619
FXPQ50 PGUM 290740
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
540 PM CHST TUE SEP 29 2026
MARIANAS SYNOPSIS
LIGHT TO GENTLE WESTERLIES PREVAIL ACROSS THE MARIANAS. SATELLITE
IMAGERY AND DOPPLER RADAR INDICATE A CONVERGENCE ZONE DEVELOPING
TO THE EAST OF THE ISLAND CHAIN. RECENT ALTIMETRY PASSES INDICATE
SEAS ARE AROUND 3 TO 4 FEET.
DISCUSSION
AN UNSETTLED WEATHER PATTERN PRODUCED BY AN EXTENSIVE MONSOON TROUGH
DOMINATED PRIMARILY BY A DEVELOPING DISTURBANCE KNOWN AS INVEST 93W
WELL TO THE EAST, WILL CONTINUE FOR AT LEAST A FEW MORE DAYS. MOSTLY
DRY CONDITIONS ARE EXPECTED OVERNIGHT, FOLLOWED BY SOME PATCHY
SHOWERS DEVELOPING WEDNESDAY AS THE SOUTHWESTERLY MONSOON CONTINUES
TO BUILD. CONDITIONS WILL DETERIORATE AS INVEST 93W CONTINUES TO
CONSOLIDATE AND PASS TO THE NORTHEAST OF THE MARIANAS SOMETIME
FRIDAY THROUGH SATURDAY, INDUCING A SIGNIFICANT MONSOON SURGE THAT
WILL BRING A PEAK IN SHOWER AND THUNDER POTENTIAL BY THE WEEKEND.
CONDITIONS ARE THEN EXPECTED TO REMAIN WET COMING INTO NEXT WEEK AS A
SOUTHERWESTERLY MONSOON REGIME CONTINUES.
MARINE
COMBINED SEAS OF 3 TO 4 FEET WILL INCREASE OVER THE COMING DAYS, AS
INVEST 93W CONTINUES TO CONSOLIDATE TO THE EAST OF THE MARIANAS AND
ALLOWS A SOUTHWESTERLY MONSOON TO RETURN ACROSS THE REGION TOWARD THE
WEEKEND. AS 93W PASSES TO THE NORTHEAST AND A MONSOON SURGE DEVELOPS,
SEAS ARE EXPECTED TO SURPASS 10 FEET BEGINNING FRIDAY, LIKELY
BECOMING HAZARDOUS TO SMALL CRAFT. A MODERATE RISK OF RIP CURRENTS
IS EXPECTED TO DEVELOP ALONG EAST FACING REEFS OF THE MARIANAS
BEGINNING WEDNESDAY, TO THEN DEVELOP ALL REEFS WEDNESDAY NIGHT AS A
STRENGTHENING SOUTHWESTERLY SWELL ENVELOPS THE REGION. THERE IS SOME
LIKELIHOOD FOR HAZARDOUS SURF TO DEVELOP ALONG SOUTH, WEST AND NORTH
FACING REEFS OF THE MARIANAS BY THE WEEKEND, HIGHLY DEPENDENT ON THE
DEVELOPMENT OF 93W AND ASSOCIATED SOUTHWESTERLY MONSOON SURGE.
TROPICAL SYSTEMS
A DEVELOPING DISTURBANCE FOUND ALONG THE MONSOON TROUGH, INVEST 93W,
IS CENTERED EAST OF SAIPAN NEAR 15.2N 155.5E. 93W IS NOW RATED
MEDIUM BY THE JOINT TYPHOON WARNING CENTER (JTWC), MEANING THAT
DEVELOPMENT INTO A SIGNIFICANT TROPICAL CYCLONE (TROPICAL
DEPRESSION) IS EXPECTED, BUT NOT WITHIN THE NEXT 24 HOURS. INVEST
93W CONTINUES TO MOVE SLOWLY WEST-NORTHWEST. CONVECTION HAS BEEN
PERSISTENT TO THE WEST THROUGH NORTH OF THE CENTER. INVEST 93W IS
EXPECTED TO SLOWLY STRENGTHEN AS IT CONTINUES MOVING WEST-NORTHWEST
TO NORTHWEST OVER THE COMING DAYS, LIKELY PASSING NORTH OF SAIPAN
LATE IN THE WEEK. RESIDENTS OF THE MARIANAS, ESPECIALLY TINIAN,
SAIPAN AND THE NORTHERN CNMI, SHOULD MONITOR FORECASTS FOR ANY
CHANGES TO EXPECTATIONS FOR INVEST 93W.
