421
FXPQ50 PGUM 182017
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
617 AM CHST THU MAR 19 2026
MARIANAS UPDATE
SATELLITE AND RADAR DEPICT AN AREA OF SHALLOW MODERATE SHOWERS
BUILDING SOUTHWEST ACROSS THE NORTHWESTERN COASTAL WATERS OF SAIPAN,
TINIAN, AND ROTA EARLY THIS MORNING. THIS IS IN SPITE OF THE DRY AIR
MASS OVER THE AREA WITH PRECIPITABLE WATER AMOUNTS AROUND 1.10
INCHES, VERY LOW FOR THE TROPICS. A SURGE IN NORTHEASTERLY WINDS IS
MOVING THROUGH THE MARIANAS AS STRONG HIGH PRESSURE TO THE EAST OF
JAPAN PUSHES SOUTHEAST, STRENGTHENING THE PRESSURE GRADIENT ACROSS
THE REGION. THE SHOWERS BUILDING THIS MORNING ARE ASSOCIATED WITH
CONVERGENCE ALONG THE LEADING EDGE OF THESE STRONGER WINDS, AND ARE
EXPECTED TO PUSH FURTHER WEST OF THE ISLANDS AND DIMINISH BY THIS
AFTERNOON. WITH THIS IN MIND, GUSTS TO 30 MPH WERE INCLUDED IN THE
FORECAST FOR TODAY.
A HIGH SURF ADVISORY FOR NORTH FACING REEFS AND HIGH RIP CURRENT
RISK FOR NORTH AND EAST FACING REEFS REMAIN IN EFFECT THROUGH FRIDAY
AFTERNOON, BUT THERE IS STILL A POTENTIAL FOR SURF AND RIP RISK TO
REMAIN ELEVATED OVER THE WEEKEND. A SMALL CRAFT ADVISORY REMAINS IN
EFFECT THROUGH THIS AFTERNOON AS THE LONG-PERIOD NORTH TO NORTHEAST
SWELLS GRADUALLY SUBSIDE, BUT BUILDING EAST TO NORTHEAST SWELL WILL
KEEP SEAS ELEVATED, POTENTIALLY REMAINING HAZARDOUS AT TINIAN AND
SAIPAN THROUGH THE WEEKEND AND NECESSITATING AN EXTENSION OR
REISSUANCE OF THE ADVISORY.
EASTERN MICRONESIA UPDATE
THERE WAS LITTLE CHANGE IN THE FORECAST OVERNIGHT, MAINLY A SLIGHT
OVERALL REDUCTION IN SHOWER CHANCES TO ALIGN WITH LATEST SATELLITE
AND MODEL TRENDS. THE HEAVIEST SHOWERS ARE BUILDING WITHIN AN AREA OF
CONVERGENCE TO THE EAST OF KOSRAE AND WITHIN AN EAST-TO-WEST
ORIENTED TROUGH JUST EAST TO NORTHEAST OF MAJURO. SHOWERS LOOK TO
INCREASE OVERNIGHT MAINLY FOR KOSRAE AS BROAD TROUGHING GRADUALLY
BUILDS JUST EAST OF THE ISLAND. A HIGH SURF ADVISORY FOR NORTH
FACING REEFS OF POHNPEI AND KOSRAE WAS EXTENDED THROUGH LATE TONIGHT,
AS THE LONG-PERIOD NORTH TO NORTHEAST SWELL REMAINS CAPABLE OF
PRODUCING HAZARDOUS SURF EXCEEDING 9 FEET.
WESTERN MICRONESIA UPDATE
THERE WAS LITTLE CHANGE TO THE FORECAST WITH A MUCH DRIER PATTERN IN
PLACE ACROSS THE REGION. SHOWERS LOOK TO BUILD SLIGHTLY NEAR CHUUK
OVERNIGHT, ALONG THE EDGE OF A BROAD EAST-TO-WEST ORIENTED TROUGH
OVER CENTRAL AND EASTERN MICRONESIA. A HIGH SURF ADVISORY REMAINS IN
EFFECT FOR NORTH FACING REEFS OF CHUUK, PALAU, AND YAP, IN EFFECT
THROUGH THIS AFTERNOON FOR CHUUK AND PALAU AND SATURDAY AFTERNOON FOR
YAP. MODELS INDICATE THE ADVISORY MAY NEED TO BE EXTENDED FOR CHUUK
AND PALAU AS ELEVATED LONG-PERIOD NORTHEAST SWELL CONTINUES TO AFFECT
THE REGION. ALTIMETRY DATA FROM YESTERDAY EVENING SHOWED COMBINED
SEAS AROUND 10 FEET JUST EAST OF PALAU, HIGHER THAN EXPECTED FROM
MODEL GUIDANCE, INDICATING THAT SEA HEIGHTS, SWELLS, AND ASSOCIATED
SURF MAY TAKE LONGER TO RELAX.
