003
FXPQ50 PGUM 130802
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
602 PM CHST WED MAY 13 2026
MARIANAS SYNOPSIS
ISLAND-EFFECT CONVECTION IS AFFECTING MUCH OF GUAM LATE THIS
AFTERNOON, WHILE SCATTERED SHOWERS WERE OBSERVED OVER THE
COMMONWEALTH OF THE MARIANA ISLANDS (CNMI) THROUGHOUT THE DAY.
COMBINED SEAS ARE BETWEEN 3 TO 5 FEET ACCORDING TO BUOY DATA. A DRY
TRADE-WIND REGIME MAY RETURN TO THE REGION THIS WEEKEND.
DISCUSSION
A SUBTROPICAL RIDGE EXTENDING FROM THE NORTHEAST HAS WEAKENED THE
TRADES, BRINGING LIGHT AND VARIABLE WINDS TO THE REGION. VISIBLE
SATELLITE IMAGERY DEPICTED SCATTERED SHOWERS OVER THE CNMI ALL DAY,
AND ISLAND-EFFECT THUNDERSTORMS OVER GUAM EARLY THIS EVENING. THE
FRICTIONAL FORCE BETWEEN THE RIDGES TO THE SOUTHWEST AND NORTHEAST AS
WELL AS ADEQUATE PRECIPITABLE WATER (PWAT) VALUES AROUND 2.10 INCHES
WILL KEEP SCATTERED SHOWERS FOR THE ENTIRE REGION IN TONIGHT'S
FORECAST. AS FOR TOMORROW, MODEL GUIDANCE SHOWS HIGHER WINDS AND
INCREASED MOISTURE FOR THE CNMI COMPARED TO GUAM, SO SCATTERED
SHOWERS WILL REMAIN IN THE FORECAST, ADDING ISOLATED THUNDERSTORMS
FOR GUAM AS ISLAND CONVECTION REMAINS A POSSIBILITY DUE TO LIGHT AND
VARIABLE WINDS. THE DRY TRADE-WIND REGIME MAY RETURN TO THE REGION
STARTING FRIDAY, POSSIBLY LIMITING SHOWERS AND INCREASING WINDS
THROUGH THE WEEKEND.
MARINE
DUE TO THE LIGHT SOUTHEAST WINDS AND LACK OF OTHER FEATURES
PRODUCING SWELLS, COMBINED SEAS HAVE CONTINUED TO TAPER DOWN TO 3 TO
5 FEET FOR THE MARIANAS. THE IPAN AND TANAPAG BUOYS ARE REPORTING 5
FEET AND 3 FEET, RESPECTIVELY. SURF REMAINS 4 TO 6 FEET ALONG EAST-
FACING SHORES AND MAY BUILD OVER THE WEEKEND AS THE TRADES RETURN. A
MODERATE RISK OF RIP CURRENTS EXISTS ALONG NORTH- AND EAST-FACING
REEFS, BUT THERE IS A POSSIBILITY OF A HIGH RISK OF RIP CURRENTS FOR
EAST-FACING REEFS ONCE THE TRADE SWELL MOVES IN FROM THE EAST.
EASTERN MICRONESIA
A CONVECTIVELY ACTIVE INTERTROPICAL CONVERGENCE ZONE (ITCZ) AND AN
EMBEDDED TROPICAL DISTURBANCE THAT IT IS INTERACTING WITH, REMAIN
THE PRIMARY WEATHER MAKERS ACROSS EASTERN MICRONESIA. A LARGELY
DISORGANIZED TROPICAL DISTURBANCE, CENTERED NEAR 6N163E JUST NORTH OF
KOSRAE, IS EXPECTED TO CONTINUE TO BRING INTENSE SHOWERS AND SOME
THUNDERSTORMS TO KOSRAE OVERNIGHT AND TO POHNPEI BEGINNING THURSDAY
NIGHT. AS THIS FEATURE FURTHER CONSOLIDATES, PEAK SHOWER COVERAGE AT
POHNPEI IS EXPECTED FRIDAY AND FRIDAY NIGHT, FOLLOWED BY A RETURN OF
A PATCHY TRADE-WIND REGIME THEREAFTER AT BOTH POHNPEI AND KOSRAE. A
SURGE IN THE ITCZ HAS BEGUN TO LINE UP AND MOVE ACROSS MAJURO, WITH
NUMEROUS HEAVY SHOWERS AND SOME THUNDERSTORMS BRINGING NEAR GALE
GUSTS OVERNIGHT AND INTO THURSDAY, WITH UP TO 4 INCHES OF RAINFALL
TOTAL POSSIBLE OVER THE NEXT 24 TO 36 HOURS. SHOWERS WILL BEGIN TO
TAPER DOWN SLOWLY AFTER, AS THE ITCZ BECOMES MORE MODERATE AND THE
BULK OF THE CONVECTION MOVES NORTH AND WEST, AWAY FROM THE REGION.
COMBINED SEAS OF 4 TO 6 FEET IN POHNPEI AND KOSRAE WATERS, AND 5 TO
7 FEET IN MAJURO WATERS, ARE EXPECTED TO INCREASE ANOTHER FOOT OR TWO
BY THE WEEKEND AS TRADE SWELL AND LOCALIZED WIND WAVES STRENGTHEN
JUST NORTH OF 10N. THIS WILL ALLOW SOME OF THE SEAS TO INTRUDE INTO
THE AFOREMENTIONED WATERS, BUT SEA CONDITIONS WILL REMAIN BELOW
LEVELS HAZARDOUS TO SMALL CRAFT FOR THE TIME BEING.
WESTERN MICRONESIA
FOR YAP, A DRY PATTERN REGIME HAS SET UP AND IS ANTICIPATED TO HOLD
THROUGH MUCH OF THE FORECAST PERIOD. SHOWERS MAY RETURN NEAR THE
BEGINNING OF NEXT WEEK.
FOR PALAU, THERE REMAINS A TROUGH NEARBY THAT IS PRODUCING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TONIGHT. PERIODS OF ON AND OFF
AGAIN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE ANTICIPATED
THROUGH THE FORECAST PERIOD. THESE SHOWERS WILL BE PRODUCED BY
TROUGHS IN THE TRADE-WIND FLOW.
FOR CHUUK, A FAIRLY WET WEEK IS EXPECTED. THE INTERACTION BETWEEN
ITCZ AND THE EMBEDDED TROPICAL DISTURBANCE (CURRENTLY SOUTH OF
KOSRAE) IS EXPECTED TO MOVE WESTWARD INTO CHUUK'S REGION. THIS IS
EXPECTED TO BRING SCATTERED SHOWERS THAT MAY BUILD INTO NUMEROUS BY
THE WEEKEND, HOWEVER, DETERMINISTIC MODELS SUGGESTS THE BULK OF THE
RAINFALL WILL BE WELL TO THE NORTH OF CHUUK, JUST NORTH OF FANANU AND
ONOUN.
ALTIMETRY SHOWS COMBINED SEAS OF 4 TO 6 FEET ACROSS THE REGION.
WINDS ARE EXPECTED TO BE LIGHT TO MODERATE EXCEPT WHERE HEAVY
SHOWERS ARE FOUND. OVERALL, FAIRLY BENIGN SEA CONDITIONS ARE
EXPECTED.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: MESA
EAST MICRONESIA: MONTVILA
WEST MICRONESIA: BOWSHER
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