812
FXPQ50 PGUM 280744
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
544 PM CHST WED JAN 28 2026
MARIANAS SYNOPSIS
SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES ACROSS THE MARIANAS WITH
SHOWERS CURRENTLY LIFTING NORTH OF SAIPAN AS THE SHEAR LINE WEAKENS.
GENTLE TO MODERATE EAST TO SOUTHEAST WINDS EXTEND ACROSS THE
MARIANAS AND SEAS ARE AROUND 4 TO 7 FEET, BASED ON IPAN BUOY AND
ALTIMETRY DATA.
DISCUSSION
THE SHEAR LINE EXTENDING THROUGH THE MARIANAS CONTINUES TO WEAKEN AS
SCATTEROMETER DATA SHOWS THE NARROW AREA OF WIND SHEAR IS DECAYING,
ALONG WITH DRIER AIR ALSO STARTING TO MIX INTO THE SHEAR LINE BASED
ON THE BLEND TOTAL PRECIPITABLE WATER SATELLITE PRODUCT. THOUGH THIS
IS DECREASING THE POTENTIAL FOR HEAVY RAINFALL, SCATTERED SHOWERS ARE
STILL DEVELOPING ALONG THE SHEAR LINE AND THESE SHOWERS MAY SHIFT
SOUTHWARD TO ROTA, TINIAN AND SAIPAN LATER TONIGHT WHILE GUAM IS
EXPECTED TO REMAIN FAIRLY DRY TONIGHT. FOR THURSDAY, THE SHEAR LINE
IS EXPECTED INTERACTS WITH A SURFACE TROUGH WEST OF THE MARIANAS,
CAUSING WINDS WEAKEN AND BECOME SOUTHERLY, WHILE POTENTIALLY CREATING
A BAND OF CONVERGENCE THAT DEVELOPS ACROSS CNMI THAT WOULD SUPPORT
AN ADDITIONAL ROUND OF SCATTERED SHOWERS WITH A SLIGHT CHANCE OF
THUNDERSTORMS. FOR GUAM, LIGHT SOUTHERLY WINDS AND PARTLY CLOUDY
SKIES WILL BE SUPPORTIVE FOR ISLAND-EFFECT CONVECTION DURING THE
AFTERNOON HOURS ALONG WITH A SLIGHT CHANCE OF THUNDERSTORMS, BUT THIS
COULD BE LIMITED BY THE DRIER AIR STARTING TO MIX INTO THE DECAYING
SHEAR LINE. THURSDAY NIGHT THROUGH SATURDAY IS EXPECTED TO FAIRLY
DRY ACROSS THE MARIANAS, BEFORE ANOTHER SHEAR LINE DROPS SOUTHWARD
TOWARDS THE MARIANAS BRING BREEZY CONDITIONS TO THE ROTA, TINIAN,
AND SAIPAN STARTING SATURDAY NIGHT AND INTO GUAM SUNDAY NIGHT OR
MONDAY. THIS NEW SHEAR LINE NOT EXPECTED TO INITIALLY HAVE THE SAME
INFLUX OF MOISTURE THAT THE CURRENTLY SHEAR LINE EXPERIENCED, SO
WHILE SHOWERS AND MOSTLY CLOUDY CONDITIONS ARE EXPECTED, THE RISK FOR
HEAVY RAINFALL AND THUNDERSTORMS WILL BE LIMITED. HOWEVER, NEXT WEEK
MODELS ARE SHOWING A POTENTIAL DISTURBANCE DEVELOPING IN CENTRAL
MICRONESIA AND THEN DRIFTING WESTWARD ACROSS WESTERN MICRONESIA. IF
THIS DISTURBANCE SHIFTS NORTHWARD, THIS COULD PULL MOISTURE UP TO THE
MARIANAS, INCREASING THE POTENTIAL FOR HEAVIER SHOWERS AND
THUNDERSTORMS.
