169
FXPQ50 PGUM 200725
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
525 PM CHST WED MAY 20 2026
MARIANAS SYNOPSIS
ISOLATED SHOWERS WILL CONTINUE THROUGH TONIGHT BEFORE BRIEFLY
INCREASING TO SCATTERED THURSDAY AFTERNOON THROUGH EVENING. COMBINED
SEAS OF 6 TO 8 FEET AND A HIGH RISK OF RIP CURRENTS ALONG EAST-
FACING REEFS CONTINUE THROUGH THURSDAY AFTERNOON BEFORE GRADUALLY
SUBSIDING. MODELS CONTINUE TO TREND TOWARDS A WETTER WEEKEND DUE TO
THE POTENTIAL OF A TROPICAL DISTURBANCE TRACKING THROUGH THE
MARIANAS.
DISCUSSION
SATELLITE IMAGERY DEPICTS A FAIRLY DRY TRADE-WIND REGIME, ALTHOUGH
SOME PATCHES OF MODERATE SHOWERS AND MOSTLY CLOUDY SKIES HAVE BEEN
INTERMITTENT ACROSS THE MARIANAS THROUGHOUT THE DAY. THIS PATTERN IS
EXPECTED TO CONTINUE, INCREASING FROM ISOLATED TO SCATTERED SHOWERS
AS A TRADE-WIND TROUGH TRACKS THROUGH THE REGION BEGINNING WITH GUAM
AS EARLY AS THURSDAY AFTERNOON FOLLOWED BY ROTA, TINIAN, AND SAIPAN
THROUGH THE EVENING. BEYOND THURSDAY, THE REGION MAY EXPERIENCE A
BRIEF RETURN TO ISOLATED SHOWERS AND WINDS FROM 15 TO 20 MILES PER
HOUR ON FRIDAY, BEFORE AN UPTICK IN SHOWER COVERAGE AND A SLIGHT
CHANCE OF THUNDERSTORMS IS POSSIBLE STARTING SATURDAY. MODEL GUIDANCE
CONTINUES TO PORTRAY A POTENTIAL DISTURBANCE DEVELOPING IN CENTRAL
MICRONESIA AND TRACKING NORTH-NORTHWEST THROUGH THE MARIANAS EARLY
NEXT WEEK. CONFIDENCE CONTINUES TO GROW IN WETTER IMPACTS ACROSS THE
REGION STARTING SATURDAY THROUGH THE HOLIDAY WEEKEND, BUT THE
DISTURBANCE ITSELF HAS YET TO BE REALIZED AS DEVELOPMENT IS STILL IN
ITS EARLIEST STAGES. WE WILL CONTINUE TO MONITOR AND COMMUNICATE
CONDITIONS AS THE WEEKEND NEARS.
MARINE
COMBINED SEAS OF 6 TO 8 FEET WILL PREVAIL ACROSS THE REGION THROUGH
THURSDAY AFTERNOON AS THE EASTERLY TRADE SWELL CONTINUES TO ELEVATE
SEA HEIGHTS. BUOY AND ALTIMETRY DATA SUPPORTS SWELLS CAPABLE OF
PRODUCING SURF UP TO 9 FEET, SO, THERE IS A HIGH RISK OF RIP CURRENTS
ALONG EAST-FACING REEFS AND IS EXPECTED TO CONTINUE THROUGH THURSDAY
AFTERNOON BEFORE DROPPING TO MODERATE THURSDAY NIGHT. A MODERATE
RISK OF RIP CURRENTS IS ALSO PREVALENT ALONG NORTH-FACING REEFS AND
WILL CONTINUE OVER THE NEXT SEVERAL DAYS. SEA HEIGHTS WILL START TO
SUBSIDE THURSDAY NIGHT AND MAY HOVER 4 TO 6 FEET THROUGHOUT THE
WEEKEND.
EASTERN MICRONESIA
THE LEADING EDGE OF THE NEAR-EQUATORIAL TROUGH (NET) INTERACTING
WITH THE INTERTROPICAL CONVERGENCE ZONE (ITCZ) REMAINS THE PRIMARY
DRIVER FOR WEATHER ACROSS EASTERN MICRONESIA. EXTENSIVE HEAVY SHOWERS
AND SOME THUNDERSTORMS ARE EXPECTED TO CONTINUE AT POHNPEI THROUGH
THURSDAY NIGHT AND AT KOSRAE THROUGH THURSDAY, FOLLOWED BY A BRIEF
AND SLIGHT DECREASE IN SHOWER COVERAGE. THEN, SHOWERS AND
THUNDERSTORMS WILL AGAIN PEAK DURING THE WEEKEND AS AN ITCZ SURGE IS
EXPECTED TO BACKBUILD ACROSS THE MARSHALLS AS TRADE-WIND FLOW
CONTINUES TO BULK AGAINST THE NET AND ASSOCIATED DEVELOPING
DISTURBANCE, FOLLOWED BY A DISINTEGRATION IN THE SOUTHEASTERLY
COMPONENT THAT WILL PUSH THE ITCZ BACK TOWARD THE CENTRAL PACIFIC BY
EARLY NEXT WEEK. THIS BACKBUILDING WILL BRING GUSTY, HEAVY AND
INTENSE SHOWERS TO MAJURO BEFORE THE WEEKEND, WITH SOME NEAR GALE-
FORCE GUSTS EXPECTED NEAR THE HEAVIEST SHOWERS. AS THE AFOREMENTIONED
DISTURBANCE HEADS FURTHER WEST AND/OR NORTHWEST, SHOWERS AND
THUNDERSTORMS WILL RETURN TO A MORE PATCHY COVERAGE ACROSS THE
REGION, BUT A DRY SPELL IS NOT LIKELY TO DEVELOP AS THE PRIMARY
CONVERGENCE ZONE REMAINS ACROSS ALL THREE ISLANDS.
