316
FXPQ50 PGUM 031959
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
559 AM CHST MON MAY 4 2026
MARIANAS UPDATE
THE MAIN UPDATE TO THE FORECAST WAS TO ADD SCATTERED SHOWERS TO THE
FORECAST FOR GUAM AND ROTA, WITH RAINFALL PROBABILITIES AT 40
PERCENT. BOTH OF THESE VALUES (COVERAGE AND PROBABILITIES) MAY NEED
TO BE INCREASED AND POSSIBLY EXPANDED NORTHWARD SOME, AS INVESTS 92W
AND 93W HAVE FORMED SOUTHWEST AND SOUTHEAST OF GUAM, WITH MORE
INFORMATION ON THAT IN THE TROPICAL SECTION BELOW.
EASTERN MICRONESIA UPDATE
THE MAIN FORECAST UPDATE WAS TO LOWER RAINFALL POTENTIAL SLIGHTLY AT
POHNPEI AND MAJURO, BASED ON SATELLITE IMAGERY. OTHERWISE, THE GOING
FORECAST REMAINS IN GOOD SHAPE.
WESTERN MICRONESIA UPDATE
INVESTS 92W AND 93W HAVE FORMED IN WESTERN MICRONESIA, WITH
INCREASING RAINFALL A DISTINCT POSSIBILITY FOR ALL THREE LOCATIONS.
TO START, WE INSERTED 30 PERCENT PROBABILITIES/SCATTERED SHOWER
COVERAGE AT PALAU FOR TODAY, WHILE MAINTAINING 40 PERCENT SCATTERED
SHOWER COVERAGE FOR TONIGHT. AT YAP, SCATTERED SHOWERS WITH 50
PERCENT PROBABILITIES WERE MAINTAINED FOR TODAY AND TONIGHT. FOR
CHUUK, WE INCREASED SHOWER COVERAGE TO NUMEROUS (70 PERCENT
PROBABILITIES FOR TODAY AND WIDESPREAD SHOWERS (80 PERCENT
PROBABILITIES) FOR TONIGHT, WHILE ALSO ADDING IN LOCALLY HEAVY
RAINFALL WORDING WITH ISOLATED GUSTS TO 25 KT ALSO MENTIONED.
TROPICAL UPDATE
INVESTS 92W AND 93W HAVE FORMED (BOTH ARE CURRENTLY RATED "SUB-LOW",
MEANING DEVELOPMENT OF A TROPICAL CYCLONE DURING THE NEXT 24 HOURS IS
NOT EXPECTED. INVEST 92W IS LOCATED SOUTHEAST OF YAP NEAR 7.9N
140.5E, AND 93W LOCATED JUST NORTHEAST OF CHUUK AT 8.5N 152.3E. OF
THIS PAIR 93W SHOWS THE MOST POTENTIAL TO ORGANIZE WITH MODELS NOW
SHOWING A TROPICAL DEPRESSION OR TROPICAL STORM POTENTIALLY (NOT
SAYING IT WILL...JUST POTENTIALLY) FORMING OVER THE NEXT 2 TO 3 DAYS
OR SO AS IT HEADS WEST. AT THIS TIME THE EFFECTS ON THIS SYSTEM WILL
IMPACT CHUUK AND YAP WITH AT LEAST LOCALLY HEAVY RAINFALL AND STRONG
WIND GUSTS TO 25 OR 30 KNOTS ON AN ISOLATED BASIS. THE RAINFALL AND
WIND POTENTIAL ABOVE THESE THRESHOLDS REMAINS UNCERTAIN AS THE SYSTEM
IS STILL FORMING AND THE MODELS HAVE STRUGGLED WITH WHAT WILL PLAY
OUT FOR THE BETTER PART OF A WEEK NOW. WITH THAT SAID, PALAU SHOULD
SEE INCREASING RAINFALL POTENTIAL WITH TIME. FOR THE MARIANAS, GUAM
AND ROTA WILL SEE SCATTERED SHOWERS THROUGH TONIGHT, POSSIBLY LONGER,
BUT AT THIS TIME, ANY WIND CONCERNS LOOK TO REMAIN SOUTH OF THE
REGION.
PREV DISCUSSION
/ISSUED 557 PM CHST SUN MAY 3 2026/
MARIANAS SYNOPSIS...
