889
FXPQ50 PGUM 210826
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
626 PM CHST SUN DEC 21 2025
MARIANAS SYNOPSIS
THERE IS A SMALL CRAFT ADVISORY (SCA), A HIGH SURF ADVISORY (HSA)
AND A HIGH RISK OF RIP CURRENTS (HRRC) STATEMENT IN EFFECT.
SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES, WHILE RADAR IMAGERY
SHOWS ONLY ISOLATED SHOWERS OUTSIDE OF GUAM'S SOUTHERN WATERS.
ALTIMETRY SHOWS 10 TO 11 FOOT SEAS JUST EAST OF THE ISLANDS. BUOY
DATA SHOWS HEIGHTS OF 8 TO 11 FEET.
DISCUSSION
A MOSTLY PLEASANT TRANSITION SEASON WEATHER PATTERN HAS SET UP OVER
THE REGION. WINDS WILL BE THE MAIN CONCERN OVER THE NEXT SEVERAL
DAYS. WINDS ARE EXPECTED TO BE 15 TO 20 MPH. MONDAY, THERE IS A BIT
OF SPEED CONVERGENCE THAT MAY BRING SOME SHOWERS TO GUAM. OVERALL A
DRY, BUT WINDIER, WEATHER PATTERN IS IN STORE FOR THE ISLANDS.
MARINE/SURF
THIS IS WHERE THE MAIN CONCERNS ARE AT. SEAS ARE EXPECTED TO REMAIN
ELEVATED AND MAY REACH UP TO 12 FEET OVER THE NEXT FEW DAYS. WINDS
ARE EXPECTED TO BE MODERATE TO STRONG. SURF ALONG NORTH AND EAST
FACING REEFS WILL ALSO BE ELEVATED AND SURF ALONG THESE REEFS MAY
REACH UP TO 13 FEET. EAST FACING REEFS ARE SLIGHTLY DELAYED BY ABOUT
12 HOURS OR SO. REGARDLESS, WHETHER YOU ARE A BOATER, SURFER OR BEACH
GOER, THE SEAS AND SURF ARE NOT EXPECTED TO BE KIND FOR THE NEXT
SEVERAL DAYS.
EASTERN MICRONESIA
THE MAIN FEATURE TO WATCH THE NEXT FEW DAYS IS THE NORTHERLY SWELL.
AS STATED IN THE ADDITIONAL DETAILS OF THE HIGH SURF ADVISORY ISSUED
EARLIER THIS MORNING, SURF DID SUBSIDE BELOW THE 9 FOOT THRESHOLD
FOR NORTH-FACING REEFS AT KOSRAE. HOWEVER, A NEW NORTHERLY SWELL WILL
ARRIVE SOMETIME DURING THE LATTER HALF OF MONDAY. SEEING THAT THIS
WAS WITHIN 12 TO 18 HOURS OF THE AFTERNOON FORECAST PACKAGE ISSUANCE
AND IN COORDINATION WITH THE PREVIOUS SHIFT'S MESSAGING, WE OPTED TO
KEEP THE ADVISORY GOING AT KOSRAE. MEANWHILE, THE POHNPEI BUOY
OBSERVATION SHOWS SEAS NEAR 8 FEET, NORTHEAST SWELL NEAR 6 FEET,
WITH A PERIOD OF 13 SECONDS, WHICH EQUATES TO A SURF OF 9 FEET. THIS
ADVISORY IS CURRENTLY SET TO EXPIRE AT 3 PM TUESDAY, BUT THIS MAY
NEED TO BE EXTENDED AS THE MODEL GUIDANCE CONTINUES TO SHOW HAZARDOUS
CONDITIONS POTENTIALLY CONTINUING THROUGH THURSDAY, POSSIBLY LONGER.
OTHERWISE, A SLOW-MOVING TROUGH STRETCHES FROM KOSRAE TO MAJURO, WITH
AN AREA OF STRONGER SURFACE CONVERGENCE NOTED BETWEEN POHNPEI AND
KOSRAE. THIS CONVERGENCE AND THE TROUGH IS ALLOWING FOR WIDELY-
SCATTERED SHOWERS TO DEVELOP NEAR BOTH OF THOSE LOCATIONS, WHILE
REMAINING MORE ISOLATED NEAR MAJURO. WE'LL KEEP AN EYE ON MAJURO
THOUGH FOR ANY POTENTIAL INCREASE IN SHOWER COVERAGE GIVEN THE
BOUNDARY IS IN YOUR NORTHWESTERN COASTAL WATERS, CLOSE ENOUGH TO
STILL ACT AS A FOCUS FOR CONVECTIVE DEVELOPMENT.
