942
FXPQ50 PGUM 281847
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
447 AM CHST SUN MAR 29 2026
MARIANAS UPDATE
THE SCATTERED SHOWERS ARE FILTERING OUT OF THE COASTAL WATERS ZONES
AT THIS TIME. THIS WILL LEAVE ISOLATED SHOWERS BEHIND, WHICH WILL
REMAIN IN PLACE FOR THE NEXT WEEK. TRADE WINDS WILL RETURN TODAY,
LIGHT TO GENTLE AT FIRST, THEN BECOMING MODERATE AROUND TUESDAY. THE
KBDI SHOULD RISE GRADUALLY AS SHOWERS WILL BE SPARSE. THERE WILL
LIKELY BE MODERATE RISKS OF RIP CURRENTS, MOSTLY ALONG NORTH AND EAST
FACING REEFS, WHICH WILL OCCASIONALLY GO HIGH.
TROPICAL SYSTEMS
INVEST AREA 99W IS CURRENTLY CENTERED NEAR 8.0 DEGREES NORTH AND
161.2 DEGREES EAST. IT HAS BEEN MOVING SLOWLY WESTWARD WITH LITTLE
CHANGE IN STRENGTH. 99W COULD END UP BEING ABSORBED INTO ANOTHER
SYSTEM WHICH MODELS INDICATE COULD AFFECT THE SOUTHERN MARSHALL
ISLANDS. THIS IS AN UNUSUAL OCCURRENCE, AND BEARS WATCHING BECAUSE
SOME OF THE NEEDED INGREDIENTS HAVE ALREADY COME TOGETHER. SO KEEP AN
EYE ON THIS OVER THE NEXT SEVERAL DAYS, AND WE WILL REPORT ON WHAT
STARTS TO SHAKE LOOSE, IF AND WHEN IT DOES.
EASTERN MICRONESIA UPDATE
INVEST AREA 99W HAS MOVED FAR ENOUGH WEST THAT MAJURO IS BACK IN
ISOLATED SHOWERS. REFLECTED THIS IN THE FORECAST FOR TODAY. SINCE THE
TREND IS FOR INCREASING SHOWERS AGAIN AT SOME POINT, WENT AHEAD AND
RAMPED IT UP TO SCATTERED SHOWERS IN THE AFTERNOON. KOSRAE AND
POHNPEI DID NOT NEED ANY SIGNIFICANT CHANGES.
WESTERN MICRONESIA UPDATE
WESTERN MICRONESIA DID NOT NEED ANY SIGNIFICANT CHANGES. YAP AND
KOROR WILL BOTH BE FAIRLY WET THE NEXT DAY OR TWO, WITH THE NET
HYBRIDIZING WITH A TROUGH EXTENDING SOUTHWESTWARD FROM A COLD FRONT
NORTHEAST OF THE MARIANAS. CHUUK WILL BE A LITTLE WET TUESDAY AND
WEDNESDAY, PERHAPS WITH SHOWERS BREAKING OFF FROM 99W.
PREV DISCUSSION
/ISSUED 624 PM CHST SAT MAR 28 2026/
MARIANAS SYNOPSIS...
SATELLITE IMAGERY EARLY THIS EVENING SHOWS A LINE OF CLOUDS THAT
EXTEND FROM NORTHER GUAM AND UP THE ISLAND CHAIN OVER ROTA, TINIAN,
AND SAIPAN LEFT OVER FROM EARLIER ISLAND-EFFECT CONVECTION, BUT
THIS SHOULD DECREASE AS HEATING FROM THE SUN IS LOST. A SURFACE
TROUGH AND EMBEDDED CIRCULATION TO THE NORTHWEST WILL SHIFT SOUTH-
SOUTHEAST, LIKELY BRING SCATTERED SHOWERS TO THE MARIANAS LATER
TONIGHT AND INTO SUNDAY WHILE CAUSING WINDS TO BECOME VARIABLE TO
SHIFT TOWARDS THE NORTH. SEAS ARE AROUND 3 TO 5 FEET AND WILL START
TO BUILD TO AROUND 6 TO 8 FEET NEXT WEEK AS GENTLE TO MODERATE
NORTHEAST WINDS AND A PULSE OF NORTHERLY SWELL MOVE INTO THE REGION.