MARINE
SURF OBSERVATIONS WITH AVAILABLE BUOY DATA AND SATELLITE ALTIMETRY
SUPPORT THAT SURF HAS DROPPED BELOW 9 FEET ALONG NORTH FACING REEFS
THIS AFTERNOON, SO THE HIGH SURF ADVISORY AND HIGH RISK OF RIP
CURRENTS HAS ENDED EARLY. MODEL GUIDANCE SHOWS THE NORTH TO NORTHEAST
SWELL REBUILDING THIS WEEKEND AS ANOTHER SHEAR LINE MOVES TOWARDS
THE MARIANAS AND STRONG WINDS DEVELOP EAST OF JAPAN. THIS WILL
ELEVATED SURF ALONG NORTH AND EAST FACING REEFS, AND POTENTIALLY
GENERATE HAZARDOUS SURF CONDITIONS ONCE AGAIN.
ALTIMETRY DATA SUGGEST SEAS ARE BETWEEN 4 TO 7 FEET ACROSS THE
MARINAS. GENTLE TO MODERATE SOUTHEAST WINDS TONIGHT WILL BECOME
SOUTHERLY AS THE DECAYING SHEAR LINE INTERACTS WITH SURFACE TROUGH
WEST OF THE REGION, POTENTIALLY GENERATING A VARIABLE WIND PATTERN
FOR THURSDAY INTO THURSDAY NIGHT AS WINDS SHIFT TOWARDS THE NORTH TO
NORTHEAST. A NEW SHEAR LINE IS EXPECTED TO START COMING DOWN OUT OF
THE NORTH THIS WEEKEND. COMBINED SEAS OF 4 TO 7 FEET WILL CONTINUE
THROUGH FRIDAY, THEN INCREASE FOR THE WEEKEND IN RESPONSE TO THE
SHEAR LINE AND NORTH TO NORTHEAST SWELL GENERATED BY STRENGTHENING
WINDS EAST OF JAPAN. HAZARDOUS MARINE CONDITIONS ARE POSSIBLE AROUND
SUNDAY WITH SEAS BUILDING TO AROUND 10 FEET AND WINDS NEARING 22 KT.
EASTERN MICRONESIA
LATEST SATELLITE IMAGERY SHOWS SHOWERS AND THUNDERSTORMS CONTINUING
ACROSS KOSRAE AND POHNPEI FROM INCREASED TRADE CONVERGENCE WITH THE
NEAR-EQUATORIAL TROUGH TO THE SOUTH AND STRENGTHENING NE TRADES TO
THE NORTH. CONVECTION WILL SLOWLY PUSH SW THROUGH THU ALLOWING SOME
DRIER AIR TO PUSH IN FROM THE NE INTO THE WEEKEND. HIGH PRESSURE
BUILDING WELL NNE OF THE MARIANAS WILL MAINTAIN THE MODERATE TO FRESH
TRADES THROUGH THE WEEKEND. LATEST MODEL GUIDANCE SHOW WINDS PEAKING
AROUND 20 KT THIS WEEKEND, PERHAPS A LITTLE HIGHER FOR THE MARSHALLS
SUN AND MON. ISOLATED TRADE-WIND SHOWERS WILL TRANSIT THE REGION
INTO THE WEEKEND BEFORE SHOWERS AND THUNDERSTORMS INCREASE FROM
KOSRAE STATE WESTWARD AS A DISTURBANCE ATTEMPTS TO EMERGE WITHIN THE
NEAR-EQUATORIAL TROUGH.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR NORTH AND WEST FACING
REEFS OF POHNPEI AND KOSRAE IN ANTICIPATION OF AN ARRIVING NW SWELL
THIS EVENING. THE NORTH POINT POHNPEI BUOY HAS JUST RECENTLY
INDICATED THE ARRIVAL OF A 15SEC NW SWELL. THIS SWELL WILL BUILD,
PUSHING SURF TO EXCEED HAZARDOUS LEVELS OF 9 FT THIS EVENING, PEAKING
AROUND 10 FT EARLY THURSDAY. COMBINED SEAS OF 5-8 FT (HIGHEST EAST
OF THE MARSHALLS) WILL CLIMB TO 7-9 FT IN THE COMING DAYS, STOPPING
JUST SHY OF SMALL CRAFT ADVY CRITERIA OF 10 FT. SIMILARLY, WINDS WILL
APPROACH CRITERIA LEVELS OF 22 KT, PARTICULARLY FOR THE MARSHALLS
THIS WEEKEND. OF NOTE, THE CURRENT NW-N SWELL HEIGHTS IN THE FORECAST
ARE SLIGHTLY HIGHER THAN MODEL GUIDANCE IN REFERENCE TO A MODEL
TENDENCY TO UNDER-PREDICT LONG-PERIOD SWELL AMPLITUDE. ELEVATED
SWELL, SURF, AND WINDS WILL ULTIMATELY CONTINUE INTO NEXT WEEK
LEADING TO CHOPPY SEA CONDITIONS SO CAUTION IS URGED ON THE WATERS.
