928
FXPQ50 PGUM 040841
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
641 PM CHST SUN JAN 4 2026
MARIANAS SYNOPSIS
SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES, WHILE RADAR IMAGERY
SHOWS A FEW ISOLATED SHOWERS OVER THE REGION. BUOY DATA SHOWS ABOUT
4 TO 5 FEET SWELLS AND 8 SECONDS AT RITIDIAN AND 15 SECONDS AT IPAN.
DISCUSSION
A FAST MOVING SHEAR LINE IS EXPECTED TO BRING SCATTERED SHOWERS INTO
THE REGION TONIGHT. THIS FEATURE WILL ENTER THE REGION FROM THE
NORTHWEST. IT WILL BRING NUMEROUS TO WIDESPREAD SHOWERS TO THE
REGION. WINDS ASSOCIATED WITH THE SHEAR LINE ARE EXPECTED TO BE 15 TO
25 MPH WITH GUSTS TO 30 MPH. MODEL SUGGEST THAT THE SHEAR LINE WILL
BEGIN TO WEAKEN ONCE IT PASSES OVER THE ISLANDS. THEN A DRY TRADE-
WIND PATTERN WILL LIKELY RETURN FOR THE REST OF THE WEEK.
MARINE/SURF
SEAS OF 4 TO 6 FEET WILL QUICKLY BUILD TO 7 TO 9 FEET AS ANOTHER
PULSE OF NORTH SWELL AND A SHEAR LINE MOVES INTO THE COASTAL WATERS
TONIGHT. THE SWELL AND SHEAR LINE ARE EXPECTED TO FIRST APPEAR IN
SAIPAN AND FILTER ITS WAY DOWN TO GUAM OVER NIGHT. SEAS ARE EXPECTED
TO BUILD UP TO BETWEEN 8 AND 10 FEET BY MONDAY. THEN, SEAS ARE
EXPECTED TO GRADUALLY FALL OVER THE REST OF THE WEEK ONCE THIS SHEAR
LINE WEAKENS. GENTLE TO MODERATE TRADE WINDS WILL INCREASE TO
MODERATE TO STRONG FOR TINIAN AND SAIPAN WATERS TONIGHT, AND MODERATE
TO FRESH FOR GUAM AND ROTA WATERS. AS THE SHEAR LINE WEAKENS, THE
WINDS ARE EXPECTED TO BECOME MODERATE TO FRESH FOR THE LATTER HALF
OF THE WEEK.
THERE WILL BE A MODERATE RISK OF RIP CURRENTS ALONG NORTH AND EAST
FACING REEFS THAT WILL ALSO QUICKLY BUILD TONIGHT. THIS INCREASE IS
EXPECTED TO ARRIVE AROUND 10 PM TONIGHT. THE ARRIVAL OF THIS SWELL
WILL SIGNIFICANTLY BUILD THE SURF UP (3 TO 5 FEET) TO HAZARDOUS
LEVELS ALONG NORTH FACING REEFS. THIS WILL ALLOW FOR THE SURF ALONG
EAST AND WEST FACING REEFS TO ALSO BUILD, ALBEIT THE EAST FACING
REEFS WILL LIKELY SEE MORE OF A RISE THAN WEST. AS THE SHEAR LINE
WEAKENS, THE SURF IS EXPECTED TO FALL FOR THE LATTER HALF OF THE
WEEK.
EASTERN MICRONESIA
FAIR WEATHER CONTINUES ACROSS POHNPEI, KOSRAE, AND MAJURO THIS
AFTERNOON. A STRONG PRESSURE GRADIENT BETWEEN A CIRCULATION NEAR
14N176E AND THE SUBTROPICAL RIDGE TO THE NORTHWEST CONTINUES TO USHER
IN DRIER AIR AND DIRECT NORTH-NORTHEASTERLY SWELL INTO THE REGION.
VISIBLE SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES ACROSS THE MAIN
ISLANDS OF POHNPEI, KOSRAE, AND MAJURO WITH A BAND OF SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS DRAPED ACROSS THE EASTERN AND
SOUTHERN PART OF THE REGION, INCLUDING KAPINGAMARANGI. THIS IS DUE TO
CONVERGENCE OF MODERATE AND DRY NORTHEAST TRADES COLLIDING WITH
LIGHT TO GENTLE WINDS AND A THINNING BAND OF TROPICAL MOISTURE NEAR
THE EQUATOR. THE MIMIC TPW PRODUCT CONTINUES TO SHOW AN INCREASINGLY
DRY AIRMASS ACROSS MOST OF THE REGION, WITH PRECIPITABLE WATER
AMOUNTS DROPPING BELOW 1.00 INCHES OVER MAJURO AND JUST NORTH OF
POHNPEI AND KOSRAE, SLOWLY SPREADING SOUTHWARD. SIMILAR FAIR WEATHER
CONDITIONS ARE EXPECTED THROUGH THE WEEKEND WITH STRAY, ISOLATED
LIGHT SHOWERS OVER THE NEXT SEVERAL DAYS, THEN A SURFACE TROUGH LOOKS
TO SET UP EAST OF MAJURO, POSSIBLY BRINGING AN UPTICK IN CLOUDS AND
SHOWERS TUESDAY NIGHT AND WEDNESDAY. THUNDERSTORM POTENTIALS MAY
INCREASE FOR MAJURO AS WELL DEPENDING ON THE PROXIMITY OF THE UPPER-
LEVEL LOW THAT MAY SHIFT SOUTH TO SOUTHWESTWARD MONDAY NIGHT AND
TUESDAY.
