441
FXPQ50 PGUM 180812
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
612 PM CHST TUE FEB 18 2025
MARIANAS SYNOPSIS
PARTLY CLOUDY SKIES AND ISOLATED SHOWERS ARE SEEN ACROSS THE MARIANAS
AS DRY CONDITIONS CONTINUE. THE REMNANTS OF A SHEAR LINE FRAGMENT ARE
SEEN OVER THE NORTHERN CNMI SHIFTING GRADUALLY SOUTH. SURFACE
OBSERVATIONS AND SCATTEROMETRY SHOW LIGHT TO GENTLE EAST-SOUTHEAST
WINDS ACROSS THE ISLANDS.
DISCUSSION
LITTLE CHANGE IN THE FORECAST PACKAGE. MODEL GUIDANCE SHOWS A LINE
OF SHOWERS GRADUALLY WORKING SOUTH THROUGH SAIPAN, TINIAN, AND ROTA
COASTAL WATERS LATE TONIGHT THROUGH WEDNESDAY, ASSOCIATED WITH THE
REMNANTS OF A SHEAR LINE OVER THE NORTHERN CNMI. HIMAWARI VISIBLE
SATELLITE SHOWS A FEW NARROW LINES OF SHOWERS BETWEEN ALAMAGAN AND
ANATAHAN MOVING SOUTH. PWATS REMAIN AT AROUND 1.6 INCHES OR LESS
ACROSS THE AREA AND SHOWER CHANCES WERE LEFT AT 20 PERCENT THROUGH
THE FORECAST PERIOD, WITH ONLY OCCASIONAL INCREASES DUE TO REMNANT
SHEAR LINE SHOWERS. WINDS WILL START TO INCREASE WEDNESDAY NIGHT INTO
THURSDAY AS THE SUBTROPICAL RIDGE STRENGTHENS NORTH OF THE REGION,
WHICH MAY LEAD TO SURF AND SMALL CRAFT CONCERNS BY THE END OF THE
WEEK.
MARINE/SURF
LATEST BUOY AND ALTIMETRY DATA SHOW COMBINED SEAS OF 5 TO 7 FEET
ACROSS THE MARIANAS. LIGHT TO GENTLE WINDS WILL CONTINUE TONIGHT,
INCREASING TO MODERATE TO FRESH WEDNESDAY NIGHT INTO THURSDAY AS A
STRONG SUBTROPICAL RIDGE SETS UP NORTH OF THE REGION. THIS WILL
PRODUCE A WIDESPREAD TRADE-WIND SURGE, WHICH COULD GENERATE SEAS
HAZARDOUS TO SMALL CRAFT BY THE END OF THE WEEK. ADDITIONALLY, THIS
MAY BRING HAZARDOUS SURF TO NORTH FACING REEFS, AND A HIGH RISK OF
RIP CURRENTS TO NORTH AND EAST FACING REEFS BY THE WEEKEND. IN THE
MEANTIME, THE RISK OF RIP CURRENTS WILL BE MODERATE FOR NORTH, EAST,
AND WEST FACING REEFS, WITH THE RIP CURRENT RISK DROPPING TO LOW FOR
WEST FACING REEFS BRIEFLY ON WEDNESDAY.
FIRE WEATHER
BRIEF SHOWERS BROUGHT 0.01 INCHES OF RAIN FALL YESTERDAY AND THERE
WAS NO RAINFALL TODAY, WHICH ALLOWED FOR THE KBDI TO RISE TO 633. A
WETTING RAIN OF 0.20 INCHES OR HIGHER IS NOT EXPECTED OVER THE NEXT
FEW DAYS. DAYTIME RELATIVE HUMIDITY VALUES MAY FALL BELOW 60 PERCENT
OVER THE NEXT FEW DAYS, BUT WINDS ARE EXPECTED TO REMAIN BELOW RED
FLAG WARNING CRITERIA UNTIL THURSDAY. A FIRE WEATHER WATCH CONTINUES
FOR THIS EVENING THROUGH THURSDAY AFTERNOON, AS VERY DRY CONDITIONS
AND OCCASIONAL GUSTY WINDS WILL MAINTAIN A HIGH FIRE THREAT.
