399
FXPQ50 PGUM 170803
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
603 PM CHST THU SEP 17 2026
MARIANAS SYNOPSIS
AFTERNOON SATELLITE AND RADAR IMAGERY SHOW MOSTLY CLOUDY SKIES WITH
SCATTERED SHOWERS ACROSS GUAM AND ROTA. PATCHIER SHOWERS ARE FOUND
FARTHER NORTH ACROSS TINIAN AND SAIPAN, WHILE HEAVIER SHOWERS AND
THUNDERSTORMS ARE SOUTHEAST OF GUAM WATERS, WITHIN A MONSOON SURGE.
GENTLE TO MODERATE WEST TO SOUTHWEST WINDS PERSIST ACROSS THE REGION
AND COMBINED SEAS ARE 5 TO 7 FEET.
DISCUSSION
DISTANT TROPICAL STORM DUJUAN CONTINUES TO MOVE FARTHER NORTH, AWAY
FROM THE REGION. DUJUAN IS STEERING RELATIVELY DRIER AIR SOUTH OF
20N, LEADING TO SPOTTY SHOWERS ACROSS TINIAN AND SAIPAN, THEN SHOWERS
BECOME INCREASINGLY SCATTERED ACROSS GUAM AND ROTA, CLOSER IN
PROXIMITY TO THE TRAILING MONSOON SURGE. SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ARE EXPECTED TO CONTINUE ACROSS GUAM AND ROTA
OVER THE NEXT SEVERAL DAYS, EXTENDING ACROSS TINIAN AND SAIPAN OVER
THE WEEKEND AND EARLY NEXT WEEK. THE MAIN BAND OF MONSOONAL MOISTURE
LINGERS NEAR AND SOUTH OF GUAM, WITH MODEL GUIDANCE SHOWING SOME
POTENTIAL OF A NEARBY WEAK DISTURBANCE FORMING IN THE MONSOON TROUGH
EARLY NEXT WEEK. DEPENDING ON THIS SCENARIO OR IF THE MONSOON SHIFTS
FURTHER NORTH, THIS COULD POTENTIALLY RESULT IN PERIODS OF SCATTERED
TO NUMEROUS SHOWERS WITH MODERATE TO STRONG GUSTS.
MARINE/SURF
GENTLE TO MODERATE WEST TO SOUTHWEST WINDS PERSIST THROUGH AT
LEAST FRIDAY, DECREASING TO LIGHT TO GENTLE OVER THE WEEKEND, THEN
SHIFT TO THE SOUTH AND SOUTHEAST NEXT WEEK. COMBINED SEAS OF 5 TO
7 FT DECREASE TO 4 TO 6 FEET OVER THE WEEKEND. A MIX OF SOUTHWEST
SWELL, NORTH TO NORTHEAST SWELL WILL CONTINUE TO BRING A MODERATE
RISK OF RIP CURRENTS ALONG ALL REEFS THROUGH AT LEAST THE WEEKEND.
TROPICAL SYSTEMS
TROPICAL STORM DUJUAN IS NOW 370 MILES NORTHEAST OF AGRIHAN, OR ABOUT
700 MILES NORTH-NORTHEAST OF GUAM. MAXIMUM SUSTAINED WINDS ARE
CURRENTLY 60 MPH. DUJUAN IS EXPECTED TO INTENSIFY SLOWLY, AND COULD
BECOME A TYPHOON OVER THE WEEKEND. DUJUAN IS CURRENTLY MOVING NORTH
AT 33 MPH. IT IS EXPECTED TO TURN TOWARD THE WEST-NORTHWEST WITH A
DRAMATIC DECREASE IN FORWARD SPEED. DUJUAN IS EXPECTED TO EXIT THE
WFO GUAM AREA OF RESPONSIBILITY WITHIN THE NEXT 24 HOURS. NUMEROUS
SHOWERS AND ISOLATED THUNDERSTORMS CURRENTLY EXTEND FROM 19N TO 24N
FROM 147E TO 155E. FOR FURTHER INFORMATION ON TROPICAL STORM DUJUAN,
PLEASE REFER TO THE TROPICAL CYCLONE PUBLIC ADVISORY FROM THE
NATIONAL WEATHER SERVICE UNDER WMO HEADER WTPQ31 PGUM OR THE TROPICAL
CYCLONE WARNING FROM THE JOINT TYPHOON WARNING CENTER UNDER WMO
HEADER WTPN31 PGTW.
