409
FXPQ50 PGUM 221151 AAA
AFDGUM
AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
951 PM CHST MON JUN 22 2026
UPDATED TO RAISE THE LIKELIHOOD OF FORMATION TO HIGH FOR 94W AND
REFERENCE THE TCFA FOR FURTHER INFORMATION.
TROPICAL SYSTEMS UPDATE
AS OF 9 PM CHST, INVEST 94W WAS STILL CENTERED NEAR 14.5N 147.7E, OR
ROUGHLY 150 MILES EAST-SOUTHEAST OF SAIPAN. MAXIMUM SUSTAINED WINDS
HAVE INCREASED SLIGHTLY TO BETWEEN 20 AND 25 MPH, SO THE JOINT
TYPHOON WARNING CENTER HAS UPGRADED IT TO HIGH, MEANING DEVELOPMENT
INTO A SIGNIFICANT TROPICAL CYCLONE IS NOW EXPECTED WITHIN THE NEXT
24 HOURS. FOR MORE INFORMATION ON INVEST 94W, PLEASE REFER TO THE
TROPICAL CYCLONE FORMATION ALERT ISSUED BY THE JOINT TYPHOON WARNING
CENTER UNDER WMO HEADER WTPN21 PGTW.
PREV DISCUSSION
/ISSUED 632 PM CHST MON JUN 22 2026/
MARIANAS SYNOPSIS...
VISIBLE SATELLITE IMAGERY SHOWS HEAVY SHOWERS AND ISOLATED
THUNDERSTORMS ASSOCIATED WITH INVEST 94W FILLING IN OVER TINIAN AND
SAIPAN, AS WELL AS A LINE OF CONVECTION OVER ROTA STRATIFYING OUT AS
IT MOVES WEST. BUOY DATA SUPPORTS COMBINED SEAS OF 3 TO 5 FT ACROSS
THE REGION.
DISCUSSION...
A SLOWLY-DEVELOPING TROPICAL DISTURBANCE KNOWN AS INVEST 94W WILL BE
THE PRIMARY WEATHER MAKER FOR THE MARIANAS THROUGH TUESDAY NIGHT.
MODEL GUIDANCE FAVORS A TRACK PASSING NEAR OR N OF SAIPAN, SO
RAINFALL AND CONVECTIVELY-DRIVEN GUSTS ARE EXPECTED TO BE STRONGEST
OVER TINIAN AND SAIPAN, PEAKING ON TUESDAY. ROTA AND GUAM WILL STILL
SEE SCATTERED SHOWERS, ISOLATED THUNDERSTORMS, AND MODERATELY-
SUSTAINED WINDS WITH STRONGER GUSTS NEAR HEAVIER SHOWERS. ONCE 94W
EMERGES W OF THE MARIANAS, TRAILING CONVERGENCE WILL KEEP THE REGION
IN A WET PATTERN DURING THE LATTER HALF OF THE WEEK.
MARINE...
BUOY DATA INDICATES COMBINED SEAS OF 3 TO 5 FT. INVEST 94W WILL
ELEVATE THE PRIMARY EAST SWELL BY AT LEAST A FOOT AND INDUCE HIGHER
WIND WAVES, SO TINIAN AND SAIPAN CAN EXPECT COMBINED SEAS OF 5 TO 6
FT ON TUESDAY BEFORE DROPPING BACK DOWN TO 4 TO 5 FT. THE SECONDARY
SOUTHWEST SWELL WILL SHIFT MORE OUT OF THE WEST STARTING TUESDAY
NIGHT. THERE IS A MODERATE RISK OF RIP CURRENTS ALONG EAST-FACING
REEFS AND A MODERATE RISK OF LIGHTNING FOR ALL ISLANDS.
TROPICAL SYSTEMS...
