847
FXPQ50 PGUM 090901
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
701 PM CHST MON MAR 9 2026
MARIANAS SYNOPSIS
SATELLITE IMAGERY SHOWS CLOUDY SKIES, WHILE RADAR SHOWS SCATTERED TO
NUMEROUS SHOWERS WITH MOST OF THE HEAVIER SHOWERS JUST OUTSIDE THE
COASTAL WATERS. IPAN BUOY DATA SHOWS SWELL OF 4 FEET AT 13 SECONDS,
HOWEVER, THIS BUOY IS SHIELDED BY THE ISLAND OF GUAM FROM THE NORTH
AND NORTHEASTERN SWELLS.
A SMALL CRAFT ADVISORY, HIGH SURF ADVISORY, AND A HIGH RISK OF RIP
CURRENTS STATEMENT REMAIN IN EFFECT.
DISCUSSION
AN UNSETTLED WET WEATHER PATTERN CONTINUES FOR THE MARIANAS. THIS
PATTERN IS PRODUCED BY THE INTERACTION BETWEEN SEVERAL FEATURES,
NAMELY TWO INVESTS, ONE NEAR YAP PROPER, ONE TO THE EAST OF SAIPAN, A
MONSOON-LIKE TROUGH PASSING BETWEEN THE INVESTS AND A STALLED SHEAR
LINE OVER FAR NORTHERN CNMI. IT WILL TAKE SEVERAL DAYS FOR THE
FEATURES TO MOVE OUT OF THE REGION. WITH THAT BEING SAID ONE CAN
EXPECT PERIODS OF SHOWERS AND THUNDERSTORMS THROUGH MUCH OF THE WEEK.
MARINE
A BUSY MARINE PATTERN IS EXPECTED TO CONTINUE THROUGH THE NEXT FEW
DAYS. COMBINED SEAS WILL RANGE 7 TO 10 FEET OVER MARIANAS COASTAL
WATERS. WINDS WILL BE HIGHLY VARIABLE THROUGH THE NEXT FEW DAYS DUE
TO COMPLEX INTERACTIONS WITH TWO INVESTS, A MONSOON-LIKE TROUGH AND A
SHEAR LINE, WITH SPEED AND DIRECTION DEPENDING ON THE POSITION OF
THE SHEAR LINE AND NEARBY WEAK CIRCULATIONS THAT SPIN UP WITHIN THE
MONSOON-LIKE TROUGH EXTENDING ACROSS THE AREA JUST SOUTH OF IT.
TINIAN AND SAIPAN WATERS CAN EXPECT MODERATE TO STRONG WINDS WITH
OCCASIONAL NEAR-GALE GUSTS, WITH LIGHT TO MODERATE, MORE VARIABLE
WINDS EXPECTED FOR GUAM AND ROTA WATERS. A LONGER-PERIOD PULSE OF
NORTH-NORTHEAST SWELL MOVES IN TONIGHT THROUGH MIDWEEK. SCATTERED TO
NUMEROUS SHOWERS, ISOLATED THUNDERSTORMS, OCCASIONAL STRONG TO NEAR-
GALE GUSTS, AND SEAS HAZARDOUS TO SMALL CRAFT ARE EXPECTED THROUGH AT
LEAST TUESDAY AFTERNOON.
HYDROLOGY
THE HYDROLOGICAL OUTLOOK WAS ALLOWED TO EXPIRE TODAY. HOWEVER,
SHOWERS ARE EXPECTED TO REMAIN IN THE FORECAST FOR MUCH OF THE WEEK.
THESE SHOWERS HAVE A NON ZERO CHANCE OF PRODUCING HEAVY ENOUGH
SHOWERS THAT FLOOD ADVISORIES, WATCHES AND WARNINGS MAY BE NECESSARY.
TROPICAL SYSTEMS
INVEST 95W CONTINUES TO SLOWLY TRY TO ORGANIZE JUST NORTH OF YAP. IT
REMAINS AS A MEDIUM POTENTIAL FOR DEVELOPMENT, MEANING TROPICAL
CYCLONE FORMATION IS EXPECTED BUT BEYOND 24 HOURS. OVERALL, THE
MODELS HAVE COME INTO SOMEWHAT BETTER CONTINUITY TODAY, AS BOTH THE
GFS AND EUROPEAN ENSEMBLE MEMBERS NOW PORTRAY SOME TYPE OF
CIRCULATION (POSSIBLY AS A TROPICAL DEPRESSION) PASSING THROUGH OR
VERY NEAR THE MARIANAS IN THE NEXT 3 TO 5 DAYS.
ADDITIONALLY, INVEST 96W HAS ALSO FORMED EAST OF SAIPAN NEAR 15N147E.
VISIBLE IMAGERY AND SURFACE WIND OBSERVATIONS SHOW THIS NICELY, AS
DOES THE LATEST SCATTEROMETER PASS. JTWC HAS LABELED THIS AS A "SUB-
LOW" INVEST, MEANING FURTHER DEVELOPMENT INTO A TROPICAL CYCLONE IS
UNLIKELY, AS IT CONTINUES NORTHEAST THE NEXT FEW DAYS.
IT'S VERY IMPORTANT TO NOTE THAT UNCERTAINTY IN TIMING AND STRENGTH
OF ANY POTENTIAL DEVELOPMENT REMAINS HIGH. IT'S TRUE THE MODELS HAVE
"GOTTEN MORE ON THE SAME PAGE" TODAY, BUT, THE SYSTEM IS STILL
EVOLVING AND AS IS TYPICAL WITH THESE DEVELOPING SYSTEMS, ANYTHING
REMAINS POSSIBLE, INCLUDING IT REMAINING DISORGANIZED ENOUGH TO DO
NOTHING MORE THAT BRING INCREASING RAINFALL POTENTIAL AND/OR
INTENSITY.
