533
FXPQ50 PGUM 152129
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
729 AM CHST MON MAR 16 2026
MARIANAS UPDATE
NO MAJOR UPDATES WERE MADE TO THE FORECAST. A DRY WEATHER PATTERN IS
EXPECTED THIS WEEK. A BROAD LOW PRESSURE SYSTEM TO OUR NORTHWEST IS
BRINGING MODERATE NORTH TO NORTHEAST WINDS TO THE REGION OVER THE
NEXT COUPLE DAYS AND IS HELPING CHANNEL DRIER MID-LATITUDE AIR
SOUTHWARD INTO THE TROPICS. CIMSS MIMIC LAYER PRECIPITABLE WATER
(PWAT) PRODUCT SHOWS DRY AIR BELOW 1 INCH HAS MOVED OVER THE REGION.
THIS IS EXPECTED TO SUPPRESS SHOWER POTENTIAL WITH ONLY ISOLATED
LIGHT SHOWERS EXPECTED THROUGH TONIGHT.
A NEARBY ALTIMETRY PASS YESTERDAY EVENING SHOWED SEAS HAVE INCREASED
TO 12 TO 15 FEET NEAR THE MARIANAS. THIS IS DUE TO LARGE NORTH TO
NORTHWEST SWELL FROM A LOW PRESSURE SYSTEM EAST OF JAPAN AS WELL AS
NORTHEAST SWELL FROM A STRONG KONA LOW NORTHWEST OF HAWAI'I. THE PEAK
IN SEA HEIGHTS IS EXPECTED TODAY AND TONIGHT, THEN SLOWLY DECREASE,
POSSIBLY SUBSIDING BELOW HAZARDOUS LEVELS OF 10 FEET AS EARLY AS
WEDNESDAY. THIS WILL LIKELY REQUIRE A SMALL CRAFT ADVISORY TUESDAY
AND TUESDAY NIGHT. HAZARDOUS SURF AND A HIGH RISK OF RIP CURRENTS IS
EXPECTED ALONG WEST, NORTH, AND EAST FACING REEFS. THE MAIN CONCERN
WILL BE NORTH FACING REEFS, WHERE SURF CAN REACH UP TO 16 FEET
THROUGH LATE TONIGHT. HAZARDOUS SURF OF AT LEAST 9 FEET ALONG WEST
AND NORTH AND OF AT LEAST 12 FEET ALONG EAST FACING REEFS MAY PERSIST
LONGER, SO EITHER AN EXTENSION OF THE WARNING OR AN EXTENSION AS AN
ADVISORY WILL LIKELY BE NEEDED. A MODERATE RISK OF RIP CURRENTS
CONTINUES ALONG SOUTH FACING REEFS OVER THE NEXT SEVERAL DAYS.
COASTAL INUNDATION ALONG NORTHERN SHORELINES COULD REACH 1 TO 3 FEET
THROUGH TONIGHT.
EASTERN MICRONESIA UPDATE
THE ONLY CHANGE TO THE FORECAST WAS TO INCREASE SHOWERS TO SCATTERED
AT POHNPEI THIS AFTERNOON AS A BROAD TROUGH OVER CHUUK STATE SHIFTS
EASTWARD. OTHERWISE, THE LIGHT AND VARIABLE WINDS NEAR KOSRAE BEGIN
TO SHIFT MORE SOUTH TO SOUTHEASTERLY AS THE BROAD TROUGH SHIFTS OVER
POHNPEI AND A BROAD LOW PRESSURE SYSTEM PASSES TO THE DISTANT NORTH.
ISOLATED TO SCATTERED SHOWERS REMAINS ACROSS THE REGION AS A WEAK
TRADE-WIND PATTERN LOOKS TO BUILD BACK IN LATE WEEK AND OVER THE
WEEKEND.