SATELLITE IMAGERY SHOWS A MOSTLY SUNNY DAY, AND RADAR IMAGERY SHOWS
LIGHT ISOLATED SHOWERS OVER THE MARIANAS. ALTIMETRY SHOWS COMBINED
SEAS OF 6 TO 7 FEET.
DISCUSSION...
A DRY PATTERN REGIME HAS SET UP OVER THE MARIANAS. THE MAIN CONCERN
WILL BE ELEVATED WINDS. WINDS ARE EXPECTED TO BUILD UP TO 25 MPH AS
EARLY AS TUESDAY. LATEST MODEL GUIDANCE SUGGESTS THESE WINDS WILL
REMAIN ELEVATED THROUGH THE MIDDLE OF NEXT WEEK.
MARINE...
TRADE WINDS WILL REMAIN MODERATE TO FRESH THROUGH THE BEGINNING OF
NEXT WEEK. THEN MAY BUILD TO MODERATE TO STRONG NEAR THE MIDDLE OF
NEXT WEEK. COMBINED SEAS OF 5 TO 7 FEET WILL BUILD TO 6 TO 8 FEET
FOR NEXT FEW DAYS. A FAIRLY DRY PATTERN IS EXPECTED FOR MOST OF
THE FORECAST PERIOD. HOWEVER, A PASSING TROUGH TO SOUTH OF THE
MARIANAS COULD INCREASE TRADES, SEAS, AND SHOWER POTENTIAL FOR THE
LATTER HALF OF THE WEEK.
EASTERN MICRONESIA...
LATEST SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES AND ISOLATED
SHOWERS NEAR POHNPEI, WITH MOSTLY CLOUDY SKIES WITH SCATTERED
SHOWERS FOR KOSRAE AND MAJURO. ISOLATED THUNDERSTORMS ARE ALSO SEEN
OVER KOSRAE. ALTIMETRY SHOWS SEAS OF 2 TO 4 FEET AT KOSRAE AND
POHNPEI, WITH HIGHER SEAS MOVING IN FROM THE EAST. SEAS OF 5 TO 7
FEET ARE SEEN AT MAJURO.
THE INTER-TROPICAL CONVERGENCE ZONE (ITCZ) IS NO LONGER SEEN ACROSS
THE MARSHALLS AS THE REMNANTS OF THE ITCZ HAVE MERGED WITH THE NEAR-
EQUATORIAL TROUGH (NET). THE NET NOW STRETCHES ACROSS EASTERN
MICRONESIA FROM CHUUK STATE, TO JUST NORTH OF POHNPEI AND KOSRAE. THE
NET THEN PASSES JUST SOUTH OF MAJURO, WHERE IT TURNS SOUTHEAST TO
BEYOND THE DATE LINE. MODEL GUIDANCE HAS BEEN STRUGGLING WITH
CONVECTION ASSOCIATED WITH THE NET FOR THE LAST FEW DAYS, RESULTING
IN OVER-FORECASTING POPS (PROBABILITY OF PRECIPITATION) OVER THE LAST
FEW FORECASTS. BASED ON THE UNCERTAINTY WITH THE NET, DECIDED TO KEEP
POPS AT AROUND 50 PERCENT, DOWN A BIT FROM 60 TO 80 PERCENT POPS FROM
THE LAST FEW DAYS. IF THE NET AND ANY OF THE MIGRATORY CIRCULATIONS
BECOME MORE ORGANIZED OVER THE NEXT FEW DAYS, THIS COULD CHANGE AND
RESULT IN GREATER CONFIDENCE IN HIGHER POPS. EVEN WITH THE
UNCERTAINTY, LOCALLY HEAVY RAINFALL AND STRONG GUSTS REMAIN A
POSSIBILITY.
