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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