288
FXPQ50 PGUM 131935
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
535 AM CHST WED OCT 14 2026
MARIANAS UPDATE
SHOWER COVERAGE IS EXPECTED TO REMAIN ISOLATED FOR THE NEXT COUPLE OF
DAYS. THOUGH, LIGHTER WINDS TODAY MAY ALLOW FOR SOME ISLAND-EFFECT
SHOWERS TO BUILD, BUT THE PRESENCE OF DRIER AIR WILL LIMIT ANY
THUNDERSTORM POTENTIAL. COMBINED SEAS AROUND 3 FEET TODAY WILL SLOWLY
BUILD THROUGH THURSDAY, BEFORE INCREASING SIGNIFICANTLY ON FRIDAY
AHEAD OF INVEST 96W. LIGHT EAST WINDS TODAY WILL INCREASE TO GENTLE
TO MODERATE AS THEY BECOME NORTHEAST BY THE END OF THE WORK WEEK.
OTHERWISE, A MODERATE RISK OF RIP CURRENTS WILL CONTINUE FOR THE NEXT
COUPLE DAYS ALONG NORTH AND EAST-FACING REEFS.
TROPICAL SYSTEMS UPDATE
TROPICAL DEPRESSION (TD) 28W PASSED NEAR AGRIHAN LATE YESTERDAY
EVENING AND IS LOCATED AROUND 20.1N 144.5E THIS MORNING. 28W WILL
CONTINUE TO TREK TO THE NORTHWEST AROUND 12 MILES PER HOUR THROUGH
EARLY THURSDAY. THE CURRENT INTENSITY IS 30 MILES PER HOUR AND IT IS
EXPECTED TO MAINTAIN THIS INTENSITY BEFORE WEAKENING BELOW TROPICAL
DEPRESSION CRITERIA ON THURSDAY.
ATTENTION THEN TURNS TO INVEST 96W WHICH IS LOCATED NEAR 10.1N 161.6E
THIS MORNING. 96W IS NOW THE SUBJECT OF A TROPICAL CYCLONE FORMATION
ALERT FROM THE JOINT TYPHOON WARNING CENTER, MEANING THAT
DEVELOPMENT INTO A SIGNIFICANT TROPICAL CYCLONE IS EXPECTED TO OCCUR
WITHIN THE NEXT 24 HOURS. CONSENSUS AMONGST THE ENSEMBLE GUIDANCE
SUGGESTS A PASSAGE SOMEWHERE IN THE MARIANAS THIS WEEKEND. RESIDENTS
OF THE MARIANAS SHOULD CONTINUE TO MONITOR THE FORECAST OVER THE
COMING DAYS.
FOR MORE INFORMATION ON TD 28W, PLEASE REFER TO THE TROPICAL CYCLONE
PUBLIC ADVISORIES ISSUED BY THE NATIONAL WEATHER SERVICE UNDER WMO
HEADER WTPQ31 PGUM AND THE TROPICAL CYCLONE WARNINGS ISSUED BY THE
JOINT TYPHOON WARNING CENTER UNDER WMO HEADER WTPN31 PGTW. FOR MORE
INFORMATION ON INVEST 96W, PLEASE SEE THE TROPICAL CYCLONE FORMATION
ALERT BULLETIN FROM THE JOIN TYPHOON WARNING CENTER UNDER WMO HEADER
WTPN21 PGTW AND THE SIGNIFICANT TROPICAL WEATHER ADVISORIES FROM THE
JOINT TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10 PGTW.
EASTERN MICRONESIA UPDATE
ONLY MINOR CHANGES WERE NEEDED FOR FORECAST TONIGHT. ADDED IN
FREQUENT GUSTS TO KOSRAE TO BETTER A LINE WITH WITH SMALL CRAFT
ADVISORY. SEAS REMAIN 5 TO 7 FEET AT POHNPEI, 6 TO 9 FEET AT KOSRAE
AND 4 TO 6 FEET AT MAJURO. SURF IS EXPECTED TO BE THE GREATEST ALONG
WEST FACING REEFS AND INCHING NEAR ADVISORY THRESHOLDS AT KOSRAE.
