395
FXPQ50 PGUM 181838
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
438 AM CHST MON JAN 19 2026
MARIANAS UPDATE
NO CHANGES WERE MADE TO THE INHERITED FORECAST. A DRY TRADE-WIND
PATTERN WILL CONTINUE THROUGH MIDWEEK. A SHEAR LINE IS EXPECTED TO
MOVE INTO THE REGION THURSDAY.
EASTERN MICRONESIA UPDATE
THE ITCZ REMAINS THE PRIMARY WEATHER PRODUCER ACROSS EASTERN
MICRONESIA. HOWEVER, CONVECTION IS A BIT SLOWER DEVELOPING THAN
PREVIOUSLY EXPECTED. THEREFORE, SHOWER COVERAGE WAS DECREASED AT ALL
THREE LOCATIONS DURING THE MORNING, INCREASING TO WHAT WAS
PREVIOUSLY FORECAST NEAR NOON. OTHERWISE, NO OTHER CHANGES MADE TO
THE FORECAST.
WESTERN MICRONESIA UPDATE
AN OVERALL DRY PATTERN IS EXPECTED TO CONTINUE FOR YAP AND PALAU.
HOWEVER, PALAU CAN EXPECT ISLAND CONVECTION THIS AFTERNOON. FOR
CHUUK, CONVECTION IS HOLDING BACK THIS MORNING, THOUGH THIS IS
EXPECTED TO CHANGE THIS AFTERNOON. NUMEROUS SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED THIS AFTERNOON. NO OTHER CHANGES WERE
MADE.
PREV DISCUSSION
/ISSUED 558 PM CHST SUN JAN 18 2026/
MARIANAS SYNOPSIS...
SATELLITE IMAGERY SHOWS PARTLY TO MOSTLY CLOUDY SKIES AND ISOLATED
SHOWERS ACROSS THE MARIANAS. ALTIMETRY AND BUOY DATA SHOW COMBINED
SEAS BETWEEN 4 TO 6 FEET ACROSS THE REGION.
DISCUSSION...
OVERALL, QUIET CONDITIONS CONTINUE ACROSS THE MARIANAS. THE DRY
TRADE-WIND PATTERN LOOKS TO PERSIST THROUGH WEDNESDAY. HOWEVER, TWO
FEATURES LOOK TO GREATLY SHAKEUP THE PATTERN LATER THIS WEEK. THE
FIRST FEATURE IS A BROAD TROPICAL DISTURBANCE LOCATED NEAR EASTERN
CHUUK STATE AND WESTERN POHNPEI STATE. DUAL VORTICITY CENTERS HAVE
PRODUCED SCATTERED TO WIDESPREAD SHOWERS AND ISOLATED TO SCATTERED
THUNDERSTORMS. THIS FEATURE IS EXPECTED TO MOVE TO THE WEST-
NORTHWEST OVER THE COMING DAYS, BRINGING DEEP MOISTURE TO THE
MARIANAS LATER THIS WEEK. LATEST MODEL GUIDANCE SHOWS THIS
DISTURBANCE REMAINING WEAK AND UNORGANIZED, BUT CHANGES IN MODEL
TRENDS WILL BE MONITORED OVER THE COMING FORECASTS.
THE SECOND FEATURE IS A SHEAR LINE EXTENDING FROM SOUTH OF MINAMI
TORISHIMA TO SOUTH OF IWO TO. THE SHEAR LINE IS EXPECTED TO REMAIN
NORTH OF THE MARIANAS FOR THE FIRST HALF OF THE WEEK, BUT THEN GET
RE-INFORCED BY A NEW COLD-FRONT SENDING IT SOUTHWARD. AT THIS TIME,
GUIDANCE DIFFERS GREATLY ON THE POSITION AND STRENGTH OF THE SHEAR
LINE. THE GFS STALLS IT JUST NORTH OF SAIPAN, KEEPING THE BULK OF THE
SHOWERS NORTH OF THE REGION LATE THIS WEEK AND INTO NEXT WEEKEND.
