616
FXPQ50 PGUM 220843
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
643 PM CHST THU JAN 22 2026
MARIANAS SYNOPSIS
GENTLE TO MODERATE SOUTHEASTERLIES PREVAIL ACROSS THE REGION, AS
NEARBY INVEST 92W IS BRINGING LIGHT RAIN ACROSS MUCH OF GUAM AND
ROTA WATERS AND WIDESPREAD THUNDERSTORMS WELL TO THE EAST. IPAN BUOY
SHOWS SEAS ARE AROUND 5 FEET.
DISCUSSION
TROPICAL DISTURBANCE INVEST 92W CONTINUES TO BE THE PRIMARY WEATHER
CONCERN FOR THE MARIANAS OVERNIGHT, BEFORE A SHEARLINE DESCENDS AND
INTERACTS WITH 92W TO FURTHER PRODUCE UNSETTLED WEATHER THROUGH THE
WEEKEND. NUMEROUS HEAVY SHOWERS ARE EXPECTED TO CONTINUE NEAR
MIDNIGHT TONIGHT, WITH SHOWER COVERAGE DECREASING SUBSTANTIALLY
AFTER, BEFORE PICKING UP ONCE AGAIN OVER TINIAN AND SAIPAN BEGINNING
SATURDAY WITH THE ARRIVAL OF THE SHEARLINE-DISTURBANCE COMBO. ONCE
THE SHEARLINE FINALLY DESCENDS ACROSS THE REGION, GENTLE SOUTHERLY
WINDS WILL QUICKLY SHIFT TO THE NORTHEAST AND POTENTIALLY BECOME
FRESH TO STRONG, WITH SHOWERS BECOMING MORE LIKELY OVER THE FOLLOWING
DAYS. AS THE SHEARLINE CONTINUES TO DESCEND ACROSS GUAM AND ROTA AND
EVENTUALLY BREAK DOWN BEFORE BEING CARRIED BY THE TRADES TO THE
WEST, CONDITIONS ARE MORE LIKELY TO IMPROVE IN THE SECOND HALF OF
NEXT WEEK. IN THE MEANTIME, TINIAN AND SAIPAN MAY SEE WINDY
CONDITIONS DEVELOP SUNDAY NIGHT THROUGH TUESDAY NIGHT, BUT HIGH
UNCERTAINTY REMAINS AT THIS TIME REGARDING THIS DEVELOPMENT, DUE TO
COMPLEX INTERACTIONS BETWEEN DISINTEGRATING 92W AND THE SHEARLINE.
MARINE
COMBINED SEAS OF 5 TO 7 FEET ARE EXPECTED THROUGH FRIDAY, TO THEN
RISE THIS WEEKEND AS A SHEAR LINE DESCENDS ACROSS THE REGION.
A MODERATE RISK OF RIP CURRENTS IS EXPECTED ALONG NORTH
AND EAST FACING REEFS OF THE MARIANAS THROUGH TONIGHT, BEFORE BECOMING
MODERATE ALONG ALL REEFS THEREAFTER AS A SIGNIFICANT NORTHERLY PULSE
PRODUCED BY DISTANT SYNOPTIC FEATURES AND A DESCENDING SHEARLINE
MAKE THEIR WAY ACROSS THE REGION. IN ADDITION, A SHIFTING AND
STRENGTHENING EASTERLY SWELL WILL BECOME MORE SOUTHERLY OVER THE
COMING DAYS, MIXING IN WITH EXISTING SWELLS THAT WILL KEEP SEAS
ELEVATED AND CHOPPY. HAZARDOUS SURF AND A HIGH RIP CURRENT RISK MAY
DEVELOP ALONG NORTH FACING REEFS OF THE MARIANAS AS EARLY AS LATE
THIS WEEKEND, AROUND THE TIME SEAS MAY ALSO BECOME HAZARDOUS TO SMALL
CRAFT.
TROPICAL SYSTEMS
A WEAK TROPICAL DISTURBANCE, INVEST 92W, IS FOUND SOUTH OF GUAM NEAR
10N144E, MOVING SLOWLY NORTHWEST. THE LOW-LEVEL CIRCULATION IS
WEAKENING AS IT MOVES NORTHWEST AND WILL LIKELY MERGE WITH AN
APPROACHING SHEAR LINE, LOSING DEFINITION. INVEST 92W WILL CONTINUE
TO BE MONITORED CLOSELY FOR ANY CHANGES TO THESE EXPECTATIONS.