DISCUSSION...
THE WEATHER PATTERN ACROSS THE MARIANAS HAS SO FAR BEEN EVOLVING AS
PREVIOUSLY EXPECTED. PARTLY CLOUDY SKIES AND THE LIGHT TO GENTLE
SOUTHERLY WINDS CREATED BY THE SURFACE TROUGH AND EMBEDDED
CIRCULATION TO THE NORTHWEST DID TRIGGER SOME ISLAND-EFFECT SHOWERS
THIS AFTERNOON, ESPECIALLY OVER THE NORTHERN HALF OF THE GUAM, WITH
AREAS NEAR DEDEDO SEEING AROUND 1.3 INCHES OF RAIN, WHILE THE AIRPORT
ONLY RECEIVED AROUND A TRACE BY 4 PM. GLOBAL AND HI-RES MODEL
GUIDANCE STILL SUPPORT THE SURFACE TROUGH SHIFTING SOUTH-SOUTHEAST
TONIGHT AND SUNDAY AS THE TROUGH WEAKENS AND A WEAK COLD FRONT NORTH
OF THE REGION SHIFTS SOUTHWARD NEAR MINAMITORISHIMA. THIS IS EXPECTED
TO BRING SCATTERED SHOWERS TO THE MARIANAS LATER TONIGHT AND THROUGH
SATURDAY, THOUGH THE RISK FOR THUNDERSTORM LOOKS TO BE LIMITED AS
UPPER AIR SOUNDING AND THE ADVECTED LAYERED PRECIPITABLE WATER (ALPW)
SATELLITE PRODUCT SUGGEST DRIER AIR IS MOVING INTO THE 700-500MB
LAYER. MODEL GUIDANCE THEN SHOWS NORTHEAST TRADE-WINDS PUSHING BACK
INTO THE AREA BY MONDAY, PROMOTING A DRIER WEATHER PATTERN OVERALL
FOR NEXT WEEK. THE WEATHER PATTERN ACROSS MOST OF MICRONESIA IS STILL
FAIRLY ATYPICAL FOR THIS TIME OF YEAR, WITH WEAK TRADE-WINDS AND
VARIABLE TO WESTERLY WINDS FOUND ACROSS PORTIONS OF THE REGION. THIS
PATTERN WILL INCREASE THE POTENTIAL FOR CIRCULATIONS/DISTURBANCES TO
DEVELOP SOMEWHERE IN THE REGION SO THERE IS A DEGREE UNCERTAINTY IN
THE LONG RANGE FORECAST.
MARINE...
SEAS AROUND AROUND 4 TO 6 FEET THIS EVENING WITH WINDS EXPECTED TO
BE VARIABLE IN THE EVENING THEN SHIFTING TOWARD THE NORTH AFTER
MIDNIGHT AS A SURFACE TROUGH DIPS SOUTHWARD. THIS TROUGH WILL BRING
SCATTERED SHOWERS TO THE COASTAL WATERS AFTER MIDNIGHT AND INTO
SUNDAY. A PULSE OF NORTHERLY SWELL, GENERATED BY A LOW PRESSURE
SYSTEM IN THE NORTHERN PACIFIC OCEAN, IS EXPECTED TO MOVE INTO
REGION AROUND TUESDAY TO INCREASE SEAS BACK UP TO 6 TO 8 FEET. THIS
PATTERN WILL SUPPORT A MODERATE RISK OF RIP CURRENTS ALONG NORTH AND
EAST FACING REEFS OVER THE NEXT FEW DAYS. DEPENDING ON HOW THE STRONG
THE PULSE OF NORTHERLY SWELL IS AROUND TUESDAY, THERE COULD BE A
BRIEF PERIOD OF HAZARDOUS SURF OF 9 FEET AND A HIGH RISK OF RIP
CURRENTS ALONG NORTH FACING REEFS. A DRIER TRADE-WIND PATTERN IS
THEN EXPECTED TO PUSH INTO THE REGION AROUND MONDAY.
TROPICAL SYSTEMS...