FOR THE MARINE FORECAST, A TRADE-WIND SURGE SEEN NORTH OF 9N AND
EXTENDING EAST OF THE DATE LINE LOOKS TO BRING INCREASED TRADE SWELL
INTO THE REGION DURING THE WEEK. AS OF NOW, SEAS LOOK TO REACH UP TO
9 FEET FOR MAJURO AND POHNPEI AND UP TO 8 FEET FOR KOSRAE. ALTIMETRY
CURRENTLY SHOWS SEAS TO AROUND 9 FEET, SO SMALL CRAFT ADVISORY LEVEL
SEAS ARE NOT EXPECTED AT THIS TIME. WHAT COULD HAPPEN IS FOR THE
NORTHEAST SWELL TO BUILD HIGH ENOUGH AROUND MONDAY NIGHT OR TUESDAY
TO PRODUCE HAZARDOUS SURF ALONG NORTH FACING REEFS OF POHNPEI AND
NORTH AND EAST FACING REEFS OF KOSRAE. THIS WILL BE EVALUATED MORE
OVERNIGHT AND MONDAY FOR A POSSIBLE HIGH SURF ADVISORY. ALONG WITH
THE SEAS, MODERATE TO FRESH TRADES ARE EXPECTED AT MAJURO FOR THE
NEXT COUPLE OF DAYS, BECOMING GENTLE TO MODERATE TUESDAY EVENING.
MOSTLY LIGHT TO GENTLE, WITH OCCASIONAL MODERATE, WINDS ARE EXPECTED
FOR POHNPEI AND KOSRAE.
WESTERN MICRONESIA...
THE NET ENTERS WESTERN MICRONESIA NEAR 5N130E AND EXTENDS TO THE
EAST-NORTHEAST ACROSS YAP, THEN TURNS TO THE EAST-SOUTHEAST AND
INTERSECTS A WEAK CIRCULATION SOUTHEAST OF YAP, THEN CONTINUES TO
THE EAST-SOUTHEAST AND INSECTS AN ADDITIONAL WEAK CIRCULATION JUST
SOUTH OF CHUUK. NUMEROUS TO WIDESPREAD LOCALLY HEAVY SHOWERS AND
ISOLATED THUNDERSTORMS ARE FOUND ACROSS PORTIONS OF YAP AND CHUUK
STATES ALONG AN AREA OF CONVERGENCE IN THE VICINITY OF THE NET. A
TRADE-WIND TROUGH IS LOCATED AROUND CHUUK AND WILL CONTINUE TO HELP
ENHANCE SHOWER AND THUNDERSTORM CHANCES AS THIS FEATURE MOVES
WESTWARD. SCATTERED TO NUMEROUS LOCALLY HEAVY SHOWERS AND ISOLATED
THUNDERSTORMS ARE EXPECTED TONIGHT ACROSS CHUUK AND YAP WHILE SHOWER
AND THUNDERSTORM CHANCES REMAIN ISOLATED AT PALAU. STRONG WINDS GUSTS
WILL ALSO BE POSSIBLE WITH ANY HEAVY SHOWERS AND THUNDERSTORMS.
THESE CONDITIONS WILL CONTINUE AS WE HEAD INTO THIS WEEK AS THE
AFOREMENTIONED WEAK CIRCULATIONS AND TRADE-WIND TROUGH PROPAGATE
WESTWARD. THOUGH, NUMEROUS SHOWER CHANCES WILL LIKELY DROP TO HIGH-
END SCATTERED AT BOTH CHUUK AND YAP STARTING ON MONDAY.
MODERATE WINDS WILL PERSIST AT YAP THROUGH MONDAY WITH MOSTLY LIGHT
TO GENTLE WINDS EXPECTED AT BOTH PALAU AND CHUUK THROUGH EARLY THIS
WEEK. OCCASIONAL STRONG GUSTS WILL BE POSSIBLE NEAR CHUUK AND YAP
THROUGH TONIGHT. LATEST ALTIMETRY FROM LATE THIS MORNING (AROUND
0130Z) SHOWS COMBINED SEAS AROUND 4 FEET AT CHUUK. SEAS OF 3 TO 6
FEET AT BOTH YAP AND PALAU WILL INCREASE A FOOT OR SO OVERNIGHT WHILE
SEAS BUILD 2 TO 3 FEET AT CHUUK EARLY THIS WEEK AS A ANOTHER
NORTHEAST SWELL MOVES THROUGH THE WATERS.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS/EAST AND WEST MICRONESIA UPDATE: DOLL
MARIANAS: BOWSHER
EAST MICRONESIA: KLEESCHULTE
WEST MICRONESIA: WHISNANT
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