573
FXPQ50 PGUM 010912
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
712 PM CHST TUE SEP 1 2026
MARIANAS SYNOPSIS
WIDESPREAD STRATIFORM CLOUDS ARE VISIBLE ACROSS THE MARIANAS THIS
EVENING WITH ONLY VERY LIGHT RAIN PRESENT. GENTLE NORTHWEST WINDS
ARE BECOMING LIGHT AND VARIABLE. MODELS AND OBSERVATIONS INDICATE
COMBINED SEAS OF AROUND 5 FEET.
DISCUSSION
CALM WEATHER EARLY TONIGHT WILL BE GRADUALLY REPLACED BY SCATTERED
SHOWERS AND ISOLATED THUNDERSTORMS LATE TONIGHT AND LASTING THROUGH
THURSDAY NIGHT. A LARGE AND DISORGANIZED TROPICAL DISTURBANCE THAT IS
INVEST 95W, IS LOCATED EAST-NORTHEAST OF THE MARIANAS. THIS SYSTEM IS
EXPECTED TO MOVE THROUGH OR JUST NORTH OF THE MARIANAS OVER THE NEXT
TWO DAYS. A COL HAS DEVELOPED OVER THE MARIANAS BETWEEN THIS
DISTURBANCE AND ANOTHER SYSTEM TO THE NORTHWEST. THIS WILL KEEP WINDS
FAIRLY LIGHT THROUGH WEDNESDAY. THE UNSTABLE AIRMASS AND HIGH
PRECIPITABLE WATER VALUES MAY ALLOW FOR HEAVY SHOWERS TO DEVELOP AND
STALL OVER THE ISLANDS. THIS HAS LED TO THE ISSUANCE OF A SPECIAL
WEATHER STATEMENT TO HIGHLIGHT THE POTENTIAL FLOODING RISK. HIGH
UNCERTAINTY REMAINS IN WHERE THE HIGHEST RAINFALL AMOUNTS WILL OCCUR
AND THERE MAY BE BREAKS BETWEEN INSTANCES OF HEAVY RAINFALL. BY
THURSDAY, A MONSOONAL TAIL MAY DEVELOP AND PUSH NORTH INTO THE
MARIANAS, BRINGING MORE LOCALLY HEAVY SHOWERS AND ISOLATED
THUNDERSTORMS, WITH THE HIGHEST CHANCES REMAINING OVER GUAM AND ROTA.
SUSTAINED WINDS OF 15 TO 25 MPH WILL BE POSSIBLE WITH GUSTS OF 30
MPH. A BRIEF DRY SPELL IS ANTICIPATED FRIDAY BEFORE ANOTHER TROUGH
POTENTIALLY MOVES INTO THE REGION OVER THE WEEKEND.
FOR MORE INFORMATION, PLEASE REFER TO THE SPECIAL WEATHER STATEMENT
UNDER WMO HEADER WWMY80 PGUM.
MARINE
COMBINED SEAS OF 5 TO 6 FEET WILL CONTINUE TO GRADUALLY RISE
THROUGH AT LEAST THURSDAY NIGHT, REACHING AS HIGH AS 8 TO 9 FEET
DUE TO A STRENGTHENING WEST OR SOUTHWESTERLY MONSOON SURGE. LIGHT
TO GENTLE WINDS MAY INCREASE SIGNIFICANTLY THURSDAY WITH MAXIMUM
SUSTAINED WINDS OF 25 KNOTS AND GUSTS UP TO 30 KNOTS. THEREFORE,
SEAS MAY ALSO REACH NEAR CRITERIA HAZARDOUS TO SMALL CRAFT BY
THURSDAY. THE MONSOON SURGE WILL BRING THE POTENTIAL FOR LOCALLY
HEAVY SHOWERS AND ISOLATED THUNDERSTORMS THROUGH AT LEAST THURSDAY
NIGHT.
FOR SURF, THERE WILL BE A MODERATE RISK OF RIP CURRENTS ALONG WEST-
FACING REEFS FOR THE NEXT FEW DAYS, POTENTIALLY INCLUDING NORTH AND
SOUTH- FACING REEFS BY WEDNESDAY NIGHT AS WINDS START TO PICK UP. THE
RISK MAY REACH HIGH ALONG WEST-FACING REEFS OVERNIGHT WEDNESDAY AS
THE WEST SWELL BUILDS IN. THERE WILL BE A MODERATE RISK OF LIGHTNING
FOR GUAM THROUGH AT LEAST THURSDAY NIGHT.
TROPICAL SYSTEMS
A NEWLY FORMED TROPICAL STORM KROVANH (22W), KNOWN PREVIOUSLY AS
INVEST 94W, IS CENTERED NEAR 23N132E WELL SOUTHEAST OF NAHA, OKINAWA.
KROVANH IS NEARLY STATIONARY, MOVING NORTH AT JUST AROUND 1 MPH WITH
MAXIMUM SUSTAINED WINDS TO 40 MPH NEAR THE CENTER. THE SYSTEM IS
EXPECTED TO MAKE A SLIGHT TURN TOWARD THE NORTH-NORTHWEST WITH AN
INCREASE IN FORWARD SPEED THROUGH WEDNESDAY AS IT PIVOTS TOWARD THE
RYUKYU ISLANDS. KROVANH WILL CONTINUE TO INTENSIFY THROUGH AT LEAST
WEDNESDAY, REMAINING A TROPICAL STORM DURING THIS TIME. THE SYSTEM IS
EXPECTED TO MEANDER ALONG THE NORTHWESTERNMOST FRINGES OF NWS GUAM'S
AREA OF RESPONSIBILITY, WITH NO DIRECT IMPACTS EXPECTED TO ANY OF OUR
FORECAST POINTS.
