197
FXPQ50 PGUM 062113
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
713 AM CHST SAT MAR 7 2026
MARIANAS UPDATE
FLARING, DEEP CONVECTION ALONG THE NORTHERN PERIPHERY OF A TROPICAL
DISTURBANCE, INVEST 95W, IS BEGINNING TO BUILD ACROSS GUAM THIS
MORNING. THE BULK OF SHOWERS ARE STILL SOUTHEAST OF THE ISLANDS, SO
HAVE DELAYED THE ONSET OF WIDESPREAD LOCALLY HEAVY SHOWERS TO LATE
MORNING FOR GUAM AND ROTA AND TO DEVELOPING AROUND NOON FOR TINIAN
AND SAIPAN. THE OTHER MINOR UPDATE WAS TO INCLUDE CONVECTIVE GUSTS,
OCCASIONALLY STRONG TO NEAR-GALE FORCE ARE POSSIBLE TODAY, BUT
REMAIN A POSSIBILITY THROUGH THE WEEKEND. TONIGHT AND SUNDAY, WIND
SPEEDS AND DIRECTION VARY AMONGST MODEL GUIDANCE DUE TO AN ELONGATED
CENTER AND TROUGHING FROM INVEST 95W, SO A BRIEF WEAKENING OF WINDS
OR CHANGE IN WIND DIRECTION IS POSSIBLE. NONETHELESS, AN UNSETTLED
PATTERN REMAINS ACROSS THE REGION OVERALL. A SMALL CRAFT ADVISORY,
A HIGH SURF ADVISORY, A HIGH RISK OF RIP CURRENTS, AND A FLOOD WATCH
REMAIN IN EFFECT. SEE PREVIOUS FORECAST DISCUSSION FOR MORE DETAILS.
TROPICAL SYSTEMS UPDATE
INVEST 95W REMAINS A VERY BROAD, WEAK DISTURBANCE, LOCATED OVER YAP
STATE NEAR 7.4N 140.4E, ROUGHLY 250 MILES SOUTHEAST OF YAP PROPER.
INVEST 95W IS RATED "LOW" FOR DEVELOPMENT, MEANING DEVELOPMENT INTO A
SIGNIFICANT TROPICAL CYCLONE (TROPICAL DEPRESSION) IS POSSIBLE OVER
THE NEXT FEW DAYS BUT NOT EXPECTED WITHIN THE NEXT 24 HOURS. MODERATE
TO DEEP CONVECTION AROUND INVEST 95W IS SEEN OVER 700 MILES OUTWARD
FROM THE CENTER, WITH THE HEAVIEST SHOWERS AND THUNDERSTORMS
CONSOLIDATED ALONG 95W'S NORTHEAST AND EASTERN FLANKS, AND FOCUSED
ALONG A BROAD TRADE-WIND TROUGH THAT EXTENDS SOUTHWEST INTO IT JUST
EAST OF GUAM. MODEL GUIDANCE MAINTAINS A GENERAL NORTHWEST TRACK
THROUGH TODAY, SHIFTING NORTH TO NORTH-NORTHEAST LATE TONIGHT,
ELONGATING NORTHEAST ACROSS THE MARIANAS AS IT BEGINS TO INTERACT
WITH A SHEAR LINE EXTENDING ACROSS THE NORTHERN CNMI. THIS WILL BRING
PERIODS OF HEAVY RAINFALL, BREEZY WINDS, CHOPPY SEAS, AND STRONGER
GUSTS ACROSS THE MARIANAS, ESPECIALLY IN HEAVIER SHOWERS AND
THUNDERSTORMS. THE BULK OF THE RAINFALL LOOKS TO FALL LATE TONIGHT
THROUGH SUNDAY, WITH MODEL CONSENSUS SHIFTING MORE OF THE HEAVY
SHOWERS TOWARD SAIPAN AND TINIAN AROUND EARLY SUNDAY MORNING AS THE
CENTER SHIFTS OR RECONSOLIDATES NEARBY. THE LONGEVITY OF HEAVY
SHOWERS ACROSS THE MARIANAS IS DIFFICULT TO FORECAST BEYOND SUNDAY,
DEPENDENT ON COMPLEX INTERACTION BETWEEN INVEST 95W AND THE SHEAR
LINE, AND THE MOVEMENT OF BOTH FEATURES. SOME MODELS DEPICT 95W
STALLING NEARBY TO THE WEST INTO MIDWEEK, KEEPING HEAVY SHOWERS AND
THUNDERSTORMS AROUND LONGER, WHILE OTHERS SHOW THE TWO FEATURES
SHIFTING EAST OF THE MARIANAS BY WEDNESDAY.
