507
FXPQ50 PGUM 221929
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
529 AM CHST WED APR 23 2025
MARIANAS UPDATE
THERE WAS LITTLE CHANGE TO THE FORECAST. IR SATELLITE SHOWS PATCHY
LOW-LEVEL CLOUD COVER ACROSS THE MARIANAS EARLY THIS MORNING, WITH
GREATER COVERAGE AND HIGHER CLOUD TOPS SEEN OVER ROTA, TINIAN, AND
SAIPAN COASTAL WATERS. THIS ALIGNS WITH THE LEADING EDGE OF A SHALLOW
TRADE-WIND TROUGH MOVING WEST INTO THE AREA, IN ADDITION TO AN AREA
OF HIGHER PWATS AROUND 2 INCHES. THIS WAS REFLECTED IN THE FORECAST
AS LOW-END SCATTERED SHOWERS (30 PERCENT CHANCE) FOR THE CNMI THIS
MORNING, WHILE GUAM WAS KEPT AT ISOLATED (20 PERCENT CHANCE)
THROUGHOUT THE DAY. THROUGH THE REMAINDER OF THE FORECAST PERIOD,
SHOWERS ARE ISOLATED AT MOST WITH A DRIER PATTERN SETTING UP THURSDAY
THROUGH THE END OF THE WEEK.
NEARBY BUOYS AND ALTIMETRY DATA INDICATE COMBINED SEAS OF 3 TO 5
FEET, WHICH ARE EXPECTED TO CONTINUE FOR THE NEXT FEW DAYS. THIS
WEEKEND WILL SEE AN INCREASE IN TRADE SWELL AND INCOMING NORTH SWELL,
WHICH WILL BUMP SEAS UP BY A FEW FEET, WHICH IN TURN MAY INCREASE
THE RISK OF RIP CURRENTS TO MODERATE FOR NORTH-FACING REEFS, AND
MAINTAIN THE MODERATE RIP RISK FOR EAST-FACING REEFS.
FIRE WEATHER
0.07 INCHES OF RAIN FELL AT THE GUAM INTERNATIONAL AIRPORT YESTERDAY,
NOT ENOUGH TO DIMINISH THE KBDI AFTER SEVERAL DAYS OF ONLY A TRACE
TO NO RAIN. THE KBDI HAS INCREASED SLIGHTLY WITH TODAY'S READING AT
664, WHICH REMAINS IN THE HIGH CATEGORY. GENTLE TO MODERATE TRADE
WINDS ARE EXPECTED UNTIL AT LEAST THE END OF THE WEEK, WHICH WILL
PREVENT CRITICAL RED FLAG CONDITIONS FROM BEING MET FOR THE NEXT FEW
DAYS. FIRE DANGER WILL REMAIN ELEVATED, WITH INCREASED RISK OF FIRE
SPREAD AT HIGHER TERRAIN WHERE STRONGER WINDS ARE EXPECTED.
AFTERNOON RELATIVE HUMIDITY VALUES WILL CONTINUE TO FALL NEAR 60
PERCENT. A WETTING RAIN IS NOT EXPECTED FOR THE NEXT FEW DAYS AND THE
KBDI WILL LIKELY CONTINUE TO CLIMB THROUGH THE END OF THE WEEK.
EASTERN MICRONESIA UPDATE
EASTERN MICRONESIA IS BEING AFFECTED BY TWO TRADE-WIND TROUGHS, ONE
NEAR MAJURO AND ONE NEAR POHNPEI, BOTH RUNNING MAINLY NORTH-SOUTH. AS
A RESULT OF THESE TROUGHS, ALL THREE LOCATIONS WILL BE FAIRLY WET
AFTER TODAY, WITH KOSRAE BEING A LITTLE DRIER TODAY ONLY.
ALL LOCATIONS WILL HAVE 10 TO 15 KNOT TRADE WINDS THROUGH THE
FORECAST PERIOD (WEDNESDAY THROUGH SUNDAY). SEAS FOR ALL 3 LOCATIONS
WILL START OUT AT 4 TO 6 FEET AND END AT 5 TO 7 FEET, LEADING TO
OVERALL BENIGN WEATHER CONDITIONS FOR MARINERS.
WESTERN MICRONESIA UPDATE
WESTERN MICRONESIA IS BEING AFFECTED BY A TRADE-WIND TROUGH NEAR YAP
AND A NEAR-EQUATORIAL TROUGH NEAR KOROR. THE TRADE-WIND TROUGH NEAR
POHNPEI WILL MOVE NEAR CHUUK SOON, BRINGING SHOWERS THERE AROUND
THURSDAY, LASTING THROUGH SUNDAY. THE SHOWERS AT YAP SHOULD WEAR OUT
SOON, BUT COULD MAKE AN ENCORE TONIGHT. SUNDAY THEY COULD BE BACK
AGAIN. SHOWERS AT KOROR COULD APPEAR THURSDAY, DISAPPEAR THAT NIGHT,
THEN RETURN FRIDAY THROUGH SUNDAY.