LONG-PERIOD NORTH TO NORTHEAST SWELL AND NORTHEAST TRADE SWELL WILL
CONTINUE TO PRODUCE ELEVATED SURF ALONG NORTH AND EAST FACING REEFS,
ALTHOUGH THIS IS NOT EXPECTED TO PRODUCE HAZARDOUS SURF AT THIS TIME.
COMBINED SEAS OF 6 TO 8 FEET ARE EXPECTED THROUGH TONIGHT, THEN
GRADUALLY SUBSIDE TO 4 TO 6 FEET BY MONDAY NIGHT. A LONG-PERIOD
NORTH TO NORTHWEST SWELL ENTERS THE REGION TUESDAY, BECOMING THE
DOMINANT SWELL FOR POHNPEI TUESDAY NIGHT AND FOR KOSRAE WEDNESDAY.
BRINGING AN INCREASE IN SURF ALONG WEST AND NORTH FACING REEFS, AS
WELL AS INCREASING SEAS BACK UP TO 5 TO 7 FEET. IN THE COMING DAYS,
WE WILL CONTINUE TO MONITOR SUBSEQUENT WAVE MODEL DATA AND
BUOY/ALTIMETRY DATA TO ASSESS ANY POTENTIAL FOR HIGH SURF FOR THIS
ROUND OF NORTH SWELL. OVERALL, LIGHT TO MODERATE WINDS NORTHEAST
WINDS ARE EXPECTED OVER THE NEXT SEVERAL DAYS, WITH THE EXCEPTING OF
LIGHT TO GENTLE NORTH TO NORTHWEST TONIGHT AND MONDAY AT MAJURO.
LASTLY, A COASTAL FLOOD STATEMENT REMAINS IN EFFECT FOR MAJURO
THROUGH LATE MONDAY NIGHT FOR MINOR INUNDATION ALONG NORTHERN AND
EASTERN SHORELINES DURING TIMES OF HIGH TIDE, DUE TO THE FULL MOON
CYCLE.
WESTERN MICRONESIA
SCATTERED SHOWERS ARE CONTINUING AROUND PALAU DUE TO THE CONVERGENT
FLOW NORTH OF THE NEAR-EQUATORIAL TROUGH (NET). THE POTENTIAL FOR
SHOWERS WILL DECREASE TO ISOLATED AT PALAU MONDAY AS DRIER AIR
SPREADS ACROSS FROM YAP TO PALAU AND THE NET SHIFTS CLOSER TO THE
EQUATOR. THE BLENDED TOTAL PRECIPITABLE WATER (TPW) SATELLITE
PRODUCT CONTINUES TO SHOW DRY AIR WITH TPW VALUES OF 1.00-1.20 INCHES
ACROSS CHUUK STATE AND SUPPORTING THE FAIRER WEATHER AT CHUUK. THIS
DRIER AIR, ALONG WITH A LACK OF NOTABLE SURFACE FEATURES WILL
CONTINUE TO KEEP THE POTENTIAL FOR SHOWERS AROUND 10 TO 20 PERCENT
FOR MOST OF THE WEEK.
ALTIMETRY AND DRIFTING BUOY DATA SHOWS SEAS ARE BUILDING TO THE NORTH
OF PALAU AND YAP AS THE NORTHWEST TO NORTH SWELL CONTINUES TO MOVE
INTO THE REGION, WHILE SEAS ARE CURRENTLY AROUND 6 TO 7 FEET AROUND
PALAU, YAP, AND CHUUK. THE HIGH SURF ADVISORY REMAINS IN EFFECT FOR
PALAU AND YAP THROUGH TUESDAY AS MODEL DATA SHOWS SEAS BUILDING TO
AROUND 6 TO 9 FEET WITH HAZARDOUS SURF AROUND 8 TO 10 FEET ALONG WEST
AND NORTH FACING REEFS OF PALAU AND YAP OVERNIGHT AND THEN SLOWLY
DECREASING MONDAY NIGHT AND TUESDAY. BASED ON LATEST MODEL GUIDANCE,
THIS ELEVATED NORTH SWELL IS NOT EXPECTED TO REACH CHUUK LAGOON
UNTIL ABOUT LATE MONDAY NIGHT OR TUESDAY. HIGH SURF ADVISORIES ARE
POSSIBLE FOR CHUUK, BUT MODEL DATA SHOWS THE SWELL HEIGHT DECREASING
AS IT REACHES CHUUK WITH ONLY A SLIGHT INCREASE IN THE SWELL PERIOD.
THIS COULD KEEP SURF JUST BELOW 9 FEET ALONG WEST AND NORTH FACING
REEFS OF CHUUK, BUT MODELS COULD HAVE A LOW BIAS, SO THIS DATA WILL
COMPARED WITH BUOY DATA IN THE MARIANAS AS THIS SWELL WILL FIRST MOVE
THROUGH THE MARIANAS BEFORE REACHING CHUUK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK FROM 10 PM CHST THIS EVENING THROUGH LATE
MONDAY NIGHT FOR GUZ001.
HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 6 AM CHST TUESDAY FOR
GUZ001.
MP...HIGH RIP CURRENT RISK FROM 10 PM CHST THIS EVENING THROUGH LATE
MONDAY NIGHT FOR MPZ001>003.
HIGH SURF ADVISORY FROM 10 PM THIS EVENING TO 6 AM CHST TUESDAY FOR
MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY FROM 6 AM MONDAY TO 6 AM CHST TUESDAY FOR
PMZ151-152.
SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 AM CHST TUESDAY
FOR PMZ153-154.
MARIANAS: BOWSHER
EAST MICRONESIA: CRUZ
WEST MICRONESIA: SCHANK
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