173
FXPQ50 PGUM 012227 CCA
AFDGUM
AREA FORECAST DISCUSSION...CORRECTED
NATIONAL WEATHER SERVICE TIYAN GU
827 AM CHST MON JUN 2 2025
CORRECTED WESTERN MICRONESIA UPDATE TO INCLUDE CORRECT DISCUSSION
MARIANAS UPDATE
THE MAIN FORECAST CHALLENGE, AND UPDATE, WAS FOR THE LATE MORNING
INTO THE AFTERNOON TIME FRAME (10 AM-6PM). YESTERDAY, THE GRADIENT
WIND WAS NEAR 10 KNOTS, AND SURFACE OBSERVATIONS SHOWED 5-7 KNOTS
WHICH ALLOWED OUTFLOW BOUNDARIES TO PROPAGATE EAST-SOUTHEASTWARD,
ALLOWING THEM TO ACT AS FOCI FOR NEW CONVECTIVE DEVELOPMENT.
THE GRADIENT WIND ON TONIGHT'S UPPER AIR BALLOON WAS DOWN TO 6
KNOTS, SO WE'RE EXPECTING MORE OF A LIGHT AND VARIABLE WIND (6 KNOTS
OR LESS, GENERALLY), WHICH MAY ALLOW FOR HIGHER COVERAGE OF SHOWERS
AND THUNDERSTORMS.
FOR NOW, OPTED TO GIVE THE WESTERN HALF OF THE ISLANDS HIGHER
RAINFALL PROBABILITIES AT 50 PERCENT BETWEEN 10 AM AND 6PM.
FIRE WEATHER UPDATE
0.04 INCHES OF RAIN FELL YESTERDAY AT THE GUAM INTERNATIONAL
AIRPORT, WHICH ALLOWED THE KBDI TO FALL TO 713. THIS IS IN THE HIGH
CATEGORY DUE TO WINDS REMAINING BELOW THE 20 MPH THRESHOLD. WINDS
SHOULD REMAIN BELOW THE RED FLAG WARNING CRITERIA THE NEXT FEW DAYS,
THOUGH RHS CONTINUE TO DROP TO AROUND 60 PERCENT. THERE WILL BE A FEW
CHANCES FOR SCATTERED SHOWERS THE NEXT COUPLE OF DAYS, BUT A
WIDESPREAD WETTING RAIN REMAINS UNLIKELY THROUGH THE EARLY WEEK
PERIOD. EVEN THOUGH RED FLAG WARNING CRITERIA IS NOT EXPECTED, THE
VERY DRY CONDITIONS ACROSS THE ISLAND WILL MAINTAIN A HIGH FIRE
DANGER.
EASTERN MICRONESIA UPDATE
THE INTERTROPICAL CONVERGENCE ZONE (ITCZ) CONTINUES TO MEANDER
ACROSS THE REGION, BRINGING SCATTERED SHOWER ACROSS MAJURO AND
KOSRAE, BUT SOUTH OF POHNPEI. THE ONLY CHANGE TO THE FORECAST WAS TO
TREND DOWN SHOWERS TO ISOLATED FOR POHNPEI TODAY, ALTHOUGH SCATTERED
SHOWERS ARE EXPECTED TO BUILD BACK IN TONIGHT AS THE ITCZ TILTS
NORTHWARD.
BUOY AND ALTIMETRY DATA SHOW COMBINED SEAS OF 4 TO 6 FEET ACROSS
POHNPEI AND KOSRAE AND UP TO 7 FEET AT MAJURO. SCATTEROMETRY DATA
INDICATES GENTLE TO MODERATE TRADES NEAR KOSRAE AND MAINLY MODERATE
TRADES NEAR POHNPEI AND MAJURO.
WESTERN MICRONESIA UPDATE
SATELLITE IMAGERY SHOWS SCATTERED TO NUMEROUS SHOWERS ACROSS PALAU,
ISOLATED TO SCATTERED SHOWERS ACROSS YAP STATE, AND MAINLY
SCATTERED SHOWERS ACROSS CHUUK STATE, ASSOCIATED WITH TRADE-WIND
CONVERGENCE PATTERN IN THE REGION. 850MB VORTICITY SHOWS AN AREA OF
MODERATE VORTICITY SOUTH OF PALAU, WHERE A DEVELOPING TROUGH IS
EXPECTED TO BRING AN INCREASE IN THE SHOWERS TO PALAU TODAY. SLIGHTLY
ADJUSTED THE FORECAST FOR NUMEROUS SHOWERS TO DEVELOP AROUND NOON.
