178
FXPQ50 PGUM 230855
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
655 PM CHST FRI JAN 23 2026
MARIANAS SYNOPSIS
PATCHY ISOLATED SHOWERS AND MOSTLY CLOUDY SKIES ARE SEEN ACROSS THE
MARIANAS, WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS JUST
NORTH OF SAIPAN COASTAL WATERS. RECENT ALTIMETRY SHOWS COMBINED SEAS
OF 6 TO 8 FEET TO THE WEST OF GUAM WATERS.
DISCUSSION
THE WEAK ELONGATED CIRCULATION PREVIOUSLY DESIGNATED AS INVEST 92W
BY THE JOINT TYPHOON WARNING CENTER SITS TO THE WEST OF THE
MARIANAS, CONNECTED WITH A BROAD SHEARLINE WHICH EXTENDS NORTHEAST
ACROSS THE NORTHERN CNMI, WITH MODERATE TO DEEP CONVECTION FOCUSED
ALONG THE BOUNDARY. THIS SHEARLINE WILL GRADUALLY DROP SOUTH ACROSS
THE MARIANAS OVER THE NEXT FEW DAYS, BRINGING BREEZY CONDITIONS AND
SCATTERED SHOWERS, WHICH MAY BECOME NUMEROUS AND LOCALLY HEAVY AT
TIMES. THE SHEARLINE AND ASSOCIATED WINDS AND SHOWERS WILL ARRIVE
FIRST TO TINIAN AND SAIPAN AROUND SUNDAY EVENING, DESCENDING FURTHER
SOUTH OVER ROTA AND GUAM WATERS THROUGH MONDAY NIGHT, THEN GRADUALLY
BREAKING DOWN AS IT MOVES AWAY TO THE WEST AROUND MIDWEEK. FOR NOW,
FAIRLY QUIET CONDITIONS ARE EXPECTED, ESPECIALLY FOR GUAM AND ROTA
AS WINDS DIMINISH OVER THE NEXT DAY OR TWO, BECOMING LIGHT AND
VARIABLE SUNDAY JUST SOUTH OF THE SHEARLINE. WINDS WILL GRADUALLY
SHIFT TO THE NORTHEAST THROUGH SUNDAY EVENING, AND WILL REMAIN
SUFFICIENTLY LIGHT DURING THE DAYTIME TO SUPPORT POSSIBLE ISLAND
EFFECT SHOWERS OVER GUAM IN THE AFTERNOON. UNCERTAINTY IS STILL HIGH
AS THIS WILL DEPEND STRONGLY ON A FAVORABLE WIND AND CLOUD FORECAST,
BUT THIS SETUP COULD LEAD TO PERIODS OF HIGHLY LOCALIZED HEAVY
RAINFALL OVER THE ISLAND THROUGH SUNDAY AFTERNOON.
MARINE/SURF
COMBINED SEAS AROUND 6 TO 8 FEET WILL INCREASE TO LEVELS HAZARDOUS
TO SMALL CRAFT SATURDAY EVENING, DUE TO A SIGNIFICANT PULSE OF
NORTHWEST TO NORTH SWELL AND ELEVATED WIND WAVES, STEMMING FROM A
DESCENDING SHEARLINE. THIS WILL ALSO BRING HAZARDOUS SURF EXCEEDING
9 FEET AND A HIGH RISK OF RIP CURRENTS TO WEST AND NORTH FACING
REEFS. SEAS WILL RISE TO EXCEED 10 FEET DUE TO THE SWELLS BEFORE THE
HIGHER WINDS ARRIVE, FIRST ALONG MAINLY THE NORTHERN AND WESTERN
COASTAL WATERS. THE SHEARLINE, AND ASSOCIATED STRONG WINDS, WILL
ARRIVE FIRST TO TINIAN AND SAIPAN SUNDAY, DESCENDING FURTHER SOUTH
OVER ROTA AND GUAM WATERS MONDAY, BEFORE WIND SPEEDS GRADUALLY RELAX
BELOW HAZARDOUS LEVELS EARLY NEXT WEEK. IN THE MEANTIME, MODERATE TO
FRESH WINDS WILL DIMINISH TO BECOME LIGHT TO GENTLE OVER THE NEXT
FEW DAYS, BEFORE PICKING BACK UP SUNDAY NIGHT, ESPECIALLY FOR TINIAN
AND SAIPAN WITH BREEZY CONDITIONS EXPECTED THROUGH EARLY NEXT WEEK.
EASTERN MICRONESIA
SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES WITH ISOLATED TO
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS. ALTIMETRY AND BUOY
DATA SHOW COMBINED SEAS BETWEEN 4 AND 6 FEET ACROSS THE REGION.