FOR MORE INFORMATION ON INVEST 95W, PLEASE SEE THE BULLETIN ISSUED
BY THE JOINT TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10 PGTW.
EASTERN MICRONESIA UPDATE
SATELLITE EARLY THIS MORNING DEPICTS CLUSTERS OF MODERATE TO DEEP
CONVECTION PROPAGATING WESTWARD THROUGH THE REGION, WITH THE HEAVIEST
SHOWERS BUILDING ALONG A TRADE-WIND TROUGH JUST WEST OF POHNPEI.
SHOWERS CONTINUE TO BUILD WITHIN THE CONVERGENT FLOW ALONG THE
BACKSIDE OF THIS TROUGH, AND PROBABILITY OF PRECIPITATION (POP) WAS
INCREASED TO 50 PERCENT FOR POHNPEI, AND 40 PERCENT FOR KOSRAE. A
SHALLOW TRADE-WIND TROUGH IS ALSO SEEN MOVING WEST THROUGH THE
SOUTHERN MARSHALL ISLANDS TO THE SOUTH OF MAJURO. PATCHY CONVECTION
IS ROUGHLY FOCUSED ABOUT THE TROUGH AND LOOKS TO MAINLY STAY SOUTH OF
MAJURO TODAY, BUT WITH ENOUGH SHOWERS ALONG THE PERIPHERY THAT
SHOWER CHANCES FOR MAJURO WERE LEFT AT 30 PERCENT (SCATTERED) FOR
TODAY. SHOWERS WILL INCREASE THERE AS A BROADER INTERTROPICAL
CONVERGENCE ZONE (ITCZ)-LIKE DISTURBANCE BUILDS ACROSS THE MARSHALLS
LATE TONIGHT. POHNPEI AND KOSRAE LOOK TO STAY ON THE WETTER SIDE
OVERNIGHT AS ADDITIONAL WEAK TROUGHS SHIFT WEST THROUGH THE AREA,
PROPAGATING ALONG THE BROAD ITCZ-LIKE TROUGH.
RECENT BUOY AND ALTIMETRY DATA SHOWS COMBINED SEAS AROUND 5 TO 7 FEET
ACROSS THE REGION, COMPRISED OF A PRIMARY LONGER-PERIOD NORTH SWELL
AND A SECONDARY EAST SWELL. A STRONGER PULSE OF NORTH SWELL WILL MOVE
INTO THE REGION AROUND SUNDAY NIGHT, WHICH MAY PRODUCE HAZARDOUS SURF
ALONG NORTH FACING REEFS OF POHNPEI AND KOSRAE THROUGH AT LEAST
MONDAY.
WESTERN MICRONESIA UPDATE
A BROAD TROPICAL DISTURBANCE, INVEST 95W, CONTINUES TO BRING
UNSETTLED WEATHER ACROSS MUCH OF YAP STATE AND WESTERN CHUUK STATE.
A BROAD AREA OF CONVECTION, ALONG CONVERGENT SOUTH TO SOUTHEASTERLY
FLOW, REMAINS WEST OF CHUUK LAGOON THIS MORNING, HOWEVER, CONTINUE TO
EXPECT SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS TODAY DUE TO THE
NEARBY CONVERGENCE. THE MAIN UPDATE WAS TO INCREASE SHOWERS TO
NUMEROUS LOCALLY HEAVY FOR YAP BASED ON THE RAPID BUILD UP OF SHOWERS
FROM THE EAST, ASSOCIATED WITH 95W. ELEVATED NORTH TO NORTHEAST
SWELLS ARE EXPECTED TO BRING HAZARDOUS SURF ALONG NORTH-FACING REEFS
OF YAP TODAY AND POTENTIALLY TO CHUUK STARTING SUNDAY NIGHT. AT THIS
TIME, A HIGH SURF ADVISORY IS IN EFFECT FOR YAP THROUGH EARLY MONDAY
MORNING.
PREV DISCUSSION
/ISSUED 622 PM CHST FRI MAR 6 2026/
MARIANAS SYNOPSIS...
