995
FXPQ50 PGUM 280742
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
542 PM CHST WED OCT 28 2026
MARIANAS SYNOPSIS
LIGHT AND VARIABLE WINDS ARE VISIBLE OVER GUAM AND ROTA WITH MODERATE
EASTERLIES OVER TINIAN AND SAIPAN. RADAR AND SATELLITE IMAGERY
INDICATE SCATTERED SHOWERS FOR TINIAN AND SAIPAN, AND ISLAND EFFECT
SHOWERS FOR GUAM AND ROTA. MODEL AND OBSERVATIONS INDICATE COMBINED
SEAS OF 4 TO 7 FEET.
DISCUSSION
A LONG ELONGATED TROUGH CONNECTING ALL THE WAY INTO TYPHOON IN-FA
HAS WEAKENED SLIGHTLY FROM LAST NIGHT AND IS STARTING TO DRIFT SOUTH.
THIS FEATURE IS NOW EXPECTED TO BRING SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS TO TINIAN AND SAIPAN EARLY TONIGHT, ROTA ALL NIGHT,
AND GUAM BY LATE TONIGHT. ISOLATED SHOWERS WILL RETURN ONCE THE
TROUGH HAS PASSED EACH ISLAND. ISOLATED SHOWERS WILL LIKELY CONTINUE
FOR MUCH OF THE FORECAST PERIOD FOR GUAM AND ROTA. SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS MAY RETURN FRIDAY FOR TINIAN AND SAIPAN
DUE TO SLIGHTLY CLOSER PROXIMITY TO IN-FA AS PASSES SOMEWHERE THROUGH
THE FAR NORTHERN CNMI BETWEEN SARIGAN AND MAUG. SHOWERS FOR TINIAN
AND SAIPAN WILL LIKELY RETURN TO ISOLATED FOR THE REST OF THE
FORECAST PERIOD BY SATURDAY. CURRENT TYPHOON IN-FA IS EXPECTED TO
MAKE IT'S CLOSEST POINT OF APPROACH MIDDAY FRIDAY. BREEZY CONDITIONS
ARE POSSIBLE FOR TINIAN AND SAIPAN FRIDAY WITH FREQUENT GUSTS OF 30
MPH, PARTICULARLY IN THUNDERSTORMS. THIS SITUATION WILL CONTINUE TO
BE MONITORED CLOSELY FOR ANY POTENTIAL CHANGES. SEE THE "TROPICAL
SYSTEMS" SECTION FOR MORE DETAILS.
MARINE
GENTLE NORTHEAST WINDS WILL PREVAIL ACROSS TINIAN AND SAIPAN THROUGH
AT LEAST TONIGHT, WHILE LIGHT WINDS PREVAIL OVER ROTA AND GUAM.
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL BE POSSIBLE FOR
TINIAN AND SAIPAN EARLY TONIGHT, ALL NIGHT OVER ROTA, AND LATE
TONIGHT FOR GUAM AS A TROUGH SHIFTS SOUTH OVER THE ISLANDS. THEREFORE,
THERE IS MODERATE RISK OF LIGHTNING TONIGHT FOR ALL ISLANDS.THERE
WILL BE A MODERATE RISK OF RIP CURRENTS THROUGH THE WEEKEND FOR
NORTH- AND EAST-FACING REEFS DUE TO A PRIMARY EAST- NORTHEAST SWELL.
COMBINED SEAS ARE EXPECTED TO WAVER BETWEEN 5 AND 7 FEET THROUGH
THURSDAY. BY LATE THURSDAY, SEAS ARE EXPECTED TO INCREASE
SIGNIFICANTLY AND BECOME HAZARDOUS AHEAD OF TYPHOON IN- FA, WHICH IS
ANTICIPATED TO PASS SOMEWHERE THROUGH THE FAR NORTHERN CNMI BETWEEN
SARIGAN AND MAUG ISLAND. WIDESPREAD SEAS OF 11 TO 14 FEET ARE
EXPECTED FOR TINIAN AND SAIPAN. SEAS OF 10+ FEET ARE ALSO POSSIBLE
FOR GUAM AND ROTA.
TROPICAL SYSTEMS
AT 100 PM CHST, THE CENTER OF TYPHOON IN-FA WAS LOCATED NEAR 15.0N
159.3E, OR 560 MILES NORTH OF POHNPEI, 910 MILES EAST OF ALAMAGAN, OR
ABOUT 975 MILES EAST OF GUAM. HIMAWARI VISIBLE SATELLITE IMAGERY
THIS AFTERNOON SHOWS TYPHOON IN-FA WITH A WELL-DEVELOPED EYE AROUND
40 MILES IN WIDTH, WITH A BURST OF CONVECTION ALONG THE WEST TO
SOUTHWEST EDGES OF THE EYEWALL. THE OUTER RAINBANDS ARE SOMEWHAT
PATCHY AND DISCONTINUOUS, DISPLACED AROUND 350 TO 500 MILES FROM THE
CENTER TO THE SOUTHWEST, SOUTH, AND NORTH. IN-FA REMAINS A CATEGORY
4 TYPHOON WITH MAXIMUM SUSTAINED WINDS AT 140 MPH, AND IS EXPECTED TO
INTENSIFY TONIGHT, POSSIBLY BECOMING A SUPER TYPHOON BY MIDNIGHT WITH
MAXIMUM WINDS FORECAST TO INCREASE TO 150 MPH. CURRENTLY, IN-FA IS
MOVING WEST-NORTHWEST AT AROUND 10 MPH. IT IS EXPECTED TO MAINTAIN
THIS GENERAL COURSE WITH AN INCREASE IN FORWARD SPEED THROUGH FRIDAY
MORNING AS IT MAKES A NORTHWEST TURN TOWARD THE FAR NORTHERN
MARIANAS.