OVERALL, HEAVY SHOWERS ARE EXPECTED OVER NEXT FEW DAYS FOR POHNPEI
AND KOSRAE. MAJURO REMAINS IN THE MONSOON TROUGH ALLOWING FOR
SCATTERED SHOWERS TO CONTINUE.
WESTERN MICRONESIA UPDATE
ONLY MINOR CHANGES WERE NEEDED FOR THE FORECAST TONIGHT. ADDED
ISOLATED THUNDER AT PALAU AS THE MONSOON TROUGH LOOKS TO DIP MORE
SOUTHWARD THAN PREVIOUSLY EXPECTED. OTHERWISE, THE FORECAST REMAINS
IN GOOD SHAPE.
PREV DISCUSSION
/ISSUED 632 PM CHST TUE OCT 13 2026/
MARIANAS SYNOPSIS...
VISIBLE SATELLITE IMAGERY AND DOPPLER RADAR INDICATE PARTLY CLOUDY
SKIES AND ISOLATED SHOWERS ACROSS THE MARIANAS. COMBINED SEAS OF 2
TO 3 FT CONTINUE FOR THE REGION.
DISCUSSION...
DRIER AIR WITH PRECIPITABLE WATER (PWAT) VALUES AROUND 1.8 INCHES
CONTINUE TO SIT OVER THE REGION WITH DRIER AIR ALOFT, SO SHOWER
COVERAGE REMAINS ISOLATED AND IS EXPECTED TO CONTINUE THROUGH THE
NEXT SEVERAL DAYS. LIGHT AND VARIABLE WINDS MAY ALLOW FOR ISLAND-
EFFECT SHOWERS BEFORE INCREASING TO GENTLE TO MODERATE OUT OF THE
NORTHEAST BY THE END OF THE WORK WEEK. ENSEMBLE MODEL GUIDANCE
CONTINUES TO SHOW A PASSAGE ANYWHERE BETWEEN SOUTH OF GUAM TO NORTH
OF SAIPAN AS A TROPICAL STORM OR TYPHOON. UNCERTAINTY IS STILL HIGH
REGARDING TIMING, LOCATION, AND INTENSITY, BUT THE POTENTIAL FOR
HEAVY RAINFALL AND GUSTY WINDS CONTINUES TO INCREASE AS THE WEEKEND
APPROACHES. RESIDENTS OF THE MARIANAS CAN BEGIN BASIC EARLY
PREPAREDNESS TASKS SUCH AS CLEANING STORM DRAINS, TAKING INVENTORY OF
STORM SUPPLIES, AND TRIMMING OVERGROWN FOLIAGE AS WELL AS MONITORING
THE FORECAST THROUGH THE WEEK.
MARINE...
COMBINED SEAS OF 2 TO 3 FEET ARE EXPECTED FOR THE REGION AS AN
ALTIMETRY PASS FAR OFF TO THE WEST INDICATES 2 TO 4 FEET. SWELLS OUT
OF THE NORTH AND NORTHEAST CONTINUE TO DIMINISH TONIGHT BEFORE THE
EAST SWELL BEGINS TO BUILD WEDNESDAY NIGHT. LIGHT AND VARIABLE WINDS
WILL SHIFT TO THE NORTHEAST AND INCREASE TO GENTLE TO MODERATE BY THE
END OF THE WORK WEEK. THEN, THE EAST TO NORTHEAST SWELL AND WINDS WILL
SIGNIFICANTLY INCREASE OVER THE WEEKEND THROUGH EARLY NEXT WEEK.
HYDROLOGY...
INVEST 96W IS STILL A BROAD, DISORGANIZED DISTURBANCE LOCATED ABOUT
300 MILES NORTH OF KOSRAE. ENSEMBLE MODEL GUIDANCE CONTINUES TO SHOW
A PASSAGE ANYWHERE BETWEEN SOUTH OF GUAM TO NORTH OF SAIPAN AS A
TROPICAL STORM OR TYPHOON. UNCERTAINTY IS STILL HIGH REGARDING
TIMING, LOCATION, AND INTENSITY, BUT THE POTENTIAL FOR LOCALLY HEAVY
RAINFALL AND FLOODING CONTINUES TO INCREASE APPROACHING THIS WEEKEND.