SATELLITE AND RADAR IMAGERY SHOW SCATTERED SHOWERS DEVELOPING ACROSS
GUAM AND ROTA WITH NUMEROUS SHOWERS SEEN JUST OUTSIDE THE COASTAL
WATERS. ALTIMETRY FROM THIS MORNING SHOWS COMBINED SEAS WERE 7 TO 9
FEET WITH SEAS LIKELY REACHING 10 FEET AT THIS TIME.
DISCUSSION...
KEY MESSAGES:
* SHOWERS WILL SLOWLY BUILD THROUGH THE EVENING WITH COVERAGE AND
INTENSITY INCREASING THROUGH THE NIGHT.
* GUIDANCE CONTINUES TO SHOW THE POTENTIAL FOR TORRENTIAL RAINS AT
TIMES THIS WEEKEND. HIGHER RAINFALL RATES WOULD LEAD TO FLASH
FLOODING AND COULD LEAD TO MUDSLIDE CONCERNS.
* ALTHOUGH INVEST 95W IS EXPECTED TO REMAIN WEAK. THE TROPICAL
DISTURBANCE WILL BRING ADDITIONAL IMPACTS OF GUSTY WINDS AND
CHOPPY SEAS.
OVERALL, THERE WAS LITTLE CHANGE IN THE FORECAST PACKAGE. INVEST 95W,
ALTHOUGH STILL DISORGANIZED, HAS BEGUN TO INCREASE IN CONVECTION AND
HAS SHOWN GOOD IMPROVEMENT SINCE YESTERDAY. SHOWERS AND
THUNDERSTORMS ARE RIGHT ON THE DOORSTEP OF GUAM AND ROTA'S COASTAL
WATERS AND ARE EXPECTED TO MOVE IN AS WE PROGRESS THROUGH THE NIGHT.
WIDESPREAD SHOWERS AND ISOLATED THUNDERSTORMS ARE EXPECTED THIS
WEEKEND ACROSS THE MARIANAS, HEAVY RAINFALL MAY LEAD TO FLASH
FLOODING. IF ENOUGH RAIN FALLS DURING THE ONSET OF THIS EVENT, THEN A
RISK FOR MUDSLIDES WILL ALSO BE POSSIBLE. GUIDANCE IS SPLIT ON JUST
HOW FAST THIS FEATURE MOVES THROUGH OUR REGION, BUT THERE IS SOME
POTENTIAL FOR THE TROPICAL DISTURBANCE TO STALL NEAR THE MARIANAS.
THE CURRENT FORECAST HAS A SLOW PROGRESSION AT THIS TIME, BUT
ADJUSTMENTS IN RAINFALL TOTALS AND IMPACTS MAY BE MADE OVER TIME.
MARINE...
MARINE CONDITIONS HAZARDOUS TO SMALL CRAFT ARE CURRENTLY IMPACTING
THE MARIANAS. A LONG-PERIOD NORTH SWELL HAS CONTINUED TO BUILD INTO
THE REGION. THIS SWELL IS BEING RE-INFORCED BY A SHEAR LINE TO THE
NORTH. SEAS LOOK TO REMAIN AT OR ABOVE THE 10 FOOT THRESHOLD UNTIL AT
LEAST SUNDAY AFTERNOON. THERE MAY BE A BRIEF DECREASE IN SEAS SUNDAY
NIGHT, BUT GUIDANCE SHOWS A LARGER SWELL EVENT MOVING INTO THE
REGION ON MONDAY. SURF WILL REMAIN HAZARDOUS ALONG NORTH FACING REEFS
THROUGH MONDAY WITH A HIGH RISK FOR RIP CURRENTS ALONG EAST FACING
REEFS THROUGH MONDAY AS WELL. AS INVEST 95W APPROACHES THE MARIANAS,
SEAS WILL REMAIN CHOPPY AND GUSTY WINDS OF 30 KNOTS WILL BE POSSIBLE.
HYDROLOGY...
HEAVY RAINFALL FROM INVEST 95W INTERACTING WITH A SHEAR LINE WILL
BRING A THREAT FOR FLASH FLOODING TO THE MARIANAS THIS WEEKEND AND
INTO NEXT WEEK. THE TIMING OF THE HEAVIEST RAINFALL STARTS LATE
TONIGHT, AND TRANSITIONS INTO THE WEEKEND, AND MUCH OF THE COMING
WEEK. SEVERAL ROUNDS OF HEAVY TO VERY HEAVY RAINFALL WILL BE POSSIBLE
DURING THIS TIME FRAME. THIS COULD LEAD TO 5 TO 10 INCHES OF RAIN
ACROSS THE MARIANAS WITH LOCALLY HIGHER AMOUNTS POSSIBLE.
