508
FXPQ50 PGUM 031823
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
423 AM CHST SUN JAN 4 2026
MARIANAS UPDATE
NO CHANGES WERE NEEDED AS THE GOING FORECAST REMAINS ON TRACK. THE
MAIN ITEMS OF INTEREST WILL BE SEAS AND SURF, BOTH OF WHICH WILL
LIKELY NEED ADVISORIES BY MONDAY AFTERNOON.
EASTERN MICRONESIA UPDATE
NO CHANGES WERE NEEDED AS THE FORECAST REMAINS ON TRACK. A PRETTY
IMPRESSING SURGE OF DRY AIR, I.E. PWATS (PRECIPITABLE WATER VALUES)
OF 0.8-0.9 INCHES IS ON MAJURO'S DOORSTEP, WHILE ALSO HEADING
TOWARDS POHNPEI AND KOSRAE. THUS, RAINFALL PROBABILITIES OF ONLY 10
PERCENT ARE WELL JUSTIFIED FOR TODAY.
WESTERN MICRONESIA UPDATE
NO CHANGES WERE NEEDED GIVEN GOOD FORECAST CONTINUITY AND MODEL
TRENDS.THE MAIN ITEM OF INTEREST WILL BE THE ARRIVAL OF A
NORTHWESTERLY TO NORTH SWELL THIS AFTERNOON, WHICH LOOKS TO CONTINUE
FOR A FEW DAYS. HIGH SURF ADVISORIES FOR NORTH FACING REEFS REMAIN
IN EFFECT.
PREV DISCUSSION
/ISSUED 619 PM CHST SAT JAN 3 2026/
MARIANAS SYNOPSIS...
SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES, WHILE RADAR IMAGERY
SHOWS A FEW ISOLATED SHOWERS OVER THE REGION. ALTIMETRY SHOWS
COMBINED SEAS OF 4 TO 6 FEET TO THE WEST OF THE MARIANAS, AND BUOY
DATA SHOWS ABOUT 4 FOOT SWELLS AT 15 SECONDS.
DISCUSSION...
A DRY TRADE-WIND PATTERN HAS SET UP OVER THE MARIANAS. THIS PATTERN
IS EXPECTED TO HOLD THROUGH SATURDAY, HOWEVER, SUNDAY IS WHEN THINGS
LOOK TO GET INTERESTING. A SHEAR LINE IS EXPECTED TO ENTER THE
NORTHWESTERN SAIPAN WATERS AROUND SUNDAY TO SUNDAY NIGHT. THIS SHEAR
LINE MAY BRING WITH IT BREEZY CONDITION AND SCATTERED SHOWERS FOR
THE BEGINNING OF NEXT WEEK. ONCE THIS SHEAR LINE PASSES, A RETURN TO
A DRY TRADE-WIND PATTERN IS ANTICIPATED.
MARINE/SURF...
SEAS OF 4 TO 6 FEET WILL CONTINUE THROUGH SUNDAY NIGHT. GENTLE TO
MODERATE TRADE WINDS WILL BECOME LIGHT TO MODERATE TONIGHT, THEN
INCREASE TO MODERATE TO FRESH STARTING SUNDAY NIGHT. LATE IN THE
WEEKEND, ANOTHER PULSE OF NORTH TO NORTH-NORTHWEST SWELL LOOKS TO
MOVE INTO THE WATERS. THIS WILL RESULT IN A SIGNIFICANT INCREASE IN
SEA HEIGHTS SUNDAY EVENING TO MONDAY. BY THEN, SEAS ARE CURRENTLY
EXPECTED TO BE BETWEEN 8 AND 10 FEET, LIKELY REQUIRING A SMALL CRAFT
ADVISORY. WINDS ARE CURRENTLY EXPECTED TO BE AROUND 20 KNOTS,
HOWEVER, WINDS COULD REACH UP TO 25 KNOTS SUNDAY OR SUNDAY NIGHT.
THE SURF PRODUCED BY THESE SWELLS WILL ALSO LIKELY RISE TO ABOVE 9
FEET ALONG NORTH AND EAST FACING REEFS. THIS WOULD WARRANT A HIGH
SURF ADVISORY (HSA) FOR NORTH FACING REEFS AND A HIGH RISK OF RIP
CURRENTS STATEMENT (HRRC) FOR NORTH AND EAST FACING REEFS. WEST
FACING REEFS ARE NOT OFF THE HOOK THROUGH, DEPENDING ON THE ANGLE OF
APPROACH FROM THIS SWELLS, SURF AND RISK OF RIP CURRENTS MAY NEED TO
BE ADJUSTED.