AS OF 4 PM CHST, INVEST 94W WAS CENTERED NEAR 14.5N 147.7E, OR
ROUGHLY 120 NM ESE OF SAIPAN, WITH WINDS AROUND 18 TO 23 MPH NEAR THE
CENTER. THE JOINT TYPHOON WARNING CENTER (JTWC) HAVE UPGRADED INVEST
94W'S RATING TO MEDIUM, MEANING DEVELOPMENT INTO A SIGNIFICANT
TROPICAL CYCLONE (A TROPICAL DEPRESSION) IS LIKELY, BUT EXPECTED TO
OCCUR BEYOND 24 HOURS. HIMAWARI VISIBLE SATELLITE IMAGERY DEPICTS A
DISORGANIZED AREA OF SHOWERS AND THUNDERSTORMS JUST EAST OF THE
MARIANAS, WITH NEW CONVECTIVE CELLS DEVELOPING MAINLY SOUTHEAST TO
EAST OF 94W'S CENTER. AN OUTFLOW BOUNDARY MOVING AHEAD OF 94W
BROUGHT HEAVY SHOWERS AND THUNDERSTORMS ACROSS ROTA AND TINIAN WATERS
EARLIER TODAY. WHILE THERE IS STILL UNCERTAINTY IN THE EXACT TRACK OF
INVEST 94W, MOST MODEL TRENDS SUPPORT THE CENTER PASSING NEAR OR
NORTH OF SAIPAN ON TUESDAY, MOST LIKELY AS A DEVELOPING TROPICAL
DISTURBANCE, OR AS A TROPICAL DEPRESSION IF IT DEVELOPS FASTER THAN
EXPECTED. A PASSAGE NEAR SAIPAN WOULD SUPPORT NUMEROUS LOCALLY HEAVY
SHOWERS, ISOLATED THUNDERSTORMS, AND GUSTY WINDS TUESDAY, WITH
CONDITIONS TAPERING TUESDAY NIGHT. AFTER INVEST 94W MOVES NORTHWEST
OF THE MARIANAS, IT LOOKS TO MAKE A GRADUAL CURVE TO THE NORTH
WEDNESDAY AND THURSDAY, EXITING THE REGION NORTH OF 25N TOWARD THE
END OF THE WEEK.
FOR MORE INFORMATION ON INVEST 94W, PLEASE REFER TO BULLETINS FROM
THE JOINT TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10 PGTW. FOR
MORE DETAILS ON IMPACTS TO THE MARIANAS, REFER TO THE SPECIAL
WEATHER STATEMENT FROM THE NATIONAL WEATHER SERVICE IN TIYAN, GUAM.
EASTERN MICRONESIA...
WE HAD A SURPRISE BLOSSOMING OF CONVECTION OVER THE LAST 24 HOURS
THAT IMPACTED POHNPEI, KOSRAE, AND AREAS IN BETWEEN. THERE WAS THAT
SUBTLE SURFACE TROUGH THERE THAT WE TALKED ABOUT YESTERDAY, AND
APPARENTLY THAT WAS ALL THAT IT TOOK. THIS HAS LED TO A CLOUDY,
COOLER, OVERCAST DAY AT POHNPEI WHERE TEMPERATURES STRUGGLED TO GET
OUT OF THE LOWER 80S. KOSRAE DID BREAK OUT INTO THE SUN AND WARMED
INTO THE MID 80S (86 AS OF THE LAST OBSERVATION). THAT TROUGH FROM
LAST NIGHT HAS DISSIPATED, WITH A COL CURRENTLY LOCATED JUST NORTH OF
THE POHNPEI TO KOSRAE AREA. THUS, A REPEAT PERFORMANCE IS UNLIKELY
TONIGHT. STILL, REMNANT OUTFLOW BOUNDARIES, OROGRAPHICS, AND THE
NOCTURNAL BOOST ARGUED FOR KEEPING "LOWER-END" SCATTERED SHOWERS IN
THE FORECAST FOR TONIGHT AND THE NEXT FEW DAYS. AT MAJURO, VISIBLE
IMAGERY AND MODEL FORECASTS SUGGEST JUST ISOLATED SHOWERS ARE ALL
THAT YOU CAN HOPE FOR THROUGH TUESDAY NIGHT.
