960
FXPQ50 PGUM 312016
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
616 AM CHST WED APR 1 2026
MARIANAS UPDATE
RADAR IMAGERY DEPICTS PATCHY SCATTERED SHOWERS MOVING WEST-SOUTHWEST
INTO ROTA COASTAL WATERS EARLY THIS MORNING, WITH SATELLITE IMAGERY
INDICATING ISOLATED TO SCATTERED SHOWERS JUST EAST-NORTHEAST OF
SAIPAN AND TINIAN WATERS MOVING INTO THE AREA. THESE ARE ASSOCIATED
WITH THE FRAGMENTS OF A NEARBY SHEAR LINE, WHICH IS EXPECTED TO
CONTINUE WEAKENING THROUGH THE NEXT DAY OR SO. LOW-END SCATTERED
SHOWERS (30 PERCENT CHANCE) WERE INCLUDED IN THE FORECAST FOR ROTA
THIS MORNING, IN ADDITION TO TINIAN AND SAIPAN, WHICH ARE THEN
EXPECTED TO BECOME ISOLATED BY THE AFTERNOON AS THE SHEAR LINE AND
ASSOCIATED SURFACE CONVERGENCE DIMINISH FURTHER.
THERE WAS LITTLE TO NO CHANGE IN THE MARINE OR SURF FORECASTS.
LATEST BUOY AND ALTIMETRY DATA INDICATE COMBINED SEAS AROUND 5 TO 8
FEET ACROSS THE CNMI AND 3 TO 5 FEET NEAR GUAM. OVERALL, SEAS ARE
EXPECTED TO DIMINISH TO 4 TO 6 FEET BY THE END OF THE WEEK AS
MODERATE TO FRESH TRADE WINDS BECOME GENTLE TO MODERATE, OUT OF THE
EAST TO NORTHEAST. THEN, COMBINED SEAS LOOK TO BUILD BY SEVERAL FEET
THROUGH THE WEEKEND AS TRADE WINDS, SWELL, AND WIND WAVES INCREASE,
CAUSED BY THE INCREASE IN REGIONAL PRESSURE GRADIENT AS HIGH PRESSURE
MOVES EASTWARD OFF THE COAST OF JAPAN. THIS WILL ALSO INCREASE SURF
ALONG EAST-FACING REEFS THROUGH THE WEEKEND. MODEL GUIDANCE
CONTINUES TO SHOW A POTENTIAL FOR SEAS TO REACH HAZARDOUS LEVELS OF
10 FEET EARLY NEXT WEEK.
EASTERN MICRONESIA UPDATE
A BROAD CIRCULATION CONTINUES TO MEANDER JUST EAST OF THE SOUTHERN
MARSHALL ISLANDS, CENTERED AROUND 2N177E, WITH A WEAK BROAD TROUGH
EXTENDING OUTWARD TO THE WEST-NORTHWEST SOUTH OF KOSRAE AND POHNPEI.
PATCHY SCATTERED SHOWERS CONTINUE NEAR POHNPEI AND MAJURO EARLY THIS
MORNING, AND TO THE SOUTH OF KOSRAE. PROBABILITY OF PRECIPITATION
(POP) WAS MAINTAINED AT 40 PERCENT FOR MAJURO TODAY AS AN AREA OF
WEAK SURFACE CONVERGENCE LINGERS NEARBY, AND INCREASED TO 30 PERCENT
FOR POHNPEI AS SCATTERED SHOWERS CONTINUE ALONG THE BACKSIDE OF THE
NEARBY TROUGH. SHOWERS LOOK TO INCREASE ONCE MORE ACROSS THE REGION
BY THE END OF THE WEEK AS THE SURFACE CIRCULATION GRADUALLY SHIFTS
WESTWARD ACROSS THE RMI, INTERACTING WITH AN APPROACHING TRADE-WIND
TROUGH. MODELS DEPICT A BROAD, ROBUST CONVERGENCE ZONE FORMING ACROSS
THE REGION THIS WEEKEND AS THE SURFACE CIRCULATION SHIFTS TO THE
SOUTH OF POHNPEI AND KOSRAE.
