271
FXPQ50 PGUM 152028
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
628 AM CHST THU APR 16 2026
MARIANAS SYNOPSIS
TYPHOON SINLAKU CONTINUES TO BE THE DOMINANT FEATURE WITHIN THE
MARIANAS. NUMEROUS SHOWERS AND ISOLATED THUNDERSTORMS ARE SEEN
ACROSS SAIPAN AND TINIAN, WHILE SCATTERED SHOWERS AND ISOLATED
THUNDERSTORMS ARE SEEN ACROSS ROTA, AND ISOLATED SHOWERS ARE SEEN
ACROSS GUAM. DANGEROUS MARINE CONDITIONS CONTINUE ACROSS THE
MARIANAS WITH 15+ FOOT SEAS ACROSS THE REGION.
DISCUSSION
TYPHOON SINLAKU REMAINS A SLOW MOVER AS IT CRAWLS NORTHWESTWARD AT
ABOUT 5 MPH AWAY FROM SAIPAN AND TINIAN. TYPHOON SINLAKU UNDERWENT
AN EYEWALL REPLACEMENT CYCLE, WHICH ALLOWED FOR AN EXPANSION IN THE
WIND FIELD. RAINBANDS FROM TY SINLAKU HAVE GENERALLY SHIFTED NORTH
OF GUAM AND ROTA, WHICH ALLOWED FOR THE FLASH FLOOD WATCH TO BE
CANCELLED. ENSEMBLE TROPICAL RAINFALL POTENTIAL (ETRAP) SHOWS AN
ADDITIONAL 2 TO 6 INCHES OF RAIN FOR SAIPAN AND TINIAN AND THE FLASH
FLOOD WATCH WAS EXTENDED UNTIL THIS AFTERNOON. SEE HYDROLOGY SECTION
FOR MORE DETAILS. LITTLE CHANGE WAS MADE TO THE NEAR-TERM FORECAST
DUE TO THE SLOW MOVEMENT OF SINLAKU. GUAM AIRPORT HAS SEEN GUSTS
JUST UNDER 55 MPH THROUGH THE NIGHT AND OKA POINT HAD A 40 MPH
SUSTAINED OB OVERNIGHT. FINALLY, THE 18Z BALLOON SHOWED 925 MB WINDS
AT 57 KNOTS. IN COMBINATION WITH ASCAT SHOWING TROPICAL STORM WINDS
OVERSTRETCHING GUAM, AND THE JTWC FORECAST KEEPING TS WINDS OVER
GUAM, THE MORNING FORECAST PACKAGE HELD ONTO GUAM'S TROPICAL STORM
WARNING. WINDS INCREASE NORTHWARD OVER THE MARIANAS WITH SAIPAN AND
TINIAN SEEING WINDS OF 60 TO 70 MPH AND GUSTS TO 85 MPH.
MARINE
DANGEROUS SEAS AND WINDS CONTINUE ACROSS THE MARIANAS. THE LARGE
SIZE OF TYPHOON SINLAKU HAS LED TO FULLY DEVELOPED WAVES. SEAS
REMAIN GREATER THAN 15 FEET ACROSS THE MARIANAS AND GREATER THAN 20
FEET ACROSS THE CNMI. TS CONDITIONS CONTINUE ACROSS ALL WATERS AND
LOOK TO PERSIST THROUGH TODAY. SEAS WILL BE SLOW TO SUBSIDE DUE TO
THE SLOW MOTION OF TY SINLAKU. SEAS LOOK TO REMAIN ABOVE 10 FEET
THROUGH SATURDAY. SURF CONTINUES TO BE DANGEROUS WITH ALL ISLANDS
HITTING 15 FT SURF FOR SOUTH, WEST, AND NORTH FACING REEFS. THIS
LOOKS TO CONTINUE UNTIL AT LEAST FRIDAY AFTERNOON. SURF MAY REMAIN
HAZARDOUS INTO THE WEEKEND ACROSS SOUTH, WEST, AND NORTH FACING
REEFS. THE COASTAL FLOOD WARNING WAS EXTENDED UNTIL 5 PM TODAY FOR
GUAM, WHICH LINES UP WITH ROTA. INUNDATION OF 1 TO 3 FEET WILL BE
POSSIBLE ACROSS GUAM TODAY WITH 2 TO 4 FEET ACROSS ROTA, AND 4 TO 6
FEET ACROSS SAIPAN AND TINIAN. COASTAL INUNDATION COULD LINGER AS
THE ASTRONOMICAL TIDES ARE ELEVATED FROM THE NEW MOON THIS WEEK.
