934
FXPQ50 PGUM 180758
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
558 PM CHST SAT OCT 18 2025
MARIANAS SYNOPSIS
MODERATE TO FRESH TRADES PREVAIL IN THE REGION. SATELLITE IMAGERY AND
DOPPLER RADAR INDICATE SLOW-MOVING STRATIFORM RAIN IN WESTERN GUAM
WATERS. BUOYS AND ALTIMETRY SHOW SEAS ARE 5 TO 8 FEET IN THE AREA.
DISCUSSION
A BROAD SURFACE TRADE-WIND TROUGH ENHANCED BY THE TUTT UPSTREAM,
BROUGHT ELEVATED RAINFALL AMOUNTS AND LIGHTNING TO THE MARIANAS AND
ADJACENT WATERS FOR MUCH OF THE AFTERNOON EARLIER TODAY, WITH
SPORADIC BUT HEAVY SHOWERS AND THUNDERSTORMS STILL EXPECTED UNTIL
MIDNIGHT, BRINGING ALONG STRONG GUSTS. SHOWER AND THUNDER COVERAGE
WILL THEN DECREASE CONSIDERABLY AFTER, FOLLOWED BY ANOTHER ALBEIT
MINOR TROUGH TO BRING PATCHY SHOWERS AND SOME THUNDERSTORMS EARLY
NEXT WEEK, FOLLOWED BY A DRIER CYCLE FOR THE REST OF THE FORECAST
PERIOD.
MARINE
COMBINED SEAS OF 6 TO 8 FEET WILL STAY ELEVATED AND CHOPPY THROUGH
AT LEAST THE FIRST HALF OF NEXT WEEK, AS NORTHERLY SWELLS AND TRADE
SWELL CONTINUE TO INTERACT AND MIX IN. SEAS ARE THEN EXPECTED TO
DECREASE ONCE THESE SWELLS WEAKEN, ESPECIALLY THE NORTHERLY SWELL,
WHICH IS EXPECTED TO DISSIPATE BY THE SECOND HALF OF NEXT WEEK.
A MODERATE RISK OF RIP CURRENTS IS EXPECTED ALONG NORTH AND EAST
FACING REEFS OF THE MARIANAS FOR MUCH OF THE FORECAST PERIOD. SURF IS
LIKELY TO TAPER DOWN ALONG ALL REEFS ONCE THE AFOREMENTIONED SWELLS
WEAKEN, POTENTIALLY ALLOWING THE RIP RISK TO DROP TO LOW ALONG NORTH
FACING REEFS BY THE SECOND HALF OF NEXT WEEK.
EASTERN MICRONESIA
MAJURO:
THE MAIN CHANGE TO THE FORECAST WAS AT MAJURO, WHERE RAINFALL
COVERAGE WAS INCREASED TO WIDESPREAD SHOWER COVERAGE WITH LOCALLY
HEAVY RAINFALL ALSO INCLUDED. THIS WAS DUE TO A FAIRLY STOUT SURFACE
TROUGH THAT'S CURRENTLY MOVING THROUGH THAT REGION. SATELLITE
ANALYSIS SHOWS PERSISTENT SHOWER DEVELOPMENT WITH CLOUD TOP
TEMPERATURES OCCASIONALLY SURPASSING -75 DEG. C. THIS TROUGH WILL
MOVE OFF TO THE WEST BY SUNDAY NIGHT THOUGH, DECREASING RAINFALL
POTENTIAL BRIEFLY, BEFORE THE NEXT TROUGH MOVES IN MONDAY NIGHT WITH
RAINFALL POTENTIAL INCREASING ONCE AGAIN.
POHNPEI AND KOSRAE:
ISOLATED SHOWERS WILL CONTINUE THROUGH SUNDAY EVENING. THEN, AS THE
MAJURO TROUGH APPROACHES, RAINFALL POTENTIAL INCREASES BY MONDAY,
CONTINUING THROUGH AT LEAST THE MIDDLE OF THE WEEK AS THE MODELS SHOW
ADDITIONAL TROUGHS CROSSING THE DATE LINE, WITH STREAMLINE AND
SATELLITE ANALYSIS CONFIRMING THIS AS WELL.