GUIDANCE HAS HINTED AT A POTENTIAL STALL OF INVEST 95W. IF THIS
OCCURS AND IT DOES SO WITH 95W NEAR OR JUST WEST OF THE MARIANAS,
THEN THE RAINFALL FORECAST WILL SEE SIGNIFICANT CHANGES HEADING INTO
NEXT WEEK AS HEAVY RAINFALL WOULD CONTINUE FOR SEVERAL DAYS.
TROPICAL SYSTEMS...
JTWC INVEST 95W IS LOCATED NEAR 8N145E WITH A BROAD BUT SLIGHTLY
BETTER LOOKING SURFACE CIRCULATION THIS AFTERNOON. GIVEN THIS SLIGHT
ORGANIZATION, INVEST 95W IS NOW RATED "LOW" FOR DEVELOPMENT, MEANING
DEVELOPMENT INTO A SIGNIFICANT TROPICAL CYCLONE (TROPICAL
DEPRESSION) IS POSSIBLE OVER THE NEXT FEW DAYS BUT UNLIKELY OVER THE
NEXT 24 HOURS. CONVECTION REMAINS DISPLACED TO THE NORTH AND EAST OF
THE CIRCULATION WITH THE HEAVY SHOWERS AND ISOLATED THUNDERSTORMS TO
THE SOUTH AND SOUTHEAST OF THE MARIANA ISLANDS. INVEST 95W IS
EXPECTED TO MOVE WEST-NORTHWEST OVER THE NEXT COUPLE OF DAYS WITH THE
CENTER STARTING TO MOVE BETWEEN YAP AND GUAM AS IT INTERACTS WITH
THE SHEAR LINE NEAR THE MARIANAS. THIS WILL BRING PERIODS OF HEAVY
RAINFALL, BREEZY WINDS, CHOPPY SEAS, AND STRONGER GUSTS ACROSS THE
MARIANAS, ESPECIALLY IN HEAVIER SHOWERS AND THUNDERSTORMS. SUNDAY
ONWARD, UNCERTAINTY ON 95W'S DEVELOPMENT INCREASES AS SOME MODELS
SHOW INVEST 95W MERGING INTO THE SHEAR LINE AND BOTH FEATURES MOVING
NORTHEAST NEAR THE MARIANAS AND EVENTUALLY PULLING AWAY TO THE
NORTHEAST NEXT WEEK, WHILE OTHERS STALL INVEST 95W NEAR YAP AND THE
MARIANAS, PROLONGING THE PERIOD OF HEAVY RAINFALL INTO MUCH OF NEXT
WEEK, WHILE KEEPING INVEST 95W FAIRLY DISORGANIZED.
FOR MORE INFORMATION ON INVEST 95W, PLEASE SEE THE BULLETIN ISSUED
BY THE JOINT TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10 PGTW.
EASTERN MICRONESIA...
SATELLITE IMAGERY SHOWS ISOLATED SHOWERS AROUND POHNPEI AND MAJURO,
WITH SCATTERED SHOWERS AROUND KOSRAE, NEAR KWAJALEIN, AND WELL
SOUTHEAST OF MAJURO ALONG A SERIES OF WEAK-TRADE WIND TROUGHS. THESE
TROUGHS WILL SUPPORT PERIODS OF SCATTERED SHOWERS AT TIMES AND
ISOLATED THUNDERSTORMS AS THEY PASS NEAR THE ISLANDS. THE GFS
APPEARS TO BE BETTER HANDLING THE OVERALL PATTERN, SO THE TIMING FOR
WHEN SHOWERS WILL BECOME ISOLATED AROUND THE ISLANDS WAS USED.