MEANWHILE, THE ECMWF SENDS IT SOUTH TOWARDS GUAM AND STALLS IT OVER
THE ROTA CHANNEL. WHERE THE SHEAR LINE STALLS AND INTERACTS WITH THE
TROPICAL MOISTURE WILL GREATLY DETERMINE WHETHER THE MARIANAS SEES
TYPICAL SCATTERED SHOWERS LATE THIS WEEK, OR HEAVY RAINFALL. FOR NOW,
USED A BLEND OF THE GEFS/GFS, ECMWF, AND CANADIAN ENSEMBLES FOR A
MIDDLE SOLUTION.
MARINE/SURF...
BENIGN SEAS OF 4 TO 6 FEET ARE EXPECTED TO PERSIST THROUGH AT LEAST
THURSDAY. THE MARINE FORECAST REMAINS QUIET THROUGH THE FIRST HALF OF
THE WEEK UNTIL THE POTENTIAL OF ISOLATED THUNDERSTORMS ARRIVES ON
WEDNESDAY. THE RISK OF RIP CURRENTS WILL FALL TO LOW ON NORTH FACING
REEFS MONDAY WITH A MODERATE RISK OF RIP CURRENTS ALONG EAST FACING
REEFS. TOWARDS THE END OF THE WEEK AND INTO NEXT WEEKEND SEAS WILL
RISE AS THE SHEAR LINE APPROACHES THE REGION. HOW FAR SOUTH THE SHEAR
LINE GETS WILL DETERMINE WHETHER OR NOT MARINE CONDITIONS BECOME
HAZARDOUS TO SMALL CRAFT OR HAZARDOUS SURF WILL BE REACHED.
EASTERN MICRONESIA...
A LARGELY INACTIVE INTERTROPICAL CONVERGENCE ZONE (ITCZ) SPANS ACROSS
MUCH OF EASTERN MICRONESIA, TO THEN END AT A LARGELY DISORGANIZED
DUAL-VORTICITY TROPICAL DISTURBANCE CENTERED NEAR 5N152E WELL SOUTH
OF WENO, CHUUK IN WESTERN MICRONESIA. THIS FEATURE HAS BEEN IN THE
STABLE PHASE FOR THE PAST 18 HOURS, WHICH IS NOW EXPECTED TO ENTER
ANOTHER CONVECTIVE CYCLE AND BRING INCREASINGLY INTENSE SHOWERS AND
THUNDERSTORMS TO MAJURO, ESPECIALLY TONIGHT AND MONDAY, AFTER WHICH
THE SECTOR WEST OF MAJURO WILL DISSIPATE AS THE TROPICAL DISTURBANCE
IN CENTRAL MICRONESIA MOVES TO THE NORTH-NORTHWEST AND AWAY FROM THE
ITCZ. IN THE MEANTIME, HIGHER-END SCATTERED SHOWERS WITH SOME
THUNDERSTORMS ARE POSSIBLE OVERNIGHT AT POHNPEI, WITH SOME SHOWERS
BEING HEAVY AT TIMES, UNLESS THE AFOREMENTIONED DISTURBANCE MOVES
AWAY FROM POHNPEI SOONER, WITH LOWER-END SCATTERED SHOWERS EXPECTED
AT KOSRAE. AFTERWARDS, SHOWER AND THUNDERSTORM COVERAGE WILL
DIMINISH QUICKLY THEREAFTER, ALLOWING A DRIER REGIME TO ENSUE OVER
POHNPEI AND KOSRAE COMING INTO THE SECOND HALF OF THE WEEK. MEANWHILE
AT MAJURO, CONDITIONS ARE EXPECTED TO BECOME NOTICEABLY BETTER
BEGINNING TUESDAY, BEFORE THE ITCZ WEAKENS ENOUGH HEADING TOWARD THE
NEXT WEEKEND.
COMBINED SEAS OF 5 TO 7 FEET NEAR POHNPEI AND KOSRAE, AND 6 TO 9 FEET
NEAR MAJURO, ARE EXPECTED TO PERSIST FOR AT LEAST THE NEXT SEVERAL
DAYS AS NORTHEASTERLY SWELL REMAINS ELEVATED, AND A NORTHERLY SWELL
PULSE MAKES ITS WAY ACROSS THE REGION BEFORE SLOWLY TAPERING DOWN IN
THE SECOND HALF OF THE WEEK.
WESTERN MICRONESIA...
