384
FXPQ50 PGUM 261954
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
554 AM CHST SAT DEC 27 2025
MARIANAS UPDATE
CLOUDINESS AND A FEW SHOWERS FROM AN OLD SHEAR LINE ARE STILL LURKING
JUST EAST OF THE MARIANAS. HOWEVER, IT SEEMS CLOUD TOPS MAY HAVE
WARMED SLIGHTLY, RADAR IS SINGULARLY UNIMPRESSIVE, AND THE DIURNAL
CYCLE IS TURNING AGAINST THEM. SO, I MADE ALL THE ISLANDS ISOLATED.
PUT A FEW POCKETS OF SCATTERED IN THE WATERS, JUST NOT ENOUGH TO
FILL THE ZONES, ONLY TO GIVE AN IDEA THAT THERE COULD BE POCKETS OUT
THERE. OTHERWISE THE FORECAST LOOKED GOOD, SO NO CHANGES MADE.
EASTERN MICRONESIA UPDATE
JUST AN OLD SHEAR LINE THAT IS SLOWLY WASHING OUT. THE INHERITED
FORECAST HAD THIS WELL HANDLED, SO NO CHANGES WERE NEEDED. ALSO RE-
ISSUED THE ADVISORIES.
WESTERN MICRONESIA UPDATE
MUCH OF THE CONVECTION IN WESTERN MICRONESIA STRATIFIED OUT AND WAS
NO LONGER SUSPECT OF LIKELY OR EVEN SCATTERED SHOWERS. SO, CHANGED
THE THREE MAJOR ISLANDS TO ISOLATED FOR TODAY, AND REMOVED THE
THUNDERSTORMS ALSO. SCATTERED RE-ENTERS THE FORECAST FOR TONIGHT,
THAT WILL HAVE TO BE RE-ASSESSED TODAY BASED ON HOW THE CONVECTION
DEVELOPS OVER THE COURSE OF THE DAY.
PREV DISCUSSION
/ISSUED 602 PM CHST FRI DEC 26 2025/
MARIANAS SYNOPSIS...
ISOLATED SHOWERS CONTINUE TO MOVE ALONG A SHEAR LINE JUST EAST AND
NORTHEAST OF SAIPAN, WITH PARTLY CLOUDY SKIES CONTINUING AREA-WIDE.
SEAS HAVE DROPPED INTO THE 6 TO 8 FOOT RANGE UNDER GENTLE TO MODERATE
WINDS.
DISCUSSION...
THE MAIN FORECAST CHALLENGE WAS RAINFALL POTENTIAL AT TINIAN AND
SAIPAN. WE DECIDED TO INCREASE SHOWER COVERAGE TO SCATTERED (30
PERCENT PROBABILITIES) AS SHOWERS ARE LURKING JUST OFFSHORE OF
SAIPAN, AS THEY MOVE NORTHWEST ALONG A SHEAR LINE. THIS SHEAR LINE
MAY SETTLE SLOWLY SOUTH TONIGHT JUST ENOUGH TO ALLOW AT LEAST A
BRIEFLY-INCREASED RAINFALL POTENTIAL. GIVEN THAT TINIAN IS JUST A FEW
MILES SOUTH, IT MADE SENSE TO INCLUDE THEM AS WELL, ALTHOUGH
POTENTIAL THERE IS MORE "IFFY". OTHERWISE, LOOK FOR A DRY TRADE-WIND
PATTERN TO CONTINUE WITH ANY INCREASED SHOWER COVERAGE/POTENTIAL TIED
TO SHEAR LINE MOVEMENT THE NEXT SEVERAL DAYS.
MARINE...
ALTIMETRY THIS AFTERNOON SHOWS SEAS HAVE DIMINISHED, WITH BUOY
OBSERVATIONS SHOWING THE SAME. AS SUCH, THE ADVISORIES WERE ALLOWED
TO EXPIRE. HOWEVER, ANOTHER BRIEF INCREASE IN SEAS AND SURF REMAINS
POSSIBLE SUNDAY INTO MONDAY. OTHERWISE, GENTLE TO MODERATE WINDS WILL
PREVAIL.
EASTERN MICRONESIA...
PARTLY CLOUDY SKIES WITH ISOLATED SHOWERS PREVAIL ACROSS EASTERN
MICRONESIA THIS AFTERNOON. ALTIMETRY DATA SHOWS SEAS OF 4 TO 6 FEET
FOR MAJURO AND 6 TO 8 FEET FOR POHNPEI AND KOSRAE. POHNPEI BUOY SHOWS
SEAS OVER 8 FEET.
A DRY TRADE-WIND PATTERN IS IN PLACE ACROSS EASTERN MICRONESIA THIS
AFTERNOON. THE SHEAR LINE FRAGMENT THAT PRODUCED A BRIEF INCREASE IN
SHOWERS THIS MORNING HAS CONTINUED TO WEAKEN, RESULTING IN DECREASED
SHOWERS. THIS DRY PATTERN LOOKS TO CONTINUE THROUGH SATURDAY. FOR
SATURDAY NIGHT, INCREASING CONVERGENCE ACROSS EASTERN MICRONESIA
LOOKS TO BRING INCREASED SHOWERS TO THE ISLANDS THE MAIN AREA OF
CONVECTION LOOKS TO BE SOUTH OF POHNPEI AND MAJURO, WITH KOSRAE
SEEING MOST OF THE SHOWERS AND POSSIBLE THUNDERSTORMS AROUND THE
MIDDLE OF NEXT WEEK. SHOWERS ARE EXPECTED TO CONTINUE AT POHNPEI AND
MAJURO THROUGH THE WEEKEND, THEN DECREASE BY THE BEGINNING OF NEXT
WEEK AS THE CONVERGENCE DRIFTS SOUTH.
