870
FXPQ50 PGUM 190747
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
547 PM CHST TUE MAY 19 2026
MARIANAS SYNOPSIS
ISOLATED SHOWERS AND PARTLY CLOUDY SKIES WILL LINGER FOR THE MARIANAS
THROUGH THE NEXT FEW DAYS. COMBINED SEAS ARE 6 TO 8 FEET AND A HIGH
RISK OF RIP CURRENTS IS IN EFFECT ALONG EAST-FACING REEFS UNTIL
THURSDAY AFTERNOON. THE REGION MAY SEE INCREASINGLY WETTER CONDITIONS
OVER THE WEEKEND.
DISCUSSION
THE MARIANAS REMAINS IN A RELATIVELY DRY TRADE-WIND REGIME FOR THE
NEXT FEW DAYS. SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES AND
ISOLATED SHOWERS THAT LOOK TO CONTINUE THROUGH TONIGHT. A BRIEF
PERIOD IN HIGHER WINDS IS IN STORE FOR WEDNESDAY AS EASTERLY WIND
SPEEDS WILL BE BETWEEN 15 AND 20 MILES PER HOUR WITH OCCASIONAL GUSTS
UP TO 30 MILES PER HOUR. AS WE ENTER THE LATTER HALF OF THE WEEK,
OVERALL CONDITIONS MAY START TO SHIFT ON THURSDAY. MODEL GUIDANCE
SHOWS A SLIGHT DECREASE IN TRADE WINDS AND AN INCREASE FROM ISOLATED
TO LOW-END SCATTERED SHOWERS UNTIL THE WEEKEND. THERE IS STILL
SUPPORT FROM THE MODELS FOR A WETTER PERIOD STARTING THIS WEEKEND
THROUGH EARLY NEXT WEEK, SO CHANCES OF SHOWERS WERE ADJUSTED HIGHER
TO REFLECT THAT TREND. A SLIGHT CHANCE OF THUNDERSTORMS REMAINS IN
THE FORECAST AS MODELS CONTINUE TO DEPICT EITHER A SURFACE TROUGH OR
A POTENTIAL DISTURBANCE ORIGINATING IN CENTRAL MICRONESIA AND
SHIFTING NORTHWEST, POSSIBLY IMPACTING THE MARIANAS BEYOND MEMORIAL
DAY. THIS WILL CONTINUE TO BE MONITORED AND COMMUNICATED THROUGHOUT
THE NEXT SEVERAL DAYS.
MARINE
COMBINED SEAS OF 6 TO 8 FEET ARE EXPECTED TO REMAIN THROUGH THURSDAY
AFTERNOON. BUOY DATA CONTINUES TO SUPPORT SWELLS CAPABLE OF
PRODUCING SURF UP TO 9 FEET, AND MODEL GUIDANCE DEPICTS LITTLE
CHANGES IN THE SEA STATE FOR THE NEXT FEW DAYS, SO THE HIGH RISK OF
RIP CURRENTS ALONG EAST-FACING REEFS IS IN EFFECT UNTIL THURSDAY
AFTERNOON. CURRENT MODEL GUIDANCE SHOWS WAVE HEIGHTS TO GRADUALLY
DECREASE BY A FOOT OR TWO STARTING THURSDAY AFTERNOON AND CONTINUING
THROUGH THE WEEKEND.
EASTERN MICRONESIA
AN INCREASINGLY UNSETTLED, BUT DISORGANIZED PATTERN CONTINUES TO
BUILD ACROSS THE REGION. AN INTERTROPICAL CONVERGENCE ZONE (ITCZ)
EXTENDS EASTWARD ACROSS POHNPEI AND KOSRAE STATES FROM OVER CENTRAL
MICRONESIA, INTERACTING WITH TRADE-WIND TROUGHS CENTERED JUST WEST
OF POHNPEI, WEST OF KOSRAE, AND WITH A VERY BROAD UPPER-LEVEL LOW
LOCATED FAR TO THE NORTH-NORTHEAST. FARTHER EAST, ANOTHER ITCZ
FRAGMENT BUILDS JUST EAST OF THE MARSHALL ISLANDS WITH A TRADE-WIND
TROUGH PROPAGATING WESTWARD ALONG IT. THESE FEATURES ARE PRODUCING
AREAS OF NUMEROUS TO WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS
WITHIN EASTERN MICRONESIA. POHNPEI AND KOSRAE ARE SITUATED ON THE
NORTHERN PERIPHERY OF THE SHOWERS AND THUNDERSTORMS ASSOCIATED WITH
THE ITCZ TO THE SOUTH, AND MAJURO SITS ALONG THE VERY WESTERN EDGE OF
THE ADVANCING TROUGH, ITCZ FRAGMENT, AND ASSOCIATED CONVECTION.
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS, WITH LOCALLY HEAVY
RAINFALL POSSIBLE AT TIMES, ARE EXPECTED FOR ALL THREE FORECAST ZONES
FOR TONIGHT, REMAINING NUMEROUS FOR POHNPEI AND KOSRAE THROUGH AT
LEAST WEDNESDAY, BUT TAPERING TO SCATTERED FOR MAJURO FOR THE NEXT
DAY OR SO.
