572
FXPQ50 PGUM 241938
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
538 AM CHST FRI APR 25 2025
MARIANAS UPDATE
THERE WAS LITTLE TO UPDATE IN THE FORECAST AS A QUIET TRADE-WIND
PATTERN PERSISTS. PWATS RANGE 1.6 TO 1.9 INCHES ACROSS THE MARIANAS,
INDICATING CONDITIONS ARE A LITTLE LESS DRY THAN THOSE OF THE LAST
COUPLE OF DAYS. RADAR REVEALS SMALL ISOLATED SHOWERS MOVING WEST-
NORTHWEST ACROSS COASTAL WATERS EARLY THIS MORNING, WITH JUST PATCHY
LOW-LEVEL CLOUD COVER OVER THE ISLANDS. CLOUDS AND SHOWERS SHOULD
DIMINISH BY THE AFTERNOON, WITH ANOTHER UPTICK EXPECTED LATE TONIGHT.
A WEAK PASSING TROUGH AND IMPROVING ATMOSPHERIC MOISTURE COULD
INCREASE SHOWER CHANCES AROUND SATURDAY NIGHT AND SUNDAY, BUT
CONFIDENCE IS LOW FOR ANYTHING GREATER THAN ISOLATED COVERAGE (20
PERCENT CHANCE) AT THIS TIME. EXPECT SIMILAR CONDITIONS TO PERSIST
THROUGH MUCH OF NEXT WEEK.
LOCAL BUOY DATA INDICATES COMBINED SEAS OF AROUND 3 TO 5 FEET ACROSS
THE MARIANAS. SEAS ARE EXPECTED TO INCREASE BY A FOOT OR SO HEADING
INTO THE WEEKEND WITH A SLIGHT INCREASE IN TRADE SWELL AND INCOMING
NORTH SWELL. THE INCREASE IN SWELL WILL CONTRIBUTE TO A GRADUAL
INCREASE IN SURF OVER THE NEXT FEW DAYS, ALONG WITH A MODERATE RISK
OF RIP CURRENTS FOR NORTH AND EAST FACING REEFS, WHICH WILL THEN
SPREAD TO WEST FACING REEFS THIS WEEKEND.
FIRE WEATHER
0.10 INCHES OF RAIN FELL AT THE GUAM INTERNATIONAL AIRPORT YESTERDAY.
THIS WAS NOT ENOUGH TO MAKE A DENT IN THE KBDI, WHICH WAS ALLOWED TO
INCREASE SLIGHTLY WITH TODAY'S READING AT 675, REMAINING IN THE HIGH
CATEGORY. TRADE WINDS HAVE BEEN ON THE INCREASE BUT WILL GENERALLY
STAY GENTLE TO MODERATE WITH OCCASIONAL FRESH GUSTS IN THE AFTERNOON,
AND ARE EXPECTED TO REMAIN BELOW CRITICAL RED FLAG CRITERIA.
HOWEVER, FIRE WEATHER DANGER REMAINS ELEVATED AS DRY CONDITIONS
CONTINUE, ESPECIALLY AT HIGHER TERRAIN WHERE STRONGER WINDS ARE
EXPECTED. A WETTING RAIN IS NOT ANTICIPATED FOR THE NEXT FEW DAYS AND
THE KBDI IS EXPECTED TO GRADUALLY RISE THROUGH THE WEEKEND.
EASTERN MICRONESIA UPDATE
THERE WAS LITTLE CHANGE IN THE FORECAST PACKAGE. IR SATELLITE REVEALS
DISORGANIZED CONVECTION AND SCATTERED SHOWERS ACROSS THE REGION EARLY
THIS MORNING, MAINLY FOCUSED ALONG AN AREA OF TROUGHING AND TRADE-
WIND CONVERGENCE JUST WEST OF MAJURO AND EAST OF KOSRAE, THEN EAST
AND SOUTH OF POHNPEI. THESE FEATURES LOOK TO ORGANIZE SLIGHTLY
TONIGHT, WITH A BROADER CONVERGENCE BOUNDARY TO SET UP ACROSS THE
REGION WEST OF THE MARSHALL ISLANDS. THIS ITCZ-LIKE FEATURE LOOKS TO
FOCUS SHOWERS JUST SOUTH OF POHNPEI AND OVER KOSRAE OVERNIGHT AS THE
TROUGH WEST OF MAJURO SHIFTS WESTWARD, AND POPS WERE ADJUSTED UPWARD
FOR KOSRAE ACCORDINGLY.
THERE WERE NO CHANGES TO THE MARINE FORECAST, WITH BENIGN SEA
CONDITIONS EXPECTED TO PERSIST THROUGH THE WEEKEND. COMBINED SEAS
WILL REMAIN AT 4 TO 6 FEET FOR POHNPEI AND KOSRAE, AND 5 TO 7 FEET
FOR MAJURO OVER THE NEXT FEW DAYS.