WESTERN MICRONESIA
AN AREA OF SURFACE CONVERGENCE THAT BROUGHT SOME SHOWERS TO PALAU
EARLIER CONTINUES TO MOVE OFF TO THE WEST, WITH SHOWER COVERAGE
DECREASING. YAP REMAINS "IN THE MIDDLE" OF AREAS OF CLOUDS AND
SHOWERS, WITH FAIR SKIES THERE. AT CHUUK, WITH THE NET (NEAR-
EQUATORIAL TROUGH) TO YOUR SOUTH, RESPECTABLE CONVERGENCE IS
ALLOWING A FEW SHOWERS TO CROSS THE AREA FROM TIME TO TIME, ALONG
WITH SOME HIGH-LEVEL CIRRUS CLOUDS. THIS WILL CONTINUE THE NEXT FEW
DAYS.
THE WEATHER LOOKS TO REMAIN FAIRLY QUIET THROUGH SATURDAY. THEN, BOTH
THE GEFS AND ECENS DEVELOP A CIRCULATION ALONG THE NET SOMEWHERE NEAR
~5N145E AND TRACK IT OFF TO THE WEST OR WEST-NORTHWEST. AS THE LEAD
WAVE NEARS PALAU NEAR THE MIDDLE OF NEXT WEEK, THERE'S SOME GUIDANCE
INDICATING A SECOND WAVE WILL FORM WEST OF CHUUK AND TRACK NORTHWEST
BETWEEN YAP AND GUAM. HOWEVER, THESE WAVES ARE 6 TO 9 DAYS OUT IN THE
FORECAST, WITH THE ONLY REASON TO MENTION THEM IS UNUSUALLY GOOD
MODEL CONTINUITY REGARDING THIS, ESPECIALLY FOR THIS TIME RANGE.
CONSIDERING THE NET IS ALREADY WELL ESTABLISHED (MINUS A COL SOUTH OF
YAP), CONFIDENCE IS GROWING IN THESE SCENARIOS, WHICH SHOULD ALLOW
FOR INCREASING RAINFALL. AS SUCH, POPS (PROBABILITY OF PRECIPITATION)
WAS INCREASED TO ABOVE 50 PERCENT FOR THE DAYS 5 THROUGH 7 TIME
FRAME (SATURDAY THROUGH MONDAY).
AS FOR MARINE CONDITIONS, GENTLE TO MODERATE WINDS AT PALAU AND YAP
WILL BECOME GENTLE TO MODERATE BY MONDAY. AT CHUUK, GENTLE TO
MODERATE WINDS WILL CONTINUE THROUGH THE FORECAST PERIOD. SEAS LOOK
TO HOLD IN THE 5 TO 7 FOOT RANGE.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE..
MARIANAS WATERS...NONE.
MARIANAS: SCHANK
EAST MICRONESIA: AYDLETT
WEST MICRONESIA: DOLL
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