WESTERN MICRONESIA UPDATE
THE MAIN CHANGE IN THE FORECAST WAS TO INCREASE SHOWERS TO 50 PERCENT
FOR CHUUK THIS MORNING AND INCLUDE ISOLATED THUNDERSTORMS, AS THE
REMNANTS OF PRIOR INVEST 99W MOVE OVERHEAD, WITH MODERATE TO DEEP
CONVECTION PERSISTING SINCE LATE LAST NIGHT. SHOWERS ARE EXPECTED TO
DIMINISH THERE THIS AFTERNOON AS THE SURFACE TROUGH AND UPPER-LEVEL
SUPPORT MOVE AWAY TO THE WEST AND SOUTHWEST. SHOWERS LOOK TO BECOME
SCATTERED NEAR PALAU AND YAP OVERNIGHT AS THE SURFACE CIRCULATION
SOUTHEAST OF PALAU, AND THE EAST-TO-WEST ORIENTED TROUGH EXTENDING
FROM IT, SHIFT CLOSER TO THE NORTHWEST, AND CONVERGENCE INCREASES
ALONG ITS NORTHERN PERIPHERY.
PREV DISCUSSION
/ISSUED 501 PM CHST TUE MAR 31 2026/
MARIANAS SYNOPSIS...
A FRAGMENTED SHEAR LINE EXTENDS ACROSS THE CNMI BRINGING MODERATE TO
FRESH WINDS, MOSTLY CLOUDY SKIES, AND SCATTERED SHOWERS ACROSS
TINIAN AND SAIPAN. MEANWHILE, A WEAK TRADE-WIND TROUGH IS BRINGING
PATCHY SHOWERS OVER GUAM AND SOUTHERN WATERS THIS AFTERNOON.
ALTIMETRY AND BUOY DATA SHOW COMBINED SEAS OF 6 TO 8 FEET FOR THE
SOUTHERN CNMI, WITH SEAS AROUND 4 FEET NEAR GUAM.
DISCUSSION...
A FRAGMENTED SHEAR LINE CONTINUES TO BRING SCATTERED SHOWERS AND
MODERATE TO FRESH WINDS TO TINIAN AND SAIPAN AND IS EXPECTED TO
PERSIST THROUGH WEDNESDAY MORNING. THEN, THE SHEAR LINE IS EXPECTED
TO WEAKEN FURTHER WITH GENTLE TO MODERATE NORTHEAST TO EAST WINDS
AND A RELATIVELY DRY PATTERN EXPECTED THROUGH THE REMAINDER OF THE
WEEK. MODEL GUIDANCE IS SHOWING ANOTHER AREA OF HIGH PRESSURE MOVING
EASTWARD OFF THE COAST OF JAPAN LATE FRIDAY NIGHT. THE RESULTING
PRESSURE GRADIENT BETWEEN THE NEAR-EQUATORIAL TROUGH TO THE SOUTH
WOULD LEAD TO WINDS INCREASING TO MODERATE TO FRESH OVER THE WEEKEND
AND EARLY NEXT WEEK. IN THIS PATTERN, THERE IS SOME SUPPORT FOR MINOR
TRADE-WIND TROUGHS TO PASS THROUGH THE REGION, BUT OVERALL SHOWERS
ARE EXPECTED TO BE MAINLY ISOLATED WITH PERIODS OF LOW-END SCATTERED
SHOWERS POSSIBLE FRIDAY AND OVER THE WEEKEND.
MARINE/SURF...
