571
FXPQ50 PGUM 240719
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
519 PM CHST SAT OCT 24 2026
MARIANAS SYNOPSIS
GENTLE TO MODERATE EASTERLY WINDS PREVAIL ACROSS THE MARIANAS THIS
EVENING. SCATTERED SHOWERS ARE VISIBLE ON RADAR AND SATELLITE, WITH
SLIGHTLY HIGHER COVERAGE OVER TINIAN AND SAIPAN. MODEL AND
OBSERVATION DATA INDICATE COMBINED SEAS OF 6 TO 8 FEET.
DISCUSSION
A WEAK LINE OF CONVERGENCE ASSOCIATED WITH A BROAD TROUGH CENTERED
NEAR YAP STATE AND EASTERLY TRADE WINDS IS SITTING OVER THE MARIANAS
AND BRINGING SCATTERED SHOWERS TO THE REGION THROUGH TOMORROW WITH
ISOLATED THUNDERSTORMS. THE RISK FOR ISOLATED THUNDERSTORMS WILL
CONTINUE THROUGH AT LEAST SUNDAY NIGHT AS AN UPPER-LEVEL TROUGH
MOVES INTO THE REGION AND WIND SHEAR INCREASES SIGNIFICANTLY.
HOWEVER, A DIFFUSIVE LOW-LEVEL FLOW AND DRY UPPER LEVEL AIR WILL
LIKELY KEEP STORM COVERAGE ISOLATED. BY MONDAY, THE UPPER LEVEL
TROUGH WILL START TO MOVE OUT AND ONLY ISOLATED SHOWERS ARE
ANTICIPATED THE REST OF THE FORECAST PERIOD. AS WINDS DECREASE OVER
THE NEXT COUPLE OF DAYS, THERE IS A SLIGHT CHANCE FOR ISLAND-EFFECT
SHOWERS TUESDAY AND WEDNESDAY OVER GUAM.
MARINE
GENTLE TO MODERATE EASTERLIES WILL PREVAIL ACROSS THE MARIANAS
THROUGH THE WEEKEND, THEN BEGIN TO LIGHTEN AS A BROAD TROUGH
EXTENDING IN EASTERN YAP STATE CONTINUES TO BRING PATCHY SHOWERS
AND ISOLATED THUNDERSTORMS THROUGH SUNDAY. INCREASED UPPER-LEVEL
INSTABILITY LATE SUNDAY THROUGH MONDAY MORNING MAY ALLOW FOR
FURTHER ISOLATED THUNDERSTORM DEVELOPMENT. COMBINED SEAS OF 6 TO 8
FEET WILL PERSIST THROUGH TONIGHT AND THEN BEGIN TO SLOWLY TAPER DOWN
THEREAFTER, AS THE EAST-NORTHEASTERLY SWELL AND WESTERLY SWELL START
TO DIMINISH. THIS IS ALSO CONTRIBUTING TO A MODERATE RISK OF RIP
CURRENTS ALONG WEST, NORTH, AND EAST-FACING REEFS. THERE IS ALSO A
MODERATE RISK OF LIGHTNING FOR THE COASTLINES THROUGH AT LEAST SUNDAY
NIGHT.
TROPICAL SYSTEMS
30W WAS UPGRADED TO TROPICAL STORM IN-FA OVER THE NORTHERN MARSHALL
ISLANDS AT 700 AM CHST THIS MORNING, AND IS CURRENTLY LOCATED NEAR
10.4N 166.2E, OR 110 MILES NORTH-NORTHEAST OF UJAE ATOLL, SOUTH OF
BIKINI AND RONGELAP ATOLLS. HIMAWARI VISIBLE SATELLITE IMAGERY THIS
AFTERNOON SHOWS INCREASINGLY ORGANIZED CONVECTIVE BANDS WRAPPING
INTO THE CENTER, WITH HEAVY SHOWERS AND THUNDERSTORMS MAINLY FOCUSED
ALONG IN-FA'S WESTERN FLANKS AND AROUND THE CENTER, COVERING UJAE,
BIKINI, AND RONGELAP ATOLLS, AND NORTHERN PORTIONS OF KWAJALEIN
ATOLL. SCATTEROMETRY DATA FROM THIS MORNING SHOWS STRONG TO NEAR-GALE
SUSTAINED WEST TO SOUTHWEST WINDS ACROSS UJAE ATOLL AND SOUTH OF THE
CENTER, AND FRESH TO STRONG WINDS EXTENDING FARTHER SOUTH AND
SOUTHEAST, ACROSS KWAJALEIN TO AROUND AILINGLAPLAP. CURRENTLY, IN-FA
HAS MAXIMUM SUSTAINED WINDS OF 50 MPH, EXTENDING OUTWARD FROM THE
CENTER UP TO 90 MILES.
