822
FXPQ50 PGUM 081915
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
515 AM CHST SUN AUG 9 2026
MARIANAS UPDATE
ONLY SPOTTY SHOWERS ARE CURRENTLY SEEN ACROSS THE MARIANAS. THIS
LOOKS TO CONTINUE THROUGH THE DAY FOR GUAM AND ROTA. FOR TINIAN AND
SAIPAN, A BAND OF SHOWERS IS FOUND TO THE WEST OF THE COASTAL
WATERS. THESE SHOWERS LOOK TO MOVE INTO TINIAN AND SAIPAN LATER
TODAY, NEAR NOON, WITH SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
THEN EXPECTED TO CONTINUE THROUGH TONIGHT. THE REMAINDER OF THE
MARIANAS FORECAST IS UNCHANGED.
TROPICAL SYSTEMS UPDATE
INVEST 13W (REMNANTS OF KUJIRA) IS CENTERED SOUTHWEST OF IWO TO NEAR
22.7N 139.5E. LATEST ASCAT ANALYSIS SHOWS A DEFINITE LOW-LEVEL
CIRCULATION CENTER (LLCC), WHILE SATELLITE SHOWS INCREASING
CONVECTION JUST SOUTH OF THE LLCC. IT IS CURRENTLY EMBEDDED WITHIN
THE MONSOON TROUGH NEAR A COL REGION. A SMALL AREA OF WIND SPEEDS IN
THE 20 TO 30 KNOT RANGE ARE SEEN TO THE SOUTH OF THE LLCC. LOW
VERTICAL WIND SHEAR, WARM SEA SURFACE TEMPERATURES AND GOOD UPPER-
LEVEL OUTFLOW INDICATE FAVORABLE CONDITIONS FOR DEVELOPMENT. MODEL
CONSENSUS IS FOR FURTHER DEVELOPMENT AS 13W MOVES EAST OVER THE NEXT
FEW DAYS. BASED ON THIS INFORMATION, THE JOINT TYPHOON WARNING
CENTER (JTWC) HAS INCREASED THE POTENTIAL FOR DEVELOPMENT TO MEDIUM,
MEANING DEVELOPMENT IS LIKELY, BUT EXPECTED TO OCCUR BEYOND 24 HOURS.
INVEST 98W IS FOUND WELL NORTHEAST OF TINIAN NEAR 20.5N 152.5E.
ENVIRONMENTAL CONDITIONS SIMILAR TO INVEST 13W INDICATE THE
POTENTIAL FOR DEVELOPMENT OF INVEST 98W. THE LATEST ASCAT ANALYSIS
SHOWS AN ORGANIZED LLCC, WITH PERIPHERY WINDS TO THE SOUTHWEST OF
THE CENTER IN THE 25 TO 30 KNOT RANGE. BASED ON THIS, JTWC HAS
INCREASED THE POTENTIAL FOR DEVELOPMENT TO MEDIUM, MEANING
DEVELOPMENT IS LIKELY, BUT EXPECTED TO OCCUR BEYOND 24 HOURS. MODEL
CONSENSUS SHOWS INVEST 98W MOVING NORTH-NORTHEAST.
FOR MORE INFORMATION ON INVEST 13W AND INVEST 98W, SEE BULLETINS
ISSUED BY JTWC UNDER WMO HEADER ABPW10 PGTW.
ANOTHER WEAK CIRCULATION, NEWLY DEVELOPED INVEST 99W, IS CENTERED
NORTH OF WAKE ISLAND NEAR 22.0N 165.7E. 99W IS RATED SUB-LOW,
MEANING DEVELOPMENT IS NOT EXPECTED FOR THE NEXT FEW DAYS. WHAT 99W
IS DOING IS GENERATING CONVECTION OVER AND NEAR WAKE ISLAND, WHERE
IT IS EXPECTED TO REMAIN FOR THE NEXT 24 HOURS.
EASTERN MICRONESIA UPDATE
A BROAD, WEAK CIRCULATION REMAINS TO THE EAST-NORTHEAST OF MAJURO.
THIS FEATURE IS GENERATING INCREASED CONVECTION ACROSS THE MARSHALLS
TO THE EAST OF KOSRAE. SHOWERS LOOK TO REMAIN ISOLATED AT KOSRAE
TODAY, THOUGH AN ISOLATED THUNDERSTORM COULD MOVE THROUGH AS THE
CONVECTION APPROACHES. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
ARE EXPECTED AT MAJURO TODAY. THE ONLY REAL CHANGE TO THE FORECAST
WAS TO INCREASE POPS (PROBABILITY OF PRECIPITATION) FROM 30 TO 40
PERCENT. IF THE CONVECTION SOUTH OF MAJURO DRIFTS FARTHER NORTH, POPS
MAY NEED TO BE INCREASED FURTHER.
