758
FXPQ50 PGUM 150739
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
539 PM CHST FRI MAY 15 2026
MARIANAS SYNOPSIS
MODERATE EASTERLIES PREVAIL ACROSS THE REGION. SATELLITE IMAGERY AND
DOPPLER RADAR INDICATE ISOLATED LIGHT SHOWERS EXITING GUAM WATERS TO
THE WEST. BUOYS SHOW SEAS ARE 3 TO 4 FEET.
DISCUSSION
AS THE SUBTROPICAL RIDGE CONTINUES TO SPAN ACROSS THE MARIANAS, A
LARGELY DIFFUSIVE AND DRY TRADE-WIND PATTERN WILL REMAIN THE NEXT
SEVERAL DAYS. BY EARLY NEXT WEEK, MULTIPLE TRADE-WIND TROUGHS WILL
MOVE ACROSS MICRONESIA BRINGING A CHANCE OF INCREASED SHOWER COVERAGE
NEAR GUAM, BUT UNCERTAINTY REMAINS HIGH FOR SHOWERS TO SHIFT NORTH OF
10N, SO KEPT LOW-END CHANCE OF SHOWERS FOR THE REST OF THE FORECAST
PERIOD.
MARINE
COMBINED SEAS OF 4 TO 5 FEET WILL QUICKLY RISE THE NEXT FEW DAYS AS
A SIGNIFICANT EASTERLY SWELL MAKES IT TO THE MARIANAS, POSSIBLY
BECOMING 6 TO 8 FEET AS EARLY AS SUNDAY. EVEN SO, SEAS ARE EXPECTED
TO REMAIN BELOW LEVELS HAZARDOUS TO SMALL CRAFT FOR THE TIME BEING.
A MODERATE RISK OF RIP CURRENTS IS EXPECTED ALONG EAST FACING REEFS
TONIGHT, TO THEN BECOME MODERATE ALONG NORTH FACING REEFS AS WELL
BEGINNING SATURDAY. SURF WILL CONTINUE TO INCREASE OVER THE COMING
DAYS AS THE EASTERLY SWELL STRENGTHENS, POTENTIALLY INTRODUCING A
HIGH RIP CURRENT RISK ALONG EAST FACING REEFS BY EARLY NEXT WEEK.
EASTERN MICRONESIA
THE MAIN FORECAST CHALLENGE WAS DETERMINING RAINFALL POTENTIAL. AN
ACTIVE PATTERN WILL CONTINUE WITH THE ITCZ (INTER-TROPICAL
CONVERGENCE ZONE) EXPECTED TO STRENGTHEN IN THE COMING DAYS.
CURRENTLY, ONE FRAGMENT HAS EXITED THE REGION TO THE WEST. HOWEVER, A
NEW LEADING EDGE HAS CROSSED THE DATE LINE AND IS NEAR 4N177E
(SOUTHEAST OF MAJURO). SATELLITE AND STREAMLINE ANALYSIS SHOW 3
ADDITIONAL WAVES EAST OF THE DATE LINE, ALL OF WHICH HAVE A
PRONOUNCED ITCZ SIGNATURE WITH A RESPECTABLE AMOUNT OF CONVECTION
(AND INTENSITY) ASSOCIATED WITH THEM. THIS WILL ALLOW THE ITCZ TO
BUILD WESTWARD AND PERHAPS "LINK UP" WITH THE TAIL OF THE FRAGMENT
WEST-SOUTHWEST OF POHNPEI. EVEN IF NOT, THE ITCZ FRAGMENT CROSSING
THE DATE LINE STRETCHES EAST TO 160W ROUGHLY. THE MODELS SHOW THE
ITCZ WILL GRADUALLY STRENGTHEN AND LIFT NORTH TO BETWEEN 5N AND 10N
OVER THE NEXT WEEK TO TEN DAYS, ALLOWING FOR A WET PATTERN TO BECOME
MORE ESTABLISHED FOR ALL OF EASTERN MICRONESIA. IN THE MEANTIME,
EMBEDDED TROUGHS (SOME SUBTLE) IN THE FLOW WILL CONTINUE TO MOVE FROM
EAST TO WEST, KEEPING SCATTERED SHOWERS (NUMEROUS AT TIMES FOR
POHNPEI AND MAJURO) IN THE FORECAST FOR THE REGION AS WE HEAD INTO
NEXT WEEK.