THIS MAY NECESSITATE AN EXTENSION OF COASTAL FLOOD PRODUCTS.
HYDROLOGY
HYDROLOGIC CONDITIONS CONTINUE TO IMPROVE ACROSS THE MARIANAS. THE
HEAVIEST RAINBANDS ARE NOW NORTH OF GUAM AND ROTA AND RAINFALL
CHANCES ARE DECREASING. AN ADDITIONAL INCH OF RAIN MAY BE POSSIBLE.
THE RISK OF FLASH FLOODING HAS DIMINISHED AND THE FLASH FLOOD WATCH
WAS CANCELLED. FOR SAIPAN AND TINIAN, THE FLASH FLOOD WATCH WAS
EXTENDED UNTIL THIS AFTERNOON. ADDITIONAL RAINFALL LOOKS TO RANGE
BETWEEN 2 TO 6 INCHES, WHICH ALIGNS WITH ETRAP. ONCE THE HEAVIER
BANDS MOVE THROUGH TODAY, THE RISK FOR FLASH FLOODING WILL HAVE
GREATLY DIMINISHED.
STORM TOTALS AT WFO GUAM WERE OVER 12 INCHES SO FAR. OVER THE COMING
DAYS DATA WILL BE COLLECTED TO DETERMINE HOW MUCH RAINFALL FELL FROM
THE STORM.
TROPICAL SYSTEMS
THE 5 AM POSITION OF TYPHOON SINLAKU WAS AT 16.7N AND 144.5E. THIS
WAS 80 MILES WEST-NORTHWEST OF ANATAHAN, 110 MILES SOUTHWEST OF
ALAMAGAN, 135 MILES NORTHWEST OF SAIPAN, AND 225 MILES NORTH OF
GUAM. SINLAKU WAS MOVING NORTHWEST AT 305 DEGREES AT 5 MPH. MAXIMUM
SUSTAINED WINDS WERE 125 MPH. SINLAKU IS FORECASTED TO BRIEFLY
INTENSIFY THIS MORNING BEFORE WEAKENING TONIGHT AND INTO FRIDAY.
TYPHOON SINLAKU CONTINUES TO MOVE AWAY FROM SAIPAN AND TINIAN. DUE
TO AN EXPANDED WIND FIELD AND SLOW MOVEMENT, WINDS HAVE BEEN SLOW TO
SUBSIDE ACROSS THE MARIANAS. SINLAKU WILL CONTINUE TO LIFT TOWARDS
THE FAR NORTHERN MARIANAS TODAY BEFORE TURNING TO THE NORTHEAST
AROUND AGRIHAN ON FRIDAY. TYPHOON CONDITIONS ARE EXPECTED ACROSS
ALAMAGAN, PAGAN, AND AGRIHAN THROUGH FRIDAY.
FOR MORE INFORMATION, PLEASE REFER TO BULLETINS FROM THE JOINT
TYPHOON WARNING CENTER (JTWC) UNDER WMO HEADER WTPN31 PGTW AND FROM
THE NATIONAL WEATHER SERVICE UNDER WMO HEADER WTPQ31 PGUM AND WTPQ81
PGUM.