EASTERN MICRONESIA
A QUIET TRADE-WIND PATTERN PREVAILS ACROSS THE REGION TODAY. ASCAT
ANALYSIS SHOWS A COUPLE OF WEAK SURFACE TROUGHS GENERATING PATCHY
SHOWERS WEST OF POHNPEI AND ACROSS THE NORTHERN MARSHALLS. AN AREA OF
DRIER AIR HAS SHIFTED OVER MAJURO, SO EXPECTED MOSTLY CLEAR
CONDITIONS TONIGHT. OVER THE NEXT SEVERAL DAYS, MODELS SHOW A SERIES
OF WEAK TROUGHS PASSING THROUGH THE REGION, BUT OVERALL, SHOWERS
LOOK TO STAY ISOLATED THIS WEEK, WITH PERIODIC UPTICKS TO SCATTERED
COVERAGE.
A HIGH SURF ADVISORY REMAINS IN EFFECT FOR POHNPEI AND KOSRAE
THROUGH WEDNESDAY NIGHT. POHNPEI BUOY SHOWS THE ARRIVAL OF LONG-
PERIOD NORTH SWELL REACHING UP TO 6.24 FEET AND 17 SECONDS EARLIER
TODAY, WHICH WOULD GENERATE HAZARDOUS SURF UP TO 10 FEET. BY LATE
WEEK, SURF IS EXPECTED TO DECREASE BACK DOWN TO BETWEEN 5 AND 8 FEET
AS NORTH SWELL SUBSIDES. HOWEVER, ANOTHER PULSE OF NORTH SWELL AND
AN INCREASE IN EAST-NORTHEAST TRADE SWELL MAY KEEP SURF ELEVATED
ALONG NORTH FACING REEFS OVER THE WEEKEND. SEAS ARE EXPECTED TO
INCREASE TO BETWEEN 7 AND 9 FEET AS THIS PULSE OF NORTH SWELL MOVES
ACROSS THE REGION, SUBSIDING ONE TO TWO FEET LATE THIS WEEK BEFORE
ANOTHER PULSE OF NORTH SWELL BRINGS IT BACK UP TO BETWEEN 7 AND 9
FEET THIS WEEKEND. GENTLE TO MODERATE EAST-NORTHEAST TRADES ARE
EXPECTED TO BECOME MODERATE TO FRESH IN THE LATTER HALF OF THE WEEK,
THEN MODERATE TO STRONG ON SUNDAY AS HIGH PRESSURE BUILDS TO THE
DISTANT NORTH, INCREASING THE PRESSURE GRADIENT ACROSS THE REGION.
WESTERN MICRONESIA
REMNANTS OF MID-LATITUDE SYNOPTIC FRONTS ARE TRICKLING IN AS THE
PRESSURE GRADIENT SHIFTS THEM SOUTHWARD TO THE TROPICS, BRINGING
LOW-END PATCHY SHOWERS AND CLOUDIER SKIES TO PALAU AND YAP THE NEXT
FEW DAYS. SHOWERS WILL DECREASE ONCE AGAIN DURING THE WEEKEND AS
SHOWERS MEANDER MOSTLY NEAR THE EQUATOR, AND NORTH OF PALAU AND YAP
PROPER. A MOSTLY DRY REGIME IS EXPECTED TO CONTINUE FOR CHUUK FOR
MUCH OF THE FORECAST PERIOD, WITH A CHANCE OF SLIGHT SHOWER INCREASE
SOMETIME EARLY NEXT WEEK DUE TO THE PROXIMITY OF A NEARBY CONVERGENCE
ZONE.
COMBINED SEAS OF 5 TO 7 FEET ARE EXPECTED AT PALAU, YAP AND CHUUK FOR
AT LEAST THE NEXT FEW DAYS, FOLLOWED BY ANOTHER ROUND OF A NORTH
SWELL PULSE MAKING ITS WAY ACROSS THE REGION, POSSIBLY INCREASING
SEAS BY ANOTHER 2 TO 3 FEET AS EARLY AS THURSDAY NIGHT NEAR PALAU AND
YAP, AND DURING THE WEEKEND NEAR CHUUK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...FIRE WEATHER WATCH THROUGH THURSDAY AFTERNOON FOR GUZ001.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: DECOU
EAST MICRONESIA: CRUZ
WEST MICRONESIA: MONTVILA
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