FOR MARINE WEATHER, YAP AND PALAU WILL HAVE SEAS OF 3 TO 4 FEET AND
WINDS OF 5 TO 10 KNOTS THROUGH THE WEEKEND, SIMPLY BEAUTIFUL. CHUUK
WON'T QUITE BE THAT GOOD, BUT IT WILL NOT BE BAD EITHER, WINDS WILL
BE 5 TO 15 KNOTS AND SEAS 3 TO 5 FEET.
PREV DISCUSSION
/ISSUED 549 PM CHST TUE APR 22 2025/
MARIANAS SYNOPSIS...
GENTLE TO MODERATE TRADES WITH OCCASIONALLY FRESH GUSTS PREVAIL.
SATELLITE IMAGERY AND DOPPLER RADAR INDICATE MOSTLY CLEAR SKIES IN
THE WATERS, WITH ISLAND HEATING PRODUCING SOME CLOUDS OFF OF APRA
HARBOUR AND DEDEDO. THE BUOYS INDICATE SEAS ARE AROUND 4 FEET.
DISCUSSION...
LITTLE CHANGE HAS BEEN MADE TO THE FORECAST. CONDITIONS ARE EXPECTED
TO REMAIN MOSTLY DRY ACROSS THE REGION, WITH STRONG INDICATORS FOR
CLEAR STARRY SKIES THURSDAY NIGHT, AS PWATS UPSTREAM CONTINUE TO SIT
AT OR BELOW 1.5 INCHES. THIS TREND IS ALSO SUPPORTED BY A SUBTROPICAL
HIGH DEVELOPING AT THE LEADING EDGE OF OKINAWA'S SOUTHEASTERN COASTAL
WATERS, ALLOWING A COL TO FORM TO THE NORTH OF THE MARIANAS, FURTHER
STABILIZING THE LOCAL ATMOSPHERE FOR EXTENDED PERIODS OF SHOWER-FREE
DAYS.
MARINE...
COMBINED SEAS OF 3 TO 5 FEET TO BEGIN TO INCREASE A FEW FEET DURING
THE WEEKEND, AS TRADE SWELL AND INCOMING NORTH SWELL INCREASE. SEAS
ARE EXPECTED TO REMAIN BELOW LEVELS HAZARDOUS TO SMALL CRAFT. A
MODERATE RISK OF RIP CURRENTS IS EXPECTED ALONG EAST FACING REEFS,
WHILE A LOW RISK IS EXPECTED ELSEWHERE. SURF IS EXPECTED TO BEGIN TO
INCREASE ALONG ALL REEFS SLOWLY STARTING THURSDAY, ALLOWING RIP
CURRENT RISK TO POTENTIALLY BECOME MODERATE ALONG NORTH FACING REEFS
AS WELL DURING THE WEEKEND.
FIRE WEATHER...
0.07 INCHES OF RAIN HAS FALLEN SO FAR TODAY, NOT ENOUGH TO PUT A DENT
IN THE KBDI VALUE, WHICH HAS RISEN FURTHER TO 659 AND REMAINING IN
THE HIGH CATEGORY. THERE IS LITTLE LIKELIHOOD FOR WETTING RAINS FOR
MUCH OF THE CURRENT FORECAST PERIOD. AS SUCH, THE KBDI IS EXPECTED TO
CONTINUE TO RISE. EVEN SO, WINDS ARE EXPECTED TO REMAIN GENTLE TO
MODERATE, SO CONDITIONS CRITICAL TO FIRE WEATHER ARE NOT EXPECTED AT
LEAST OVER THE NEXT FEW DAYS.
EASTERN MICRONESIA...