A DRY TRADE-WIND PATTERN WITH EMBEDDED TRADE-WIND TROUGHS HAS
ESTABLISHED ITSELF ACROSS EASTERN MICRONESIA. ISOLATED SHOWERS LOOK
TO PREVAIL ACROSS POHNPEI, KOSRAE, AND MAJURO THROUGH MUCH OF THE
PERIOD. KOSRAE COULD SEE ANOTHER ROUND OF SCATTERED SHOWERS TOMORROW
BEFORE BECOMING ISOLATED THROUGH THE PERIOD. A MORE ACTIVE PATTERN
APPEARS POSSIBLE LATE NEXT WEEK AS A NEAR EQUATORIAL TROUGH (NET)
DEVELOPS.
BENIGN COMBINED SEAS OF 4 TO 6 FEET WILL PERSIST THROUGH TUESDAY
NIGHT BEFORE SEAS START TO RISE IN RESPONSE TO A LONG PERIOD NORTH
SWELL. SEAS LOOK TO REMAIN BELOW HAZARDOUS CONDITIONS ACROSS EASTERN
MICRONESIA, BUT SURF COULD BECOME HAZARDOUS FOR NORTH FACING REEFS
OF POHNPEI AND KOSRAE.
WESTERN MICRONESIA
LATEST SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES WITH ISOLATED
SHOWERS ACROSS WESTERN MICRONESIA, WITH SCATTERED TO NUMEROUS
SHOWERS SEEN NORTHWEST OF PALAU. ALTIMETRY SHOWS SEAS BETWEEN 8 AND
11 FEET OVER WESTERN PALAU WATERS, WITH SOFAR BUOY TO THE NORTHWEST
OF PALAU SHOWING SEAS OF 12 TO 14 FEET. ALTIMETRY SHOWS SEAS OVER
YAP BETWEEN 7 AND 9 FEET, AND BETWEEN 4 AND 6 FEET AT WENO.
THE DRY PATTERN IS SOLIDLY IN PLACE OVER WESTERN MICRONESIA AND
LOOKS TO CONTINUE THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. HOWEVER,
THERE IS A BAND OF STRONG CONVECTION BACKBUILDING INTO THE EXTREME
SOUTHWESTERN PALAU WATERS. SHOWERS ARE NOT EXPECTED TO INCREASE
ABOVE ISOLATED FOR NOW, WITH THUNDERSTORMS EXPECTED TO REMAIN OUTSIDE
OF THE COASTAL WATERS AT PALAU, BUT WILL WATCH THIS CLOSELY OVER THE
NEXT COUPLE OF HOURS FOR ANY INDICATIONS THAT THIS WILL CHANGE.
THE MAIN CONCERN REVOLVES AROUND THE BUILDING NORTHWEST SWELL OVER
PALAU AND YAP. THE LATEST ALTIMETRY DATA NOW SHOWS SEAS OF 8 TO 11
FEET OVER WESTERN PALAU WATERS. THIS IS AVERAGING AROUND 2 FEET
HIGHER THAN WAVEWATCH GUIDANCE. BASED ON ALTIMETRY, A SMALL CRAFT
ADVISORY WAS ISSUED FOR PALAU STARTING THIS AFTERNOON, AND FOR YAP
STARTING SATURDAY MORNING. THESE SEAS ARE DUE TO A BUILDING
NORTHWEST SWELL PRODUCED BY A STRONG SHEAR LINE CURRENTLY SEEN NORTH
OF 10N. SEAS WILL GRADUALLY SUBSIDE SATURDAY NIGHT AT PALAU, FALLING
BELOW 10 FEET EARLY SUNDAY MORNING. FOR YAP, SEAS WILL GRADUALLY
SUBSIDE SUNDAY NIGHT, FALLING BELOW 10 FEET EARLY MONDAY MORNING.
FOR CHUUK, SEAS LOOK TO BE BETWEEN 3 AND 6 FEET THROUGH THE
BEGINNING OF NEXT WEEK, THEN BEGIN TO BUILD AS THE NORTHWEST SWELL
REACHES WENO. THE LARGE NORTHWEST SWELL WILL ALSO CONTINUE TO
PRODUCE HAZARDOUS SURF CONDITIONS THROUGH THE BEGINNING OF NEXT WEEK
ALONG WEST AND NORTH FACING REEFS OF YAP AND PALAU. WINDS LOOK TO
REMAIN LIGHT TO GENTLE THROUGH THE BEGINNING OF NEXT WEEK AT PALAU
AND YAP, BECOMING OCCASIONALLY MODERATE TUESDAY AT YAP. LIGHT TO
GENTLE WINDS AT CHUUK WILL BECOME GENTLE TO MODERATE OVER THE WEEKEND
AND MODERATE TO FRESH AROUND THE MIDDLE OF NEXT WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: DECOU
EAST MICRONESIA: WILLIAMS
WEST MICRONESIA: KLEESCHULTE
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