THE FORECAST FOR YAP AND CHUUK REMAINS ON TRACK.
BUOY DATA SHOWS COMBINED SEAS 2 TO 4 FEET NEAR YAP AND PALAU AND 4
TO 6 FEET NEAR CHUUK. SCATTEROMETRY DATA SHOWS LIGHT TO GENTLE
WINDS NEAR YAP AND PALAU AND MODERATE TRADES NEAR CHUUK.
PREV DISCUSSION
/ISSUED 437 PM CHST SUN JUN 1 2025/
MARIANAS SYNOPSIS...
GENTLE TO MODERATE TRADES PREVAIL. SATELLITE IMAGERY AND DOPPLER
RADAR INDICATE ISLAND CONVECTION BEGINNING TO DISSIPATE IN THE LATE
AFTERNOON HOURS. THE BUOYS INDICATE SEAS ARE 3 TO 5 FEET.
DISCUSSION...
A COMBINATION OF A MINOR UPPER-LEVEL JET OVERHEAD, SOUTHEASTERLIES
WITH INCREASING MOISTURE COLUMNS, AND A BUILDING RIDGE TO THE
NORTHWEST, ARE ALLOWING ISOLATED TO LOW-END SCATTERED SHOWERS AND
SOME THUNDERSTORMS TO MOVE IN ACROSS THE MARIANAS FOR MUCH OF THE
FIRST HALF OF THE WEEK. SHOWERS WILL BEGIN TO INCREASE MORESO
STARTING THURSDAY, AS A CONVERGENCE ZONE BUILDS ACROSS THE REGION
INTO NEXT WEEKEND.
MARINE...
LITTLE CHANGE IN THE MARINE FORECAST. COMBINED SEAS OF 3 TO 5 FEET
WILL PERSIST THROUGH AT LEAST THE MIDWEEK. A MODERATE RISK OF RIP
CURRENTS IS EXPECTED ALONG EAST FACING REEFS FOR MUCH OF THE WEEK.
FIRE WEATHER...
A TRACE OF RAIN HAS FALLEN AT THE AIRPORT SINCE MIDNIGHT. MORE
SHOWERS ARE EXPECTED TO DEVELOP NEAR THE DIURNAL MAX TONIGHT, BUT
THEY ARE NOT EXPECTED TO BRING A WETTING RAIN. AS SUCH, THE KBDI MAY
EITHER STAY AROUND THE SAME OR DROP SLIGHTLY, WHICH IS CURRENTLY AT
714. THERE WILL BE A FEW CHANCES FOR SCATTERED SHOWERS THE NEXT FEW
DAYS, BUT A WIDESPREAD WETTING RAIN REMAINS UNLIKELY THE NEXT FEW
DAYS. IN ADDITION, THE ALREADY STRESSED FOLIAGE, ESPECIALLY IN THE
SOUTHERN PORTIONS OF GUAM, STILL CONTINUE TO POSE A HIGH FIRE DANGER,
BUT RED FLAG CONDITIONS ARE NOT EXPECTED TO BE MET.
EASTERN MICRONESIA...
THE MAIN CHANGES TO THE OVERALL FORECAST ARE IN THE SHORT-TERM,
MAINLY TONIGHT. THE INTER-TROPICAL CONVERGENCE ZONE (ITCZ) REMAINS
THE MAIN PLAYER IN EASTERN MICRONESIA. THE ITCZ HAS DRIFTED FAR
ENOUGH NORTH TO BRING INCREASED CONVECTION TO MAJURO, SO HAVE
INCREASED POPS (PROBABILITY OF PRECIPITATION) TO 50 PERCENT FOR
TONIGHT. HOWEVER, THE ITCZ REMAINS A BIT TOO FAR EAST OF KOSRAE AND
POHNPEI TO PRODUCE ANY CONVECTION THERE THROUGH TONIGHT. IT STILL
APPEARS LIKELY THAT THE ITCZ WILL SPREAD WEST AS WEAK TRADE-WIND
TROUGHS MOVE INTO THE REGION. OVERALL, AN UNSETTLED PATTERN STILL
LOOKS TO BE ON TAP FOR THE NEXT SEVERAL DAYS.
