382
FXPQ50 PGUM 212034
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
634 AM CHST WED JUL 22 2026
MARIANAS UPDATE
SATELLITE SHOWS FAIRLY DRY AND QUIET WEATHER OVER THE MARIANAS EARLY
THIS MORNING. JUST REDUCED CLOUDS A LITTLE THIS MORNING BASED ON
SATELLITE PRESENTATION. OVERALL THE FORECAST OF ISLAND CONVECTION
THIS AFTERNOON LOOKS GOOD. RATHER THAN FLAT FIELDS OF TOTAL WAVE
HEIGHT THE NEXT FEW PERIODS, POPULATED WITH ECMWF WAVE, WHICH SHOWS
HIGHER HEIGHTS (NEAR WHAT THEY HAD BEEN IN THE AFTERNOON PACKAGE) AT
GUAM AND LOWER HEIGHTS AT SAIPAN. THE DIFFERENCE PROBABLY ENDED UP
BEING LITTLE MORE THAN COSMETIC. INVEST 93W, CURRENTLY IN THE
MARSHALL ISLANDS, COULD APPROACH THE MARIANAS MID TO LATE NEXT WEEK.
CURRENT TOOLS LOOK LIKE IT SHOULD STILL BE A FAIRLY WEAK SYSTEM AT
THAT TIME, NEVERTHELESS, THE NATIONAL WEATHER SERVICE AND JOINT
TYPHOON WARNING CENTER WILL CONTINUE TO MONITOR THE SITUATION FOR
CHANGES.
TROPICAL SYSTEMS
A BROAD DISTURBANCE IS TAKING SHAPE WITHIN THE MONSOON TROUGH NORTH
OF PALAU AND YAP NEAR 13N135E, CALLED INVEST AREA 92W BY THE JOINT
TYPHOON WARNING CENTER (JTWC). 92W IS NOW RATED MEDIUM, MEANING THAT
DEVELOPMENT INTO A TROPICAL DEPRESSION IS EXPECTED, BUT PROBABLY NOT
WITHIN 24 HOURS. HIMAWARI INFRARED SATELLITE IMAGERY OVERNIGHT SHOWS
FLARING CONVECTION ALONG THE SOUTH AND EAST PERIPHERY IS NOW WRAPPING
AROUND THE NORTH AND WEST SIDES. MODERATE RAINFALL PERSISTED OVER
YAP AND PALAU OVERNIGHT. OVER THE NEXT FEW DAYS, INVEST 92W LOOKS TO
GRADUALLY STRENGTHEN A BROAD CIRCULATION OVER THE PHILIPPINE SEA AS
IT MEANDERS NORTHWEST, POTENTIALLY EXITING WEST OF GUAM'S AREA OF
RESPONSIBILITY (AOR) BY THE END OF THE WEEK, AND POTENTIALLY AS A
TROPICAL DEPRESSION. OVERALL, 92W WILL HELP MAINTAIN A WET MONSOON
PATTERN OVER FAR WESTERN MICRONESIA THROUGH FRIDAY.
ADDITIONALLY, A WEAK DISTURBANCE IS SEEN TO THE NORTHEAST OF MAJURO
ATOLL NEAR 12N176E, CALLED INVEST AREA 93W BY JTWC AS OF THIS
MORNING. 93W IS RATED AS A "SUB-LOW", MEANING DEVELOPMENT IS NOT
EXPECTED OVER THE NEXT FEW DAYS. LATEST SCATTEROMETRY DATA DEPICTS A
SMALL CIRCULATION HERE DISPLACED WELL SOUTH OF THE CONVECTION, WITH
10 TO 20 MPH WINDS ALONG ITS NORTHERN FLANK. THERE IS ANOTHER WEAK
CIRCULATION NEARBY TO ITS SOUTHWEST, LOCATED SOUTH OF MAJURO NEAR
4N172E. THIS HELPS TO SHOW HOW LOOSE THE ORGANIZATION OF THIS AREA
IS, WHICH IS WHY IT'S NOT EVEN LOW YET. IT WILL CONTINUE TO BE
MONITORED FOR CHANGES BY THE NATIONAL WEATHER SERVICE AND THE JOINT
TYPHOON WARNING CENTER.
EASTERN MICRONESIA UPDATE
THE FORECASTS FOR KOSRAE AND MAJURO LOOKED FINE AS THEY WERE, SO NO
CHANGES WERE MADE IN EITHER PLACE. THE ONLY CHANGE MADE IN POHNPEI
WAS TO DECREASE MORNING CLOUD COVER, AS THEY HAVE A CLEAR SLOT MOVING
IN, THEN IT SHOULD CLOUD UP AGAIN FOR THE AFTERNOON.