SEAS AND SWELLS ARE ANTICIPATED TO START FALLING SHORTLY AFTER THE
SHEAR LINE PASSES OVER THE ISLANDS. HOWEVER, THIS DIP IS EXPECTED TO
BE SHORT LIVED AS TRADES LOOK TO BUILD NEAR THE LATTER HALF OF NEXT
WEEK.
EASTERN MICRONESIA...
PLEASANT WEATHER CONTINUES ACROSS POHNPEI, KOSRAE, AND MAJURO THIS
AFTERNOON. VISIBLE SATELLITE IMAGERY STILL SHOWS A BAND OF SCATTERED
SHOWERS DRAPED ACROSS THE EASTERN AND SOUTHERN PART OF THE REGION,
SOUTH OF THE MAIN FORECAST LOCATIONS, BUT STRETCHES ACROSS
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 CIMMS MIMIC TPW
PRODUCT CONTINUES TO SHOW AN INCREASINGLY DRY AIRMASS ACROSS MOST OF
THE REGION, WITH PRECIPITABLE WATER BETWEEN 1.00 AND 1.50 INCHES.
VERY DRY AIR WITH VALUES BELOW 1.00 INCHES IS NOW PUSHING ACROSS THE
NORTHERN MARSHALLS AND MAY MAKE IT A LITTLE FURTHER SOUTH IN THE NEXT
COUPLE DAYS. PLEASANT WEATHER IS EXPECTED THROUGH THE WEEKEND WITH
STRAY, ISOLATED LIGHT SHOWERS OVER THE NEXT SEVERAL DAYS, THEN A
SURFACE TROUGH LOOKS TO SET UP NEAR THE DATE LINE OVER THE NEXT DAY
OR SO. THIS MAY ALSO LINK UP TO AN UPPER-LEVEL LOW, POSSIBLY BRINGING
AN UPTICK IN CLOUDS AND SHOWERS TUESDAY NIGHT AND WEDNESDAY NEAR
MAJURO.
RECENT OBSERVATIONS FROM THE WEATHER SERVICE OFFICES AT POHNPEI AND
MAJURO REPORT AN ABSENCE OF HAZE AND CLEAR SKIES. LEFT OFF THE
HEADLINE FOR VOLCANIC HAZE FOR NOW, BUT MAY PROVIDE UPDATES
DEPENDING ON WHETHER ANOTHER ERUPTIVE EPISODE OCCURS AT KILAUEA AND
IF VOLCANIC SMOG OR HAZE CAN MAKE ITS WAY TO THE REGION AGAIN. FOR
MORE INFORMATION ON KILAUEA'S ACTIVITY, REFER TO THE USGS WEBSITE AT
USGS.GOV/VOLCANOES/KILAUEA/VOLCANO-UPDATES.
A HIGH SURF ADVISORY REMAINS IN EFFECT ALONG EAST-FACING REEFS OF
KOSRAE THROUGH LATE TONIGHT. MODERATE TRADE SWELL AND A PULSE OF
LONG-PERIOD NORTH TO NORTHEAST SWELL ARE EXPECTED TO PRODUCE
ELEVATED SURF ALONG NORTH AND EAST FACING REEFS, OCCASIONALLY
REACHING HAZARDOUS LEVELS OF 8 FEET ALONG EAST-FACING REEFS OF
KOSRAE. AS THIS PULSE OF NORTHERLY SWELL SUBSIDES, SURF MAY DROP
BELOW HAZARDOUS LEVELS LATE TONIGHT OR EARLY SUNDAY MORNING.
MEANWHILE, A STRONG PRESSURE GRADIENT BETWEEN A CIRCULATION NEAR
16N180 AND THE HIGH PRESSURE RIDGE TO THE NORTHWEST WILL ALSO SUPPLY
ANOTHER SET OF NORTH-NORTHEASTERLY SWELL IN THE COMING DAYS,
ALTHOUGH SURF IS NOT EXPECTED TO REACH HAZARDOUS LEVELS AT THIS TIME.
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. THE HIGHEST HIGH TIDE FOR THIS
FULL MOON CYCLE IS EXPECTED SUNDAY AFTERNOON. COMBINED SEAS OF 6 TO 9
FEET ARE EXPECTED THROUGH TONIGHT, THEN GRADUALLY SUBSIDE TO 5 TO 7
FEET EARLY NEXT WEEK. GENTLE TO FRESH NORTHEASTERLIES CONTINUE FOR
POHNPEI THROUGH SUNDAY, DECREASING TO LIGHT TO MODERATE SUNDAY NIGHT.