INVEST 99W CONTINUES TO REMAIN QUASI-STATIONARY NORTH OF KOSRAE,
WITH THE CURRENT SATELLITE ESTIMATED PLACING THE CENTER NEAR 7.9N
161.6E. CONVECTION HAS GREATLY INCREASED SINCE YESTERDAY WITH 99W,
ESPECIALLY ALONG IT'S NORTHERN THROUGH EASTERN THROUGH SOUTHERN
FLANKS. VORTICITY ANALYSIS EARLIER THIS MORNING SHOWED A 'STAGGERED
APPROACH" TO VORTICITY CENTERS BETWEEN 925MB AND 500MB, LEANING
EASTWARD WITH HEIGHT. HOWEVER, CONVECTION IS NOW ATTEMPTING TO BUILD
CLOSER TO THE CENTER, SO WE'RE KEEPING AN EYE ON IT AND HAVE HAD A
GREAT COORDINATION CALL WITH JTWC (THE JOINT TYPHOON WARNING CENTER)
EARLIER THIS MORNING CONCERNING OBSERVATIONAL TRENDS, THE OVERALL
PATTERN, AND MODEL CONTINUITY (FORECAST MODELS).
THE LATEST MODEL TRENDS REMAIN SHOW A DELAY IN WEAKENING 99W,
ALLOWING IT TO DRIFT WESTWARD TO NEAR POHNPEI DURING THE NEXT 36 TO
48 HOURS. THEREAFTER, THE REMNANT "ENERGY" GETS ABSORBED INTO A NEW,
BUT SLOWLY-DEVELOPING A NEW CIRCULATION SOUTHEAST OF MAJURO/EAST OF
MAKIN IN ABOUT 5 TO 7 DAYS. THIS SYSTEM THEN SLOWLY (ALMOST AT A
CRAWL) LIFTS NORTH-NORTHWEST AS A TRADE WIND SURGE NORTH OF THE
REGION STARTS TO AFFECT THE NEW CIRCULATION'S DEVELOPMENT. CURRENT
INDICATIONS DO SHOW THE POTENTIAL FOR A NOTABLE IMPACT TO MUCH OF THE
SOUTHERN HALF OF THE RMI, BUT, BEYOND THE DAY 7 PERIOD (ABOUT 10
DAYS OUT).
AS WE MENTIONED IN YESTERDAY'S SECTION, THIS IS AN ATYPICAL SYSTEM
FOR THE REGION. DUE TO THE OVERALL BEHAVIOR OF THE NET (NEAR-
EQUATORIAL TROUGH) AND THE ABOVE NORMAL TROPICAL ACTIVITY ALREADY
SEEN THIS YEAR, INVEST 99W BEARS CLOSE MONITORING OVER THE NEXT
SEVERAL DAYS. WITH THE FAVORABLE MJO POSITIONING AND LIGHT TO VERY
LIGHT WIND SHEAR, A PATTERN FOR FAVOR CONDITIONS IS POSSIBLE OVER THE
NEXT 1-2 WEEKS. THE ENSEMBLE MODELS ARE IN REMARKABLY GOOD AGREEMENT
IN THE ABOVE SCENARIO PLAYING OUT, WITH THE GEFS LATEST RUN SHOWING
A CIRCULATION TRACKING FROM NEAR OR JUST SOUTH OF MAJURO, AS IT HEADS
TOWARDS THE NORTHERN PORTION OF KOSRAE, AND THEN TOWARDS POHNPEI. IT
REMAINS UNCLEAR AS TO EXACT TRACK AND WIND FIELD STRENGTH OF ANY
POTENTIAL DISTURBANCE, THOUGH SCATTERED TO NUMEROUS SHOWERS, SOME
LOCALLY HEAVY, AND VARIABLE WIND DIRECTIONS WOULD LIKELY BE NOTED BY
RESIDENTS IN THE REGION.
WITH THIS IN MIND, WE WANTED TO CONTINUE GIVING HEADS UP THAT
"SOMETHING MAY BE BREWING" OVER THE NEXT 7 TO 10 DAYS, BUT,
UNCERTAINTY IN REGARDS TO SPECIFICS REMAIN HIGH. WE'RE CONFIDENT IN
THE RAINFALL LIKELIHOOD THAT SOME MAY BE "HEAVIER THAN NORMAL" NEXT
WEEK AND BEYOND, BUT BEYOND THAT, WE JUST HAVE TO SIMPLY WAIT AND SEE
WHAT "MOTHER NATURE HAS IN STORE FOR US." STAY TUNED!