WESTERN MICRONESIA UPDATE
ONLY SIGNIFICANT CHANGE WAS TO BACK OFF ON POP'S A LITTLE BIT FOR
YAP, DUE TO LESS IMPRESSIVE SATELLITE PRESENTATION, AND A NOT EXACTLY
THUNDEROUS 0.14 INCHES OF RAIN OVER THE PAST 12 HOURS. THE STRONGER
CONVERGENCE ASSOCIATED WITH 92W IS BEGINNING TO PULL AWAY FROM YAP
ALSO. THE FORECASTS FOR PALAU AND CHUUK, HOWEVER, LOOKED FINE AS THEY
WERE. SO NOW YAP IS NUMEROUS TODAY AS OPPOSED TO CATEGORICAL.
PREV DISCUSSION
/ISSUED 611 PM CHST TUE JUL 21 2026/
MARIANAS SYNOPSIS...
SATELLITE SHOWS ISOLATED TO LOW-END SCATTERED SHOWERS ACROSS THE
MARIANAS THIS EVENING AS WEAK SHOWER BANDS FROM INVEST 92W MOVE
THROUGH. MORE SCATTERED BANDS ARE EXPECTED TONIGHT, MAINLY FOR GUAM.
WINDS TODAY WERE MOSTLY HIGH ENOUGH TO LIMIT ISLAND EFFECT AND ARE
ALREADY STARTING TO MAKE A TURN TO THE SOUTH OVER GUAM. ALTIMETRY,
BUOY, AND MODEL DATA SUGGEST COMBINED SEAS ARE 4 TO 5 FEET.
DISCUSSION...
THE MONSOON TROUGH WITH EMBEDDED INVEST 92W TO THE SOUTHWEST OF THE
MARIANAS CONTINUES TO PUSH OCCASIONALLY SCATTERED SHOWERS INTO THE
REGION ALONG WITH INCREASINGLY SOUTHERLY WINDS. THIS DISTURBANCE IS
EXPECTED TO KEEP ITS DISTANCE AND KEEP THE MARIANAS DRY OVERALL FOR
THE NEXT FEW DAYS, WITH THE EXCEPTION OF INCREASING ISLAND EFFECT
SHOWERS AND THUNDERSTORMS. GUAM MAY RECEIVE SLIGHTLY MORE RAINFALL
DUE TO ITS CLOSER PROXIMITY TO 92W. LIGHT TO GENTLE WINDS WILL SLOWLY
DROP OFF TO LIGHT AND VARIABLE WINDS TOMORROW NIGHT. THIS WILL ALLOW
ISLAND EFFECT SHOWERS AND THUNDERSTORMS TO DEVELOP IN THE AFTERNOON
THROUGH SATURDAY FOR GUAM, TINIAN, AND SAIPAN. WINDS MAY EVEN BE
LIGHT ENOUGH THURSDAY FOR ROTA TO RECEIVE ISLAND EFFECT SHOWERS.
COVERAGE WILL DEPEND ON HOW CLEAR CONDITIONS ARE IN THE MORNINGS. AS
A SHEARLINE/COLD FRONT AND THE BAND OF CONVERGENCE NEAR CHUUK
INTERACT, THIS MAY INCREASE THE CHANCE FOR PRECIPITATION OVER THE
MARIANAS WEDNESDAY NIGHT. HOWEVER, THIS REMAINS UNCERTAIN SO ISOLATED
SHOWERS AND THUNDERSTORMS REMAIN IN THE FORECAST. AFTERWARDS,
OVERALL SHOWER COVERAGE IS EXPECTED TO RETURN TO ISOLATED OVER THE
WEEKEND, WITH ISOLATED THUNDERSTORMS RETURNING AT THE END OF THE WEEK
AS INVEST 93W POTENTIALLY APPROACHES THE MARIANAS.
MARINE...
LIGHT TO GENTLE SOUTHEASTERLIES WILL PREVAIL ACROSS THE REGION
THROUGH EARLY TONIGHT, SHIFTING SOUTH BY MIDNIGHT. COMBINED SEAS OF
4 TO 5 FEET ARE EXPECTED TO REMAIN FAIRLY STEADY WITH A SLIGHT
INCREASE WEDNESDAY POSSIBLE DEPENDING ON THE MONSOON SURGE TO THE
SOUTHWEST. OTHERWISE, SEAS LOOK TO DROP THURSDAY NIGHT. THE MAIN
SWELLS ARE THE DOMINANT SOUTHWEST SWELL, THE WEAK EASTERLY TRADE
SWELL, AND A WEAK SOUTHEAST SWELL. A MODERATE RISK OF RIP CURRENTS IS
IN EFFECT FOR SOUTH AND WEST FACING REEFS. A FOURTH WEAK, BUT VERY
LONG PERIOD SOUTHEAST SWELL IS ALSO POSSIBLE SOMETIME TOMORROW.