EASTERN MICRONESIA
SATELLITE THIS AFTERNOON SHOWS A FAIRLY QUIET TRADE-WIND PATTERN
WITH PATCHY SHOWERS THROUGHOUT THE REGION. SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ARE SEEN JUST EAST OF THE NORTHERN RMI,
SUPPORTED BY STRONG NORTHEASTERLIES ALOFT. THE WEAK ITCZ FRAGMENT
FROM YESTERDAY HAS DIMINISHED WITH A REMNANT TRADE-WIND TROUGH
CONTINUING WESTWARD BEYOND THE MARSHALLS, WHICH LOOKS TO BRING LOW-
END SCATTERED SHOWERS (30 PERCENT CHANCE) TO KOSRAE OVERNIGHT. THE
ITCZ IS REORGANIZING JUST OVER AND EAST OF THE DATE LINE, EXTENDING
WEST INTO THE REGION AROUND 4N180, WITH A BAND OF SCATTERED TO
NUMEROUS SHOWERS EXTENDING ACROSS THE AREA SOUTHEAST OF MAJURO. THE
ITCZ LOOKS TO SHIFT SOUTHWARD THROUGH THE END OF THE WEEK AS IT
EXTENDS FURTHER WEST INTO THE REGION, REMAINING TO THE SOUTH OF
MAJURO, BRIEFLY INCREASING SHOWERS NEAR KOSRAE FRIDAY BEFORE
DISSIPATING THIS WEEKEND.
BUOY AND ALTIMETRY DATA SHOW COMBINED SEAS OF 5 TO 7 FEET NEAR
POHNPEI AND KOSRAE, AND 6 TO 8 FEET NEAR MAJURO. SEAS ARE COMPRISED
OF THE BACKGROUND TRADE SWELL AND A SECONDARY NORTH SWELL, WHICH
LOOKS TO PERSIST THROUGHOUT THE FORECAST PERIOD FOR KOSRAE AND
POHNPEI AND DIMINISH THIS WEEKEND NEAR MAJURO, BEFORE A STRONG PULSE
OF NORTHWEST TO NORTH SWELL LOOKS TO MOVE IN EARLY NEXT WEEK. WINDS
WILL REMAIN LIGHT TO MODERATE THROUGHOUT THE FORECAST PERIOD, BUT
LOOK TO INCREASE AROUND THE MIDDLE OF NEXT WEEK AS A TRADE-WIND SURGE
BUILDS INTO THE REGION.
WESTERN MICRONESIA
THE LATEST SATELLITE DATA SHOWS MOSTLY CLOUDY SKIES OVER YAP AND
PALAU, WITH PARTLY CLOUDY SKIES OVER CHUUK. ONLY PATCHY SHOWERS ARE
SEEN ACROSS THE REGION.
AS INVEST 92W CONTINUES TO MOVE NORTHWEST, AWAY FROM WESTERN
MICRONESIA, AN OVERALL DRY PATTERN HAS MOVED INTO THE REGION. ONLY
10 TO 20 PERCENT POPS (PROBABILITY OF PRECIPITATION) ARE EXPECTED
THROUGH THE FIRST HALF OF NEXT WEEK.
FARTHER NORTH, A SHEAR LINE APPROACHING THE AREA IS PRODUCING A
LARGE NORTHWEST SWELL THAT IS NOW ENTERING PALAU WATERS. THIS SWELL
IS LARGE ENOUGH TO PRODUCE MARGINAL HAZARDOUS SURF ALONG WEST FACING
REEFS WITH SURF UP TO 10 FEET ALONG NORTH FACING REEFS. THEREFORE, A
HIGH SURF ADVISORY WAS ISSUED FOR WEST AND NORTH FACING REEFS OF
PALAU. THIS SWELL IS EXPECTED TO ALSO AFFECT YAP A BIT LATER,
POSSIBLY AS EARLY AS FRIDAY NIGHT. THE ARRIVAL TIME FOR THE
NORTHWEST SWELL AT YAP IS STILL QUESTIONABLE, SO HELD OFF ON A HIGH
SURF ADVISORY FOR NOW. ALSO, SEAS LOOK TO BUILD HIGH ENOUGH IN YAP
WATERS TO BECOME HAZARDOUS TO SMALL CRAFT OPERATIONS SUNDAY AND
SUNDAY NIGHT. THIS WILL BE WATCHED CLOSELY, WITH A SMALL CRAFT
ADVISORY AND HIGH SURF ADVISORY POSSIBLE OVER THE WEEKEND. WINDS WILL
BE LIGHT TO GENTLE THROUGH THE FORECAST PERIOD.
FOR CHUUK, GENTLE TO MODERATE WINDS WILL BECOME LIGHT TO GENTLE BY
MORNING, REMAINING LIGHT TO GENTLE THROUGH SATURDAY NIGHT. WINDS
WILL AGAIN BECOME GENTLE TO MODERATE SUNDAY THROUGH TUESDAY.
COMBINED SEAS LOOK TO REMAIN BETWEEN 4 AND 6 FEET THROUGH THE WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: MONTVILA
EAST MICRONESIA: DECOU
WEST MICRONESIA: KLEESCHULTE
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