WESTERN MICRONESIA UPDATE
AN OVERALL DRY PATTERN LOOKS TO CONTINUE FOR WESTERN MICRONESIA.
VERY LITTLE CONVECTION IS SEEN ACROSS THE REGION. ONLY A BAND OF MID-
TO UPPER-LEVEL CLOUDS ARE SEEN ACROSS PALAU AND YAP. DISTANT TYPHOON
DOLPHIN WILL CONTINUE TO PRODUCE SWELL LARGE ENOUGH TO MAINTAIN
HAZARDOUS SURF ALONG NORTH FACING REEFS OF YAP.
PREV DISCUSSION
/ISSUED 604 PM CHST SAT AUG 8 2026/
MARIANAS SYNOPSIS...
HIMAWARI VISIBLE SATELLITE IMAGERY SHOWS SWATHS OF MIDDLE AND UPPER-
LEVEL CLOUDS CROSSING THE MARIANAS, WHILE RADAR SHOWS ISOLATED
SHOWERS, MAINLY TO THE NORTH AND WEST OF TINIAN AND SAIPAN COASTAL
WATERS. A BAND OF WIDESPREAD SHOWERS AND SCATTERED THUNDERSTORMS IS
SEEN WITHIN THE MONSOON SURGE ROUGHLY 400 MILES WEST-NORTHWEST OF THE
MARIANAS, SOUTH OF THE REMNANTS OF 13W. ELSEWHERE IN THE REGION,
NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ARE SEEN EAST OF THE FAR
NORTHERN CNMI, ASSOCIATED WITH INVEST 98W.
DISCUSSION...
DISTURBANCES WITHIN THE MONSOON TROUGH ARE PROMOTING AN ACTIVE
WEATHER REGIME JUST NORTH AND WEST OF THE MARIANAS THIS AFTERNOON,
WHILE THE SOUTHERNMOST ISLANDS EXPERIENCE A RELATIVE LULL. MODERATE
TO STRONG WESTERLIES ARE EXPECTED TO CONTINUE ACROSS THE AREA OVER
THE NEXT FEW DAYS, INCREASING SUNDAY THROUGH MONDAY AS THE REMNANTS
OF 13W SWING EAST-SOUTHEASTWARD, DIPPING OVER OR NEAR THE FAR
NORTHERN CNMI LEADING TO A RESURGENCE IN MONSOON WINDS ACROSS THE
AREA. MODEL GUIDANCE SHOWS THE SOUTHERN EDGE OF THE DEVELOPING
MONSOON SURGE SHIFTING OVER TINIAN AND SAIPAN, MAINTAINING BREEZY
CONDITIONS AND SCATTERED SHOWERS THERE FOR MUCH OF THE COMING WEEK.
A MAJOR FACTOR IN THE SHORT-TERM FORECAST CONCERNS THE REMNANTS OF
13W, WHICH ARE CURRENTLY RATED AS "LOW" FOR DEVELOPMENT BY THE JOINT
TYPHOON WARNING CENTER (JTWC), MEANING 13W IS BEING MONITORED BUT IS
NOT EXPECTED TO DEVELOP INTO A SIGNIFICANT TROPICAL CYCLONE IN THE
NEXT DAY OR SO. SOME DETERMINISTIC MODELS DO SHOW 13W QUICKLY
DEVELOPING NORTH OF THE MARIANAS BEFORE IT RACES OFF TO THE EAST-
NORTHEAST, FOLLOWING BEHIND INVEST 98W. THE MAGNITUDE AND RATE OF
13W'S DEVELOPMENT, AS WELL AS HOW FAR SOUTH ITS TRACK TAKES IT, WILL
BE THE MAIN INFLUENCING FACTORS IN THE STRENGTH OF THE MONSOON SURGE
ACROSS THE CNMI OVER THE NEXT FEW DAYS.
MARINE/SURF...