MEANWHILE, LIGHT TO MODERATE WINDS PERSIST AT KOSRAE AND MAJURO FOR
MUCH OF THE WEEK, MOMENTARILY TURNING NORTH TO NORTHEAST SUNDAY AND
MONDAY DUE TO THE BROAD CIRCULATION TO THE DISTANT NORTHEAST.
WESTERN MICRONESIA...
THE COMBINATION OF THE NEAR-EQUATORIAL TROUGH (NET) AND THE SURFACE
TROUGH NEAR PALAU AND YAP ARE GENERATING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ACROSS PALAU AND INTO YAP THIS EVENING. AS THE
SURFACE TROUGH CONTINUES TO SHIFT WESTWARD AND THE NET SHIFTS
SOUTHWARD, SHOWERS AND THE POTENTIAL FOR THUNDERSTORMS WILL DECREASE
AT YAP LATER TONIGHT, WHILE SHOWERS AND THUNDERSTORMS WILL CONTINUE
AT PALAU THROUGH SUNDAY. THE POTENTIAL FOR SHOWERS WILL CONTINUE TO
DECREASE AT PALAU MONDAY AS A DRIER AIR SPREADS ACROSS YAP AND
PALAU. THE BLENDED TOTAL PRECIPITABLE WATER (TPW) SATELLITE PRODUCT
SHOWS DRY AIR WITH TPW VALUES OF 1.20-1.35 INCHES SPREADING ACROSS
CHUUK STATE AND SUPPORTING THE DRY WEATHER CURRENTLY AT CHUUK. THIS
DRIER AIR WILL CONTINUE TO KEEP THE POTENTIAL FOR SHOWERS AROUND 10
TO 20 PERCENT, ESPECIALLY WITH THE LACK OF NOTABLE SURFACE FEATURES,
SUPPORTING AN EXTENDED PERIOD OF DRY WEATHER OVER THE NEXT SEVERAL
DAYS.
SCATTEROMETER DATA SHOWS A LARGE AREA OF STRONG NORTH-NORTHWEST WINDS
BEHIND A COLD FRONT/SHEAR LINE THAT EXTENDS FROM THE NORTHERN
PHILIPPINES AND UP TO JAPAN. THESE WINDS ARE GENERATING A NORTHWEST
TO NORTH SWELL THAT WILL BE MOVING INTO THE REGION AROUND PALAU AND
YAP SUNDAY AFTERNOON SPREADING INTO CHUUK BY TUESDAY. BASED ON ALL
AVAILABLE MODEL GUIDANCE, ALTIMETRY AND BUOY DATA, IT LOOKS LIKE
THIS NORTHERLY SWELL WILL BE CAPABLE OF PRODUCING HAZARDOUS SURF
AROUND 8 TO 10 FEET ALONG WEST AND NORTH FACING REEFS OF PALAU AND
YAP SUNDAY AFTERNOON THROUGH TUESDAY, SO A HIGH SURF ADVISORY WAS
ISSUED FOR BOTH LOCATIONS. SEAS ARE CURRENTLY BETWEEN 5 AND 7 FEET
ACROSS THE REGION, AND MODEL GUIDANCE SHOW SEAS BUILDING TO AROUND 7
TO 9 FEET ACROSS THE REGION SUNDAY AFTERNOON THROUGH TUESDAY, JUST
BELOW THE HAZARDOUS THRESHOLD OF 10 FEET. ALTIMETRY AND BUOY WILL
HAVE TO BE WATCHED CLOSELY IN CASE MODELS HAVE A LOW BIAS FOR SEA
HEIGHTS.
RECENT OBSERVATIONS FROM THE WEATHER SERVICE OFFICES AT CHUUK REPORT
AN ABSENCE OF HAZE AND PARTLY CLOUDY TO MOSTLY SUNNY SKIES, AND THIS
IS SUPPORTED BY VISIBLE SATELLITE IMAGERY. THIS HAS LEAD TO THE
REMOVAL OF THE HEADLINE ON VOLCANIC HAZE. ANY FURTHER DISCUSSIONS OR
MENTIONS OF VOLCANIC HAZE WILL DEPEND ON WHETHER ANOTHER ERUPTIVE
EPISODE OCCURS AT KILAUEA AND IF VOLCANIC SMOG OR HAZE CAN MAKE ITS
WAY TO THE REGION AGAIN. FOR MORE INFORMATION ON KILAUEA'S ACTIVITY,
REFER TO THE USGS WEBSITE AT:
USGS.GOV/VOLCANOES/KILAUEA/VOLCANO-UPDATES.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: DOLL
REFER TO THE USGS WEBSITE AT:
MARIANAS: BOWSHER
EAST MICRONESIA: CRUZ
WEST MICRONESIA: SCHANK
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