IN-FA REMAINS NEARLY STATIONARY, WITH ITS RECENT MOTION SHOWING A
SLIGHT SOUTH-SOUTHWEST DRIFT AT AROUND 2 MPH, BUT IT IS FORECAST TO
BEGIN SLOWLY MEANDERING NORTH-NORTHWEST THROUGH TONIGHT. THEN, IN-FA
WILL SEE A SLIGHT INCREASE IN FORWARD SPEED SUNDAY AS IT BEGINS TO
EXIT THE MARSHALL ISLANDS. CURRENTLY, THERE ARE NO TROPICAL STORM
WATCHES OR WARNINGS IN EFFECT ACROSS THE REGION, BUT THIS MAY CHANGE
IF IN-FA DEVELOPS MORE RAPIDLY THAN THE CURRENT FORECAST INDICATES,
OR IS SLOWER TO MOVE OUT OF THE RMI THAN EXPECTED. IN-FA IS FORECAST
TO INTENSIFY THROUGH SUNDAY, POSSIBLY BECOMING A STRONG TROPICAL
STORM BY THIS EVENING, AND THEN POTENTIALLY STRENGTHEN INTO A
CATEGORY 1 TYPHOON EARLY SUNDAY MORNING.
FOR MORE INFORMATION ON TROPICAL STORM 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
HIMAWARI VISIBLE SATELLITE THIS AFTERNOON SHOWS A STRENGTHENING,
NEARLY-STATIONARY TROPICAL STORM IN-FA POSITIONED OVER THE NORTHERN
MARSHALL ISLANDS, DISCUSSED ABOVE. POHNPEI AND KOSRAE SIT JUST SOUTH
OF THE STRONGER WESTERLY INFLOW AND ASSOCIATED SHOWERS, BUT SWATHS
OF UPPER-LEVEL DEBRIS CLOUDS ARE DRIFTING OVER BOTH ISLANDS THIS
AFTERNOON, FROM PRIOR CONVECTION TO THE NORTH. MODELS DEPICT AN
INCREASE IN SHOWERS NEAR POHNPEI LATE OVERNIGHT THROUGH SUNDAY AS
IN-FA'S INFLOW BANDS, AND ASSOCIATED LOW-LEVEL CONVERGENCE, MOVE
INTO THE AREA, WHILE KOSRAE REMAINS JUST FARTHER SOUTH. FOR MAJURO, A
SURFACE RIDGING PATTERN WILL DOMINATE OVER THE COMING DAYS AS IN-FA
SLOWLY LIFTS OUT OF THE MARSHALL ISLANDS, AND SHOWERS ARE EXPECTED TO
REMAIN ISOLATED THERE FOR MUCH OF THE FORECAST PERIOD. WINDS WILL
REMAIN LIGHT TO MODERATE AT ALL THREE LOCATIONS THROUGH THE COMING
WEEK, LARGELY INFLUENCED BY THE POSITION OF TS IN-FA, WITH WINDS
SHIFTING FROM NORTHWEST TO WEST FOR POHNPEI, WEST TO SOUTHWEST FOR
KOSRAE, AND REMAINING OUT OF THE SOUTHWEST FOR MAJURO THROUGH THE
REMAINDER OF THE WEEKEND AND EARLY NEXT WEEK.
GENERALLY BENIGN MARINE CONDITIONS ARE EXPECTED AT POHNPEI, KOSRAE,
AND MAJURO, WITH COMBINED SEAS AROUND 4 TO 7 FEET, COMPRISED OF A
PRIMARY SWELL OUT OF THE NORTH TO NORTHEAST, AND A SECONDARY
SOUTHEAST SWELL. SEAS LOOK TO INCREASE BY A FOOT OR TWO FOR MAJURO
THROUGH SUNDAY NIGHT AS WEST TO SOUTHWEST SWELL BUILDS INTO THE
AREA, THEN SUBSIDE EARLY NEXT WEEK. SEAS WILL BE HAZARDOUS TO SMALL
CRAFT ACROSS MUCH OF THE NORTHWESTERN MARSHALL ISLANDS, AND DANGEROUS
WITHIN THE TROPICAL STORM-FORCE CONDITIONS NEAR THE CENTER OF IN-FA.
DO NOT ATTEMPT INTER-ISLAND TRAVEL. CONDITIONS WILL GRADUALLY EASE
ACROSS THE NORTHERN RMI THROUGH EARLY NEXT WEEK.
WESTERN MICRONESIA
ONLY PATCHES OF SHOWERS BROUGHT ON BY A BROAD TROUGH, OVER EASTERN
YAP STATE, ARE SEEN ON SATELLITE THIS EVENING FOR MUCH OF WESTERN
MICRONESIA. FAIRLY BENIGN WEATHER IS IN STORE FOR MUCH OF THE REGION
WITH A FEW PERIODS OF SCATTERED SHOWERS FOR THE FORECAST PERIOD.
ANOTHER CONCERN IS FOR PALAU, THE SMOKE FROM THE INDONESIAN WILD
FIRES. THIS MAY CAUSE FOLK WITH RESPIRATORY ILLNESS TO HAVE A HARDER
TIME.
ALTIMETRY SHOWS COMBINED SEAS NEAR 6 FEET THROUGH OUT THE REGION.
THESE SEAS ARE EXPECTED TO GRADUALLY DECREASE THROUGH THURSDAY TO
AROUND 3 TO 5 FEET. WINDS ARE EXPECTED TO REMAIN LIGHT TO GENTLE.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA/TROPICAL SYSTEMS: DECOU
WEST MICRONESIA: BOWSHER
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page