LOOKING AHEAD, PRECIPITATION-WISE, THE GFS GDI FORECASTS ARE RATHER
PALTRY WITH UPSTREAM SATELLITE IMAGERY NOT SHOWING MUCH CONVECTION
ASSOCIATED WITH AN UPSTREAM AREA OF CONVERGENCE LOCATED NEAR 170W.
IT REMAINS TO BE SEEN IF TROUGH GENESIS WILL TAKE PLACE, ALLOWING
MOISTURE TO POOL ALONG IT. SHOULD THIS OCCUR, CONVECTIVE COVERAGE
WOULD INCREASE AS IT HEADS WEST ACROSS THE DATE LINE AND INTO EASTERN
MICRONESIA. WE'VE SEEN THIS SCENARIO PLAY OUT LIKE THAT A FEW TIMES
OVER THE LAST FEW MONTHS, BUT, MORE OFTEN THAN NOT IT ISN'T AS ROBUST
OR WIDESPREAD AS THE MODELS SHOW. THUS, LATER FORECASTS MAY NEED TO
TREND DOWN RAINFALL POTENTIAL FOR THE LATTER HALF OF THE WEEK.
WESTERN MICRONESIA
THE LATEST SATELLITE DATA SHOWS PARTLY CLOUDY SKIES WITH SPOTTY
SHOWERS OVER YAP AND CHUUK. MOSTLY CLOUDY SKIES WITH SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS ARE FOUND OVER PALAU. ALTIMETRY
SHOWS SEAS OF 5 TO 7 FEET FOR PALAU AND YAP, WITH 5 TO 8 FEET NEAR
AND NORTHEAST OF CHUUK.
AN OVERALL DRY PATTERN IS IN PLACE ACROSS WESTERN MICRONESIA. THE
ONLY EXCEPTION IS OVER PALAU. AT PALAU, LOW-END SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS REMAIN OVER THE REPUBLIC THIS AFTERNOON.
HOWEVER, THIS CONVECTION IS DRIFTING NORTHWEST, WITH THE DRIER
PATTERN MOVING INTO PALAU LATER THIS EVENING. FOR CHUUK, INCREASING
SHOWERS LOOK TO MOVE INTO THE AREA MONDAY AFTERNOON OR EVENING AS A
COUPLE OF WEAK TRADE-WIND TROUGHS APPROACH. THE TROUGHS WILL BRING
POPS (PROBABILITY OF PRECIPITATION) OF 30 TO 40% TO WENO THROUGH
TUESDAY NIGHT. DRY CONDITIONS THEN LOOK TO RETURN TO CHUUK AROUND
MIDWEEK. FOR YAP AND PALAU, THE TROUGHS MOVING THROUGH CHUUK LOOK TO
APPROACH THE REGION LATER IN THE WEEK, BRINGING AN INCREASE IN
SHOWERS AND A SLIGHT CHANCE OF THUNDERSTORMS TO THE AREA THURSDAY
INTO FRIDAY.
THE MARINE FORECAST REMAINS RELATIVELY UNCHANGED. A BUILDING
NORTHEAST TRADE-WIND SWELL LOOKS TO MOVE INTO THE REGION BEGINNING
MONDAY NIGHT. 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. HIGHER SEAS ARE EXPECTED TO MOVE
INTO CHUUK MONDAY AFTERNOON OR EVENING. THE TRADE SWELL LOOKS TO BE
IN THE 6 TO 8 FOOT RANGE, RESULTING IN HAZARDOUS SURF CONDITIONS
ALONG NORTH FACING REEFS. THEREFORE, A HIGH SURF ADVISORY WAS ISSUED
FOR NORTH FACING REEFS OF CHUUK BEGINNING MONDAY AFTERNOON. SEAS OF
UP TO 10 FEET REMAIN A POSSIBILITY FOR CHUUK FOR TUESDAY AND TUESDAY
NIGHT. THEREFORE, A SMALL CRAFT ADVISORY IS A POSSIBILITY AS EARLY AS
TUESDAY MORNING. 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 MONDAY NIGHT FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 AM CHST TUESDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH LATE MONDAY NIGHT FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 AM CHST TUESDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM CHST TUESDAY FOR
PMZ151>154.
MARIANAS: BOWSHER
EAST MICRONESIA: DOLL/KLEESCHULTE
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