FOR MORE INFORMATION ON TS KROVANH, SEE BULLETINS FROM THE JOINT
TYPHOON WARNING CENTER (JTWC) UNDER WMO HEADER WTPN31 PGTW, AND
PUBLIC ADVISORIES FROM THE NATIONAL WEATHER SERVICE UNDER WMO HEADER
WTPQ31 PGUM.
A WEAK MONSOON DISTURBANCE, INVEST 95W AND THE TCFA, IS SEEN ALONG
THE MONSOON TROUGH TO THE E OF ROTA, CENTERED NEAR 14.1N 149.8E. 95W
REMAINS SUB-LOW, MEANING DEVELOPMENT IS NOT EXPECTED FOR AT LEAST
THE NEXT DAY OR TWO. INVEST 95W WILL CONTINUE MOVING NNW OVER THE
COMING DAYS, LIKELY PASSING THROUGH THE NORTHERN CNMI AS A WEAK
DISTURBANCE, POSSIBLY AS A TROPICAL DEPRESSION. INVEST 95W WILL
CONTINUE TO BE MONITORED FOR ANY INDICATION THAT DEVELOPMENT WILL
BEGIN EARLIER OR FOR ANY CHANGE IN EXPECTED TRACK.
EASTERN MICRONESIA
A FEW CHANGES WERE MADE TO THE PREVIOUS FORECAST. A FAIRLY DRY
PATTERN LOOKS TO CONTINUE INTO THE WEEKEND FOR MAJURO, NO CHANGE
THERE. FOR POHNPEI, DRIER CONDITIONS MOVED IN A BIT QUICKER, WITH
POPS (PROBABILITY OF PRECIPITATION) DROPPING TO 20 PERCENT FOR
TONIGHT. HOWEVER, KOSRAE IS SEEING SCATTERED SHOWERS THIS AFTERNOON.
THESE SHOWERS DO LOOK TO DECREASE THROUGH THE EVENING, WITH SHOWERS
EXPECTED TO BECOME ISOLATED LATER THIS EVENING, NEAR OF JUST AFTER
MIDNIGHT. LATER IN THE WEEK, A COUPLE OF TROUGHS MOVING THROUGH THE
REGION WILL BRING INCREASED SHOWERS TO POHNPEI THURSDAY NIGHT, KOSRAE
AROUND MIDWEEK AND THEN MAJURO LATE IN THE WEEKEND. FAIRLY BENIGN
WINDS AND SEAS WILL CONTINUE ACROSS THE REGION THROUGH THE WEEK.
WESTERN MICRONESIA
A MONSOONAL CONVERGENCE ZONE IS EXPECTED TO FORM ALONG THE LEADING
EDGE OF A LARGELY DISORGANIZED TROPICAL DISTURBANCE MOVING INTO THE
VICINITY OF THE MARIANAS, ALLOWING SHOWERS AND THUNDERSTORMS TO
INCREASE IN COVERAGE AND INTENSITY NEAR YAP OVER THE COMING DAYS.
CURRENT MODEL CONSENSUS INDICATES THAT PEAK SHOWER INTENSITY IS
EXPECTED AT YAP WEDNESDAY NIGHT AND THURSDAY, TO THEN IMPROVE
CONSIDERABLY THEREAFTER AS A TROPICAL HIGH AND ASSOCIATED RIDGE BRING
A DRY SPELL TOWARD THE WEEKEND. THE AFOREMENTIONED TROPICAL RIDGE
WILL CONTINUE TO BRING MOSTLY DRY CONDITIONS TO PALAU FOR MUCH OF THE
WEEK, WITH A BRIEF PERIOD OF LOW-END SCATTERED SHOWERS TRICKLING IN
WEDNESDAY NIGHT AND THURSDAY DURING PEAK CONVECTIVE REGIME OVER AND
NEAR YAP. AT CHUUK, PATCHY SHOWERS AND SOME THUNDERSTORMS ARE
EXPECTED THROUGH WEDNESDAY, TO THEN SLOWLY TAPER DOWN THEREAFTER AS
THE PREVIOUSLY MENTIONED TROPICAL HIGH SETTLES NEARLY OVERHEAD BY THE
NEXT WEEKEND, ALLOWING A DRY REGIME TO RETURN.
COMBINED SEAS OF 3 TO 4 FEET NEAR PALAU, ARE EXPECTED TO REMAIN AS
SUCH FOR MUCH OF THE FORECAST PERIOD. COMBINED SEAS OF 4 TO 6 FEET
NEAR YAP ARE EXPECTED TO INCREASE A FOOT OR TWO AROUND MIDWEEK AS
LOCALIZED WIND WAVES BUILD, TO THEN DROP SEVERAL FEET BY THE END OF
THE WEEK. COMBINED SEAS OF 6 TO 7 FEET NEAR CHUUK, WILL SLOWLY TAPER
DOWN TO 3 TO 5 FEET BY THE WEEKEND A WESTERLY SWELLS AND LOCAL WINDS
DIMINISH.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MP...NONE.
MARIANAS WATERS...NONE.
MARIANAS: OGLE
EAST MICRONESIA/TROPICAL: KLEESCHULTE
WEST MICRONESIA/TROPICAL: MONTVILA
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