TANAPAG BUOY REVEALED SEAS REACHED UP TO 9.3 FEET THIS MORNING DUE
TO HIGHER WIND WAVES ALONG THE SHEAR LINE, BUT HAS SINCE DECREASED TO
AROUND 8 FEET THIS AFTERNOON. THE SHEAR LINE IS EXPECTED TO WEAKEN
FURTHER WEDNESDAY NIGHT, WITH WINDS DIMINISHING TO GENTLE TO MODERATE
AND COMBINED SEAS OF 5 TO 8 FEET DECREASING TO 4 TO 6 FEET LATE THIS
WEEK. OVER THE WEEKEND, EASTERLY TRADE WINDS AND SWELL ARE EXPECTED
TO INCREASE, WITH WINDS BECOMING MODERATE TO FRESH AND SEAS QUICKLY
INCREASING TO 6 TO 9 FEET, POTENTIALLY REACHING HAZARDOUS LEVELS OF
10 FEET EARLY NEXT WEEK. CURRENTLY THERE IS A MODERATE RISK OF RIP
CURRENTS ALONG NORTH AND EAST FACING REEFS AND LOW RISK ALONG SOUTH
AND WEST FACING REEFS OVER THE NEXT FEW DAYS, WITH PRIMARY SWELL FROM
THE NORTH TO NORTHEAST. THEN SURF IS EXPECTED TO BUILD ALONG EAST-
FACING REEFS OVER THE WEEKEND AND INTO NEXT WEEK DUE TO AN INCREASE
IN EASTERLY SWELL.
EASTERN MICRONESIA...
INVEST 99W HAS DISSIPATED, AND SO HAVE THE SHOWERS AND THUNDERSTORMS
AT POHNPEI AND KOSRAE, WITH JUST HIT AND MISS SHOWERS ABOUT ALL
THAT'S EXPECTED THE NEXT FEW DAYS. MAJURO ON THE OTHER HAND, HAD
NUMEROUS SHOWER COVERAGE EARLIER TODAY, WITH THE RECENT INFRARED
SATELLITE IMAGERY SHOWING RAPIDLY WARMING CLOUD TOPS, MAKING
THUNDERSTORMS LESS OF A CONCERN AS IT LOOKS LIKE THE ATMOSPHERE IS
STRATIFYING-OUT/STABILIZING. AS SUCH, JUST HIGH-BASED CLOUD COVER
AND LIGHT RAIN SHOWERS SHOULD DOMINATE THE FIRST PART OF THE NIGHT,
BEFORE THINGS POSSIBLY INCREASE TOWARDS SUNRISE.
ATTENTION THEN TURNS TO A CIRCULATION WELL EAST-SOUTHEAST OF MAJURO
NEAR 4N179E. THIS CIRCULATION HAS BECOME BETTER ORGANIZED TODAY, AND
BOTH THE JOINT TYPHOON WARNING CENTER (JTWC) AND US ARE KEEPING AN
EYE ON IT. IT'S POSSIBLE JTWC MAY LIST IT AS AN INVEST IN THE NEXT 24
HOURS OR SO, DEPENDING HOW THE CIRCULATION EVOLVES. THE OPERATIONAL
GEFS AND HAS TRENDED STRONGLY TOWARDS THE OPERATIONAL ECMWF, IT'S
ENSEMBLE MEMBERS, AND THE NBM (NATIONAL BLEND OF MODELS). THEY ALL
TAKE THIS CIRCULATION SOUTHWEST TOWARDS EQ170E OVER THE WEEKEND. THEY
THEN SHOW THIS SYSTEM BYPASSING KOSRAE JUST TO THE SOUTH, AND
POHNPEI TO THE WEST, BUT CLOSE ENOUGH TO AFFECT THOSE LOCATIONS. IN
GENERAL, ALL OF EASTERN MICRONESIA WILL LIKELY SEE A SOMEWHAT
PROLONGED PERIOD OF NUMEROUS SHOWERS (SOME HEAVY) AND ISOLATED
THUNDERSTORMS. WITH THAT SAID, IT'S STILL WAY, WAY TOO EARLY TO TALK
ABOUT WHAT STRENGTH OR TRACK THIS SYSTEM WILL ULTIMATELY TAKE. FOLKS
SHOULD CONTINUE TO MONITOR THE FORECASTS THROUGH EARLY NEXT WEEK!