LONG-PERIOD NORTHEASTERLY SWELL FROM A KONA LOW WELL NORTHEAST OF
THE REGION CONTINUES TO PRODUCE HAZARDOUS SURF ALONG NORTH-FACING
REEFS OF POHNPEI AND NORTH- AND EAST-FACING REEFS OF KOSRAE. NORTH-
NORTHWEST SWELL FROM A BROAD LOW PRESSURE SYSTEM EAST OF JAPAN WILL
ALSO KEEP SURF HAZARDOUS ALONG NORTH FACING REEFS THROUGH AT LEAST
WEDNESDAY MORNING. THERE WILL ALSO BE AN INCREASE IN SURF ALONG WEST-
FACING REEFS, BUT IS NOT EXPECTED TO REACH HAZARDOUS LEVELS AT THIS
TIME.
WESTERN MICRONESIA UPDATE
A BROAD LOW PRESSURE SYSTEM TO THE DISTANT NORTHEAST IS BRINGING
MODERATE NORTH TO NORTHEAST WINDS TO YAP AND PALAU AND DRIER MID-
LATITUDE AIR SOUTHWARD INTO THE TROPICS, AS WELL AS SIGNIFICANT,
LONG-PERIOD NNW SWELL TO THE REGION. CIMSS MIMIC LAYER PRECIPITABLE
WATER (PWAT) PRODUCT SHOWS PWATS HAVE DECREASED TO 1.1 TO 1.3 INCHES
AT PALAU AND YAP. THE TROUGH AXIS SOUTH OF PALAU LOOKS TO STAY
QUASI-STATIONARY AS A NEAR-EQUATORIAL TROUGH WITH THE EASTERN
PORTION LIFTING NORTHEAST TO MEET A WEAK FRONTAL FEATURE NEAR WAKE.
NO MAJOR CHANGES WERE MADE TO FORECAST. FAIR WEATHER PERSISTS AT YAP
AND PALAU THROUGH TONIGHT, WITH SCATTERED SHOWERS AT CHUUK INCREASING
TO NUMEROUS TONIGHT. HIGH SURF ADVISORIES AND SMALL CRAFT ADVISORIES
REMAIN IN EFFECT. LONG-PERIOD NORTHERLY SWELL FROM A LOW PRESSURE
SYSTEM EAST OF JAPAN CONTINUES TO BUILD ACROSS WESTERN MICRONESIA,
GENERATING 9 TO 12 FOOT SURF, LIKELY REACHING 14 FT AT YAP. LONG-
PERIOD NORTHEASTERLY SWELL CONTINUES TO PRODUCE HAZARDOUS SURF ALONG
NORTH-FACING REEFS AT CHUUK, THEN AS THE LOW PRESSURE SYSTEM MOVES
EASTWARD, NORTH-NORTHWESTERLY SWELL WILL START TO BUILD INTO CHUUK
TONIGHT, LIKELY NEEDING THE ADVISORY TO BE EXTENDED PAST TUESDAY
AFTERNOON.
PREV DISCUSSION
/ISSUED 646 PM CHST SUN MAR 15 2026/
MARIANAS SYNOPSIS...
SATELLITE IMAGERY SHOWS PARTLY TO MOSTLY CLOUDY SKIES OVER THE
ISLANDS. RADAR IMAGERY SHOWS NO SHOWERS OVER THE ISLANDS. ALTIMETRY
SHOWS COMBINED SEAS OF 10 TO 12 FEET AND IPAN BUOY DATA SHOWS 7 FEET
AT 17 SECONDS
DISCUSSION...
A DRY SEASON REGIME HAS SET UP OVER THE ISLANDS AND IS EXPECTED TO
CONTINUES THROUGH NEXT WEEKEND. WINDS ARE EXPECTED TO REMAIN AROUND
10 TO 15 MPH.
MARINE/SURF...