A BROAD TROPICAL DISTURBANCE CONTINUES TO PRODUCE UNSETTLED WEATHER
ACROSS MUCH OF CHUUK STATE. THIS DISTURBANCE REMAINS POORLY
ORGANIZED, WITH AN ELONGATED CIRCULATION LINGERING NEAR NUKUORO IN
SOUTHERN POHNPEI STATE AND BROAD TROUGH EXTENDING NORTHWEST, MEETING
ANOTHER VORTICITY FEATURE WEST OF CHUUK LAGOON. A SPECIAL WEATHER
STATEMENT FOR CHUUK REMAINS IN EFFECT FOR NUMEROUS LOCALLY HEAVY
SHOWERS, ISOLATED THUNDERSTORMS, GUSTY WINDS, AND CHOPPY SEAS
ASSOCIATED WITH THIS UNSETTLED PATTERN THROUGH MONDAY MORNING. RECENT
OBSERVATIONS SHOW STRONG GUSTS BECOMING LESS FREQUENT SINCE LAST
NIGHT, HOWEVER OCCASIONAL GUSTS TO 25 KT REMAIN POSSIBLE NEAR HEAVIER
SHOWERS. AROUND 3 TO 5 INCHES OF RAIN HAS FALLEN SINCE FRIDAY AND AN
ADDITIONAL 1 TO 2 INCHES ARE POSSIBLE THROUGH MONDAY. ONCE THIS
DISTURBANCE MOVES WEST OF CHUUK, SCATTERED TO NUMEROUS SHOWERS AND
ISOLATED THUNDERSTORMS WITHIN THE TRAILING TRADE-WIND CONVERGENCE MAY
PROLONG SHOWERY WEATHER THROUGH MIDWEEK, BUT THE THREAT OF HEAVY
RAINFALL, GUSTY WINDS AND CHOPPY SEAS SUBSIDES. FURTHER UPDATES WILL
BE PROVIDED AS WE MONITOR TRENDS IN SATELLITE OBSERVATIONS AND MODEL
GUIDANCE. COMBINED SEAS OF 6 TO 8 FEET ARE EXPECTED TO DECREASE TO 5
TO 7 FEET AROUND TUESDAY, AT WHICH TIME TRADE WINDS ARE EXPECTED TO
DIMINISH TO GENTLE TO MODERATE. BY FRIDAY, MARINE CONDITIONS SUBSIDE
FURTHER TO LIGHT TO GENTLE WINDS AND COMBINED SEAS OF 4 TO 6 FEET.
LIGHT TO GENTLE WINDS AND QUIET CONDITIONS CONTINUE NEAR YAP AND
PALAU THIS EVENING. INCLUDED THE POSSIBILITY OF ISLAND-EFFECT
SHOWERS, MAINLY BUILDING ALONG THE SOUTHERN HALF OF BABELDAOB, DUE
TO LIGHT NORTH TO NORTHEAST WINDS MONDAY AFTERNOON. AS THE TROPICAL
DISTURBANCE MOVES INTO EASTERN YAP STATE IN THE NEXT FEW DAYS, A
TREND TOWARDS WETTER WEATHER IS EXPECTED IN THE LATTER HALF OF NEXT
WEEK WITH WINDS INCREASING TO LIGHT TO MODERATE AT YAP BY FRIDAY.
DEPENDING ON THE DEVELOPMENT OF THIS TROPICAL DISTURBANCE AND
POTENTIAL FOR A SHEAR LINE TO PASS ALONG THE NORTH SIDE OF IT, THIS
WILL BE MONITORED OVER THE NEXT SEVERAL DAYS AS WE CONTINUE TO
ASSESS THE POTENTIAL FOR UNSETTLED WEATHER LATE THIS WEEK AND OVER
THE WEEKEND. COMBINED SEAS OF 4 TO 6 FEET ARE EXPECTED OVER THE NEXT
SEVERAL DAYS, THEN THE ARRIVAL OF NORTH-NORTHWEST SWELL MAY BEGIN TO
BUILD SEAS TO 6 TO 8 FEET LATE WEEK AND OVER THE WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: KLEESCHULTE
MARIANAS: WILLIAMS
EAST MICRONESIA: MONTVILA
WEST MICRONESIA: CRUZ
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