COMBINED SEAS OF 4 TO 6 FEET NEAR POHNPEI AND KOSRAE, AND 5 TO 7
FEET NEAR MAJURO, ARE EXPECTED TO TAPER DOWN A FOOT OVER THE COMING
DAYS, TO THEN REMAIN AS SUCH FOR THE REST OF THE FORECAST PERIOD AS
TRADE SWELL REMAINS MODERATE.
WESTERN MICRONESIA
SATELLITE OBSERVATIONS SHOW ISOLATED TO SCATTERED SHOWERS ACROSS THE
REGION. ALTIMETRY SHOWS COMBINED SEAS BETWEEN 4 AND 7 FEET.
A RELATIVE LULL IS ONGOING ACROSS WESTERN MICRONESIA. FOR PALAU AND
YAP, WEATHER CONDITIONS LOOK TO BE IN AND OUT OF AN ACTIVE PHASE
THROUGH MUCH OF THE WEEK WITH 30 TO 40 PERCENT POPS THROUGH
SATURDAY. AS WE HEAD INTO NEXT WEEK, A MONSOON TAIL LOOKS TO DEVELOP
ACROSS THE REGION, BRINGING INCREASED SHOWER ACTIVITY. ADDITIONALLY,
A TROPICAL DISTURBANCE MAY RESIDE WITHIN OR JUST NORTH OF THE REGION
NEXT WEEK. THIS WOULD HELP ENHANCE RAINFALL ACROSS PALAU AND YAP IN
THE EXTENDED RANGE. UNCERTAINTY REMAINS HIGH ON THE LOCATION OR
STRENGTH OF ANY POTENTIAL TROPICAL DISTURBANCE NEXT WEEK, BUT THERE
IS MEDIUM CONFIDENCE FOR INCREASED RAINFALL, EITHER DUE TO DIRECT
IMPACTS OF A TROPICAL DISTURBANCE OR FROM THE MONSOON TAIL THAT FORMS
SOUTH OF IT.
ACROSS CHUUK STATE, INITIAL CONDITIONS ARE RELATIVELY QUIET WITH
SCATTERED SHOWERS. SHOWER COVERAGE LOOKS TO INCREASE TO NUMEROUS
TOMORROW DUE TO THE CONVERGENCE FROM THE MONSOON-LIKE TROUGH TO THE
WEST, THE NET TO THE SOUTH, AND THE ITCZ TO THE EAST MEETS ACROSS
CHUUK STATE. AS THIS CONVERGENCE COMES TOGETHER, LOW-LEVEL VORTICITY
WILL BEGIN TO CONCENTRATE OVER CHUUK STATE AS THE EARLY STAGES OF A
TROPICAL DISTURBANCE BEGINS TO FORM. WIDESPREAD LOCALLY HEAVY
RAINFALL IS EXPECTED FRIDAY NIGHT THROUGH SATURDAY NIGHT FOR CHUUK,
AS THE TROPICAL DISTURBANCE SHIFTS WEST AND SHIFTS THE INFLOW BAND
OVER CHUUK. SHOWERS AND THUNDERSTORM COVERAGE WILL SLOWLY DECREASE
STARTING SUNDAY, BUT AN ACTIVE PATTERN LOOKS TO REMAIN.
MARINE CONDITIONS ARE BETWEEN 4 AND 7 FEET AND LOOK TO STAY BENIGN
THROUGH THE WEEK. SOME CHOPPY SEAS WILL BE POSSIBLE ACROSS CHUUK
STATE NEAR HEAVIER SHOWERS. AS THE MONSOON TAIL INTENSIFIES NEXT
WEEK, SEAS LOOK TO RISE NEAR PALAU AND YAP. THOSE WITH MARINE
INTEREST ACROSS PALAU AND YAP SHOULD CONTINUE TO MONITOR THE
FORECAST TO REMAIN UP TO DATE.
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: MONTVILA
WEST MICRONESIA: WILLIAMS
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