WINDS AND SEAS:
GENTLE TO MODERATE WINDS BY SUNDAY AT MAJURO WILL REACH KOSRAE MONDAY
AND POHNPEI TUESDAY. SEAS OF 4 TO 6 FEET WILL INCREASE A FOOT OR SO
TOWARDS THE MIDDLE OF NEXT WEEK.
WESTERN MICRONESIA
SATELLITE THIS AFTERNOON REVEALS A QUIETER PATTERN ACROSS FAR WESTERN
MICRONESIA, WITH A SURFACE RIDGE EXTENDING SOUTHEAST ACROSS THE
REPUBLIC OF PALAU, PASSING SOUTH OF KOROR. THERE IS A WEAK SURFACE
TROUGH JUST NORTHEAST OF THIS FEATURE, WITH THE AXIS ORIENTED
SOUTHEAST TO NORTHWEST BETWEEN PALAU AND YAP, EXTENDING TOWARD
TROPICAL DEPRESSION FENGSHEN. HOWEVER, THE ASSOCIATED CONVERGENCE AND
CONVECTION HAS SHIFTED NORTHWEST AWAY FROM THE REGION, WITH ONLY
ISOLATED SHOWERS SEEN OVER YAP AND PALAU COASTAL WATERS. EXTENSIVE
UPPER-LEVEL CLOUD COVER PERSISTS OVER YAP FROM PRIOR DEEP CONVECTION,
AND SKIES WILL REMAIN MOSTLY CLOUDY FOR MUCH OF TONIGHT. CONDITIONS
ARE SIMILARLY QUIET OVER CHUUK, WITH A SURFACE RIDGE JUST SOUTH OF
WENO AND A BROAD TROUGH JUST WEST TO NORTHWEST OF COASTAL WATERS,
MOVING AWAY.
SIMILARLY WEAK, TRANSIENT FEATURES WILL BE THE MAIN FOCUS FOR ANY
WEATHER ACROSS THE REGION FOR MUCH OF THE FORECAST PERIOD. STRONGER
CONVERGENCE AHEAD OF A BROAD TRADE-WIND TROUGH WILL INCREASE SHOWERS
NEAR YAP AROUND SUNDAY NIGHT. THIS TROUGH LOOKS TO AMPLIFY SLIGHTLY
AS IT MOVES INTO FAR WESTERN MICRONESIA AROUND MONDAY NIGHT,
INCREASING SHOWERS MORE DIRECTLY OVER YAP AND PALAU THROUGH MIDWEEK.
A BROAD RIDGE BEHIND THIS DISTURBANCE WILL ALLOW FOR QUIETER
CONDITIONS COME THURSDAY. CHUUK WILL CONTINUE TO SEE ISOLATED SHOWERS
THROUGH SUNDAY WITH SCATTERED SHOWERS BEGINNING TO BUILD SUNDAY
NIGHT, DUE TO INCREASING CONVERGENCE ALONG THE BACKSIDE OF THE
AFOREMENTIONED BROAD TROUGH. A SLIGHTLY STRONGER TROUGH LOOKS TO
ARRIVE DURING THE MIDWEEK, WITH WEAKER, MORE TRANSIENT FEATURES IN
BETWEEN.
BENIGN MARINE CONDITIONS CONTINUE WITH LITTLE CHANGE IN THE FORECAST.
LATEST ALTIMETRY DATA CONTINUES TO INDICATE COMBINED SEAS AROUND 3
TO 5 FEET NEAR PALAU AND YAP AND AROUND 4 TO 6 FEET NEAR CHUUK,
COMPRISED OF A PRIMARY NORTHEAST SWELL. SIMILAR SEA CONDITIONS WILL
PREVAIL FOR PALAU AND YAP FOR MUCH OF THE FORECAST PERIOD, WITH SEAS
GRADUALLY DIMINISHING BY A FOOT OR SO THROUGH THE WEEK AS THE
INCOMING TRADE SWELL RELAXES. CHUUK WILL SEE AN INCREASE IN WINDS
AND SEAS AROUND MIDWEEK, AS TRADE WINDS AND ASSOCIATED SWELL BEGIN TO
PICK UP. WINDS WILL REMAIN LIGHT TO MODERATE FOR PALAU AND YAP
THROUGH THE PERIOD.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: MONTVILA
EAST MICRONESIA: DOLL
WEST MICRONESIA: DECOU
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