182
FXPQ50 PGUM 240642
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
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: WILLIAMS
EAST MICRONESIA: STANKO
WEST MICRONESIA: CRUZ
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