FOR MORE INFORMATION ON INVEST 93W, SEE BULLETINS ISSUED BY JTWC
UNDER WMO HEADER ABPW10 PGTW.
EASTERN MICRONESIA
NOT MUCH HAPPENING ACROSS EASTERN MICRONESIA THIS AFTERNOON. LATEST
GUIDANCE STILL SHOWING A VERY DRY PATTERN CONTINUING FOR THE NEXT
SEVERAL DAYS ACROSS POHNPEI AND KOSRAE, WITH POPS (PROBABILITY OF
PRECIPITATION) REMAINING IN THE 10 PERCENT RANGE FOR POHNPEI AND 20
PERCENT FOR KOSRAE. FOR MAJURO, INFLOW AND INCREASED CONVERGENCE DUE
TO STRENGTHENING INVEST 93W IS STILL EXPECTED TO BRING INCREASED
CONVECTION TO THE MARSHALLS BEGINNING WEDNESDAY NIGHT AND CONTINUING
THROUGH THE WEEKEND. NO MAJOR CHANGES WERE MADE TO THE MARINE
FORECAST.
WESTERN MICRONESIA
THE MONSOON TROUGH REMAINS THE DOMINANT FEATURE EFFECTING THE
REGION. THE SHOWERS ASSOCIATED WITH THIS FEATURE ARE OVER PALAU AND
YAP, THIS FEATURE IS PRODUCING UP TO SCATTERED AND ISOLATED
THUNDERSTORMS, WITH THE MOST ACTIVE SHOWERS ARE NORTHWEST OF PALAU.
AS INVEST 93W CONSOLIDATES AND MOVES WEST-NORTHWEST, THE MONSOON
TROUGH IS NORTH OF THE DOMAIN IS EXPECTED TO TURN INTO A MORE NE-SW
DIRECTION.
PALAU IS INBETWEEN DECAYING SHOWERS PRODUCED BY THE CONVERGENCES OF
THE MONSOON TROUGH AND SOUTHWESTERLY WINDS, SHOWERS WILL VARY
BETWEEN ISOLATED AND SCATTERED THROUGH ABOUT THURSDAY AS THIS
CONVERGENCE SHIFTS WITH 93W'S CONSOLIDATION. FOR THE WEEKEND,
SHOWERS ARE EXPECTED TO SCATTERED AS THE MONSOON SURGE PASSES OVER
THE ISLAND.
TODAY AT YAP, SHOWERS OF DIMINISHED OVER THE ISLAND. SHOWERS ARE
EXPECTED TO BUILD BACK IN THIS EVENING AND REMAIN THROUGH THE REST
OF THE WEEK AS 93W CONSOLIDATES AND BRING A MONSOON SURGE OVER THE
ISLAND. MODEL GUIDANCE SUGGESTS UP TO 1 INCH OF RAIN EACH DAY THROUGH
THE REMAINDER OF THE WEEK. OVERALL, A WET WEEK IS TO BE EXPECTED.
CHUUK IS ON THE SOUTHERN EDGE OF THE CONVECTIVE ACTIVITY PRODUCED BY
THE MONSOON TROUGH. HERE IS WHERE BLOW-OFF CLOUD COVER IS THE
GREATEST. THIS CLOUD COVER IS EXPECTED TO PRODUCE ISOLATED SHOWERS
WHILE THE TROUGH REMAINS IN A E-W ORIENTATION. ONCE 93W STARTS
PULLING THE TROUGH AWAY, DRIER CONDITIONS ARE EXPECTED TO RETURN
FOR THE WEEKEND AND INTO NEXT WEEK.
ALTIMETRY SHOWS COMBINED SEAS BETWEEN 3 AND 5 FEET ACROSS THE
REGION. WINDS WILL BE LIGHT TO MODERATE THROUGH THURSDAY, THEN WINDS
ARE EXPECTED TO BUILD TO GENTLE TO FRESH NEAR THE WEEKEND. SEA
CONDITIONS ARE EXPECTED TO REMAIN BENIGN THROUGH THURSDAY, THEN SEAS
ARE ANTICIPATED TO BUILD TO AROUND 7 TO 8 FEET FOR THE WEEKEND AND
BEGINNING OF NEXT WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: MONTVILA
EAST MICRONESIA/TROPICAL SYSTEMS: KLEESCHULTE
WEST MICRONESIA: BOWSHER
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