WESTERN MICRONESIA UPDATE
OVERALL, LITTLE CHANGE WAS MADE WITH THIS FORECAST PACKAGE. SHOWERS
WERE KEPT ISOLATED DURING THE MORNING HOURS FOR PALAU AND CHUUK, BUT
SHOWER COVERAGE IS EXPECTED TO INCREASE TO SCATTERED THIS AFTERNOON
FOR BOTH WITH HIGH END SCATTERED (50%) EXPECTED FOR CHUUK.
OTHERWISE, NO CHANGES WERE MADE TO THE FORECAST.
A BROAD CIRCULATION LOCATED NEAR 4.5N AND 131E MAY BRING UNSETTLED
WEATHER FOR THE SOUTHERN ISLANDS OF PALAU OVER THE NEXT SEVERAL DAYS.
ORGANIZED DEVELOPMENT IS NOT EXPECTED OVER THE NEXT FEW DAYS, BUT
ENSEMBLE GUIDANCE HAS SHOWN THAT SOME DEVELOPMENT MAY BE POSSIBLE
EARLY NEXT WEEK. WITH LITTLE MOVEMENT EXPECTED OVER THE COMING DAYS,
THIS COULD BRING INCREASED SHOWERS TO PARTS OF PALAU THROUGH THE
WEEKEND. IF ENSEMBLE TRENDS CONTINUE TO SHOW DEVELOPMENT EARLY NEXT
WEEK, AN SPS MAY BE NEEDED FOR PALAU WITH A FUTURE FORECAST PACKAGE.
THOSE IN PALAU SHOULD CONTINUE TO MONITOR FORECASTS FOR FUTURE
UPDATES.
NO CHANGES WERE MADE TO THE MARINE FORECAST. COMBINED SEAS OF 3 TO 5
FEET WILL PERSIST THROUGH MUCH OF THE PERIOD.
PREV DISCUSSION
/ISSUED 442 PM CHST THU APR 24 2025/
MARIANAS SYNOPSIS...
GENTLE TO MODERATE TRADES PREVAIL ACROSS THE REGION. SATELLITE AND
DOPPLER RADAR OBSERVATIONS SHOW A FEW ISOLATED SHOWERS MOVING INTO
THE EASTERN COASTAL WATERS OF GUAM AND ROTA. BUOYS AND ALTIMETRY
SHOW COMBINED SEAS NEAR 4 FEET.
DISCUSSION...
ALL IN ALL, THIS FORECAST PACKAGE DOESN'T FEATURE MANY CHANGES FROM
THE PREVIOUS FORECAST. POPS WERE BUMPED UP TO 20% FOR TONIGHT BASED
ON SLIGHTLY HIGHER ISOLATED SHOWER COVERAGE SEEN ON SATELLITE AND
DOPPLER RADAR. AS WE HEAD INTO THE WEEKEND, THE ECMWF AND GFS HAVE
BEGUN TO DIVERGE FOR THE SATURDAY NIGHT AND SUNDAY TIME FRAMES. THE
ECMWF IS SHOWING INCREASED SHOWER COVERAGE ACROSS THE MARIANAS WHILE
THE GFS MAINTAINS THE DRY TRADE-WIND PATTERN. THIS DIFFERENCE IS SEEN
WITHIN THE ECMWF AND GFS TIME-HEIGHTS. THE ECMWF HAS DEEPER MOISTURE
THROUGH THE COLUMN WHILE THE GFS KEEPS THE DEEPER MOISTURE
SUPPRESSED BELOW 850 MB. LOOKING UPSTREAM ON THE MIMIC-TPW PRODUCT,
PWATS APPEARS TO PREDOMINATELY BELOW 1.75". THIS GIVES CREDENCE TO
THE GFS, WHICH THIS FORECAST PACKAGE HAS A SLIGHT LEAN TOWARDS. THAT
SAID, GEFS, EPS, AND GEPS GUIDANCE SHOW AN AMPLIFYING MJO INTO PHASE
7 THE NEXT FEW DAYS. THIS COULD ALLOW A BACKGROUND STATE MORE
FAVORABLE FOR CONVECTION LATER THIS WEEKEND.
MARINE...
NO UPDATES WERE MADE TO THE MARINE FORECAST. GENTLE TO MODERATE
TRADES ARE EXPECTED TO CONTINUE THROUGH MUCH OF THE PERIOD. COMBINED
SEAS NEAR 4 FEET WILL RISE 1 TO 2 FEET ON FRIDAY AND WILL PERSIST
INTO THE WEEKEND. BENIGN MARINE CONDITIONS ARE EXPECTED THROUGH THE
PERIOD.
FIRE WEATHER...
A TRACE OF RAIN HAS FALLEN TODAY AND THE KBDI REMAINS HIGH AT 670. A
WETTING RAIN IS NOT EXPECTED OVER THE NEXT SEVERAL DAYS, WHICH WILL
ALLOW THE KBDI TO CONTINUE TO INCREASE. CRITICAL FIRE WEATHER
CONDITIONS ARE NOT EXPECTED THE NEXT FEW DAYS AS BOTH WINDS AND RH
VALUES ARE FORECASTED TO BE BELOW CRITERIA.