THIS IS EXPECTED TO PRODUCE 5 TO 8 INCHES OF RAINFALL BETWEEN
SATURDAY AND MONDAY, WITH LOCALIZED AMOUNTS UP TO 12 INCHES POSSIBLE.
AS SHOWERS ARE LIKELY TO PERSIST, CONSISTENT RAINFALL IS LIKELY TO
SATURATE THE SOILS ENOUGH TO INCREASE CHANCE FOR MUDSLIDES. RESIDENTS
ON THESE ISLANDS NEED TO CLOSELY MONITOR THIS DEVELOPING SITUATION
AS FLOOD WATCHES, ADVISORIES, AND FLASH FLOOD WARNINGS COULD BE
ISSUED LATER THIS WEEKEND.
TROPICAL SYSTEMS...
TD 28W CONTINUES TO HEAD NORTHWEST, LOCATED AT 16.7N 146.4E.
RECENTLY DEEP CONVECTION HAS DEVELOPED ALONG THE SOUTHERN FLANK, SO
WE'LL SEE IF THIS SYSTEM TRIES TO STRENGTHEN OR IF THIS IS JUST A
BRIEF "FLARE-UP". MAXIMUM SUSTAINED WINDS REMAIN AT 35 MPH. IT'S
EXPECTED TO TURN MORE NORTH THAN NORTHEAST OVER THE NEXT FEW DAYS, AS
IT SLOWLY WEAKENS.
THE MAIN ITEM OF INTEREST HAS BEEN INVEST 96W, LOCATED NEAR 9.7N
163.8E, CURRENTLY LOCATED EAST OF UJELANG IN THE RMI. IT WAS UPGRADED
TO "MEDIUM" BY THE JOINT TYPHOON WARNING CENTER. THIS MEANS THE
FORMATION OF A TROPICAL CYCLONE IS LIKELY, BUT BEYOND 24 HOURS. AT
THIS TIME, UNCERTAINTY HAS GROWN AS THE CONSISTENT ECMWF (CONSISTENT
THE LAST FEW DAYS) HAS TRENDED WEAKER AND FURTHER NORTH TODAY,
SIMILAR TO THE GEFS. MEANWHILE, THE ECAIE, GFS-FV3, GFS-WNV3, AND
THE GFS-GENCE REMAIN IN LOCKSTEP AGREEMENT THAT A POTENTIALLY
SIGNIFICANT TROPICAL CYCLONE WILL PASS THROUGH THE MARIANAS, MUCH
STRONGER THAN THE ECENS AND GEFS IMPLY. GIVEN THAT THE SYSTEM IS
JUST NOW STARTING TO SHOW DEEP CONVECTION DEVELOPING NEAR ITS LLCC
(LOW-LEVEL CIRCULATION CENTER), AND CONSIDERING ITS OVER 1,300 MILES
AWAY FROM ANDERSEN AFB, "THE JURY IS STILL OUT" REGARDING IF IT'LL
BE A TROPICAL STORM/WEAK TYPHOON VERSUS SOMETHING MORE SIGNIFICANT.
THE MAIN THING WE'RE TELLING FOLKS IS STAY CALM, CONTINUE TO PREPARE
FOR A POTENTIAL TROPICAL STORM OR TYPHOON PASSAGE, MAKE SURE YOU CALL
GPA TO CUT DOWN AND LIMBS NEAR NEAR LINES BEFORE THE STORM, STAY
INFORMED, AND CONTINUE TO FOLLOW US EITHER ON SOCIAL MEDIA OR AT
WEATHER.GOV/GUM.
EASTERN MICRONESIA...
THE MAIN FEATURE OF INTEREST CONTINUES TO BE INVEST 96W, WHICH WAS
UPGRADED TO "MEDIUM" BY THE JOINT TYPHOON WARNING CENTER. THIS MEANS
THE FORMATION OF A TROPICAL CYCLONE IS LIKELY, BUT BEYOND 24 HOURS.
