713
FXPQ50 PGUM 161957
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
557 AM CHST MON FEB 17 2025
MARIANAS UPDATE
ONLY MINOR EDITS WERE MADE TO THE ZONE FORECAST.
DEWPOINTS WERE NUDGED DOWN A BIT FOR TODAY AND TOMORROW. THIS MAINLY
LEANING ON THE ECMWF, WHICH HAS PERFORMED WELL WITH OUR DEWPOINTS
THE LAST FEW DAYS. OTHERWISE, THE FORECAST REMAINS MAINLY THE SAME
FROM THE PREVIOUS PACKAGE.
NO CHANGES WERE MADE TO THE MARINE FORECASTS. SEAS ARE EXPECTED TO
REMAIN BENIGN THROUGH THE MIDDLE OF THE WEEK BEFORE ANOTHER LARGE
SWELL EVENT LOOKS TO IMPACT THE REGION. SEAS COULD BECOME HAZARDOUS
TO SMALL CRAFT BY THE END OF THE WEEK.
FIRE WEATHER UPDATE
A RED FLAG WARNING WAS ISSUED FOR GUAM TODAY. CRITICAL FIRE WEATHER
CONDITIONS ARE EXPECTED TO BE MET, ESPECIALLY IN THE HIGHER TERRAINS
ACROSS SOUTHERN GUAM. TONIGHT AND INTO TUESDAY THE INFLUENCE FROM THE
SURFACE HIGH PRESSURE WILL BEGIN TO WANE AND WINDS WILL COME DOWN.
RELATIVE HUMIDITY VALUES ALSO LOOK TO INCREASE WEDNESDAY AND
THURSDAY. THIS WOULD BRING CRITICAL FIRE WEATHER CONDITIONS BELOW
CRITERIA FOR TUESDAY AND WEDNESDAY. THE FIRE WEATHER WATCH WAS
CONTINUED FOR CONSISTENCY, BUT MAY NEED TO BE CANCELED IN AN UPCOMING
PACKAGE IF THE FORECAST CONTINUES TO TREND AWAY FROM RED FLAG
CRITERIA.
EASTERN MICRONESIA UPDATE
POHNPEI LOOKS SET UP FOR A FAIRLY DRY WEEK. SUNDAY WILL BE BREEZY AS
A RIDGE OF HIGH PRESSURE PASSES TO THE NORTH, INCREASING THE LOCAL
PRESSURE GRADIENT.
KOSRAE WILL BE A LITTLE MOISTER TODAY, THEN SHOULD BE ABLE TO DRY OUT
A BIT TONIGHT THROUGH FRIDAY. THERE SHOULD THEN BE A SLIGHT INCREASE
IN SHOWERS AGAIN FRIDAY NIGHT THROUGH SUNDAY.
MAJURO COULD ALSO BE SLIGHTLY MOISTER TODAY, EMPHASIS ON SLIGHTLY
THOUGH. AFTER DRYING OUT TONIGHT, THEY COULD MOISTEN UP AGAIN
SATURDAY, THEN DRY OUT FOR THE REST OF THE WEEKEND.
THE COASTAL FORECAST IS LITTLE CHANGED. WAVES WERE REFRESHED FROM THE
MODELS FOR THE FIRST 3 PERIODS, CHANGES WERE COSMETIC ONLY. THE
MARINE FORECAST ONLY GOES OUT TO FRIDAY, SO THE NEXT BUILDUP IN WINDS
ISN'T QUITE SHOWING UP YET. UNTIL THEN, NO ADVISORIES ARE EXPECTED.
WESTERN MICRONESIA UPDATE
BASED ON SATELLITE PRESENTATION OF WARMING TOPS, MADE KOROR ISOLATED
SHOWERS TODAY. THERE IS STILL AN AREA OF HIGHER SHOWER ACTIVITY TO
THE EAST, SO LEFT THE REST OF THE SCATTERED SHOWERS AS THEY WERE,
THEY SHOULD MOVE TOWARD KOROR. THESE SHOULD LAST THROUGH WEDNESDAY,
THEN KOROR CAN DRY OUT A LITTLE FOR THE SECOND HALF OF THE WEEK.
YAP WILL HAVE ONLY ISOLATED SHOWERS TODAY AND TONIGHT, THEN SCATTERED
BRIEFLY TUESDAY. BEING THE CLOSEST TO THE HIGH PRESSURE THAT'S COMING
SOON, YAP WILL BE GETTING THE WINDS EARLIER, POSSIBLY FROM TUESDAY
NIGHT ON.