COMBINED SEAS REMAIN BETWEEN 5 AND 7 FEET AT MAJURO AND BETWEEN 4 AND
6 FEET AT KOSRAE AND POHNPEI. SEAS ARE EXPECTED TO SLOWLY SUBSIDE
THROUGH THE WEEK, REACHING 3 TO 5 FEET ACROSS EASTERN MICRONESIA BY
THE END OF THE WEEK. GENTLE TO OCCASIONALLY MODERATE WINDS WILL
CONTINUE THROUGH FRIDAY.
WESTERN MICRONESIA...
SATELLITE THIS AFTERNOON SHOWS A BAND OF MID- TO UPPER LEVEL CLOUDS
EXTENDING EAST-NORTHEAST OVER PALAU TO JUST SOUTH OF YAP PROPER, WITH
ISOLATED TO SCATTERED SHOWERS ACROSS THE AREA. A BROAD TRADE-WIND
TROUGH EXTENDS NORTH-NORTHEAST OVER THE REPUBLIC OF PALAU, HAVING
SHIFTED WEST OF YAP PROPER, BUT SHOWERS ARE FAIRLY PATCHY WITHIN IT.
CONVERGENT FLOW AND SCATTERED SHOWERS ASSOCIATED WITH THE TROUGH
HAVE SHIFTED WEST OF YAP AS WELL, AND YAP CAN EXPECT JUST ISOLATED
SHOWERS FOR TONIGHT, WHILE SCATTERED SHOWERS PERSIST NEAR PALAU.
SHOWERS LOOK TO INCREASE TO NUMEROUS FOR PALAU ON MONDAY AS A TRADE-
WIND CONVERGENCE BOUNDARY SETS UP OVER THE AREA, ASSOCIATED WITH A
TROUGH LIFTING NORTHWEST INTO THE ROP. YAP WILL SEE AN INCREASE IN
SHOWERS AS WELL, BUT WILL LARGELY REMAIN IN A DRIER PATTERN FOR THE
NEXT FEW DAYS AS THE SUBTROPICAL RIDGE DIPS SLIGHTLY FURTHER SOUTH
AND OVERHEAD.
TO THE EAST, CHUUK REMAINS FAIRLY QUIET THIS AFTERNOON, WITH ISOLATED
TO SCATTERED SHOWERS ACROSS THE STATE ASSOCIATED WITH WEAK TRADE-WIND
CONVERGENCE, DOWNSTREAM OF A BROAD TROUGH WITHIN A DEVELOPING ITCZ.
CHUUK WILL SEE INCREASING SCATTERED SHOWERS OVER THE NEXT FEW DAYS AS
AN ITCZ FRAGMENT LIFTS NORTH INTO THE AREA, ACCOMPANYING A ROBUST
TRADE-WIND TROUGH OR TWO.
BENIGN MARINE CONDITIONS CONTINUE. BUOY AND ALTIMETRY DATA SHOW
COMBINED SEAS OF 2 TO 3 FEET NEAR PALAU, AROUND 3 FEET EAST OF YAP,
AND 4 TO 6 FEET NEAR CHUUK LAGOON. SWELLS WERE REDUCED SLIGHTLY IN
THE MARINE FORECAST FOR PALAU AND YAP IN THE NEAR-TERM TO REFLECT
OBSERVATIONAL DATA. WINDS WILL REMAIN MOSTLY GENTLE FOR PALAU AND YAP
THROUGHOUT THE FORECAST PERIOD, BECOMING MODERATE AT TIMES FURTHER
EAST OVER CHUUK. SEAS WILL INCREASE AROUND A FOOT NEAR PALAU AND YAP
THROUGH MIDWEEK WITH A SLIGHT STRENGTHENING IN THE PRIMARY SWELL,
REMAINING STEADY AT AROUND 4 TO 6 FEET FOR CHUUK FOR THE NEXT FEW
DAYS BEFORE A SLIGHT DECREASE THERE BY THE END OF THE WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS UPDATE: DOLL
EAST/WEST MICRONESIA UPDATE: CRUZ
MARIANAS: MONTVILA
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: DECOU
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