EASTERN MICRONESIA
THE MAIN CHANGE THIS FORECAST UPDATE WAS TO INCREASE RAINFALL
COVERAGE AND PROBABILITIES AT KOSRAE. SATELLITE IMAGERY SHOWS
CONVERGENT OUTFLOW BOUNDARIES HEADING TOWARDS THE REGION, WITH
STREAMLINE ANALYSIS HINTING THAT A SUBTLE TROUGH MAY BE EMBEDDED IN
THE FLOW. AS SUCH, INCREASED SHOWER COVERAGE TO SCATTERED, WITH 40
PERCENT PROBABILITIES TODAY AND 30 PERCENT TONIGHT. A SIMILAR
FEATURE IS APPROACHING MAJURO, BUT, THE GOING FORECAST HAS THIS WELL-
COVERED. AT POHNPEI, YOU'RE LOCATED IN A WEAK CONVERGENCE AREA NORTH
OF A COL, WITH NO APPRECIABLE CONVECTION UPSTREAM. THUS, ISOLATED
SHOWERS IN THE FORECAST LOOKS GOOD.
WESTERN MICRONESIA
THE ONLY WEATHER FEATURE AFFECTING WESTERN MICRONESIA AT THIS TIME IS
TYPHOON SINLAKU, AND EVEN THOSE EFFECTS ARE INDIRECT, BEING SWELL.
FOR KOROR, PALAU, LOOKS LIKE ISOLATED SHOWERS FOR THE ENTIRE FORECAST
PERIOD. WINDS WILL BE 5 TO 15 KNOTS THROUGH FRIDAY, THEN 5 TO 10
KNOTS THROUGH MONDAY. SEAS OF 6 TO 8 FEET TODAY WILL DIMINISH TO
BETWEEN 4 AND 6 FEET BY THE WEEKEND. MARINE CONDITIONS WILL LIKELY
START CHALLENGING BUT BECOME BENIGN BY THE WEEKEND.
AT YAP, IT ALSO LOOKS LIKE ISOLATED SHOWERS FOR THE ENTIRE FORECAST
PERIOD. WINDS WILL BE 10 TO 15 KNOTS THROUGH FRIDAY, THEN 5 TO 10
KNOTS THROUGH MONDAY. SEAS OF 10 TO 13 FEET TODAY WILL DIMINISH TO
BETWEEN 6 AND 8 FEET BY THE WEEKEND. MARINE CONDITIONS WILL START
HAZARDOUS, BUT BY THE WEEKEND WILL BECOME JUST CHALLENGING. HIGH SURF
AND SMALL CRAFT ADVISORIES HAVE BEEN ISSUED TO COVER THESE
CONDITIONS.
IN CHUUK, IT LOOKS LIKE ISOLATED SHOWERS THROUGH SUNDAY, THEN SHOWERS
COULD BECOME SCATTERED FOR MONDAY. WINDS WILL BE 10 TO 15 KNOTS
THROUGH TONIGHT, THEN 5 TO 10 KNOTS THROUGH MONDAY. SEAS WILL START
AT 6 TO 8 FEET TODAY, THEN DIMINISH TO BETWEEN 4 AND 5 FEET BY
SUNDAY. MARINE CONDITIONS WILL START CHALLENGING, BECOMING GENTLE BY
THE WEEKEND.
GUM WATCHES/WARNINGS/ADVISORIES
GU...COASTAL FLOOD WARNING UNTIL 5 PM CHST THIS AFTERNOON FOR GUZ001.
HIGH SURF WARNING UNTIL 5 PM CHST FRIDAY FOR GUZ001.
TROPICAL STORM WARNING FOR GUZ001.
TYPHOON WATCH FOR GUZ001.
MP...COASTAL FLOOD WARNING UNTIL 5 PM CHST THIS AFTERNOON FOR MPZ001.
HIGH SURF WARNING UNTIL 5 PM CHST FRIDAY FOR MPZ001>003.
TYPHOON WARNING FOR MPZ001>003.
COASTAL FLOOD WARNING UNTIL NOON CHST FRIDAY FOR MPZ002-003.
FLOOD WATCH THROUGH THIS AFTERNOON FOR MPZ002-003.
MARIANAS WATERS...TROPICAL STORM WARNING FOR PMZ151.
TYPHOON WATCH FOR PMZ151.
TYPHOON WARNING FOR PMZ152>154.
MARIANAS: WILLIAMS
EAST MICRONESIA: DOLL
WEST MICRONESIA: STANKO
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