850
FXPQ50 PGUM 300731
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
531 PM CHST MON MAR 30 2026
MARIANAS SYNOPSIS
A WEAK FRAGMENTING SHEAR LINE EXTENDS THROUGH THE MARIANAS JUST NORTH
OF SAIPAN AND IS GENERATING MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS
NEAR TINIAN AND SAIPAN AND OVER THE ISLANDS TO THE NORTH. FURTHER
SOUTH PARTLY CLOUDY SKIES AND ISOLATED SHOWERS EXTEND OVER ROTA AND
GUAM, WITH SOME LINGERING ISLAND-ENHANCED CONVECTION FOUND IN THE
WATERS WEST OF GUAM. SEAS ARE AROUND 5 TO 7 FEET ACCORDING TO
ALTIMETRY AND TANAPAG BUOY WITH GENTLE TO MODERATE NORTHEAST WINDS
ACROSS THE COASTAL WATERS.
DISCUSSION
THE MAIN FEATURE CURRENTLY NEAR THE MARIANAS IS THE FRAGMENTING SHEAR
LINE THAT EXTENDS FROM A WEAK COLD FRONT WELL NORTHEAST OF THE
ISLANDS. HI-RES MODELS SHOW A SLIGHT NORTHWARD SHIFT IN THE BROKEN
BAND OF CLOUD COVER AND SCATTERED SHOWERS ASSOCIATED WITH THE SHEAR
LINE LATE THIS EVENING, SO EXPECT SHOWERS TO BECOME ISOLATED AT
TINIAN AND SAIPAN BY MIDNIGHT. HI-RES MODELS THEN SHOW SHOWERS
SHIFTING BACK IN TUESDAY MORNING AS THE SHEAR LINE CONTINUES TO
FRAGMENT AND ONE OF THESE FRAGMENTS SHIFT OVER SAIPAN AND TINIAN.
GUAM AND ROTA ARE EXPECTED TO REMAIN FAIRLY DRY AND WELL SOUTH OF ANY
OF THESE FRAGMENTS. AS THE TRADE-WINDS SLOWLY STRENGTHEN, THIS
SHOULD PUSH WHAT REMAINS OF THE SHEAR LINE WEST OF THE MARIANAS, WITH
A RELATIVELY DRY PATTERN EXPECTED FOR MOST OF THE WEEK, THOUGH
GLOBAL MODELS SHOW A COUPLE OF WEAK TROUGHS PASSING NEAR THE MARIANAS
AROUND FRIDAY AND THEN MONDAY WHICH MAY LEAD TO A COUPLE PERIODS OF
INCREASED CLOUD COVER AND LOW-END SCATTERED SHOWERS. LONG-RANGE
GUIDANCE SHOWS A POTENTIAL SURGE IN THE TRADE WINDS LATE IN THE
WEEKEND THAT COULD CAUSE BREEZY CONDITIONS AROUND 25 MPH TO DEVELOP
ACROSS THE MARIANAS.
MARINE
ALTIMETRY AND BUOY DATA NEAR SAIPAN SHOW SEAS ARE AROUND 5 TO 7 FEET
THIS EVENING, DRIVEN BY NORTH TO NORTHEAST SWELL AND WEAK EASTERLY
TRADE SWELL. WINDS ARE EXPECTED TO BE GENTLE TO MODERATE OUT OF THE
NORTHEAST TO EAST FOR MOST OF THE WEEK. SEAS MAY INCREASE BY A FOOT
OR SO IN THE LATTER HALF OF THE WEEK AS THE TRADE WINDS AND SWELL
STRENGTHEN SLIGHTLY. THIS PATTERN WILL SUPPORT A MODERATE RISK OF RIP
CURRENTS ALONG NORTH AND EAST FACING REEFS THROUGH THE REST OF THE
WEEK.
