683
FXPQ50 PGUM 070837
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
637 PM CHST TUE APR 7 2026
MARIANAS SYNOPSIS
A TRADE-WIND TROUGH IS STARTING TO MOVE OFF TO THE WEST THIS EVENING,
WITH MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS LINGERING OVER THE
NEXT FEW HOURS. BUOY DATA AROUND GUAM AND SAIPAN ARE REPORTING SEAS
AROUND BETWEEN AROUND 7 TO 8 FEET, WHILE ALTIMETRY AND DRIFTING
BUOYS SHOWING SEAS AROUND 10 TO 12 FEET EAST OF 150E.
DISCUSSION
THE TRADE-WIND TROUGH THAT MOVED INTO THE MARIANAS THIS MORNING IS
STARTING TO MOVE OFF TO THE WEST THIS EVENING AND WILL CONTINUE TO
MOVE AWAY OVERNIGHT. MOSTLY CLOUDY SKIES AND SCATTERED SHOWERS
EXTEND ACROSS THE MARIANAS BEHIND THE TROUGH AND SHOULD DECREASE TO
PARTLY CLOUDY AND ISOLATED SHOWERS NEAR MIDNIGHT. THE TRADE-WIND
SURGE REMAINS A NOTABLE FEATURE NORTH OF POHNPEI AND KOSRAE, DRIVEN
BY THE PRESSURE GRADIENT BETWEEN THE BROAD CIRCULATION (INVEST 90W)
WITHIN THE NEAR-EQUATORIAL TROUGH AND THE RIDGE OF HIGH PRESSURE
NORTH OF THE REGION. WINDS ARE EXPECTED TO BE AROUND 15 TO 20 MPH
ACROSS THE MARIANAS THROUGH THURSDAY, BRIEFLY DROPPING TO 10 TO 15
MPH WEDNESDAY NIGHT. INVEST 90W, CURRENTLY BETWEEN CHUUK AND POHNPEI,
IS EXPECTED TO GRADUAL DEVELOPMENT AS IT MOVES NORTHWEST. THERE IS
STILL SOME UNCERTAINTY IF INVEST 90W WILL HEAD DIRECTLY TOWARDS THE
MARIANAS OR IF THERE WILL BE A MORE NORTHEAST OR SOUTHERN TRACK
OVERALL. FOR NOW, WE ARE WATCHING THE POTENTIAL FOR SHOWERS,
THUNDERSTORMS, AND GUSTY WINDS AROUND THE MARIANAS, WITH CURRENT
TIMING BEING SOMETIME BETWEEN FRIDAY AND EARLY NEXT WEEK, BASED ON
CURRENT GUIDANCE. THIS FORECAST WILL BE CLOSE MONITORED AND UPDATED
AS IT BECOMES MORE CLEAR HOW INVEST 90W WILL DEVELOP IN EASTERN
MICRONESIA.
MARINE
WINDS ARE MODERATE TO FRESH ACROSS THE MARIANAS. THE TRADE-WIND
SURGE TO EAST IS KEEPING THE EAST SWELL ELEVATED. SEAS ARE
EXPECTED TO BE JUST BELOW 10 FT, THE THRESHOLD FOR HAZARDOUS TO SMALL
CRAFT, TONIGHT THROUGH AT LEAST WEDNESDAY NIGHT SO THE SMALL CRAFT
ADVISORY WAS ALLOWED TO EXPIRE. THE CIRCULATION CURRENTLY NEAR
POHNPEI, INVEST 90W, IS EXPECTED TO GRADUALLY DEVELOP AS IT MOVES
NORTHWEST, POTENTIALLY APPROACHING THE MARIANAS THIS WEEKEND OR
EARLY NEXT WEEK. THOUGH THE EVENTUAL TRACK IS UNCERTAIN, THIS COULD
CAUSE WINDS AND SEAS TO REBUILD HAZARDOUS LEVELS TO SMALL CRAFT LATER
THIS WEEK. THIS WOULD ALSO INCREASE THE POTENTIAL FOR SHOWERS AND
THUNDERSTORMS ACROSS THE MARIANAS. THERE WILL BE A HIGH RISK OF RIP
CURRENTS ALONG EAST FACING REEFS THROUGH THURSDAY AFTERNOON, AND
POTENTIALLY LONGER INVEST 90W, BECOMES MORE ORGANIZED AND STARTS TO
LIFT NORTHWEST. THERE IS A MODERATE RISK OF RIP CURRENTS ALONG NORTH,
SOUTH AND WEST FACING REEFS.