THEREFORE, EAST REEFS WILL NEED TO BE MONITORED FOR THE POTENTIAL TO
REACH A MODERATE RISK OF RIP CURRENTS AS SOON AS WEDNESDAY NIGHT.
ISOLATED THUNDERSTORMS ARE POSSIBLE THROUGH AT LEAST FRIDAY, CAUSING
A MODERATE RISK OF LIGHTNING ALONG COASTLINES.
TROPICAL SYSTEMS...
A VERY BROAD, WEAK DISTURBANCE HAS BEGUN TO TAKE SHAPE WITHIN THE
MONSOON TROUGH NORTH OF PALAU AND YAP NEAR 13N136E, NOW DUBBED
INVEST 92W BY THE JOINT TYPHOON WARNING CENTER (JTWC). 92W IS RATED
"SUB-LOW", MEANING IT IS NOT EXPECTED TO DEVELOP INTO A SIGNIFICANT
TROPICAL CYCLONE (A TROPICAL DEPRESSION) OVER THE NEXT FEW DAYS, BUT
WILL CONTINUE TO BE MONITORED FOR DEVELOPMENT. HIMAWARI VISIBLE
SATELLITE IMAGERY THIS AFTERNOON SHOWS AN AREA OF BROAD, FLARING
CONVECTION WITHIN THE CONVERGENCE ALONG 92W'S SOUTHERN AND EASTERN
FLANK, ASSOCIATED WITH THE MONSOON PATTERN FEEDING INTO IT. MODERATE
TO LOCALLY HEAVY RAINFALL PERSISTED OVER YAP THROUGH THE MORNING,
BUT IS BEGINNING TO BREAK UP THIS AFTERNOON. WHILE SHOWERS ARE ALSO
FAIRLY PATCHY TO THE SOUTHWEST NEAR PALAU, LOCALLY HEAVY RAINFALL
WILL BE POSSIBLE AT TIMES THROUGH AT LEAST TONIGHT AS 92W SHIFTS
NORTHWESTWARD. OVER THE NEXT FEW DAYS, INVEST 92W LOOKS TO GRADUALLY
DEVELOP A VERY BROAD CIRCULATION OVER THE PHILIPPINE SEA AS IT
MEANDERS NORTHWEST, POTENTIALLY EXITING WEST OF GUAM'S AREA OF
RESPONSIBILITY (AOR) BY THE END OF THE WEEK, AND POTENTIALLY AS A
TROPICAL DEPRESSION. OVERALL, 92W WILL HELP MAINTAIN A WET MONSOON
PATTERN OVER FAR WESTERN MICRONESIA FOR MUCH OF THE REMAINDER OF THE
WEEK.
ADDITIONALLY, A WEAK DISTURBANCE IS SEEN TO THE NORTHEAST OF MAJURO
ATOLL NEAR 12N178E, NOW DUBBED INVEST 93W BY JTWC AS OF THIS
MORNING. 93W IS ALSO RATED AS A "SUB-LOW", AND DEVELOPMENT IS NOT
EXPECTED OVER THE NEXT FEW DAYS. LATEST SCATTEROMETRY DATA DEPICTS A
SMALL CIRCULATION HERE WITH 15 TO 20 MPH WINDS ALONG ITS NORTHERN
FLANK, AND A SMALL EMBEDDED AREA OF 25 MPH WINDS ASSOCIATED WITH
NEARBY CONVECTION. THERE IS ANOTHER WEAK CIRCULATION NEARBY TO ITS
SOUTHWEST, LOCATED SOUTHEAST OF MAJURO NEAR 4N174E. CIMSS 850MB
VORTICITY ANALYSIS SHOWS THE STRONGER LOW-LEVEL VORTICITY IS FOCUSED
AROUND 93W, AND MODELS SUPPORT SLIGHT CONSOLIDATION AROUND THIS AREA
OVER THE NEXT FEW DAYS. AT THE SAME TIME, SOME OF THE VORTICITY NEAR
MAJURO LOOKS TO SHIFT WESTWARD AND AWAY, POTENTIALLY SLOWING THE
DEVELOPMENT OF INVEST 93W SOMEWHAT AS IT MEANDERS WEST-
NORTHWESTWARD.
EASTERN MICRONESIA...