MODERATE TO STRONG WESTERLIES PREVAIL ACROSS THE MARIANAS AS
ANOTHER RESURGENCE IN THE MONSOON BUILDS OVER THE NORTHERN CNMI,
LIKELY TO MAINTAIN MODERATE TO STRONG WINDS THROUGH THE MIDDLE OF
NEXT WEEK, WITH THE STRONGEST WINDS EXPECTED OVER TINIAN AND
SAIPAN WATERS. COMBINED SEAS OF 8 TO 11 FEET ARE EXPECTED OVER THE
NEXT FEW DAYS, REMAINING HAZARDOUS TO SMALL CRAFT THROUGH AT
LEAST EARLY TUESDAY MORNING. SEAS LOOK TO FALL BELOW HAZARDOUS
LEVELS FOR GUAM AND ROTA BY MIDWEEK, BUT ARE EXPECTED TO REMAIN
HAZARDOUS FOR TINIAN AND SAIPAN INTO THE LATTER HALF OF THE WEEK
AS THE SOUTHERN EDGE OF THE MONSOON SURGE PERSISTS OVER THE AREA.
SO, THE SMALL CRAFT ADVISORY WAS EXTENDED FOR GUAM AND ROTA WATERS
THROUGH EARLY TUESDAY MORNING, AND TINIAN AND SAIPAN WATERS
THROUGH THURSDAY AFTERNOON.
MEANWHILE, HAZARDOUS SURF AND A HIGH RISK OF RIP CURRENTS ARE
EXPECTED TO CONTINUE ALONG WEST AND NORTH FACING REEFS THROUGH
THE MIDDLE OF NEXT WEEK, AND THE HIGH SURF ADVISORY AND HIGH RIP
CURRENT RISK HAVE BEEN EXTENDED THROUGH THURSDAY AFTERNOON. A
MODERATE RISK OF LIGHTNING IS EXPECTED SUNDAY THROUGH EARLY NEXT
WEEK, MAINLY FOR TINIAN AND SAIPAN.
TROPICAL SYSTEMS...
INVEST 98W CONTINUES TO GRADUALLY ORGANIZE. IT'S NOW LOCATED ROUGHLY
120 MILES EAST OF THE MAUG ISLANDS NEAR 19N 147.5E. THE ECENS AND
GEFS ARE MUCH MORE ALIGNED WITH ONE ANOTHER TODAY REGARDING BOTH THE
DEVELOPMENT AND MOVEMENT OF 98W, AND THE REMNANTS OF 13W (CURRENTLY
NEAR 20N 139E). IT NOW LOOKS LIKE SUFFICIENT WAVE SEPARATION WILL
EXIST BETWEEN THE REMNANTS AND 98W, AS BOTH MODELS ALSO TRY TO
DEVELOP A LLCC (LOW-LEVEL CIRCULATION CENTER) WITH IT. AS 98W SLOWLY
INTENSIFIES AND LIFTS NORTHEAST TO THE NORTH OF WAKE ISLAND, THE
REMNANTS AND ITS DEVELOPING CIRCULATION GRADUALLY DEVELOP AND HEAD ON
A SIMILAR TRACK, WITH ALL OF THIS OCCURRING OVER THE NEXT 48 TO 72
HOURS. BEYOND THAT...STAY TUNED!
THEN, LOOKING FARTHER SOUTH AND EAST IN THE "VERY LONG RANGE OF
FORECASTING", A LEAD WAVE (SURFACE CIRCULATION) CURRENTLY NORTHEAST
OF MAJURO NEAR 10N177E, LOOKS TO DRIFT WEST FOR THE NEXT 24 HOURS,
THEN SOUTHWEST AND BECOME QUASI-STATIONARY, WHILE REMAINING AT THE
TAIL END OF A MONSOON TROUGH'S EASTERN EDGE (THE MONSOON TROUGH IS IN
THE PROCESS OF RETREATING TO THE WEST, SLOWLY). AS THIS OCCURS, A
DISTURBANCE EAST OF THE DATE LINE NEAR 8N177W ON THE 925MB ANALYSIS
LOOKS TO ALSO CONTINUE WEST, EVENTUALLY DEVELOPING A LLCC.
WITH THE LEAD WAVE, A MOISTURE SURGE (ADVECTION) IS OCCURRING, WITH
SIGNIFICANTLY HIGHER PWATS (PRECIPITABLE WATER VALUES INCREASE FROM
~1.5 INCHES AHEAD OF IT, TO ABOVE 2.5 INCHES ALONG AND EAST OF IT.
SO, ESSENTIALLY THE LEAD WAVE IS "PRECONDITIONING THE ENVIRONMENT,
MAKING IT MORE FAVORABLE FOR LATER CYCLOGENESIS (THE FORMATION OF A
LLCC). THEN, AS THE CIRCULATION CURRENTLY EAST OF THE DATE LINE
CATCHES OF TO THE LEAD WAVE THAT MAKES A "PIT STOP" NORTH OF
KOSRAE/EAST OF POHNPEI/WEST OF MAJURO AND THE RMI. SOME GUIDANCE
SUGGESTS A BETTER-ORGANIZED LLCC WILL DEVELOP 6 TO 8 DAYS FROM NOW
(PROBABLY MORE SO 7-9 DAYS, AS THE MODELS TEND TO HAVE A +24 HOUR
BIAS AT THIS FORECAST RANGE).