TROPICAL SYSTEMS
INVEST 90W IS STILL A BROAD DISTURBANCE WITHIN THE NEAR-EQUATORIAL
TROUGH (NET) BETWEEN POHNPEI AND CHUUK. THE JOINT TYPHOON WARNING
CENTER HAS INVEST 90W CENTER NEAR 4N155E, TRACKING A BROAD
CIRCULATION, BUT SATELLITE IMAGERY SHOWS A MID-LEVEL AND POTENTIAL
SURFACE CIRCULATION FURTHER NORTH NEAR 8N155E. MULTIPLE CIRCULATIONS
ARE ALWAYS POSSIBLE DURING THE EARLY STAGES OF SYSTEMS TRYING TO
DEVELOP BEFORE THEY ORGANIZE AROUND A CLEARLY DEFINED CENTER. THIS
MAY INDICATE THAT INVEST 90W WILL TAKE A COUPLE OF DAYS TO
CONSOLIDATE. INVEST 90W IS HELPING TO PRODUCE NUMEROUS LOCALLY HEAVY
SHOWERS, AND ISOLATED THUNDERSTORMS AROUND THE ISLANDS OF CHUUK,
POHNPEI AND KOSRAE. GUSTY WINDS ARE POSSIBLE IN THIS CONVECTION,
ESPECIALLY AS A TRADE-WIND SURGE CONTINUES ACROSS THE REGION NEAR AND
TO NORTH OF THE MAIN ISLANDS OF CHUUK, POHNPEI, KOSRAE. INVEST 90W
IS EXPECTED TO SHIFT NORTHWEST OVER THE NEXT FEW DAYS WITH
DEVELOPMENT CURRENTLY EXPECTED TO BE GRADUAL, SO WHILE DEVELOPMENT
INTO A SIGNIFICANT TROPICAL CYCLONE (TROPICAL DEPRESSION) IS NOT
LIKELY OVER THE NEXT COUPLE OF DAYS, MODELS GUIDANCE DO SUPPORT
INVEST 90W EVENTUALLY DEVELOPING INTO A TROPICAL CYCLONE. THE EXACT
TIMING AND EVENTUAL TRACK IS STILL UNCERTAIN AND IT IS NOT CLEAR
WHETHER INVEST 90W WILL HEAD DIRECTLY TOWARDS THE MARIANAS OR TRACK
MORE NORTHEAST OR SOUTH OF THE MARIANAS. GLOBAL ENSEMBLE MODELS HAVE
SHOWN A MORE SOUTHERLY TREND IN THE POTENTIAL TRACK TODAY, BUT THE
AIGFS AND EC-AIFS STILL SHOWS A NORTHERLY TURN THAT HAS INVEST 90W
PASSING EAST OF THE MARIANAS. FOR NOW, THE MARIANAS HAVE THE
POTENTIAL FOR INCREASING SHOWERS, THUNDERSTORMS, AND GUSTY WINDS
DEVELOPING OVER THE WEEKEND OR EARLY NEXT WEEK AND SHOULD MONITOR THE
FORECAST FOR UPDATES AS INVEST 90W DEVELOPS.