LATEST ALTIMETRY PASS SHOWS ELEVATED SEA HEIGHTS FOR THE ISLANDS OF
PAGAN NORTHWARD. LOOKING FURTHER NORTH ON ALTIMETRY, SEA HEIGHTS ARE
SHOWING 16 TO 20 FEET. THIS IS DUE TO STRONG WINDS AROUND A VIGOROUS
LOW PRESSURE SYSTEM NEAR JAPAN AND A KONA LOW THAT IS NORTHWEST OF
HAWAI'I, WHICH HAVE BEEN PRODUCING LONG-PERIOD NNW AND NE SWELLS IN
THE REGION. AS THIS FEATURE MOVES EASTWARD WINDS ARE EXPECTED TO
SHIFT MORE NORTHERLY MONDAY, THEN BECOME GENTLE TO FRESH
NORTHEASTERLIES MONDAY NIGHT. HAZARDOUS SEAS OF 11 TO 13 FEET COULD
BRIEFLY INCREASE TO 15 FEET OR MORE FOR MONDAY AND MONDAY
NIGHT. HAZARDOUS SURF AND A HIGH RISK OF RIP CURRENTS ARE EXPECTED
ALONG NORTH AND EAST FACING REEFS. SURF IS EXPECTED TO BUILD TO
AROUND 16 FEET ALONG NORTH FACING REEFS, THEREFORE, A HIGH SURF
WARNING HAS BEEN ISSUED. ADVISORY LEVEL SURF WILL CONTINUE ALONG EAST
FACING REEFS. AS NNW SWELL BUILDS OVER THE COMING DAYS, IT COULD
POTENTIALLY BUILD TO HAZARDOUS LEVELS OF 9 FEET ALONG WEST FACING
REEFS, LIKELY REQUIRING THE ADVISORY TO BE EXTENDED TO WEST FACING
REEFS. THE COASTAL FLOODING ALONG NORTH FACING REEFS COULD REACH 1 TO
3 FEET. ONCE THE SEAS CREST AND BEGIN TO FALL, LESSER ADVISORY
CONDITIONS WILL STILL APPLY.
EASTERN MICRONESIA...
IT LOOKS LIKE THE MODEL RUNS FROM A FEW DAYS AGO WERE CORRECT, AS
THIS AFTERNOON'S ALTIMETRY CAME IN A FOOT HIGHER (7.5-8 FOOT SEAS),
WITH MODEL SWELL NOW SHOWING 8 FEET AT 13 SECONDS, WHICH EQUATES TO
AN 11 FOOT SURF. GIVEN THESE TRENDS, WE DECIDED TO REINSERT A
HEADLINE FOR ELEVATED SURF FOR NORTH AND EAST-FACING REEFS AT MAJURO,
WHILE CONTINUING THE HIGH SURF ADVISORY AT POHNPEI AND KOSRAE. ALL
HEADLINES ARE CURRENTLY IN EFFECT THROUGH 3 AM WEDNESDAY.
OTHERWISE, MAINLY ISOLATED SHOWERS WILL CONTINUE THROUGH MONDAY NIGHT
AT POHNPEI AND KOSRAE, BEFORE YOUR RAINFALL POTENTIAL INCREASES.
MEANWHILE, MAJURO HAS SCATTERED SHOWERS IN THE AREA, AND THIS TREND
LOOKS TO CONTINUE AS YOU REMAIN ON THE EDGE OF THE HIGH-END ISOLATED
COVERAGE (20% POTENTIAL) AND LOW-END SCATTERED SHOWERS (30%
POTENTIAL). THIS WILL PRIMARILY BE DRIVEN BY A COMBINATION OF AN OLD
OUTFLOW BOUNDARY INTERACTING WITH SURFACE CONVERGENCE WITHIN A WEAK
ITCZ (INTER-TROPICAL CONVERGENCE ZONE). IT REMAINS UNCLEAR IF THIS
WILL PERSIST BEYOND THE NEXT 48 HOURS.
SEAS LOOK TO REMAIN JUST UNDER HAZARDOUS CONDITIONS FOR SMALL CRAFT
AT POHNPEI, WITH SEAS OF 7 TO 9 FEET EXPECTED AREA-WIDE FOR THE NEXT
48 HOURS, BEFORE SUBSIDING A FOOT OR TWO THEREAFTER. LIGHT TO GENTLE
WINDS WILL PREVAIL THROUGH THE FORECAST.
WESTERN MICRONESIA...
THE MAIN WEATHER FEATURES AFFECTING WESTERN MICRONESIA ARE A
WEAKENING COLD FRONT THAT TRANSITIONS TO A TROUGH NEARING CHUUK, AND
DRY MIDLATITUDE AIR THAT HAS SETTLED OVER KOROR AND YAP.