EASTERN MICRONESIA...
A SERIES OF TRADE-WIND TROUGHS IS CREATING AN AREA OF SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS OVER EASTERN MICRONESIA AT THIS
TIME. POHNPEI IS CURRENTLY WITHIN A GAP, SO THEY HAVE ISOLATED
SHOWERS TONIGHT. SHOWERS WILL GRADUALLY RAMP UP, PEAKING AT LIKELY
LEVELS WEDNESDAY AND WEDNESDAY NIGHT, THEN TAPER OFF THURSDAY. AT
KOSRAE, SHOWERS WILL BE SCATTERED THROUGH TUESDAY, THEN PEAK AT
LIKELY TUESDAY NIGHT AND WEDNESDAY, THEN TAPER OFF SIMILARLY. MAJURO
WILL HAVE SCATTERED SHOWERS THROUGH FRIDAY NIGHT, THEN A SHORT PERIOD
OF ISOLATED SHOWERS SATURDAY, BUILD UP TOWARD LIKELY MONDAY NIGHT,
THEN SETTLE BACK DOWN TO SCATTERED FOR TUESDAY THROUGH THURSDAY.
LOOKS LIKE A FAIRLY WET WEEK FOR ALL, PERHAPS WETTEST AT KOSRAE
THOUGH. COULD BE SUBSTANTIALLY DRIER FOR ISLANDS TO THE NORTH,
THOUGH.
POHNPEI AND KOSRAE WATERS WILL HAVE WINDS OF 10 TO 15 KNOTS AND SEAS
OF 4 TO 6 FEET, LEADING TO GENERALLY BENIGN CONDITIONS. MAJURO WATERS
WILL SEE WINDS OF 10 TO 20 KNOTS, WITH GUSTS TO 25 KNOTS ON MONDAY
AND TUESDAY. ALSO, SEAS OF 5 TO 7 FEET WILL BUILD TO BETWEEN 6 AND 8
FEET FOR MONDAY AND TUESDAY. IT'S UNCERTAIN WHETHER THIS WILL REQUIRE
A SMALL CRAFT ADVISORY (PROBABLY DEPENDS ON WHETHER THE GUSTS ARE
FREQUENT OR NOT), BUT IT WILL BE CHALLENGING AT LEAST, NOT BENIGN.
WESTERN MICRONESIA...
A NEAR-EQUATORIAL TROUGH (NET) STRETCHES ACROSS THE SOUTHWEST CORNER
OF THE REGION, EXTENDING FROM AN EMBEDDED CIRCULATION NEAR 4N132E
AND CONTINUES TO EQ142E. MODERATE TO DEEP CONVECTION IS FOCUSED NEAR
THE CIRCULATION AND ALONG THE SOUTHERN PORTION OF THE NET. SATELLITE
TRENDS SHOW EQUATORIAL WESTERLIES USHERING DEEP MOISTURE INTO THE
REGION WITH SOME PRECIPITABLE WATER AMOUNTS (PWATS) REACHING NEAR 3
INCHES ACROSS THE FAR SOUTHERN ISLANDS OF THE REPUBLIC OF PALAU.
SCATTEROMETRY DATA SHOWS LIGHT TO MODERATE WINDS NORTH OF THE NET,
WHEREAS ARE MODERATE TO STRONG NEAR AND SOUTH OF THE EMBEDDED
CIRCULATION. NORTH OF THE NET, OVER THE MAIN ISLANDS OF YAP AND
PALAU, CONDITIONS ARE STILL RELATIVELY QUIET. A SERIES OF WEAK TRADE-
WIND TROUGHS CONTINUE PRODUCE BRIEF UPTICKS IN SHOWERS OVER THE NEXT
FEW DAYS. A BROADER TROUGH AND MODERATE CONVERGENCE NEAR CHUUK IS
EXPECTED TO MAINTAIN SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS
OVER THE NEXT DAY OR SO. THEN, A NORTHWARD SHIFT OF THE NET IS
EXPECTED TO INCREASE CONVERGENCE ACROSS THE MAIN FORECAST LOCATIONS
OVER THE WEEKEND AND THROUGH THE MIDDLE OF NEXT WEEK. THE EMBEDDED
NET CIRCULATION WILL CONTINUE TO BE THE FOCUS OF UNSETTLED WEATHER
FOR THE NEXT COUPLE DAYS, THEN ENSEMBLE MODELS GRADUALLY SHOW THE
CIRCULATION SHIFTING TO THE NORTHWEST, PASSING WELL WEST OF KOROR,
WITH LITTLE TO NO DEVELOPMENT.
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 LONGER-PERIOD NORTH SWELL REACHES THE REGION OVER
THE WEEKEND, THIS MAY SLIGHTLY ADD TO SEAS, BUT WOULD MAINLY BOOST
SURF ALONG NORTH-FACING REEFS. 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 MICRONESIA UPDATE: DECOU
WEST MICRONESIA UPDATE: WILLIAMS
MARIANAS: WILLIAMS
EAST MICRONESIA: STANKO
WEST MICRONESIA: CRUZ
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