525
FXPQ50 PGUM 252007
AFDGUM
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
607 AM CHST MON AUG 26 2019
MARIANAS SYNOPSIS
SATELLITE AND RADAR SHOW ISOLATED SHOWERS IN THE MARIANAS WATERS, BUT
WIDESPREAD RAIN AND SHOWERS ARE INDICATED OUTSIDE THE WATERS. ON
RADAR, THE TREND SEEMS TO BE TOWARDS STRATIFYING AND SLOW WEAKENING
OF THE CONVECTION. WINDS ARE GENTLE FROM EAST TO SOUTHEAST, AND SEAS
ARE AROUND 4 FEET AT THE BUOYS. WELL OUT TO THE WEST, JTWC INVEST
AREA 99W IS CENTERED NW OF KOROR AND YAP AROUND 13N AND 133E.
DISCUSSION
FOR THIS MORNING, RADAR AND SATELLITE INDICATE THAT CONVECTION IS
SPREADING OUT AND WEAKENING AS IT TRIES TO APPROACH THE ISLANDS, AND
CLOUD TOPS ARE WARMING--ANOTHER SIGN OF DISSIPATION. AS A RESULT,
HAVE KEPT SHOWERS AND THUNDERSTORMS ISOLATED THIS MORNING AND THROUGH
THE DAY. ALSO HAVE EXTENDED ISOLATED THUNDERSTORMS THROUGH WED NIGHT,
AS THE GFS KEEPS CONDITIONS UNSETTLED AROUND THE MARIANAS WITH RANDOM
LITTLE BATCHES OF SHOWERS AT TIMES. A BRIEF PERIOD OR TWO OF
SCATTERED SHOWERS MAY OCCUR THROUGH WEDNESDAY, ESPECIALLY AT NIGHT,
AND WILL HAVE TO MONITOR THE SITUATION CLOSELY DAY TO DAY. BY
THURSDAY, GFS AND ESPECIALLY THE ECMWF BRING IN MID-LEVEL DRYING,
WHICH SHOULD SHUT OFF THUNDERSTORMS FOR A FEW DAYS.
MARINE
SEAS ARE SLOWLY SETTLING DOWN AS BOTH EAST AND WEST SWELL SLOWLY
DIMINISH THE NEXT FEW DAYS. OUR MODERATE RIP RISK ALONG EAST FACING
REEFS COULD DIP TO LOW LATE IN THE WEEK.
TROPICAL SYSTEMS
INVEST 99W IS VERY LOOSELY ORGANIZED, WITH ASCAT SHOWING MAX WINDS
OF 20 TO 25 KNOTS IN SMALL AREAS ON THE WESTERN AND NORTHWESTERN
PERIPHERY OF ITS LARGE CIRCULATION. IT IS NOW THE SUBJECT OF A
TROPICAL CYCLONE FORMATION ALERT BY JTWC, BUT IT APPEARS TO BE
MOVING WEST FAIRLY QUICKLY, AND BY THE TIME IT DEVELOPS INTO
ANYTHING SIGNIFICANT IT SHOULD BE APPROACHING THE PHILIPPINES.
EASTERN MICRONESIA AND CHUUK
A SURFACE RIDGE IS SHIFTING WESTWARD AWAY FROM CHUUK AND POHNPEI THIS
MORNING. IN ITS WAKE, A FEW MODEST TRADE-WIND DISTURBANCES ARE
APPROACHING FROM NEAR KOSRAE AND WILL SPREAD SPORADIC CONVECTION OVER
BOTH PLACES LATER TODAY. WET WEATHER ASSOCIATED WITH THESE SAME
DISTURBANCES WILL ALSO PERSIST NEAR KOSRAE AND MAJURO THRU TUESDAY.
FARTHER EAST, A TRADE-WIND CONVERGENCE BOUNDARY STRETCHES NORTHEAST
FROM 5N180 TO BEYOND 10N160W. THIS BOUNDARY IS GOING TO TRANSFORM
INTO A NEAR-EQUATORIAL TROUGH AND PROLONG UNSTABLE WEATHER ACROSS
THE ENTIRE REGION THRU THURSDAY. AS THE NEAR-EQUATORIAL TROUGH LIFTS
WEST-NORTHWESTWARD AWAY FROM THE REGION TOWARD THE WEEKEND, SURFACE
RIDGING IN ITS WAKE SHOULD FINALLY PROMOTE DRIER CONDITIONS FROM
EAST TO WEST.
WESTERN MICRONESIA FOR YAP AND KOROR
INVEST 99W, THE BROAD MONSOONAL CIRCULATION NORTHWEST OF YAP NEAR
12N133E, CONTINUES TO MOVE NORTHWESTWARD ACROSS THE PHILIPPINE SEA
THIS MORNING. MODEST CONVERGING MONSOONAL WINDS SHOULD STILL SPARK
A FEW SHOWERS AND THUNDERSTORMS OVER KOROR AND YAP THRU TUESDAY.
BY TUESDAY NIGHT, A SURFACE HIGH BUILDING NORTHWESTWARD FROM NEAR
5N148E SHOULD USHER IN PARTLY CLOUDY SKIES ACROSS FAR WESTERN
MICRONESIA. THINGS MIGHT BECOME WETTER AGAIN TOWARD THE WEEKEND AS
THE LEADING EDGE OF A NEAR-EQUATORIAL TROUGH ARRIVES FROM THE EAST.
GUM WATCHES/WARNINGS/ADVISORIES
GU...NONE.
MARIANAS WATERS...NONE.
MIDDLEBROOKE/CHAN
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