EASTERN MICRONESIA
NOT A LOT HAS CHANGED SINCE YESTERDAY, AS WE HAVE A RIDGE AXIS OVER
POHNPEI, A QUASI-STATIONARY ELEVATED AREA OF LOW PRESSURE NEAR MAJURO
(WITH SOME SEMBLANCE OF A BROAD/"BAGGY" AREA OF SURFACE LOW
PRESSURE, AND A "RIBBON" OF GOOD SURFACE CONVERGENCE THAT COINCIDES
WITH HIGHER PWATS (PRECIPITABLE WATER VALUES). IN THIS "RIBBON"
SCATTERED SHOWERS AND A FEW THUNDERSTORMS HAVE BEEN DEVELOPING, AND
NEAR THE MAJURO LOW PRESSURE AREA, WHICH IS LOCATED ALONG THE MONSOON
TROUGH. THE TROUGH THEN EXTENDS EAST NORTHEAST, WITH ADDITIONAL
SHOWER AND THUNDERSTORM DEVELOPMENT ALONG IT AS IT CROSSES THE DATE
LINE. THE MAIN FOCUS WAS ON TIMING THE WESTWARD PROGRESSION OF THESE
FEATURES, AND TIMING WHEN AND WHERE THE HIGHER RAINFALL POTENTIAL
WOULD BE, AND THIS WAS REFLECTED IN THE FORECAST.
AS FOR MARINE CONDITIONS, DUE TO A TIGHTER PRESSURE GRADIENT NEAR
THIS "RIBBON", GENTLE TO MODERATE WINDS WILL PREVAIL AT KOSRAE
TONIGHT AND TOMORROW, WITH LIGHT TO GENTLE WINDS FOR THE REMAINDER OF
THE FORECAST THERE. POHNPEI AND MAJURO WILL SEE LIGHT TO GENTLE WINDS
THROUGHOUT THE FORECAST PERIOD. SEAS WILL HOLD IN THE 4 TO 6 FOOT
RANGE.
WESTERN MICRONESIA
THE MONSOON BAND FLOWING INTO TROPICAL STORM DUJUAN HAS SHIFTED
NORTHWEST OF CHUUK AND NORTH OF KOROR, WHICH FOR NOW IS LEAVING MOST
OF THE HEAVY WEATHER AND WINDS AT YAP. WE STILL HAVE A SMALL CRAFT
ADVISORY. LOOKING AT JUST SHORT OF HIGH SURF ADVISORY CONDITIONS
ALONG WEST FACING REEFS OF YAP.
FOR KOROR, WEST TO SOUTHWEST WINDS OF 10 TO 15 KNOTS WILL DIMINISH TO
BETWEEN 5 AND 15 KNOTS TUESDAY. SHOWERS WILL REMAIN ISOLATED THROUGH
SUNDAY, THEN COULD GO SCATTERED AGAIN MONDAY AND TUESDAY. SEAS WILL
START AT 4 TO 6 FEET, BECOME 3 TO 5 FEET SATURDAY, THEN 2 TO 4 FEET
SUNDAY. THIS WILL LEAD TO BENIGN MARINE CONDITIONS THROUGH THE ENTIRE
FORECAST PERIOD OF TONIGHT THROUGH TUESDAY.
AT YAP, THEY'RE RIGHT BENEATH THE MONSOON BAND AT THIS TIME, SO THEY
HAVE WEST WINDS 15 TO 25 KNOTS THROUGH FRIDAY, WHICH WILL BE COME 10
TO 20 KNOTS FRIDAY NIGHT, THEN WEST TO SOUTHWEST AT 10 TO 15 KNOTS
THROUGH TUESDAY. SCATTERED SHOWERS WILL CONTINUE THROUGH SUNDAY, THEN
COULD BUILD TO WIDESPREAD SHOWERS FOR MONDAY AND TUESDAY. SEAS WILL
BE 7 TO 9 FEET THROUGH FRIDAY, 6 TO 8 FEET FRIDAY NIGHT THROUGH
TUESDAY. THIS WILL LEAD TO MARINE CONDITIONS THAT WILL BE HAZARDOUS
THROUGH FRIDAY, CHALLENGING THROUGH THE WEEKEND, THEN COULD BECOME
BENIGN NEXT WEEK.
WITHIN CHUUK LAGOON, WINDS WILL BE SOUTHWEST 10 TO 15 KNOTS THROUGH
SATURDAY, THEN SOUTHWEST 5 TO 10 KNOTS THROUGH MONDAY, THEN SOUTHWEST
AT JUST 5 KNOTS TUESDAY. SHOWERS WILL BE ISOLATED THROUGH SATURDAY
NIGHT, THEN COULD BECOME SCATTERED AGAIN SUNDAY THROUGH TUESDAY. SEAS
WILL BE 3 TO 5 FEET THROUGH SATURDAY, THEN 2 TO 4 FEET THROUGH
TUESDAY. THIS WILL LEAD TO BENIGN MARINE CONDITIONS THROUGH THE
ENTIRE FORECAST PERIOD, FROM TONIGHT THROUGH TUESDAY.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: CRUZ
EAST MICRONESIA: DOLL
WEST MICRONESIA/TROPICAL: STANKO
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