074
FXPQ50 PGUM 191856
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
456 AM CHST THU FEB 20 2025
MARIANAS UPDATE
NO MEANINGFUL CHANGES WERE NEEDED TO THE FORECAST. OVERNIGHT MODEL
GUIDANCE SUGGEST AND SATELLITE IMAGERY SUGGESTS A DEVELOPING A WEAK
CONVERGENCE ZONE TO THE EAST OF THE MARIANAS. HOWEVER, THE SHOWERS
THIS CONVERGENCE WILL PRODUCE, ARE SUGGESTED TO REMAIN TO THE EAST
OF THE ISLANDS. SHOWERS OVER THE FORECAST PERIOD IS EXPECTED TO
REMAIN ISOLATED THROUGH THE BEGINNING OF THE WEEKEND. SHOWERS MAY
BECOME SCATTERED OVER THE WEEKEND, THEN, DIMINISH BACK TO ISOLATED
FOR THE BEGINNING OF NEXT WEEK.
ALTIMETRY SHOWS 6 TO 8 FEET TO THE WEST OF THE ISLANDS. RITIDIAN AND
TANAPAG BUOYS ARE SHOWING ABOUT 6 FEET. A NORTH SWELL IS BUILDING.
SEAS AND SURF MAY BECOME HAZARDOUS OVER THE WEEKEND. WINDS ARE
ANTICIPATED TO BECOME BREEZY AT TIMES THROUGH THE WEEKEND.
EASTERN MICRONESIA UPDATE
THE MIDNIGHT ALTIMETRY PASS DIDN'T "DO US ANY FAVORS", WITH THE
POHNPEI BUOY SUGGESTING WE'RE CURRENTLY A LITTLE BELOW HEADLINE
CRITERIA. HOWEVER, THIS IS LIKELY DUE TO LESS WIND WAVES/DIURNAL
MIXING AS THE SEA AND SWELL GRAPH SHOWED OSCILLATIONS BETWEEN MINIMAL
AND MAXIMUM HEIGHTS OVER THE LAST 48 HOURS. ALSO, ANOTHER SHEAR LINE
FRAGMENT IS APPROACHING. CONSIDERING THIS, WE AGREE WITH THE
PREVIOUS FORECASTER THINKING. AS SUCH, HEADLINES REMAIN IN PLACE FOR
HIGH SURF AT POHNPEI AND KOSRAE FOR THE NORTH FACING REEFS. OTHERWISE,
THE SHORT TERM PORTION OF THE FORECAST (TODAY AND TONIGHT) REMAINS
UNCHANGED.
WESTERN MICRONESIA UPDATE
NO SIGNIFICANT CHANGES WERE MADE TO THE SHORT TERM (TODAY AND
TONIGHT), AS THE PREVIOUS THINKING ALIGNS WITH THE CURRENT MODEL
GUIDANCE. ONE THING WE'LL NEED TO KEEP AN EYE ON THOUGH IS MODEL
TRENDS VERSUS OBSERVATIONS AND ANALYSIS, AS THE MODELS IN EASTERN
MICRONESIA WERE A GOOD FOOT OR TWO BELOW OBSERVED VALUES.
IF THAT TREND CONTINUES THEN THE POTENTIAL IS THERE FOR HAZARDOUS
SEAS AND SURF CONDITIONS TO DEVELOP AT YAP AS EARLY AS LATE TONIGHT,
AND PALAU FRIDAY. WE THOUGHT ABOUT HOISTING HEADLINES TONIGHT FOR
YAP, BUT UPSTREAM ALTIMETRY RAISED SOME DOUBTS, SO WE OPTED TO HOLD
OFF ANOTHER COUPLE OF MODEL RUNS TO LET THE DAY SHIFT HAVE ANOTHER
LOOK AT THESE CONCERNS. OTHERWISE, THE FORECAST REMAINS ON TRACK WITH
PREVIOUS THINKING.
PREV DISCUSSION
/ISSUED 617 PM CHST WED FEB 19 2025/
MARIANAS SYNOPSIS...