THE LATEST FORECAST TRACK FROM THE JOINT TYPHOON WARNING
CENTER SHOWS THE CENTER OF IN-FA TRACKING CLOSE TO OR OVER AGRIHAN
FRIDAY NIGHT AS IT TURNS SLIGHTLY TOWARD THE NORTHWEST. AS IN-FA
APPROACHES THE FAR NORTHERN MARIANAS, THE THREAT OF DESTRUCTIVE WINDS
WILL INCREASE THROUGH FRIDAY EVENING, WITH THE ONSET OF DAMAGING
WINDS BEGINNING AS EARLY AS FRIDAY AFTERNOON. THE CURRENT FORECAST
TRACK SUGGESTS THAT THE THREAT FOR DESTRUCTIVE TYPHOON-FORCE WINDS
WILL BE HIGHEST FOR AGRIHAN AND PAGAN CLOSE TO THE CENTER OF TYPHOON
IN-FA, BUT KEEP INFORMED OF POSSIBLE CHANGES TO THE FORECAST LOCATION
OF THE CENTER. A TYPHOON WATCH IS CURRENTLY IN EFFECT FOR THE
ISLANDS OF ALAMAGAN, PAGAN, AND AGRIHAN IN THE NORTHERN CNMI.
FOR MORE INFORMATION ON TYPHOON IN-FA, PLEASE REFER TO BULLETINS
FROM THE JOINT TYPHOON WARNING CENTER UNDER WMO HEADER WTPN31 PGTW
AND FROM THE NATIONAL WEATHER SERVICE UNDER WMO HEADER WTPQ31
PGUM.
EASTERN MICRONESIA
DESPITE TYPHOON IN-FA DEVELOPING JUST NORTH OF THE REGION, FAIRLY
QUIET CONDITIONS PREVAIL ACROSS MUCH OF EASTERN MICRONESIA THIS
AFTERNOON. KOSRAE AND MAJURO ARE SITUATED WITHIN A BROAD SURFACE
RIDGE THAT IS SET UP BEHIND IN-FA. POHNPEI CAN EXPECT SCATTERED
SHOWERS OVER THE NEXT DAY OR SO AS CONVERGENT WESTERLIES TO THE SOUTH
OF IN-FA'S PASSAGE SET UP NEARBY, BUT SO FAR THIS AFTERNOON, MOST OF
THE SHOWERS REMAIN SOUTH OF THE ISLAND. ISOLATED SHOWERS WILL
CONTINUE NEAR MAJURO THROUGH THURSDAY NIGHT, INCREASING TO SCATTERED
FRIDAY AS THE BROAD CONVERGENCE BOUNDARY, AND ASSOCIATED SHOWERS TO
ITS EAST, GRADUALLY SHIFT WESTWARD INTO THE AREA.
RECENT BUOY AND ALTIMETRY DATA SHOW COMBINED SEAS OF 4 TO 6 FEET,
COMPRISED OF A PRIMARY NORTH TO NORTHEAST SWELL AND SECONDARY
SOUTHEAST SWELL. WINDS WILL BE LIGHT TO MODERATE THROUGHOUT THE
FORECAST PERIOD, DECREASING TO MOSTLY LIGHT BY EARLY NEXT WEEK AS A
BROAD, WEAK, ELONGATED TROUGH SETS UP ACROSS THE AREA.
WESTERN MICRONESIA
LIGHT TO GENTLE WINDS WILL PERSIST THROUGH THE FORECAST PERIOD, WHICH
COULD ALLOW ISLAND CONVECTION TO DEVELOP FROM TIME TO TIME AT PALAU
DURING THE LATE MORNING INTO AFTERNOON HOURS. YAP, WHICH TYPICALLY
DOESN'T SEE THE "STRING AND TAIL" OF CONVECTION DEVELOP, HAD ISLAND
CONVECTION TODAY ALONG WESTERN SIDES OF THE ISLAND, BEFORE TAILING
OFF IN COVERAGE OVER THE OPEN WATERS. THIS WAS DUE TO A FAVORABLE 210
DEGREES WIND DIRECTION ALIGNING WITH THE ~400-500 FOOT HILLS JUST
NORTH-NORTHEAST OF THE AIRPORT, WHICH PROVIDED JUST ENOUGH
OROGRAPHIC LIFT FOR THE LIGHT, SOUTHWEST OCEAN BREEZE TO ACT ON. WITH
TYPHOON IN-FA HEADING TOWARDS THE FAR NORTHERN CNMI, THIS WIND
DIRECTION IS EXPECTED TO HOLD FOR ANOTHER DAY OR TWO, WHICH MAY ALLOW
FOR YAP TO SEE ADDITIONAL ISLAND CONVECTION DEVELOP. HOWEVER,
SPATIAL COVERAGE OF ISLAND CONVECTION AT EITHER LOCATION IS
SUFFICIENTLY SMALL ENOUGH TO KEEP ISOLATED SHOWER COVERAGE/20 PERCENT
PROBABILITIES, BUT THIS WILL BE MONITORED FOR MORE ROBUST
DEVELOPMENT.
OTHERWISE, ISOLATED SHOWERS UNDER LIGHT TO GENTLE WINDS AND SEAS OF
3 TO 5 FEET MAY INCREASE A FOOT FRIDAY INTO SATURDAY, AS A NORTH TO
NORTHEASTERLY SWELL FROM IN-FA ARRIVES.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA/TROPICAL SYSTEMS: DECOU
WEST MICRONESIA: DOLL
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