A FAIRLY QUIET WEATHER PATTERN CONTINUES ACROSS THE REGION WITH A
WEAK TRADE-WIND TROUGH PRODUCING SPOTTY TO SCATTERED SHOWERS JUST
NORTHEAST OF KOSRAE, WITH ADDITIONAL SHOWERS AND THUNDERSTORMS
DEVELOPING ALONG A SERIES OF SURFACE TROUGHS AND BAND OF CONVERGENCE
SOUTH-SOUTHWEST OF MAJURO AND EXTENDING BACK TO THE DATE LINE. AS
THESE FEATURES PUSH WESTWARD, SCATTERED SHOWERS SHOULD QUICKLY MOVE
INTO KOSRAE TONIGHT, WITH SCATTERED SHOWERS EXPECTED LATER TONIGHT AT
POHNPEI AND MAJURO. THE POTENTIAL FOR THUNDERSTORMS REMAINS LIMITED,
ESPECIALLY WITHOUT STRONG SURFACE FORCING OR UPPER-LEVEL SUPPORT, SO
DELAYED THE MENTION OF ISOLATED THUNDERSTORMS AT POHNPEI AND MAJURO
TO TOMORROW, AND AFTER MIDNIGHT AT KOSRAE WERE NOCTURNAL COOLING OF
THE ATMOSPHERE MAY AID SLIGHTLY IN THUNDERSTORM DEVELOPMENT ALONG
THE WEAK TRADE-WIND TROUGH. OVERALL, MODEL GUIDANCE STILL SUPPORTS A
WETTER PATTERN FOR THE LATER HALF OF THE WEEK, ESPECIALLY THE ECMWF
WHICH FAVORS A BAND OF CONVERGENCE QUICKLY DEVELOPING ACROSS THE
REGION OVER THE NEXT COUPLE OF DAYS. THE GFS HOWEVER IS SLIGHTLY
SLOWER ON DEVELOPMENT OF THE BAND OF CONVERGENCE ACROSS THE REGION,
SUPPORTING SHOWERS MAINLY ALONG THE AFOREMENTIONED TROUGHS, BEFORE
THE CONVERGENCE BUILDS ACROSS THE REGION LATE THIS WEEK. GIVEN THIS
SLIGHT DIFFERENCE IN TIMING, CAPPED POPS FOR POHNPEI AND KOSRAE TO
AROUND 30 PERCENT THROUGH THURSDAY, WHILE NOT MAKING MUCH CHANGES TO
MAJURO FORECAST SINCE THERE ALREADY IS A BAND OF CONVERGENCE SOUTH-
SOUTHWEST OF THE ATOLL.
WINDS ACROSS THE REGION ARE GENTLE TO MODERATE WITH SEAS MAINLY BELOW
6 FEET, DRIVEN BY THE PRIMARY TRADE SWELL. BESIDES FOR SLIGHTLY
STRONGER GUSTS NEAR SHOWERS, SUSTAINED WINDS ARE NOT EXPECTED TO
CHANGE MUCH THROUGH THE REST OF THE WEEK. WAVE MODELS SHOW A WEAK
NORTH SWELL MOVING INTO THE REGION THIS WEEKEND, FROM A DISTANT
SYSTEM CURRENTLY DEVELOPING EAST OF JAPAN, BUT SEA HEIGHTS ARE NOT
EXPECTED TO CHANGE MUCH DUE TO THIS SWELL.
WESTERN MICRONESIA...
SATELLITE IMAGERY SHOWS ISOLATED SHOWERS ACROSS THE MOST OF THE
REGION THIS AFTERNOON. A NEAR EQUATORIAL TROUGH (NET) CONTINUES TO
LINGER IN THE SOUTHWEST CORNER OF THE REGION, STRETCHING ACROSS THE
FAR SOUTHERN ISLANDS OF THE REPUBLIC OF PALAU. THE NET CURRENTLY HAS
A COUPLE OF WEAK CIRCULATIONS EMBEDDED WITH THE FEATURE, ROUGHLY NEAR
5N130E AND THE OTHER NEAR 2N138E. HOWEVER, CONVECTION IS LARGELY
UNORGANIZED WITH SCATTERED SHOWERS ON THE NORTHERN AND WESTERN
PERIPHERIES AND CONVECTION DEEPENING ALONG THE SOUTHERN AND EASTERN
PERIPHERIES, CLOSER TO THE EQUATOR AND 140E. MODEL GUIDANCE IS NOT
POINTING TO SIGNIFICANT DEVELOPMENT WITH THESE CIRCULATIONS, BUT A
NORTHWARD SHIFT OF THE NET WILL LEAD TO INCREASED CONVERGENCE ACROSS
THE MAIN FORECAST LOCATIONS LATE WEEK AND INTO EARLY NEXT WEEK,
MAINLY FOR PALAU AND CHUUK AND TO A LESSER EXTENT, YAP.
BENIGN MARINE CONDITIONS CONTINUE OVER THE NEXT SEVERAL DAYS WITH COMBINED
SEAS OF 3 TO 5 FEET EXPECTED, COMPRISED OF MINOR TRADE SWELL AND
WIND WAVES. A BROAD LOW PRESSURE SYSTEM EAST OF JAPAN IS GENERATING
NORTH SWELL THAT IS EXPECTED TO REACH THE REGION OVER THE WEEKEND.
THIS LONGER-PERIOD NORTH SWELL MAY SLIGHTLY ADD TO SEAS, BUT WOULD
MAINLY BOOST SURF ALONG NORTH-FACING REEFS. ALTHOUGH, NEITHER SEAS
NOR SURF ARE EXPECTED TO REACH HAZARDOUS LEVELS AT THIS TIME.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS UPDATE: DECOU
EAST/WEST MICRONESIA UPDATE: STANKO
MARIANAS: MONTVILA
EAST MICRONESIA: SCHANK
WEST MICRONESIA: CRUZ
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page