATEST ALTIMETRY DATA INDICATES COMBINED SEAS AROUND 5 TO 7 FEET NEAR
PALAU, AND 6 TO 8 FEET FOR YAP AND CHUUK. A BUILDING NORTHEAST TRADE
SWELL WILL MOVE INTO THE REGION THIS EVENING, AND IS EXPECTED TO
BRING HAZARDOUS SURF UP TO 10 FEET FOR NORTH FACING REEFS OF CHUUK,
POTENTIALLY INCREASING AS HIGH AS 11 FEET TUESDAY. A HIGH SURF
ADVISORY IS IN EFFECT UNTIL 5 PM CHST THURSDAY, WHEN THE NORTHEAST
SWELL AND ASSOCIATED SURF ARE EXPECTED TO DIMINISH BELOW HAZARDOUS
LEVELS FOR CHUUK. FOR NOW, SEAS AND SURF LOOK TO REMAIN BELOW
HAZARDOUS LEVELS AT PALAU AND YAP, HOWEVER, A SLIGHT INCREASE IN THE
EXPECTED NORTHEAST SWELL COULD CHANGE THIS. SEAS MAY STILL SEE AN
INCREASE UP TO AROUND 10 FEET FOR CHUUK FOR TUESDAY AND TUESDAY
NIGHT, BUT MODEL TRENDS HAVE BACKED OFF SLIGHTLY WITH THE 10-FOOT
SEAS REMAINING FURTHER NORTH, AND COMBINED SEAS ARE EXPECTED TO
INCREASE TO AROUND 7 TO 9 FEET OVER CHUUK COASTAL WATERS. GENTLE TO
MODERATE WINDS ARE EXPECTED AT CHUUK THROUGH THE WEEK. FOR YAP AND
PALAU, GENTLE TO MODERATE WINDS WILL BECOME LIGHT TO GENTLE BY
MIDWEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH LATE TUESDAY NIGHT FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 AM CHST WEDNESDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH LATE TUESDAY NIGHT FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 AM CHST WEDNESDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 6 PM CHST TUESDAY FOR PMZ151>154.
MARIANAS: BOWSHER/DECOU
EAST MICRONESIA: CRUZ
WEST MICRONESIA: DECOU
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page