EASTERN MICRONESIA...
MUCH OF THE FORECAST CONCERNS ARE MENTIONED IN THE TROPICAL SECTION
ABOVE. IN GENERAL, IT LOOKS LIKE AN INTERESTING WEEK OR TWO OF
POTENTIALLY IMPACTFUL WEATHER IS "IN THE CARDS" FOR ALL OF EASTERN
MICRONESIA. THIS WILL FEATURE PERIODS OF SOME VERY HEAVY RAINFALL,
SOMETIMES WITH INTENSE RAINFALL RATES AND/OR AMOUNTS, LIKELY
ACCOMPANIED BY CONVECTIVELY-DRIVEN STRONG WIND GUSTS OF 30 KNOTS OR
MORE, AT LEAST ON A PERIODIC BASIS (NOT HAPPENING OFTEN, JUST
SLIGHTLY MORE THAN USUAL), ESPECIALLY FOR THE LATTER HALF OF NEXT
WEEK.
MAINLY LIGHT TO GENTLE WINDS WILL PERSIST FOR MARINERS, BUT THEY
COULD BECOME MODERATE AT TIMES, ESPECIALLY NEXT WEEK. SEAS OF 4 TO 6
FEET MAY INCREASE A FOOT BY THE MIDDLE OF NEXT WEEK FOR KOSRAE AND/OR
MAJURO.
WESTERN MICRONESIA...
THE MAIN FEATURE IN THE REGIONS IS A BROAD SURFACE TROUGH THAT WAS
FORMERLY PART OF THE NEAR EQUATORIAL TROUGH. IT ENTERS THE REGION
NEAR 8N130E AND EXTENDS EAST THROUGH YAP PROPER AND CONTINUES EAST-
NORTHEAST AS IT EXIT THE REGION NEAR 10N141E. THIS TROUGH HAS MOVE
FURTHER NORTH THAN WAS EXPECTED SINCE THE PREVIOUS DISCUSSION. THIS
FEATURE IS NOW SLOWLY MOVING IN A SOUTHEASTERLY DIRECTION.
FOR YAP AND PALAU, THE BROAD SURFACE TROUGH IS EXPECTED TO BRING
SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TO BOTH LOCATIONS,
ALBEIT THESE SHOWERS MAY BE DELAYED AT PALAU. THIS TROUGH IS
ANTICIPATED TO REMAIN OVER THIS PORTION OF THE REGIONS THROUGH ABOUT
TUESDAY. MODELS SUGGEST THAT THE TROUGH WILL MOVE INTO OPEN WATERS TO
SOUTHEAST OF THESE ISLANDS AROUND THE MIDDLE OF NEXT WEEK. FOR THE
LATTER HALF OF NEXT WEEK MODELS SUGGEST A SOMEWHAT DRY PATTERN REGIME
MAY SET UP.
FOR CHUUK, THIS REGION REMAINS IN A COL. THIS MEANS MORE BENIGN
WEATHER IS EXPECTED FOR WENO. THIS COL IS ANTICIPATED TO LINGER OVER
CHUUK FOR THE NEXT SEVERAL DAYS. MODEL GUIDANCE SUGGESTS AROUND THE
MIDDLE OF NEXT WEEK SHOWERS FROM EASTERN MICRONESIA ARE ANTICIPATED
TO MOVE INTO THE REGION. HOWEVER, THIS WILL ALL DEPEND ON WHAT AND
WHERE INVEST 99W AND ITS ASSOCIATED TROUGHS MOVE TO.
MARINE CONDITIONS ARE FAIRLY BENIGN. ALTIMETRY SHOWS COMBINED SEAS OF
3 TO 5 FEET. WINDS ARE EXPECTED TO LIGHT TO MODERATE, WITH YAP SEEING
SLIGHTLY HIGHER WINDS TONIGHT AT GENTLE TO FRESH. THESE ELEVATED
WINDS AT YAP ARE DUE THE SHOWERS NEAR BY.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA/TROPICAL UPDATE: STANKO
MARIANAS: SCHANK
TROPICAL: KLEESCHULTE
EAST MICRONESIA/TROPICAL: DOLL
WEST MICRONESIA: BOWSHER
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