NORMALLY, WE WOULDN'T MENTION SOMETHING THIS FAR OUT, BUT, HAVING
ALREADY HAD A BUSY "DRY" (QUIET) SEASON, AND SINCE WE'RE JUST NOW
STARTING TO ENTER THE BUSIER "WET" SEASON, WE JUST WANTED FOLKS TO
KNOW THAT WE'RE WATCHING IT. AS WE TYPICALLY STATE AT ANYTHING BEYOND
5 DAYS, IT'S WAY, WAY TOO EARLY TO SAY WHAT WILL HAPPEN (WILL THE
SYSTEM DEVELOP, HOW STRONG WILL IT BE, WHERE WILL IT GO, AND WHEN).
JUST KNOW WE'RE KEEPING AN EYE ON IT, AND CONTINUE TO STAY INFORMED.
EASTERN MICRONESIA...
THE FORECAST REMAINS ON TRACK WITH NOT MANY CHANGES MADE. IN GENERAL,
RAINFALL POTENTIAL WILL INCREASE AS MOISTURE INCREASES FROM MONDAY
ONWARD, THE DETAILS OF SUCH ARE DISCUSSED IN MORE DETAIL IN THE
BOTTOM THREE PARAGRAPHS OF THE TROPICAL SECTION ABOVE.
AS FOR MARINE CONDITIONS, LIGHT TO GENTLE WINDS WILL CONTINUE THROUGH
EARLY NEXT WEEK, WITH SEAS IN THE 5 TO 7 FOOT RANGE CONTINUING INTO
THE FIRST HALF OF NEXT WEEK.
WESTERN MICRONESIA...
SATELLITE OBSERVATIONS SHOW PARTLY CLOUDY SKIES AND LITTLE TO NO
SHOWER ACTIVITY ACROSS WESTERN MICRONESIA. ALTIMETRY SHOWS COMBINED
SEAS BETWEEN 6 AND 8 FEET ACROSS THE REGION.
THE NEAR AND SHORT TERM FORECAST REMAINS STATUS QUO ACROSS THE
REGION. THE STOUT RIDGE ANCHORED SOUTH OF CHUUK CONTINUES TO PRODUCE
HOT AND DRY WEATHER ACROSS THE REGION. THIS RIDGE LOOKS TO REMAIN
STOUT THROUGH THE WEEKEND, KEEPING SHOWER ACTIVITY LOW ACROSS
WESTERN MICRONESIA. TOWARDS THE EARLY PART OF NEXT WEEK, WE SHOULD
SEE A BREAKDOWN AND A SHIFT WEST IN THE RIDGE. THIS WILL ALLOW FOR
SOME WESTERLY MOVING TROPICAL DISTURBANCES TO MOVE INTO CHUUK STATE
TOWARDS THE LATTER HALF OF THE WEEK. AT THIS TIME, THESE
DISTURBANCES LOOK TO REMAIN WEAK, BUT WILL HELP USHER IN A PATTERN
CHANGE.
CHOPPY SEAS OF 6 TO 8 FEET ARE SEEN ACROSS YAP, WHILE SEAS OF 4 TO 7
FEET ARE SEEN ACROSS PALAU AND CHUUK. SEAS WILL GRADUAL DECREASE
OVER THE NEXT SEVERAL DAYS, BECOMING BENIGN ACROSS THE REGION.
SWELLS WILL REMAIN ELEVATED UNTIL SUNDAY AFTERNOON FOR YAP, LEADING
TO HAZARDOUS SURF ALONG NORTH FACING REEFS. SWELLS LOOKS TO FALL
THROUGH THE DAY ON SUNDAY, ALLOWING SURF TO FALL BELOW HAZARDOUS
LEVELS BY SUNDAY NIGHT.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 PM CHST THURSDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 PM CHST THURSDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 AM CHST TUESDAY FOR
PMZ151-152.
SMALL CRAFT ADVISORY UNTIL 5 PM CHST THURSDAY FOR PMZ153-154.
MARIANAS/EAST AND WEST MICRONESIA/TROPICAL UPDATE: KLEESCHULTE
MARIANAS: DECOU
EAST MICRONESIA/TROPICAL: DOLL
WEST MICRONESIA: WILLIAMS
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