CHUUK WILL FEATURE WEST WINDS OF 10 TO 15 KNOTS THROUGH MONDAY, THEN
MONDAY NIGHT THROUGH FRIDAY WINDS WILL DIMINISH TO BETWEEN 5 AND 10
KNOTS WHILE ROTATING THROUGH NORTHWEST, NORTH AND FINALLY NORTHEAST
AS THE FRONT/TROUGH PASSES. LOOK FOR SCATTERED SHOWERS THROUGH
MONDAY, NUMEROUS MONDAY NIGHT, SCATTERED TUESDAY, THEN ISOLATED
SHOWERS THROUGH FRIDAY AS THE DRY AIR REACHES CHUUK. SEAS WILL BE 8
TO 10 FEET THROUGH AT LEAST LATE MONDAY NIGHT, POSSIBLY INTO TUESDAY
NIGHT, THEN WILL DIMINISH TO BETWEEN 6 AND 8 FEET FOR WEDNESDAY
THROUGH FRIDAY. THIS WILL MAINTAIN HAZARDOUS MARINE CONDITIONS
THROUGH AT LEAST MONDAY NIGHT, THEN CHALLENGING CONDITIONS
THEREAFTER. A SMALL CRAFT ADVISORY HAS BEEN ISSUED, BECAUSE THE WAVES
ARE A LITTLE BIGGER THAN ORIGINALLY THOUGHT YESTERDAY. THE HIGH SURF
ADVISORY REMAINS IN EFFECT.
YAP WILL RECEIVE THE BRUNT OF THE WAVE ACTIVITY, BEING FARTHER NORTH.
LOOK FOR NO MORE THAN A FEW SPRINKLES THROUGH TUESDAY, THEN JUST
ISOLATED SHOWERS THROUGH FRIDAY. WINDS WILL BE NORTH TO NORTHEAST AT
10 TO 15 KNOTS. SEAS WILL BE 11 TO 14 FEET THROUGH MONDAY NIGHT, 8 TO
12 FEET THROUGH THURSDAY, AND 7 TO 9 FEET FRIDAY. HIGH SURF AND SMALL
CRAFT ADVISORIES REMAIN IN EFFECT. MARINE CONDITIONS WILL BE
HAZARDOUS THROUGH THURSDAY BECOMING CHALLENGING ON FRIDAY.
KOROR, PALAU WILL SEE NORTH WINDS 5 TO 10 KNOTS WHICH ON WEDNESDAY
WILL BECOME NORTHEAST WINDS 5 TO 15 KNOTS. THERE WILL BE NO MORE THAN
A FEW SPRINKLES THROUGH TUESDAY NIGHT, THEN JUST ISOLATED SHOWERS
THROUGH FRIDAY. SEAS WILL BE 9 TO 12 FEET THROUGH TUESDAY, 7 TO 10
FEET THROUGH WEDNESDAY, THEN 5 TO 8 FEET THROUGH FRIDAY. HIGH SURF
AND SMALL CRAFT ADVISORIES REMAIN IN EFFECT. MARINE CONDITIONS WILL
BE HAZARDOUS THROUGH WEDNESDAY THEN CHALLENGING THROUGH FRIDAY.
GUM WATCHES/WARNINGS/ADVISORIES
GU...COASTAL FLOOD WATCH THROUGH LATE TONIGHT FOR GUZ001.
HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR GUZ001.
HIGH SURF WARNING UNTIL 5 AM CHST TUESDAY FOR GUZ001.
MP...COASTAL FLOOD WATCH THROUGH LATE TONIGHT FOR MPZ001>003.
HIGH RIP CURRENT RISK THROUGH LATE TONIGHT FOR MPZ001>003.
HIGH SURF WARNING UNTIL 5 AM CHST TUESDAY FOR MPZ001>003.
MARIANAS WATERS...HAZARDOUS SEAS WARNING UNTIL 5 AM CHST TUESDAY FOR PMZ151>154.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: CRUZ
MARIANAS: BOWSHER
EAST MICRONESIA: DOLL
WEST MICRONESIA: STANKO
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