EASTERN MICRONESIA
AFTERNOON SATELLITE IMAGERY SHOWS A BROAD TROPICAL DISTURBANCE,
INVEST 90W, LOCATED SOUTH OF POHNPEI, CURRENTLY CENTERED IN THE
VICINITY OF 4N155E. SEVERAL VORTICITIES/CIRCULATIONS ARE NOTED
WITHIN THE BROAD DISTURBANCE AND IT REMAINS TO BE SEEN WHICH OF THESE
INDIVIDUAL CIRCULATIONS THE DISTURBANCE CONSOLIDATES AROUND AS IT
STRENGTHENS AND MOVES TO THE NORTH-NORTHWEST THROUGH THE WEEK. THE
SITUATION WILL CONTINUE TO BE MONITORED DURING THE COMING DAYS.
UNSETTLED WEATHER WILL CONTINUE FOR THE NEXT FEW DAYS ACROSS EASTERN
MICRONESIA AS THE DISTURBANCE SLOWLY DRIFTS TO THE NORTH-NORTHWEST.
SCATTERED TO NUMEROUS SHOWERS, WHICH MAY PRODUCE HEAVY RAINFALL,
ALONG WITH ISOLATED THUNDERSTORMS CAN BE EXPECTED AT POHNPEI AND
KOSRAE THROUGH THURSDAY. A SERIES OF WEAK TROUGHS FROM A FRAGMENTING
ITCZ WILL LIKELY KEEP ELEVATED SHOWER AND ISOLATED THUNDERSTORM
CHANCES ACROSS THE REGION FOR THE REMAINDER OF THE WEEK AT ALL
FORECAST SITES. WINDS WILL REMAIN MODERATE TO FRESH THROUGH THURSDAY,
BECOMING GENTLE BY THE WEEKEND. GUST UP TO 30 KNOTS ARE POSSIBLE
THROUGH WEDNESDAY, ESPECIALLY WITH HEAVY SHOWERS AND THUNDERSTORMS.
AN EAST TO NORTHEAST SWELL WILL REMAIN THROUGHOUT THE WATERS AND IN
COMBINATION WITH A TRADE-WIND SURGE TO THE NORTH, CONTINUE TO PRODUCE
HAZARDOUS SURF ALONG NORTH-FACING REEFS OF POHNPEI AND NORTH AND
EAST-FACING REEFS OF KOSRAE THROUGH AT LEAST THURSDAY AFTERNOON.
HAVE EXTENDED THE HIGH SURF ADVISORY AT KOSRAE TO REFLECT THIS AND
HAZARDOUS SURF ALONG EAST-FACING REEFS AT KOSRAE WILL LIKELY CONTINUE
INTO FRIDAY. HAZARDOUS SURF ALONG NORTH-FACING REEFS OF KOSRAE MAY
DROP BELOW 9 FEET WEDNESDAY AFTERNOON AND MAY NEED TO BE REMOVED
FROM THE ADVISORY WITH THE AFTERNOON ISSUANCE ON WEDNESDAY. A SMALL
CRAFT ADVISORY WAS ISSUED FOR POHNPEI THIS AFTERNOON THROUGH
WEDNESDAY AFTERNOON FOR SEAS UP TO 10 FEET AND GUSTS OF 25 KT.
WESTERN MICRONESIA
THE MAIN TWO FEATURES THAT ARE EFFECTING THE REGION ARE THE NEAR
EQUATORIAL TROUGH (NET) AND THE INCOMING INVEST 90W (MORE ON THIS
FEATURE IN THE CHUUK SECTION). THE NET ENTERS THE REGION NEAR 2N130E
AND EXTENDS EASTWARD ACROSS THE SOUTHERN PORTION OF WESTERN
MICRONESIA WHERE IT CONTINUES INTO EASTERN MICRONESIA. SOUTH OF THE
NET AXIS, SCATTERED TO NUMEROUS SHOWERS ARE SEEN ON SATELLITE
IMAGERY.
