920
FXPQ50 PGUM 310701
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
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: CRUZ
EAST MICRONESIA: DOLL
WEST MICRONESIA: WHISNANT
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