210
FXPQ50 PGUM 250801
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
601 PM CHST THU JUN 25 2026
MARIANAS SYNOPSIS
A DRY TRADE WIND PATTERN IS PRESENT WITH ISOLATED SHOWERS THROUGH
EARLY TONIGHT. A TROUGH AND TRADE WIND SURGE WILL START TO BRING
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LATE TONIGHT THROUGH
FRIDAY. COMBINED SEAS WILL RISE TO 6 TO 8 FEET FRIDAY WITH THE
PASSING TROUGH BEFORE DROPPING BACK DOWN.
DISCUSSION
THE DRY, PLEASANT CONDITIONS TODAY WITH ONLY ISOLATED SHOWERS WILL
BE REPLACED BY SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LATE
TONIGHT THROUGH TOMORROW AS A TROUGH MOVES THROUGH. WINDS WILL
INCREASE SLIGHTLY WITH THE TROUGH'S ARRIVAL, PARTICULARLY ON THE
NORTH SIDE OF THE TROUGH THAT IS AMPLIFIED BY THE TRADE WINDS. THE
CENTER OF THE TROUGH WILL LIKELY BE NEAR OR SOUTH OF GUAM, SO
EXPECTING RAINFALL TO BE SLIGHTLY HIGHER FOR GUAM AND ROTA THAN
TINIAN AND SAIPAN. THE DRYER TRADE WIND PATTERN APPEARS TO RETURN FOR
THE WEEKEND AND EARLY NEXT WEEK WITH THE EXCEPTION OF A SLIGHT
CHANCE OF THUNDERSTORMS SUNDAY NIGHT. THIS IS DUE TO MODELS
CONTINUING TO INDICATE A WEAK UPPER-LEVEL LOW MOVING INTO THE
MARIANAS AROUND THAT TIME, ALLOWING FOR SLIGHTLY MORE CONVECTION. THE
SIGNAL REMAINS WEAK, HOWEVER MID LEVEL SHEAR INCREASED SLIGHTLY OVER
MOST MODELS, HENCE ADDING ISOLATED THUNDERSTORMS TO THE FORECAST.
MARINE
MODERATE WINDS AND COMBINED SEAS OF 5 TO 6 FEET WILL INCREASE TO
MODERATE TO FRESH WINDS AND 6 TO 8 FOOT SEAS TOMORROW WITH THE
PASSING TROUGH. THIS WILL CAUSE A MODERATE RISK OF RIP CURRENTS ALONG
THE EAST- AND WEST-FACING REEFS TONIGHT, ALL REEFS FRIDAY, AND THEN
JUST EAST- FACING REEFS FRIDAY NIGHT THROUGH THE WEEKEND. THE TROUGH
WILL BRING SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LATE TONIGHT
THROUGH TOMORROW. FRESH TO MODERATE WINDS WILL BECOME BRIEFLY
MODERATE TOMORROW. SEAS CONSIST OF THE TYPICAL EASTERLY TRADE SWELL
AND A WEST SWELL FROM DISTANT TROPICAL STORM MEKKHALA. ISOLATED
THUNDERSTORMS MAY ALSO OCCUR SUNDAY NIGHT.