CHUUK WILL HAVE ONLY ISOLATED SHOWERS FOR THE ENTIRE FORECAST PERIOD.
THE ONE EXCEPTION COULD BE TONIGHT, WHEN THEY MAY HAVE NO SHOWERS AT
ALL.
WINDS WILL START TO BUILD THURSDAY AND FRIDAY IN WESTERN MICRONESIA.
THEY WILL NOT YET REACH SMALL CRAFT ADVISORY CRITERIA, IT COULD BE
SUNDAY BEFORE THEY'RE GETTING THERE. UNTIL THEN, JUST A GRADUAL
INCREASE. YAP AND CHUUK LOOK THE MOST LIKELY AT THIS TIME.
PREV DISCUSSION
/ISSUED 600 PM CHST SUN FEB 16 2025/
MARIANAS SYNOPSIS...
SKIES ARE PARTLY CLOUDY ACROSS THE MARIANAS WITH A FEW SHOWERS SEEN
OVER SAIPAN AND TINIAN COASTAL WATERS, ASSOCIATED WITH A SHEAR LINE
FRAGMENT DRAPED OVER THE NORTHERN CNMI. SURFACE OBSERVATIONS AND
ALTIMETRY DATA SHOW MOSTLY MODERATE TRADE WINDS WITH FREQUENT GUSTS
TO AROUND 25 MPH.
DISCUSSION...
A DRY TRADE WIND REGIME CONTINUES. MODERATE TO FRESH TRADES WILL
DIMINISH OVER THE NEXT FEW DAYS BEFORE A TRADE-WIND SURGE SETS UP
FOR THE LATTER HALF OF THE WEEK. THIS WILL MAINLY IMPACT THE MARINE
AND SURF FORECASTS LATER IN THE WEEK, AS SEA CONDITIONS MAY BECOME
HAZARDOUS TO SMALL CRAFT AROUND THURSDAY ONWARD. IN THE MEANTIME,
MUCH OF THE WEATHER FOR THE MARIANAS WILL BE INFLUENCED BY NEARBY
PASSING SHEAR LINE FRAGMENTS, PROPAGATED BY LOW-PRESSURE SYSTEMS
FURTHER NORTH. THE DECAYING SHEAR LINE OVER THE NORTHERN CNMI WILL
GRADUALLY LIFT NORTHWEST AND AWAY FROM SAIPAN TONIGHT INTO TOMORROW,
BUT GUAM AND ROTA COULD SEE A SHOWER OR TWO ALONG THE OUTER PERIPHERY
OF ANOTHER SUCH FEATURE EAST OF THE ISLANDS. OVERALL, ONLY ISOLATED
SHOWERS ARE EXPECTED DURING THE FORECAST PERIOD, AND DRY CONDITIONS
LOOK TO CONTINUE.
MARINE...
LATEST BUOY AND ALTIMETRY DATA SHOWS COMBINED SEAS OF 5 TO 7 FEET
ACROSS THE MARIANAS. GENTLE TO MODERATE WINDS ARE EXPECTED TO
CONTINUE THROUGH MONDAY, WANING MONDAY NIGHT INTO TUESDAY, BECOMING
LIGHT TO GENTLE AS THE SUBTROPICAL RIDGE WEAKENS NORTH OF THE
MARIANAS. WINDS AND SEAS WILL INCREASE IN THE LATTER HALF OF THE WEEK
AS A STRONG SUBTROPICAL RIDGE SETS UP NORTH OF THE REGION, PRODUCING
A WIDESPREAD TRADE-WIND SURGE. A MODERATE RISK OF RIP CURRENTS IS
EXPECTED TO CONTINUE FOR WEST, NORTH, AND EAST FACING REEFS FOR THE
NEXT FEW DAYS.
FIRE WEATHER...
A TRACE OF RAIN FELL AT THE AIRPORT YESTERDAY AND THERE HAS NOT BEEN
A WETTING RAIN IN SEVERAL DAYS, WHICH ALLOWED FOR THE KBDI TO RISE TO
618. A WETTING RAIN OF 0.20 INCHES OR HIGHER IS NOT EXPECTED OVER THE
NEXT FEW DAYS. THE CURRENT FORECAST SHOWS RELATIVE HUMIDITY VALUES
INCREASING ABOVE 60% FOR TOMORROW AS WINDS LOOK TO DECREASE, WHICH
WILL BRING FIRE WEATHER CONDITIONS BELOW RED FLAG CRITERIA. AS SUCH,
THE RED FLAG WARNING IS NO LONGER IN EFFECT. HOWEVER, A FIRE WEATHER
WATCH IS NOW IN EFFECT, AS VERY DRY CONDITIONS AND OCCASIONALLY GUSTY
WINDS WILL MAINTAIN A HIGH FIRE THREAT. WINDS ARE EXPECTED TO DIMINISH
THROUGH TUESDAY BEFORE INCREASING FOR THE LATTER HALF OF THE WEEK.