PREV DISCUSSION
/ISSUED 557 PM CHST WED MAR 18 2026/
MARIANAS SYNOPSIS...
MODERATE TO FRESH NORTHEAST WINDS AND ISOLATED SHOWERS PREVAIL ACROSS
THE REGION THIS AFTERNOON. NEARBY ALTIMETRY DATA SHOWS HAZARDOUS SEAS
AROUND 8 TO 11 FEET NEAR THE MARIANAS. A SMALL CRAFT ADVISORY REMAINS
IN EFFECT THROUGH THURSDAY AFTERNOON. A HIGH SURF ADVISORY REMAINS IN
EFFECT ALONG NORTH FACING REEFS AND THERE IS A HIGH RISK OF RIP
CURRENTS ALONG NORTH AND EAST FACING REEFS THROUGH FRIDAY AFTERNOON.
DISCUSSION...
THE DRY WEATHER PATTERN CONTINUES FOR THE REGION WITH PRECIPITABLE
WATER AMOUNTS STILL VERY LOW FOR THE TROPICS, AT AROUND 0.95 INCHES.
THE OVERNIGHT TEMPERATURES DROPPED ANOMALOUSLY LOW TO 68 DEGREES AT
TIYAN AND THE MINIMUM RELATIVE HUMIDITY FOR THE DAY GOT DOWN TO 51
PERCENT. THIS IS LARGELY DUE TO THE DRIER AIR THAT HAS BEEN USHERED
IN BY A BROAD, MID-LATITUDE LOW PRESSURE SYSTEM AND THE RESULTING
NORTHERLY WINDS OVER THE PAST FEW DAYS. AN AREA OF HIGH PRESSURE IS
NOW PUSHING EASTWARD OFF THE COAST OF JAPAN. FROM THE RESULTING
PRESSURE GRADIENT, MODERATE TO FRESH NORTHEAST WINDS AND OCCASIONALLY
STRONG DAYTIME GUSTS ARE EXPECTED FOR THE MARIANAS OVER THE NEXT FEW
DAYS.
MARINE/SURF...
ELEVATED LONG-PERIOD NORTH TO NORTHEAST SWELLS FROM DISTANT LOW
PRESSURE SYSTEMS WILL CONTINUE TO PRODUCE HAZARDOUS SEAS OF 8 TO 10
FEET ACROSS THE MARIANAS COASTAL WATERS THROUGH AT LEAST THURSDAY
AFTERNOON AND WILL CONTINUE TO PRODUCE HAZARDOUS SURF ALONG NORTH
FACING REEFS, AND A HIGH RISK OF RIP CURRENTS ALONG NORTH AND EAST
FACING REEFS THROUGH FRIDAY AFTERNOON. OVERALL, LONG-PERIOD
NORTHEASTERLY SWELLS ARE EXPECTED TO GRADUALLY SUBSIDE, BUT BUILDING
EAST TO NORTHEAST SWELL WILL KEEP SEAS ELEVATED, POTENTIALLY
REMAINING AT HAZARDOUS LEVELS OF 8 TO 10 FEET AT TINIAN AND SAIPAN
THROUGH THE WEEKEND. ADDITIONALLY, THERE IS STILL A POTENTIAL FOR
SURF AND RIP RISK TO REMAIN ELEVATED OVER THE WEEKEND. A MODERATE
RISK OF RIP CURRENTS WILL CONTINUE ALONG WEST AND SOUTH FACING REEFS
THROUGH AT LEAST THURSDAY NIGHT. THE COASTAL FLOOD WATCH WAS ALLOWED
TO EXPIRE THIS AFTERNOON, BUT MINOR COASTAL INUNDATION STILL REMAINS
POSSIBLE ALONG NORTHERN SHORELINES WHERE SURF OF 9 TO 12 FEET IS
EXPECTED THROUGH FRIDAY AFTERNOON.
EASTERN MICRONESIA...
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL PERSIST AT ALL
SITES THROUGH THURSDAY AS TROUGHING CONTINUES TO IMPACT EASTERN
MICRONESIA. BROAD TROUGHING OVER CENTRAL MICRONESIA WILL TRY TO NUDGE
EASTWARD OVER THE NEXT DAY OR SO AS A TRADE-WIND PATTERN ESTABLISHES
ACROSS THE REGION. CURRENT MODEL GUIDANCE HAS THE TROUGH STALLING
AND EVENTUALLY PUSHING BACK WESTWARD BY THE WEEKEND. IN THE SHORT
TERM, LOCALLY HEAVY SHOWERS WILL BE POSSIBLE TONIGHT AT KOSRAE AS THE
TROUGHING STALLS IN THE VICINITY OF THE ISLAND AND ALSO FOR PORTIONS
OF THE NORTHERN MARSHALL ISLANDS AS ANOTHER TROUGH AND WEAK
CIRCULATION IMPACT THE ISLANDS. WINDS WILL REMAIN LIGHT TO GENTLE AT
ALL FORECAST SITES THROUGH THE PERIOD, WITH WINDS EVENTUALLY BECOMING
EAST TO SOUTHEAST BY EARLY FRIDAY AS A TRADE- WIND ESTABLISHES
ACROSS EASTERN MICRONESIA. GUSTY AND ERRATIC WINDS WILL BE POSSIBLE
WITH ANY HEAVY SHOWERS AND STRONG THUNDERSTORMS.