ALTIMETRY AND BUOY DATA SHOW SEAS ARE AROUND 6 TO 7 FEET, DRIVEN BY
A LONG-PERIOD NORTH SWELL AND BACKGROUND EASTERLY SWELL. POHNPEI
BUOY, DRIFTING BUOYS, AND MODEL GUIDANCE STILL SUPPORT SURF BEING
ELEVATED ALONG NORTH FACING REEFS OF POHNPEI, KOSRAE, AND MAJURO BUT
REMAINING JUST BELOW THE 9 FOOT THRESHOLD FOR POHNPEI AND KOSRAE AND
WELL BELOW THE 12 FEET FOR MAJURO. SEAS AND SURF ARE EXPECTED TO
REMAIN FAIRLY STEADY THROUGH SATURDAY, BUT BY SUNDAY, ANOTHER LONG-
PERIOD NORTH SWELL, GENERATED BY A DISTANT SYSTEM NEAR JAPAN, WILL
START TO MOVE INTO THE REGION. THIS WILL LIKELY CAUSE SURF TO BECOME
HAZARDOUS ALONG NORTH FACING REEFS AT POHNPEI AND KOSRAE, AND WILL
APPROACH HAZARDOUS LEVELS AT MAJURO EARLY NEXT WEEK. THE POTENTIAL OF
NUISANCE COASTAL FLOODING AT MAJURO IS CURRENTLY DECREASING, BUT
WITH SURF EXPECTED TO BUILD EARLY NEXT WEEK, WE WILL HAVE TO MONITOR
TO SEE IF THAT RISK WILL RETURN.
WESTERN MICRONESIA...
THE LATEST SATELLITE DATA SHOWS SCATTERED TO NUMEROUS SHOWERS ACROSS
MOST OF WESTERN MICRONESIA THIS EVENING. HOWEVER, YAP PROPER AND
PALAU ARE CURRENTLY SEEING MOSTLY CLOUDY SKIES WITH ISOLATED
SHOWERS. ALTIMETRY SHOWS SEAS BETWEEN 4 AND 6 FEET.
THE NEAR-EQUATORIAL TROUGH (NET) REMAINS THE PRIMARY WEATHER PRODUCER
ACROSS WESTERN MICRONESIA. EMBEDDED WITHIN THE NET IS A WEAK TROPICAL
DISTURBANCE, INVEST 95W, DISCUSSED ABOVE IN THE TROPICAL SYSTEM
SECTION. AS INVEST 95W PROGRESSES WEST-NORTHWEST OVER THE NEXT FEW
DAYS, THE INVEST, ALONG WITH THE NET, WILL MAINTAIN A WET MONSOON-
LIKE PATTERN ACROSS THE REGION. THERE IS STILL LOW CONFIDENCE IN THE
DEVELOPMENT OF INVEST 95W AS MODELS VARY ON EXPECTED MOVEMENT AND A
LITTLE ON STRENGTH. THE MAIN THING TO TAKE AWAY IS THE PATTERN LOOKS
TO REMAIN UNSETTLED OVER THE NEXT SEVERAL DAYS UNTIL 95W MOVES OUT OF
THE REGION. ALTHOUGH WIDESPREAD HEAVY SHOWERS ARE NOT EXPECTED
ACROSS WESTERN MICRONESIA, LOCALLY HEAVY SHOWERS ARE POSSIBLE.
RESIDENTS OF CHUUK, YAP AND PALAU SHOULD CONTINUE TO MONITOR
FORECASTS OVER THE NEXT FEW DAYS FOR ANY POSSIBLE CHANGES.
LATEST ALTIMETRY SHOWS SEAS BETWEEN 4 AND 6 FEET ACROSS THE REGION.
SEAS LOOK TO SLOWLY BUILD OVER THE NEXT FEW DAYS DUE TO A BUILDING
NORTH SWELL, REACHING 5 TO 7 FEET AT PALAU AND CHUUK, AND 6 TO 9
FEET AT YAP. MOSTLY LIGHT TO GENTLE WINDS ARE EXPECTED THROUGH THE
MIDDLE OF NEXT WEEK, WITH OCCASIONAL MODERATE WINDS AT YAP AND CHUUK
THROUGH SATURDAY.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 PM CHST MONDAY FOR GUZ001.
FLOOD WATCH THROUGH TUESDAY MORNING FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH MONDAY AFTERNOON FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 PM CHST MONDAY FOR MPZ001>003.
FLOOD WATCH THROUGH TUESDAY MORNING FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 5 PM CHST SUNDAY FOR PMZ151>154.
MARIANAS/WEST MICRONESIA UPDATE: CRUZ
EAST MICRONESIA/TROPICAL UPDATE: DECOU
MARIANAS: WILLIAMS
EAST MICRONESIA: SCHANK
WEST MICRONESIA: KLEESCHULTE
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