FAIRLY DRY CONDITIONS PREVAIL ACROSS EASTERN MICRONESIA AS A
DOLDRUM-LIKE PATTERN BEGINS TO SET UP. THE HEAVY SHOWERS ASSOCIATED
WITH THE BROAD SOUTHEASTWARD CONVERGENCE NEAR POHNPEI AND KOSRAE,
SOUTH OF THE MONSOON TROUGH, ARE SHIFTING FARTHER WEST. ONLY PATCHY
ISOLATED TO SCATTERED SHOWERS REMAIN, MAINLY BETWEEN MAJURO AND
KOSRAE, AND SOUTHWEST OF KOSRAE AND POHNPEI. MEANWHILE, A PAIR OF
WEAK SURFACE CIRCULATIONS PERSIST OVER THE EASTERN RMI AND NORTHEAST
OF MAJURO, BUT SKIES ARE PARTLY CLOUDY WITH ONLY ISOLATED SHOWERS
SEEN THROUGHOUT THE AREA, DUE TO WEAK LOW-LEVEL FORCING AND LIGHT
SURFACE WINDS. THE CIRCULATION TO THE NORTHEAST IS NOW DUBBED INVEST
93W BY THE JTWC, AND IS DISCUSSED IN MORE DETAIL IN THE TROPICAL
SYSTEMS SECTION ABOVE. MODELS DEPICT VERY SLOW DEVELOPMENT AND
MOVEMENT OF 93W AS IT MEANDERS NORTHWEST OVER THE NEXT FEW DAYS,
SKIRTING THE FAR NORTHERN RMI, WITH VERY LITTLE TO NO DIRECT IMPACT
TO EASTERN MICRONESIA. WETTER CONDITIONS RESUME TOWARD THE END OF THE
WEEK, MAINLY FOR POHNPEI AND KOSRAE, AS CONVERGENCE INCREASES ACROSS
THE AREA ALONG THE FAR NORTHERN EDGE OF A NORTHWARD-LIFTING BUFFER
CIRCULATION.
ALTIMETRY DATA SHOWS COMBINED SEAS BETWEEN 3 AND 5 FEET ACROSS MUCH
OF THE REGION, COMPRISED MAINLY OF A SOUTHEAST SWELL EMANATING FROM
DISTANT FEATURES IN THE SOUTHERN HEMISPHERE, WITH A LIGHT, SECONDARY
WEST TO SOUTH-SOUTHWEST SWELL. SEAS MAY SEE A GRADUAL, SLIGHT
DIMINISHING BY THE END OF THE WEEK AS SWELLS SUBSIDE.
WESTERN MICRONESIA...
FOR PALAU AND YAP, A SPECIAL WEATHER STATEMENT REMAINS IN EFFECT
FOR THE DEVELOPING MONSOON PATTERN AND INVEST 92W. THESE FEATURES
ARE PRODUCING UP TO FRESH TO STRONG WINDS WITH GUSTS UP TO NEAR-GALE
FORCE OVER THE NEXT FEW DAYS. SCATTERED TO WIDESPREAD LOCALLY HEAVY
SHOWERS ARE TO BE EXPECTED THROUGH AT LEAST THURSDAY. MODEL GUIDANCE
SUGGESTS 2 TO 4 INCHES THROUGH WEDNESDAY, AND AN ADDITIONAL 1 TO 3
INCHES FROM WEDNESDAY NIGHT THROUGH FRIDAY, TOTALING 3 TO 7 INCHES
BY THE WEEKEND. IF THESE SHOWERS DEVELOP AS EXPECTED, SOILS WILL
BECOME SATURATED ENOUGH TO POSE A RISK FOR MUDSLIDES TOWARD THE END
OF THE WEEK. AT THIS TIME, THE RISK REMAINS LOW. THESE FEATURES
WILL KEEP SEAS CHOPPY NEAR PALAU AND YAP BUT REMAINING BELOW SMALL
CRAFT ADVISORY CRITERIA (OF SUSTAINED 22 KNOT WINDS AND 10 FT SEAS).
AS 92W, EMBEDDED WITHIN THE MONSOON TROUGH, ATTEMPTS TO CONSOLIDATE,
IT WILL MOVE NORTH AND CARRY THE BULK OF THE CONVECTIVE MONSOON WITH
IT, EASING THE SHOWERS AND WINDS NEAR PALAU AND YAP AS EARLY AS
SATURDAY.
FOR CHUUK, A BAND OF CONVERGENCE WILL PRODUCE SCATTERED SHOWERS FOR
THE LAGOON FOR THE NEXT DAY OR SO. THEN, A DRIER WEATHER PATTERN IS
EXPECTED TO SET UP. SEAS NEAR CHUUK ARE EXPECTED TO REMAIN BENIGN AT
3 TO 4 FEET THROUGH THE WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA/TROPICAL UPDATE: STANKO
MARIANAS: OGLE
EAST MICRONESIA: DECOU
WEST MICRONESIA: BOWSHER
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