MODELS CONTINUE TO BE AGGRESSIVE IN DEPICTING A VERY WET PATTERN
THROUGHOUT THE WEEK, AND SHOWERS WILL LIKELY INCREASE TO BECOME
WIDESPREAD FROM TIME TO TIME OVER THE NEXT FEW DAYS, WITH LITTLE
CERTAINTY IN EXACT TIMING. THE UPPER-LEVEL LOW NORTH-NORTHEAST OF
THE REGION IS EXPECTED TO REMAIN SEMI-STATIONARY AS IT WEAKENS,
EXTENDING WESTWARD AS AN OPEN TROUGH OVER THE NEXT FEW DAYS. DESPITE
WEAKENING, THE TROUGH'S POSITION AND ORIENTATION LOOK TO MAINTAIN
GOOD UPPER-LEVEL SUPPORT FOR SHOWERS AND THUNDERSTORMS ACROSS
CENTRAL AND EASTERN MICRONESIA, MAINLY OVER POHNPEI AND KOSRAE
STATES THIS WEEK. MEANWHILE, THE ITCZ TO THE SOUTH LOOKS TO FRAGMENT
AND SHIFT WESTWARD, HELPING TO FORM A BROAD, DISORGANIZED
DISTURBANCE ACROSS CENTRAL MICRONESIA. STRONG CONVERGENCE UPSTREAM OF
THIS DISTURBANCE, WITH DECENT UPPER-LEVEL SUPPORT, LOOKS TO MAINTAIN
AT LEAST SCATTERED SHOWERS ACROSS THE REGION THROUGH THE LATTER HALF
OF THE WEEK.
BENIGN MARINE CONDITIONS ARE EXPECTED THROUGH THE WEEK. LATEST
ALTIMETRY DATA INDICATES COMBINED SEAS BETWEEN 6 AND 7 FEET ACROSS
MUCH OF THE REGION. MODELS DEPICT A VERY GRADUAL RELAXATION OF THE
EAST TO NORTHEAST TRADE SWELL THROUGHOUT THE WEEK, ALLOWING SEAS TO
DIMINISH BY A FOOT OR SO OVER THE NEXT SEVERAL DAYS.
WESTERN MICRONESIA
SATELLITE OBSERVATIONS SHOW SCATTERED SHOWERS OVER YAP AND CHUUK
WITH ISOLATED SHOWERS OVER PALAU. ALTIMETRY DATA SHOWS COMBINED SEAS
BETWEEN 4 AND 7 FEET.
THE ROBUST CONVECTION THAT MOVED OVER YAP TODAY HAS BEGUN TO WANE,
BUT SCATTERED SHOWERS ARE STILL OCCURRING BENEATH THE WARMING CIRRUS.
ACROSS CHUUK STATE INCLUDING WENO, SCATTERED SHOWERS ARE SEEN FROM
TRADE-WIND CONVERGENCE RESIDING OVER THE REGION. AN ACTIVE WEATHER
PATTERN WILL SETUP ACROSS MUCH OF WESTERN MICRONESIA OVER THE NEXT
WEEK. A MONSOON-LIKE TROUGH IS DEVELOPING SOUTH OF PALAU AND WILL
INTENSIFY THROUGH THE WEEK. EVENTUALLY, THIS LOOKS TO BECOME A FULL
FLEDGED MONSOON TROUGH THIS WEEKEND OR EARLY NEXT WEEK. THIS MONSOON-
LIKE OR MONSOON TROUGH IS EXPECTED TO INTERACT WITH A TROPICAL
DISTURBANCE AS WELL. THE COMBINATION OF THESE TWO FEATURES WILL BRING
UNSETTLED WEATHER, BEGINNING ACROSS CHUUK ON WEDNESDAY AND THEN
EASTERN YAP STATE THIS WEEKEND AND INTO NEXT WEEK. UNCERTAINTY
REMAINS HIGH WITH GUIDANCE SPLIT ON WHETHER THERE WILL BE A NORTHWARD
PULL OF MOISTURE, OR IF WE'LL SEE A MORE WESTWARD PUSH. THE FORMER
SCENARIO WOULD DELAY ACTIVE WEATHER FOR YAP PROPER AND PALAU, BUT
WOULD KEEP THEM IN WESTERLY FLOW AS THE MONSOON TAIL FORMS, PLACING A
TRAIN OF SHOWERS AND THUNDERSTORMS OVER THEM. THE LATTER SCENARIO
WOULD SHIFT THE BULK OF THE DISTURBANCE OVER YAP AND PALAU, BUT WOULD
ALSO EXIT THE REGION FASTER. CURRENTLY, BOTH THE ECMWF AND GFS
DETERMINISTIC FAVOR SCENARIO ONE WITH THEIR RESPECTIVE ENSEMBLES
CLOSER TO SCENARIO ONE BUT MORE IN THE MIDDLE. THE CANADIAN (CMC) AND
IT'S ENSEMBLES FAVOR SCENARIO TWO MORE. FOR NOW, THE FORECAST TRIES
TO REMAIN IN THE MIDDLE OF THESE SCENARIOS.
COMBINED SEAS ARE BETWEEN 4 AND 7 FEET ACROSS WESTERN MICRONESIA. ON
A BROADER SCALE, COMBINED SEAS ARE EXPECTED TO FALL THIS WEEK AS
WINDS BEGIN TO WEAKEN DUE TO TRADE-WINDS TO THE NORTH AND STRONG
WESTERLIES TO THE SOUTH; WITH THE ISLANDS CAUGHT IN BETWEEN WITHIN A
LULL. SEAS COULD BECOME ELEVATED ACROSS YAP AND PALAU LATE IN THE
FORECAST PERIOD AS THE POTENTIAL MONSOON TROUGH BUILDS INTO THE
REGION.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR MPZ001>003.
MARIANAS WATERS...NONE.
MARIANAS: MESA
EAST MICRONESIA: DECOU
WEST MICRONESIA: WILLIAMS
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