TROPICAL SYSTEMS
INVEST 99W LOOKS LIKE IT'S FINALLY STARTING TO WEAKEN AS MOST OF THE
CONVECTION HAS DISSIPATED SINCE THIS MORNING, AS IT'S LOCATED
NORTHWEST OF POHNPEI NEAR 11N157E, AND IS DRIFTING WEST. CIMSS
ANALYSIS SHOWS A TITLING VORTICITY FIELD FROM THE SURFACE TO 700MB,
THEN SOUTHWARD AT 500MB. THE MODELS DISSOLVE THIS FEATURE IN THE NEXT
18 TO 36 HOURS.
THEN, ANOTHER CIRCULATION 3.5N180. IT'S CENTER REMAINS BROAD, WITH
NO SIGNIFICANT CONVECTION NEAR IT'S CENTER. THE LATEST OPERATIONAL
AND ENSEMBLE MEMBERS DRIFT THIS FEATURE WEST-SOUTHWEST THE NEXT FEW
DAYS WITH PERHAPS A SLIGHT IMPROVEMENT IN ORGANIZATION BY THE
WEEKEND. LONG-RANGE MODEL GUIDANCE AND ENSEMBLE MEMBERS ALSO HAVE IT
BECOMING BETTER ORGANIZED, BUT NOT UNTIL THE FIRST PART OR THE
MIDDLE OF NEXT WEEK, AT WHICH TIME THE CENTER MAY BE NEAR KOSRAE.
THUS, IF THE DELAY TRENDS CONTINUE, MAJURO AND POINTS SOUTH STILL MAY
GET SOME HEAVY RAINFALL, BUT THAT LOOKS TO BE ABOUT IT.
EASTERN MICRONESIA
AS 99W CONTINUES TO WEAKEN AND MOVE AWAY FROM THE REGION, CONVECTION
MAY DECREASE THE NEXT FEW DAYS, WITH A PERIOD OF ISOLATED SHOWER
COVERAGE NOT TOTALLY OUT OF THE QUESTION FOR POHNPEI, AND MAYBE
KOSRAE. WITH THAT SAID, A TROUGH STRETCHING NEAR BOTH PLACES WILL
PROBABLY KEEP SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS GOING FOR
MOST OF THE FORECAST AT BOTH LOCATIONS, WHILE CONTINUING AT MAJURO AS
WELL. LIGHT TO GENTLE WINDS WILL BE GENTLE TO MODERATE AT TIMES. SEAS
OF 4 TO 6 FEET WILL INCREASE A FOOT BY THE WEEKEND.
WESTERN MICRONESIA
AFTERNOON SATELLITE IMAGERY SHOWS A MONSOON-LIKE NET BLANKETED
ACROSS WESTERN MICRONESIA WITH AN EMBEDDED CIRCULATION SOUTH-
SOUTHEAST OF PALAU. MOSTLY CLOUDY SKIES AND ISOLATED TO SCATTERED
SHOWERS ACCOMPANY THE NET AND EMBEDDED CIRCULATION AND THESE
CONDITIONS CAN BE EXPECTED AT BOTH YAP AND PALAU THROUGH TUESDAY.
ISOLATED THUNDERSTORMS WILL BE POSSIBLE AT PALAU TONIGHT, MAINLY
AFTER MIDNIGHT. GENERALLY DRIER CONDITIONS ARE EXPECTED FOR PALAU
AND YAP FROM WEDNESDAY THROUGH FRIDAY. INVEST 99W WILL CONTINUE TO
WEAKEN AS IT MOVES WESTWARD AND IS EXPECTED TO BRING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS STARTING TUESDAY NIGHT FOR CHUUK
AS THE WEAKENING DISTURBANCE APPROACHES. DRIER CONDITIONS ARE THEN
EXPECTED AT CHUUK FOR THE BACK HALF OF THE WORK WEEK.
WINDS WILL REMAIN GENTLE TO MODERATE AT YAP THROUGH MUCH OF THE
WEEK, WITH GENTLE TO MODERATE WINDS WEAKENING TO MOSTLY GENTLE AT
PALAU STARTING WEDNESDAY. WINDS WILL INCREASE FROM LIGHT TO GENTLE TO
GENTLE TO MODERATE STARTING TUESDAY NIGHT AT CHUUK AS THE WEAKENING
DISTURBANCES APPROACHES. COMBINED SEAS OF 3 TO 6 FEET WILL PREVAIL
AT ALL FORECAST SITES THROUGH MUCH OF THE WEEK, WITH SEAS INCREASING
TO AROUND 7 FEET AT CHUUK BY THE WEEKEND AND POTENTIALLY UP TO 10
FEET BY THE END OF THE WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: SCHANK
EAST MICRONESIA/TROPICAL: DOLL
WEST MICRONESIA: WHISNANT
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page