FOR PALAU AND YAP, A DRY TRADE-WIND PATTERN REMAINS OVER THE REGION
WITH A CAVEAT. A PASSING TROUGH IS EXPECTED TO MOVE THROUGH YAP
PROPER ON WEDNESDAY. THIS TROUGH IS EXPECTED TO PRODUCES SCATTERED
SHOWERS. OTHERWISE, ISOLATED SHOWERS ARE EXPECTED TO REMAIN THROUGH
THE WEEK FOR BOTH LOCATIONS. WINDS ARE EXPECTED TO BE AROUND 10 TO 15
KNOTS AROUND PALAU, THEN THESE WINDS ARE ANTICIPATED TO BEGIN TO
FALL TO 5 TO 10 KTS AROUND TUESDAY. WINDS AROUND YAP ARE EXPECTED TO
BE 5 TO 15 KTS THROUGH SUNDAY.
FOR CHUUK, AN UNSETTLED WEATHER PATTERN IS IN STORE FOR THE AREA.
INVEST 90W IS LOCATED WEST OF POHNPEI, AND IS PRODUCING SHOWERS
AROUND CHUUK. TONIGHT, SHOWERS ARE EXPECTED TO BUILD FROM
SCATTERED TO WIDESPREAD. THESE SHOWERS ARE EXPECTED FALL TO NUMEROUS
AROUND WEDNESDAY. THIS SLOW DOWNWARD TREND WILL REMAIN WHILE INVEST
90W MOVES NORTH TO NORTHWEST THROUGH THE REGION. DURING THIS TIME,
SHOWERS MAY BE HEAVY AT TIMES, WITH RAIN RATES IN THE 2 TO 4 INCHES
FOR A 24 HOUR PERIOD ON OUR MOST AGGRESSIVE MODELS. MODEL GUIDANCE
SUGGEST THAT INVEST 90W MAY LEAVE THE REGION AROUND WEDNESDAY NIGHT
INTO THURSDAY MORNING. OVER THE LATTER HALF OF THE WEEK THE OUTER
BANDS OF INVEST 90W WILL TAKE OVER AS THE WEATHER MAKER FOR THE
REGION. THESE SHOWERS ARE ANTICIPATED TO BE AROUND 20 TO 30 PERCENT
AS THEY ARE FORMED ALONG THE WESTERLY INFLOW OF INVEST 90W. NEAR THE
BEGINNING OF NEXT WEEK, CHUUK MAY RETURN TO A DRIER PATTERN.
COMBINED SEAS VARY OVER THE REGION WITH THE LOWEST IN THE WEST AND
THE HIGHEST IN THE EAST. SEAS OVER THE REGION ARE BETWEEN 3 TO 5
FEET TO THE WEST OF PALAU, SEAS NEAR YAP ARE 4 TO 7 FEET AND BUILD TO
7 TO 10 FEET NEAR CHUUK. AT CHUUK, A SMALL CRAFT ADVISORY (SCA) AND
A HIGH SURF ADVISORY (HSA) ALONG NORTH FACING REEFS ARE IN EFFECT.
SEAS FOR CHUUK ARE EXPECTED TO CREST AROUND TONIGHT. THE SEAS AND
SURF WILL TAKE SOME TIME TO FALL BELOW THE 10 FOOT (FOR SEAS) AND 9
FOOT (FOR SURF) THRESHOLDS. CURRENT ESTIMATIONS ARE FOR WEDNESDAY
AFTERNOON, HOWEVER, SEAS AND SURF MAY REMAIN ELEVATED FOR A BIT
LONGER. SEAS ARE EXPECTED TO CONTINUE TO SUBSIDE FOR THE REMAINDER OF
THE WEEK.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH THURSDAY AFTERNOON FOR MPZ001>003.
MARIANAS WATERS...NONE.
MARIANAS: SCHANK
EAST MICRONESIA: WHISNANT
WEST MICRONESIA: BOWSHER
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