THEN, FOR THE LATTER HALF OF THE WEEK, A ROBUST SURGE OF MOISTURE
(CURRENTLY SEEN SOUTH OF HAWAII) WILL MOVE INTO THE REGION,
SPREADING FROM EAST TO WEST WITH TIME. EMBEDDED IN THE FLOW WILL
POSSIBLY BE SOME DISTURBANCES TO HELP FOCUS CONVECTION. IN FACT, THE
GEFS, ECENS, AND GOOGLE DEEPMIND SUGGEST A TROPICAL DISTURBANCE WILL
EITHER FORM BEFORE CROSSING THE DATE LINE, OR FORM SOON AFTER
CROSSING IT. KEEP IN MIND THIS IS VERY FAR OUT/AT THE END OF THE
FORECAST PACKAGE. HOWEVER, THIS HAS BEEN IN EVERY MODEL RUN THE PAST
SEVERAL DAYS. AS SUCH, THERE'S A GOOD CHANCE THAT MUCH WETTER
CONDITIONS WILL ENCOMPASS ALL OF EASTERN MICRONESIA AND A VAST
MAJORITY OF THE RMI, WITH IT BEING WAY TOO EARLY TO GET SPECIFIC ON
DETAILS. THUS, WE OPTED TO JUST GIVE A REASON FOR THE "HIGHER-THAN-
AVERAGE" CONFIDENCE IN THIS OCCURRING. AS SUCH, LIKELY WORDING WAS
USED FOR THURSDAY AND FRIDAY AT MAJURO. THIS COULD EXTEND INTO THE
WEEKEND, DEPENDENT ON HOW THE SYNOPTIC PATTERN UNFOLDS.
SEAS WILL GENERALLY BE LIGHT TO GENTLE AREA-WIDE, BUT THEY COULD
BECOME GENTLE TO MODERATE TOWARDS THE END OF THE WEEK AT MAJURO. SEAS
WILL REMAIN IN THE 3 TO 5 FOOT RANGE.
WESTERN MICRONESIA...
AN UNSETTLED, DISORGANIZED PATTERN WILL CONTINUE. LATEST SATELLITE
IMAGERY SHOWS SWATHS OF MID TO UPPER-LEVEL CLOUDS ACROSS MUCH OF FAR
WESTERN MICRONESIA, INCLUDING OVER PALAU AND YAP PROPER, LEFT OVER
FROM SCATTERED THUNDERSTORMS THAT DEVELOPED THIS MORNING WITHIN THE
SOUTHWEST MONSOON FLOW. NOW, ONLY CLOUDY SKIES AND ISOLATED TO
SCATTERED SHOWERS REMAIN, AND MODEL AND SATELLITE TRENDS FAVOR DRIER
CONDITIONS DEVELOPING TONIGHT AS A BROAD RIDGE DOMINATES THE WEATHER
PATTERN. SHOWERS REDEVELOP NEAR YAP ON TUESDAY AS CONVERGENCE
INCREASES NEARBY, ASSOCIATED IN PART WITH THE MOVEMENT AND
DEVELOPMENT OF INVEST 94W TO THE NORTHEAST. THE BROADER RIDGE WILL
DIMINISH AND SHIFT WESTWARD FROM AROUND WEDNESDAY ONWARD, ALLOWING AN
UNSETTLED PATTERN TO RESUME ACROSS WESTERN MICRONESIA WITHIN A BROAD
MONSOON-LIKE TROUGH THAT LOOKS TO REBUILD ACROSS THE REGION. PERIODS
OF SCATTERED SHOWERS ARE EXPECTED FOR PALAU AND YAP, MAINLY IN THE
LATTER HALF OF THE WEEK. TO THE EAST, CHUUK WILL CONTINUE TO SEE
PERIODS OF SCATTERED SHOWERS THROUGHOUT THE FORECAST PERIOD,
ASSOCIATED WITH CONVERGENCE AND WEAK DISTURBANCES ALONG THE BROAD
FORMER MONSOON-LIKE TROUGH WHICH IS SEEN JUST NORTH OF WENO.
BENIGN SEA CONDITIONS CONTINUE ACROSS THE REGION. LATEST ALTIMETRY
AND YAP BUOY DATA SHOW COMBINED SEAS BETWEEN 3 AND 5 FEET ACROSS THE
REGION, WITH A PRIMARY SOUTHWEST TO WEST SWELL FOR PALAU AND YAP, AND
A SOUTHEAST TO EAST SWELL FOR CHUUK, WITH A LIGHT SECONDARY SWELL OUT
OF THE NORTHEAST.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
TROPICAL UPDATE: STANKO
MARIANAS: MESA
EAST MICRONESIA: DOLL
WEST MICRONESIA: DECOU
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