TROPICAL SYSTEMS
HIGOS (08W) STRENGTHENED INTO A TROPICAL STORM EARLIER THIS MORNING
AND HAS MOVED NORTHWEST TO NEAR 18N137E THIS AFTERNOON, ABOUT 610
MILES NORTHWEST OF GUAM. TS HIGOS CONTINUES TO MOVE NORTHWEST AT 15
MPH THROUGH THE PHILIPPINE SEA, POTENTIALLY EXITING THE REGION FRIDAY
NIGHT. MAXIMUM SUSTAINED WINDS HAVE INCREASED TO 45 MPH WITH
TROPICAL STORM FORCE WINDS EXTENDING UP TO 115 MILES OUTWARDS FROM
THE CENTER. WIDESPREAD CLOUDINESS AND FLARING DEEP CONVECTION
CONTINUES NEAR ITS CENTER, WITH DENSER CLOUD COVER FOCUSED ALONG ITS
NORTHWESTERN QUADRANT. RELATIVELY DRIER AIR ATTEMPTS TO WRAP INTO THE
SYSTEM, FRAGMENTING CLOUD BANDS ON THE SOUTHEASTERN PERIPHERY. HIGOS
IS FORECAST TO INTENSIFY THROUGH FRIDAY, POSSIBLY REACHING MAXIMUM
SUSTAINED WINDS OF 60 MPH AS IT CONTINUES MOVING THROUGH THE
PHILIPPINE SEA, GRADUALLY MAKING A TURN TOWARD THE NORTH-NORTHWEST,
STEERED BY THE SUBTROPICAL RIDGE. IT LOOKS TO EXIT THE REGION FRIDAY
NIGHT AS IT MOVES NORTH OF 25N, AND IT IS FORECAST TO BEGIN ITS
WEAKENING PHASE AND POSSIBLY MERGING WITH MEKKHALA (07W) AS IT MOVES
NEAR JAPAN.
FOR MORE INFORMATION PLEASE REFER TO BULLETINS FROM THE JOINT
TYPHOON WARNING CENTER UNDER WMO HEADER WTPN32 PGTW AND FROM
THE NATIONAL WEATHER SERVICE UNDER WMO HEADER WTPQ32 PGUM.
INVEST 95W IS NOW RATED LOW FOR DEVELOPMENT, MEANING THAT
DEVELOPMENT IS POSSIBLE, BUT UNLIKELY WITHIN THE NEXT 24 HOURS. THE
JOINT TYPHOON CENTER (JTWC) HAS REPOSITIONED THE BROAD DISTURBANCE
ON THE OTHER SIDE OF THE DATE LINE, ROUGHLY LOCATED NEAR 5N178W, TO
ALIGN WITH AN AREA OF HIGHER VORTICITY. EQUATORIAL WESTERLIES
CONTINUE TO FEED MOISTURE INTO THE DISTURBANCE, WITH WIDESPREAD
CLOUDS AND SHOWERS SEEN ACROSS NORTHWESTERN KIRIBATI AND ACROSS THE
SOUTHERN SIDE OF INVEST 95W TO THE EQUATOR. SCATTERED TO NUMEROUS
SHOWERS ARE SLOWLY ORGANIZING ALONG THE NORTHERN SIDE OF THIS SYSTEM
ALONG A BROAD TROUGH EXTENDING FROM INVEST 95W TO NEAR 11N180.
FAVORABLE DIFFLUENT FLOW ALOFT WILL CONTINUE TO SUPPORT SHOWER
DEVELOPMENT OVER THE NEXT DAY OR TWO AS INVEST 95W DRIFTS NORTHWEST
TOWARDS THE NORTHERN MARSHALLS.
FOR MORE INFORMATION PLEASE REFER TO BULLETINS FROM THE JOINT
TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10 PGTW.
EASTERN MICRONESIA
A NEAR-EQUATORIAL TROUGH (NET) CONTINUES TO PRODUCE AN UNSETTLED
PATTERN ACROSS THE REGION. SCATTERED TO NUMEROUS SHOWERS ARE FOUND
ALONG THE TROUGH, WITH THE DEEPEST CONVECTION SOUTH OF THE NET AXIS,
ALONG MOIST EQUATORIAL WESTERLIES. AN EMBEDDED WEAK CIRCULATION EAST
OF KOSRAE WILL HELP FOCUS SHOWERS ACROSS THE ISLAND TONIGHT, BUT
LOOKS TO WEAKEN OVERNIGHT. AT THE EASTERN END OF THE NET, A BROAD
TROPICAL DISTURBANCE, INVEST 95W (SEE TROPICAL SYSTEMS SECTION FOR
MORE DETAILS), DRIFTS NORTHWEST TOWARDS THE NORTHERN MARSHALLS,
CAUSING THE NET TO TILT NORTH OVER MAJURO IN THE COMING DAYS,
HOWEVER, A POSSIBLE BUFFER CIRCULATION FORMING OVER THE WEEKEND MY
INDUCE SOME DIFFLUENT FLOW TO THE SOUTH AND POTENTIALLY LEADING TO A
FRAGMENTED NET PATTERN EARLY NEXT WEEK. PERIODS OF SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS ARE EXPECTED OVER THE NEXT SEVERAL DAYS,
ESPECIALLY FOR KOSRAE AND MAJURO, DUE TO THE PROXIMITY OF THE NET.