FOR THE MARINE FORECAST, THE LARGE, LONG-PERIOD NORTH SWELL CONTINUES
TO AFFECT POHNPEI AND IS NOW PUSHING INTO KOSRAE. THIS NORTH SWELL
WILL MAINTAIN HAZARDOUS FOR POHNPEI ALONG NORTH FACING REEFS THROUGH
EARLY SUNDAY MORNING, AND IS NOW PRODUCING HAZARDOUS SURF AT KOSRAE
ALONG NORTH FACING REEFS. AS THE NORTH SWELL SUBSIDES, IT WILL MOVE
OUT OF KOSRAE FIRST ON SUNDAY AND POHNPEI SUNDAY AFTERNOON.
THEREFORE, THE HIGH SURF ADVISORY (HSA) FOR POHNPEI REMAINS IN
EFFECT AND A HSA WAS ISSUED FOR KOSRAE. IF THE NORTH SWELL REMAINS
HIGH ENOUGH THROUGH SUNDAY, THE HSA FOR POHNPEI MAY NEED TO BE
EXTENDED FOR ANOTHER PERIOD. FOR KOSRAE, AS THE NORTH SWELL SUBSIDES,
THE TRADE SWELL IS EXPECTED TO BUILD AND WILL THEN PRODUCE HAZARDOUS
SURF ALONG EAST FACING REEFS FROM SUNDAY THROUGH AT LEAST TUESDAY
AFTERNOON. FOR POHNPEI, COMBINED SEAS ARE EXPECTED TO REACH 10 FEET
FOR A BRIEF PERIOD. SEAS COULD BUILD TO 10 FEET AS EARLY AS MIDNIGHT
TONIGHT, BUT IS EXPECTED TO FALL BELOW 10 FEET AGAIN BY SATURDAY
AFTERNOON. A SMALL CRAFT ADVISORY IS IN EFFECT FOR POHNPEI FROM
MIDNIGHT TONIGHT THROUGH SATURDAY AFTERNOON.
WESTERN MICRONESIA...
A WEAK CIRCULATION SOUTH OF PALAU, NEAR 4N135E, AND TRAILING TRADE-
WIND CONVERGENCE ARE PRODUCING AN UNSETTLED PATTERN ACROSS THE
REGION. CONVECTION IS SPREAD OUT ACROSS PALAU AND YAP, BUT IS SOUTH
OF WENO, ACROSS SOUTHERN CHUUK STATE. LATEST MODEL GUIDANCE SUGGESTS
SCATTERED SHOWERS FOR PALAU AND SCATTERED TO NUMEROUS SHOWERS FOR YAP
TONIGHT BEFORE THE CIRCULATION WEAKENS FURTHER AND OPENS UP INTO A
TROUGH. THIS, HOWEVER, WILL STILL CONTRIBUTE TO AN UNSETTLED
WEATHER PATTERN, BUT THE BULK OF CONVECTION SETS UP TO THE WEST AS
THE BROAD TROUGH PROPAGATES WESTWARD, ALSO INTERACTING WITH A SHEAR
LINE DRAPED TO NORTH, NEAR 15N. VARIOUS TRADE-WIND TROUGHS AND
POCKETS OF TRADE-WIND CONVERGENCE BEHIND THIS PATTERN WILL STILL
BRING PERIODIC UPTICKS IN SHOWERS. HOWEVER, THIS IS MAINLY FOR
PALAU, SINCE YAP AND CHUUK LOOK TO STAY NORTH OF THE BULK OF
CONVECTION.
ALTIMETRY DATA SHOWS 5 TO 7 FEET NEAR YAP AND PALAU AND 6 TO 8 FEET
NEAR CHUUK. LONG-PERIOD NORTH TO NORTHEAST SWELL EMANATING FROM
STRONG MID-LATITUDE SYNOPTIC SYSTEMS CONTINUES TO ELEVATE SURF ALONG
NORTH AND EAST FACING REEFS AND CHUUK. A HIGH SURF ADVISORY WAS
ISSUED THIS AFTERNOON AS WE EXPECT HAZARDOUS SURF OF 7 TO 10 FEET
ALONG NORTH-FACING REEFS OF CHUUK THROUGH AT LEAST SUNDAY AFTERNOON.
THIS IS ALSO EXPECTED TO INCREASE COMBINED SEAS TO 7 TO 9 FEET
THROUGH SATURDAY NIGHT. FOR YAP AND PALAU, A NOTABLE PULSE OF
NORTHERLY SWELL LOOKS TO ARRIVE SUNDAY NIGHT AND MONDAY, POSSIBLY
INCREASING SURF TO HAZARDOUS LEVELS ALONG NORTH-FACING REEFS.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: STANKO
MARIANAS: DOLL
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: CRUZ
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