MOSTLY CLOUDY SKIES AND ISOLATED SHOWERS ARE SEEN ACROSS THE MARIANAS
AS A SHEAR LINE FRAGMENT DIPS SOUTH ACROSS THE ISLANDS. HIMAWARI
VISIBLE SATELLITE REVEALS LINES OF LIGHT SHOWERS AND LOW TO MID-
LEVEL CLOUD COVER MAINLY COVERING GUAM AND ROTA WATERS. SURFACE
OBSERVATIONS AND SCATTEROMETRY SHOW MOSTLY MODERATE NORTH-NORTHEAST
TO EAST-NORTHEAST WINDS ACROSS THE AREA.
DISCUSSION...
A SHEAR LINE FRAGMENT CONTINUES TO PUSH SOUTH ACROSS THE MARIANAS
TONIGHT AS A STRENGTHENING SUBTROPICAL RIDGE BUILDS EAST ACROSS THE
REGION. WINDS WILL SEE AN INCREASE OVERNIGHT INTO TOMORROW, BECOMING
BREEZY AT TIMES THURSDAY INTO EARLY NEXT WEEK AS A TRADE-WIND SURGE
DEVELOPS OVER THE MARIANAS AND WESTERN MICRONESIA. CONDITIONS WILL
REMAIN MOSTLY DRY WITH OCCASIONAL INCREASES IN SHOWERS FROM PASSING
SHEAR LINE FRAGMENTS. ONE SUCH FEATURE WILL BRING A FEW STRONGER
SHOWERS AND POSSIBLY A THUNDERSTORM OR TWO THIS WEEKEND, WITH MODEL
GUIDANCE PLACING THE BEST SHOWER CHANCES NEAR GUAM AND ROTA. THE MAIN
FORECAST CONCERNS BY THE END OF THE WEEK WILL BE THE POSSIBILITY OF
MARINE AND SURF HAZARDS, BUT A FIRE WEATHER THREAT CONTINUES INTO
THIS WEEKEND AS WELL.
MARINE/SURF...
LATEST BUOY AND ALTIMETRY DATA SHOW COMBINED SEAS OF 4 TO 6 FEET
ACROSS THE MARIANAS. WINDS WILL CONTINUE TO INCREASE TONIGHT,
BECOMING MODERATE TO FRESH BY TOMORROW 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, LASTING INTO EARLY NEXT WEEK. A MODERATE RISK OF
RIP CURRENTS IS EXPECTED TO CONTINUE FOR NORTH, EAST, AND WEST FACING
REEFS THROUGH AT LEAST THURSDAY NIGHT. HOWEVER, AS WINDS, SWELLS,
AND CORRESPONDING SURF INCREASE, SURF MAY BECOME HAZARDOUS FOR NORTH
FACING REEFS, AND A HIGH RISK OF RIP CURRENTS MAY BE EXPECTED FOR
NORTH AND EAST FACING REEFS BY THE END OF THE WEEK LASTING INTO EARLY
NEXT WEEK.
FIRE WEATHER...
NO RAIN FELL YESTERDAY, WHICH ALLOWED FOR THE KBDI TO RISE TO 641.
LIGHT SHOWERS ASSOCIATED WITH A SHEAR LINE FRAGMENT HAVE BROUGHT
0.02 INCHES OF RAIN SO FAR THIS AFTERNOON. A WETTING RAIN OF 0.20
INCHES OR HIGHER IS NOT EXPECTED OVER THE NEXT FEW DAYS, BUT MAY BE
POSSIBLE ON SATURDAY AND SUNDAY AS ANOTHER SHEAR LINE SETS UP OVER
THE MARIANAS. THERE IS A GRADUAL MOISTENING TREND, BUT DAYTIME
RELATIVE HUMIDITY VALUES MAY FALL BELOW 60 PERCENT OVER THE NEXT FEW
DAYS WHILE WINDS ARE EXPECTED TO INCREASE, POSSIBLY MEETING RED FLAG
CRITERIA THURSDAY. A FIRE WEATHER WATCH CONTINUES FOR THIS EVENING
THROUGH SUNDAY AFTERNOON, AS VERY DRY CONDITIONS AND GUSTY WINDS WILL
MAINTAIN A HIGH FIRE THREAT.
EASTERN MICRONESIA...