EASTERN MICRONESIA...
TWO AREAS OF TRADE CONVERGENCE ARE GENERATING MODERATE CONVECTION IN
THE REGION. ONE IS SOUTH TO SOUTHWEST OF KOSRAE, AND THE OTHER IS
NEAR AND EAST OF MAJURO THIS AFTERNOON. THESE FEATURES ARE EXPECTED
TO SLOWLY DRIFT NORTH-NORTHWEST AND WEAKEN, BRINGING SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS TO MAJURO THROUGH AT LEAST
TONIGHT AND TO KOSRAE AROUND MIDNIGHT THROUGH MONDAY. RELATIVELY DRY
WEATHER IS EXPECTED AT POHNPEI THIS WEEK. MODELS SHOW A SERIES OF
WEAK TROUGHS PASSING THROUGH, BUT OVERALL, SHOWERS LOOK TO STAY
ISOLATED THIS WEEK. THIS DRIER TRADE PATTERN IS EXPECTED TO EXTEND TO
KOSRAE AND MAJURO BY TUESDAY. ADDITIONALLY, MODERATE EAST TO
NORTHEAST TRADES BECOME MODERATE TO FRESH AROUND MIDWEEK AS HIGH
PRESSURE BUILDS TO THE DISTANT NORTH, INCREASING THE PRESSURE
GRADIENT ACROSS THE REGION.
THE HIGH SURF ADVISORY FOR POHNPEI AND KOSRAE WAS ALLOWED TO EXPIRE
THIS AFTERNOON. LONG-PERIOD NORTH SWELL CONTINUES TO MOVE ACROSS THE
REGION, HOWEVER, SURF HEIGHTS HAVE FALLEN BELOW HAZARDOUS CRITERIA.
ANOTHER PULSE OF NORTH SWELL ARRIVES TUESDAY AND WEDNESDAY, LIKELY
PRODUCING HAZARDOUS SURF ONCE AGAIN. ALTIMETRY AND BUOY DATA SHOW
COMBINED SEAS OF 6 TO 8 FEET, EXPECTED TO DECREASE TO 5 TO 7 FEET
TONIGHT, THEN INCREASE BACK UP TO 7 TO 9 FEET WITH THE ARRIVAL OF
NORTH SWELL.
WESTERN MICRONESIA...
A SEASONAL TRADE-WIND REGIME IS EXPECTED TO PERSIST ACROSS THE REGION
FOR MUCH OF THE FORECAST PERIOD. ISOLATED SHOWERS TONIGHT WILL BE
FOLLOWED BY INCREASING SHOWERS AT PALAU MONDAY, AND MONDAY NIGHT AT
YAP, AS A BROAD SURFACE TROUGH MOVES ACROSS THE WESTERN PORTIONS OF
MICRONESIA. AS ANOTHER HIGH PRESSURE CELL MOVES OFF THE COAST OF
CHINA AND THEN ACROSS JAPAN, A DRIER REGIME WILL RETURN ONCE AGAIN IN
THE SECOND HALF OF THE WEEK. CHUUK WILL NOT SEE A SIGNIFICANT CHANGE
IN WEATHER, WITH ONLY ISOLATED SHOWERS AND OCCASIONALLY BREEZY
CONDITIONS EXPECTED FOR MUCH OF THE WEEK.
COMBINED SEAS OF 5 TO 7 FEET ARE EXPECTED AT PALAU, YAP AND CHUUK FOR
AT LEAST THE NEXT SEVERAL DAYS, FOLLOWED BY ANOTHER ROUND OF A NORTH
SWELL PULSE MAKING ITS WAY ACROSS THE REGION, POSSIBLY INCREASING
SEAS BY ANOTHER 2 TO 4 FEET BEFORE THE NEXT WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...RED FLAG WARNING UNTIL 7 PM CHST THIS EVENING FOR GUZ001.
FIRE WEATHER WATCH FROM THIS EVENING THROUGH THURSDAY AFTERNOON FOR
GUZ001.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: WILLIAMS
EAST/WEST MICRONESIA: STANKO
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