AS FOR MARINE CONDITIONS, MAINLY GENTLE TO MODERATE WINDS WILL
PREVAIL (SLIGHTLY HIGHER AT MAJURO FOR TONIGHT). SEAS OF 4 TO 6 FEET
WILL INCREASE A FOOT OR SO FOR THE WEEKEND, AS THE TRADE SWELL
AND WIND WAVES INCREASE SOMEWHAT.
WESTERN MICRONESIA
LIGHT TO GENTLE WINDS AND PATCHY SHOWERS CONTINUE ACROSS PALAU AND
YAP, MEANWHILE, AN UNSETTLED PATTERN CONTINUES TO DEVELOP ACROSS
CHUUK STATE. SCATTERED TO NUMEROUS LOCALLY HEAVY SHOWERS AND SEVERAL
OUTFLOW BOUNDARIES ARE FOUND WITHIN THIS ITCZ FRAGMENT, BUT EMBEDDED
TROUGHS ARE FOCUSING SHOWERS AT THE LEADING EDGE, IN WESTERN CHUUK
STATE AND GRADUALLY MOVING INTO EASTERN YAP STATE. THE GREATER
CONCENTRATION OF SHOWERS AND THUNDERSTORMS ARE FOUND NEAR THE SECOND
EMBEDDED TROUGH, BETWEEN CHUUK AND POHNPEI. SATELLITE IMAGERY
INDICATES A BRIEF LULL IN SHOWERS AT CHUUK LAGOON THIS AFTERNOON,
BUT SHOWERS ARE EXPECTED TO BUILD BACK IN TONIGHT, WITH OCCASIONAL
GUSTS TO 25 KT POSSIBLE NEAR HEAVIER SHOWERS THROUGH SATURDAY. MODEL
GUIDANCE SUGGESTS SLIGHT DEVELOPMENT WITH ONE OF THE EMBEDDED
TROUGHS, POSSIBLY BREAKING AWAY FROM THE ITCZ PATTERN AND SHIFTING
THIS AREA OF CONVECTION NORTHWEST. THIS IN TURN, WOULD BRING AN
INCREASE IN SHOWERS TO YAP STARTING AROUND MONDAY. THERE IS SOME
SUPPORT FOR A WEAK EMBEDDED DISTURBANCE TO DEVELOP WITHIN THIS
PATTERN, BUT THERE IS STILL REMAINS SOME UNCERTAINTY DUE TO THE LACK
OF MODEL CONSENSUS. THIS WILL FURTHER ASSESSED IN SUBSEQUENT FORECAST
CYCLES AND MODEL RUNS.
OVERALL, BENIGN MARINE CONDITIONS ARE EXPECTED OVER THE NEXT SEVERAL
DAYS. A BUILDING TRADE SWELL IS EXPECTED TO INCREASE SEAS TO 5 TO 7
FEET AT CHUUK THROUGH THE WEEKEND. THIS IS PUSHING WESTWARD TOWARDS
YAP PROPER, BUILDING SEAS TO 4 TO 6 FEET SUNDAY AND MONDAY. AS TRADE
WINDS AND SWELL SUBSIDE, SEAS ARE EXPECTED TO DECREASE BACK DOWN TO
3 TO 5 FEET TOWARDS THE SECOND HALF OF THE WEEK. FOR PALAU, SEAS LOOK
TO REMAIN AROUND 2 TO 4 FEET THROUGH MUCH OF THE UPCOMING WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: MONTVILA
EAST MICRONESIA: DOLL
WEST MICRONESIA: CRUZ
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