FOR MORE INFORMATION ON INVESTS 95W AND 96W, PLEASE SEE THE BULLETIN
ISSUED BY THE JOINT TYPHOON WARNING CENTER UNDER WMO HEADER ABPW10
PGTW.
EASTERN MICRONESIA
THE MAIN CONCERN THROUGH THE NEXT 24 HOURS IS HIGH SURF FOR NORTH-
FACING REEFS AT POHNPEI AND KOSRAE. THE POHNPEI BUOY SHOWS SEAS
BARELY REACHING 9 FEET. I SERIOUSLY THOUGHT ABOUT DROPPING THE
ADVISORY AS THE LATEST DATA SHOW TRENDS ARE DOWNWARD AND THE LATEST
MODEL GUIDANCE SAYS SURF WILL BE BELOW HAZARDOUS LEVELS BY MIDNIGHT.
WITH THAT SAID, WE DECIDED TO MAINTAIN THE ADVISORY THROUGH 3 AM
TONIGHT TO GIVE THE MIDNIGHT SHIFT MORE TIME TO DIGEST THIS
POTENTIAL.
OTHERWISE, SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS LOOK GOOD FOR
MOST OF THE FORECAST PERIOD, BEFORE DRIER CONDITIONS POTENTIALLY WORK
INTO THE REGION FROM EAST TO WEST TOWARDS THE WEEKEND. AS FOR MARINE
CONDITIONS, SEAS OF 5 TO 7 FEET MAY BUILD A FOOT OR TWO TOWARDS THE
WEEKEND. MAINLY LIGHT TO GENTLE WINDS WILL PERSIST.
WESTERN MICRONESIA
THE WEATHER FEATURES AFFECTING WESTERN MICRONESIA THIS EVENING ARE A
TRADE-WIND TROUGH NEAR CHUUK AND A MONSOON-LIKE TROUGH NEAR KOROR,
PALAU, YAP AND THE MARIANAS. THE PATTERN IS MOVING SLOWLY AND COULD
CONTINUE AT THE MAJOR ISLANDS FOR A FEW DAYS AT LEAST.
AT CHUUK, THERE WILL BE NUMEROUS SHOWERS TONIGHT, THEN SCATTERED
SHOWERS THROUGH THURSDAY, ISOLATED SHOWERS ON FRIDAY, THEN BACK TO
SCATTERED FOR SATURDAY. WINDS WILL BE 5 TO 10 KNOTS. SEAS OF 4 TO 6
FEET WILL CONTINUE THROUGH FRIDAY, THEN COULD CLIMB TO BETWEEN 6 AND
8 FEET SATURDAY. THE HIGH SURF ADVISORY WAS JUST ALLOWED TO EXPIRE,
HOWEVER IT COULD BE NEEDED AGAIN NEXT SATURDAY. MARINE CONDITIONS
WILL BE BENIGN THROUGH FRIDAY THEN COULD BECOME CHALLENGING SATURDAY
DUE TO THE SWELLS.
FOR YAP, LOOK FOR WIDESPREAD SHOWERS TONIGHT, THEN NUMEROUS TUESDAY
AND TUESDAY NIGHT, THEN SCATTERED THROUGH FRIDAY, AND POSSIBLY
INCREASING TO NUMEROUS AGAIN ON SATURDAY. WINDS WILL BE 5 TO 15 KNOTS
THROUGH TUESDAY, THEN 5 TO 10 KNOTS THROUGH SATURDAY. SEAS WILL BE 7
TO 9 FEET THROUGH TUESDAY, THEN 6 TO 8 FEET THROUGH SATURDAY. THE
HIGH SURF ADVISORY REMAINS IN EFFECT THROUGH AT LEAST WEDNESDAY
MORNING, AND MAY NEED TO BE EXTENDED. MARINE CONDITIONS WILL BE
CHALLENGING THROUGH AT LEAST TUESDAY, THEN COULD BECOME BENIGN LATER
IN THE WEEK.
KOROR, PALAU WILL FEATURE SCATTERED SHOWERS THROUGH THE ENTIRE
PERIOD, FROM TONIGHT THROUGH SATURDAY. WINDS WILL BE 5 TO 10 KNOTS
THROUGH THURSDAY, THEN COULD BUILD TO BETWEEN 5 AND 15 KNOTS FOR
FRIDAY AND SATURDAY. SEAS WILL BE 6 TO 8 FEET THROUGH THE ENTIRE
PERIOD. THE HIGH SURF ADVISORY REMAINS IN EFFECT THROUGH AT LEAST
WEDNESDAY MORNING, AND MAY NEED TO BE EXTENDED. MARINE CONDITIONS,
HOWEVER, WILL GENERALLY BE BENIGN DUE TO THE SLIGHTLY LOWER SWELLS.
GUM WATCHES/WARNINGS/ADVISORIES
GU...HIGH RIP CURRENT RISK THROUGH TUESDAY AFTERNOON FOR GUZ001.
HIGH SURF ADVISORY UNTIL 4 PM CHST TUESDAY FOR GUZ001.
MP...HIGH RIP CURRENT RISK THROUGH TUESDAY AFTERNOON FOR MPZ001>003.
HIGH SURF ADVISORY UNTIL 4 PM CHST TUESDAY FOR MPZ001>003.
MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 4 PM CHST TUESDAY FOR
PMZ151>154.
TROPICAL: DOLL
MARIANAS/HYDROLOGICAL: BOWSHER
EAST MICRONESIA: DOLL
WEST MICRONESIA: STANKO
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