96W CONTINUES TO STRUGGLE TO ORGANIZE, BUT THE MODELS SHOW THIS WILL
CHANGE IN THE NEXT 18 TO 48 HOURS, WITH THE SYSTEM HEADING WEST-
NORTHWEST OR NORTHWEST BY WEDNESDAY AFTERNOON, WITH THE INFLOW INTO
THIS TROPICAL DISTURBANCE PERSISTING INTO LATE WEDNESDAY NIGHT OR
THURSDAY. AS SUCH, THE SPECIAL WEATHER STATEMENT (SPS) WAS REISSUED
FOR POHNPEI AND KOSRAE. THERE, LOOK FOR LOCALLY HEAVY RAINFALL AND
ISOLATED WIND GUSTS TO 30 KNOTS TO REMAIN POSSIBLE THROUGH THURSDAY.
FURTHER EAST AT MAJURO, YOU'RE MORE REMOVED FROM THE INFLOW. STILL,
WITH THE MONSOON TROUGH LURKING NEAR BY, SCATTERED SHOWERS REMAIN
POSSIBLE THE NEXT FEW DAYS.
MARINERS CAN EXPECT SEAS OF 5 TO 7 FEET WITH GENTLE TO MODERATE WINDS
AT POHNPEI, SEAS OF 6 TO 9 FEET WITH MODERATE TO STRONG WINDS AT
KOSRAE, WHERE A SMALL CRAFT ADVISORY REMAINS IN EFFECT, AND 4 TO 6
FEET WITH LIGHT TO GENTLE WINDS AT MAJURO. MAJURO.
WESTERN MICRONESIA...
THE CONVERGENCE ZONE WITHIN THE SOUTHERN PERIPHERIES OF THE MONSOON
AXIS, CONTINUES TO PRODUCE PATCHY SHOWERS AND THUNDERSTORMS ACROSS
MUCH OF WESTERN MICRONESIA SOUTH OF 10N, BRINGING SAID WEATHER
CONDITIONS TO PALAU AND YAP THE NEXT FEW DAYS. AFTER, CONDITIONS ARE
EXPECTED TO STEADILY IMPROVE AS THE CONVERGENCE ZONE WEAKENS UNDER
THE EXPANSION OF THE MONSOON TROUGH, MAINLY UNDER THE INFLUENCE OF
DEVELOPING INVEST 96W THAT WILL MOVE ACROSS THE MARIANAS DURING THE
WEEKEND. CHUUK IS WELL WITHIN AN ENHANCED MONSOON SURGE BUILDING
ALONG THE SOUTHWESTERN FRINGES OF INVEST 96W, WHICH IS LIKELY TO
DEEPEN OVER THE COMING DAYS, BRINGING PEAK SHOWER AND THUNDER
POTENTIAL WEDNESDAY NIGHT THROUGH THURSDAY NIGHT. AS 96W MOVES AWAY
FROM THE AREA, WINDS WILL CONTINUE TO INCREASE ACROSS CHUUK DURING
THE WEEKEND, POTENTIALLY REACHING NEAR GALE-FORCE BY SATURDAY.
COMBINED SEAS OF 3 TO 5 FEET ACROSS PALAU AND YAP WATERS ARE EXPECTED
TO DROP A FOOT OR TWO OVER THE NEXT FEW DAYS, TO BEGIN INCREASING
NEXT WEEKEND AS DISTANT SWELLS FROM 96W ARRIVE TO THE REGION.
COMBINED SEAS OF 4 TO 5 FEET NEAR CHUUK ARE EXPECTED TO INCREASE FOR
MUCH OF THE WEEK, POTENTIALLY REACHING LEVELS HAZARDOUS TO SMALL
CRAFT OVER THE WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/TROPICAL UPDATE: WHISNANT
EAST AND WEST MICRONESIA UPDATE: BOWSHER
MARIANAS/HYDROLOGY: MESA
EAST MICRONESIA/TROPICAL: DOLL
WEST MICRONESIA: MONTVILA
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