ONLY MINOR CHANGES WERE MADE TO THE PREVIOUS FORECAST. AN OVERALL DRY
AND QUIET TRADE-WIND PATTERN WILL CONTINUE ACROSS EASTERN MICRONESIA
FOR THE NEXT FEW DAYS. MODELS CONTINUE TO SHOW A SERIES OF WEAK
TRADE-WIND TROUGHS MOVING ACROSS THE REGION, THOUGH ANY CONVECTION
ASSOCIATED WITH THE FEW TROUGHS LOOK TO REMAIN SOUTH OF THE FORECAST
POINTS. BY FRIDAY NIGHT, THE TROUGHS LOOK TO MOVE THROUGH A BIT
FARTHER NORTH, BRINGING INCREASED CONVECTION TO MAJURO AND KOSRAE
FRIDAY NIGHT. SHOWERS LOOK TO DECREASE BY SATURDAY AFTERNOON AT
MAJURO AS THE PATH OF THE TROUGHS SHIFTS SOUTH OF THE MARSHALLS.
THIS DRY PATTERN LOOKS TO PUSH INTO KOSRAE LATE IN THE WEEKEND. FOR
POHNPEI, THE TROUGHS WILL REMAIN SOUTH OF THE ISLAND UNTIL SUNDAY.
THE FIRST TROUGH WILL AFFECT POHNPEI SUNDAY, WITH A DRY PATTERN
RETURNING TO THE ISLAND BY MONDAY MORNING.
THE LONG PERIOD NORTHERLY SWELL WILL CONTINUE ACROSS THE REGION FOR
ANOTHER COUPLE OF DAYS. LATEST MODEL GUIDANCE IS UNDERESTIMATING THE
COMBINED SEAS AS MODELS SHOW SEAS OF AROUND 7 FEET WHILE POHNPEI BUOY
IS SEEING WAVE HEIGHTS OF 8.5 TO 9.5 FEET. EXPECT SEAS TO REMAIN
BELOW SMALL CRAFT ADVISORY LEVELS. HOWEVER, DUE TO THE LONG PERIOD,
THE NORTHERLY SWELL WILL MAINTAIN HAZARDOUS SURF ALONG NORTH FACING
REEFS OF POHNPEI AND KOSRAE THROUGH AT LEAST FRIDAY MORNING, POSSIBLY
INTO THE WEEKEND. ANOTHER ROUND OF MODERATE TO FRESH WINDS WITH
BUILDING TRADE SWELL AND LONG-PERIOD NORTH SWELL ARE EXPECTED TO
RESULT IN MARINE CONDITIONS THAT ARE HAZARDOUS TO SMALL CRAFT
OPERATIONS OVER THE WEEKEND INTO NEXT WEEK.
WESTERN MICRONESIA...
REMNANTS OF MID-LATITUDE SYNOPTIC FRONTS ARE STILL TRICKLING IN AS
THE PRESSURE GRADIENT SHIFTS THEM SOUTHWARD TO THE TROPICS, BRINGING
LOW-END PATCHY SHOWERS AND CLOUDIER SKIES TO PALAU TONIGHT. SHOWERS
WILL DECREASE ONCE AGAIN AT PALAU DURING THE WEEKEND, AS SHOWERS
MEANDER MOSTLY NEAR THE EQUATOR, AND NORTH OF PALAU AND YAP PROPER.
AS SUCH, PALAU AND YAP ARE EXPECTED TO REMAIN UNDER A DRIER TRADE-
WIND REGIME FOR AT LEAST THE NEXT SEVERAL DAYS. DRIER NORTHEASTERLIES
WILL CONTINUE AT 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. IN ADDITION, THE PROXIMITY TO
SAID CONVERGENCE ZONE ALLOWS THE SIGNIFICANT PORTION OF THE TRADE-
WIND SURGE TO BRING WINDY CONDITIONS TO CHUUK IN THE FIRST HALF OF
NEXT WEEK.
COMBINED SEAS OF 5 TO 7 FEET ARE EXPECTED AT PALAU, YAP AND CHUUK
THROUGH TONIGHT, 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. AS SUCH, THIS MAY PRODUCE SEA
CONDITIONS HAZARDOUS TO SMALL CRAFT BEFORE THE WEEKEND. AS CERTAINTY
INCREASES THROUGH THURSDAY, A SMALL CRAFT ADVISORY IS LIKELY TO BE
ISSUED FOR PALAU AND YAP.
GUM WATCHES/WARNINGS/ADVISORIES
GU...FIRE WEATHER WATCH THROUGH SUNDAY AFTERNOON FOR GUZ001.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: BOWSHER
EAST/WEST MICRONESIA: DOLL
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