SEAS CONTINUE TO CONTAIN TWO LONG-PERIOD SWELLS FOR THE NEXT SEVERAL
DAYS AND HAZARDOUS SURF ALONG NORTH FACING REEFS WILL LIKELY
CONTINUE THROUGH AT LEAST TONIGHT. THE HIGH SURF ADVISORY WAS
EXTENDED THROUGH 3AM THURSDAY AND MAY NEED TO BE EXTENDED AGAIN FOR
THE NORTH FACING REEFS OF POHNPEI AS THE LONG-PERIOD NORTH-NORTHWEST
SWELL BUILDS. MODEL GUIDANCE HINTS THAT HAZARDOUS SURF SHOULD FALL
BELOW 9 FEET ALONG THE NORTH FACING REEFS OF KOSRAE STARTING TONIGHT.
COMBINED SEAS ARE EXPECTED TO GENERALLY RANGE BETWEEN 5 TO 8 FEET
THROUGH FRIDAY AT ALL FORECAST POINTS, WITH SEAS FALLING THEREAFTER
TO 4 TO 6 FEET BY LATE WEEKEND.
WESTERN MICRONESIA...
A SEASONAL DRY PATTERN IS NOW IN PLACE ACROSS WESTERN MICRONESIA.
SATELLITE SHOWS A BAND OF CLOUDS AND A FEW SHOWERS NORTH OF A BROAD
SURFACE TROUGH THAT STRETCHES ACROSS THE REGION ASSOCIATED WITH WEAK
SPEED CONVERGENCE THAT MOVED THROUGH PALAU. PARTLY CLOUDY SKIES ARE
NOW SEEN ACROSS YAP AND PALAU, WHILE CHUUK IS SEEING MAINLY HIGH
CLOUDS ACROSS WENO. THIS PATTERN LOOKS TO CONTINUE THROUGH THE
WEEKEND AND INTO NEXT WEEK AT PALAU AND CHUUK, WITH THE BROAD TROUGH
TRANSITIONING INTO A NEAR-EQUATORIAL TROUGH (NET) AS IT CONTINUES TO
DRIFT SOUTH. AROUND THE BEGINNING OF NEXT WEEK, A TRADE-WIND TROUGH
LOOKS TO MOVE THROUGH THE REGION, POSSIBLY SPAWNING THE DEVELOPMENT
OF A BROAD CIRCULATION OVER YAP STATE AND WESTERN CHUUK STATE. THIS
IS EXPECTED TO PRODUCE AN INCREASE IN SHOWERS ACROSS YAP PROPER
MONDAY, AND POSSIBLY ACROSS PALAU A LITTLE LATER IN THE WEEK.
SHOWERS COULD INCREASE AT CHUUK AS WELL, THOUGH PROBABILITIES LOOK
TO REMAIN AROUND THE 20 PERCENT RANGE FOR WENO.
SEAS AND SURF REMAIN THE PRIMARY CONCERNS ACROSS THE REGION. SEAS
HAVE SUBSIDED A BIT THIS AFTERNOON, WITH THE LATEST ALTIMETRY DATA
SHOWING SEAS AT 7 TO 9 FEET ACROSS THE REGION. BASED ON THIS, THE
SMALL CRAFT ADVISORY FOR PALAU, YAP AND CHUUK WAS ALLOWED TO EXPIRE.
THE NORTH TO NORTHEAST SWELL, HOWEVER, IS EXPECTED TO REMAIN HIGH
ENOUGH TO MAINTAIN HAZARDOUS SURF ALONG NORTH FACING REEFS OF ALL
THREE LOCATIONS. AS SEAS SUBSIDE, SURF IS EXPECTED TO FALL BELOW
HAZARDOUS LEVELS THURSDAY AFTERNOON AT PALAU AND CHUUK, BUT REMAIN AT
HAZARDOUS LEVELS FOR YAP PROPER FOR THE NEXT FEW DAYS. THE SWELL IS
EXPECTED TO BECOME MORE NORTHEAST BY THE WEEKEND, WITH SURF FALLING
BELOW HAZARDOUS LEVELS AT YAP AS EARLY AS SATURDAY AFTERNOON.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH FRIDAY AFTERNOON FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 PM CHST FRIDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH FRIDAY AFTERNOON FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 PM CHST FRIDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM CHST THIS AFTERNOON FOR PMZ151>154.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: DECOU
MARIANAS: CRUZ
EAST MICRONESIA: WHISNANT
WEST MICRONESIA: KLEESCHULTE
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