BEING SLIGHTLY NORTH OF THE ACTIVE PORTIONS OF THE NET PATTERN,
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED THROUGH
FRIDAY AT POHNPEI, THEN IS EXPECTED TO DECREASE TO ISOLATED TO LOW-
END SCATTERED SHOWERS OVER THE WEEKEND AND EARLY NEXT WEEK.
BENIGN MARINE AND SURF CONDITIONS ARE EXPECTED THROUGH EARLY NEXT
WEEK. LIGHT TO GENTLE WINDS PERSIST THROUGH AT LEAST TUESDAY.
ALTIMETRY DATA SHOWS SEAS 3 TO 5 FEET, INCREASING TO AROUND 6 FEET AT
MAJURO. A DECREASE IN NORTHEAST SWELL WILL ALLOW SEAS TO SUBSIDE TO
3 TO 5 FEET AT MAJURO OVER THE WEEKEND. MEANWHILE, LIGHT SOUTHEAST
SWELL CONTINUES TO MOVE ACROSS THE REGION OVER THE NEXT SEVERAL DAYS.
LONGER-PERIOD SOUTHERLY SWELL REACHES MAJURO NEXT WEEK, WHICH MAY
BRING A SLIGHT INCREASE TO SURF ALONG SOUTH-FACING REEFS.
WESTERN MICRONESIA
FOR PALAU AND YAP, A WESTERLY WIND DRIVEN CONVERGENCE IS INTERACTING
WITH THE WESTERN EXTENT OF THE NEAR-EQUATORIAL TROUGH. THIS
INTERACTION IS EXPECTED TO BRING SCATTERED TO NUMEROUS SHOWERS TO
BOTH ISLANDS, PALAU IS EXPECT TO EXPERIENCE IT FIRST THEN EASTERN YAP
STATE. MODEL GUIDANCE SUGGESTS THAT THE NET WILL EVENTUALLY OVER
TAKE THE CONVERGENCE. OVERALL A WET PATTERN IS EXPECTED FOR THESE
REGIONS.
FOR CHUUK, THE TROUGH THAT WAS OVER CHUUK YESTERDAY HAS MOVED TO THE
WEST A BIT FASTER THAN PREVIOUSLY ANTICIPATED. TO REFLECT THIS
SHOWERS WERE LOWERED FROM THE EARLIER UPDATE OF 50 POPS DOWN TO 40
POPS. SHOWERS ARE EXPECTED BUILD IN AS THE NET CONTINUES BUILD AND
PUSH WESTWARD. OVERALL A WET PATTERN IS EXPECTED THROUGH THE WEEKEND.
THEN A DRIER PATTERN MAY PRESENT ITSELF.
COMBINED SEAS OF 3 TO 5 FEET ARE EXPECTED THROUGH THE BEGINNING OF
NEXT WEEK. WINDS ARE EXPECTED TO BE LIGHT TO GENTLE. OVERALL BENIGN
SEAS CONDITIONS ARE EXPECT, EXCEPT NEAR HEAVIER SHOWERS.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA: CRUZ
WEST MICRONESIA: BOWSHER
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