MARINERS CAN EXPECTS PERIODS OF GENTLE TO MODERATE WINDS AT TIMES,
BUT THAT CURRENTLY LOOKS TO BE THE STRONGEST THEY'LL GET. SEAS OF 5
TO 7 FEET MAY INCREASE A FOOT OR TWO BY EARLY NEXT WEEK.
WESTERN MICRONESIA...
THE NET ENTERS THE REGION AROUND 4N130E AND EXTENDS TO THE EAST,
SOUTH OF PALAU, WHERE IT INTERSECTS A WEAK CIRCULATION SOUTH-
SOUTHEAST OF PALAU AND CONTINUES EASTWARD INTO CENTRAL AND EASTERN
MICRONESIA. THE WEAK CIRCULATION AND SURFACE CONVERGENCE TO ITS NORTH
HAVE BROUGHT MOSTLY CLOUDY SKIES WITH ISOLATED TO SCATTERED SHOWERS
AND ISOLATED THUNDERSTORMS TO PORTIONS OF YAP STATE AND PALAU TODAY.
SIMILAR CONDITIONS ARE EXPECTED TO PERSIST THROUGH THIS EVENING AT
BOTH YAP AND PALAU AS THE CIRCULATION REMAINS QUASI-STATIONARY AND
CONTINUES TO WEAKEN, WITH BOTH SHOWER AND THUNDERSTORM CHANCES
DROPPING OFF AFTER MIDNIGHT. CONDITIONS WILL CONTINUE TO IMPROVE ON
WEDNESDAY WITH SHOWERS BECOMING MAINLY ISOLATED IN NATURE AND THIS IS
EXPECTED TO PERSIST THROUGH FRIDAY. THOUGH, YAP MAY STILL EXPERIENCE
SOME PERIODS OF SCATTERED SHOWERS. FORMER INVEST 99W IS CURRENTLY
TREKKING WESTWARD NORTH OF CHUUK WITH PARTLY CLOUDY SKIES AND
ISOLATED TO LOW-END SCATTERED SHOWERS ACCOMPANYING THIS FEATURE.
SIMILAR WEATHER CONDITIONS ARE EXPECTED AT CHUUK THROUGH THE REST OF
THE WEEK.
MOSTLY GENTLE TO MODERATE NORTHEAST WINDS WILL PREVAIL DURING THE
NEXT COUPLE OF DAYS AT YAP AND PALAU, WITH THESE CONDITIONS
DEVELOPING AT CHUUK STARTING ON WEDNESDAY. LOW-END FRESH WINDS WILL
BE POSSIBLE AT YAP THROUGH THE END OF THE WEEK. WINDS WILL INCREASE
TO FRESH AT CHUUK STARTING LATE ON SATURDAY. COMBINED SEAS OF 3 TO 5
FEET WILL PERSIST AT ALL SITES THROUGH WEDNESDAY, WITH SEAS CLIMBING
TO 5 TO 6 FEET AT CHUUK STARTING EARLY THURSDAY. SEAS WILL THEN
REMAIN STEADY AT ALL SITES DURING THE LATTER PART OF THE WEEK, WITH
SEAS THEN INCREASING AGAIN AT CHUUK THIS WEEKEND AS A LARGER
NORTHEAST SWELL MOVES THROUGH THE REGION, AND POTENTIALLY REACHING
HAZARDOUS LEVELS OF 10 FEET BY LATE THIS WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: DECOU
MARIANAS: CRUZ
EAST MICRONESIA: DOLL
WEST MICRONESIA: WHISNANT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page