486  
FXPQ60 PGUM 210848  
AFDPQ  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE TIYAN GU  
648 PM CHST SUN OCT 21 2018  
   
MARIANAS SYNOPSIS
 
 
ISOLATED SHOWERS PREVAILED OVER THE MARIANAS EARLY THIS EVENING.  
A WEAK SURFACE CIRCULATION WAS LOCATED SOUTH OF GUAM. COMBINED  
SEAS WERE 3 TO 4 FEET AT THE BUOYS.  
 

 
   
DISCUSSION
 
 
AFTER SOME DECENT ISLAND CONVECTION TODAY, CONDITIONS APPEAR TO BE  
SETTLING DOWN. THERE IS ABUNDANT DRY AIR ALOFT AND WITH STRONGER  
WIND FORECAST ON MONDAY AND TUESDAY, EXPECT JUST ISOLATED SHOWERS.  
 
WEDNESDAY AND THURSDAY'S FORECAST IS ENTIRELY DEPENDENT ON THE  
TRACK AND STRENGTH OF A DEVELOPING TROPICAL DISTURBANCE NEAR  
8N159E. CURRENT GUIDANCE HAS COME INTO BETTER AGREEMENT THAT THIS  
SYSTEM WILL MOVE TOWARD THE NORTHERN MARIANAS. THEREFORE, HAVE  
STARTED AND UPWARD TREND ON SEAS, WIND AND SHOWERS IN THE  
WEDNESDAY AND THURSDAY TIME FRAME. THERE WILL BE FURTHER REVISIONS  
TO THE FORECAST AND THERE WILL LIKELY BE CHANGES IN TIMING (SLOWER  
OR FASTER) AS WELL.  
 
DID NOT MAKE ANY CHANGES BEYOND THURSDAY AS ANY IMPACTS FROM THE  
TROPICAL SYSTEM SHOULD BE WINDING DOWN AND OVER AS WE MOVE TOWARD  
THE END OF THE WEEK INTO THE WEEKEND.  
 

 
   
MARINE
 
 
CONDITIONS ARE EXPECTED TO BE RELATIVELY QUIET ON THE MARINE AREA  
THROUGH TUESDAY WITH LIGHT WIND AND SEAS OF 3 TO 4 FEET. HOWEVER,  
THINGS WILL BEGIN TO RAMP UP BEGINNING TUESDAY NIGHT, ESPECIALLY  
FOR TINIAN AND SAIPAN AS A TROPICAL DISTURBANCE MOVES TOWARD THE  
NORTHERN MARIANAS. BEGAN THE TREND THIS CYCLE OF INCREASING WIND  
AND SEAS. DEPENDING ON THE ULTIMATE TRACK AND STRENGTH, THEY COULD  
STILL BE TOO LOW IN SOME AREAS. MARINE HEADLINES WILL LIKELY BE  
NEEDED FOR A PORTION OF THE AREA DURING AT LEAST THE WEDNESDAY  
THURSDAY TIME FRAME. RIP CURRENT RISK, WHICH IS CURRENTLY  
MODERATE, WILL LIKELY BECOME HIGH BY MIDWEEK AS WELL.  
 

 
   
TROPICAL SYSTEMS
 
 
A TROPICAL DISTURBANCE, CURRENTLY NORTH OF POHNPEI, NEAR 8N159E IS  
MOVING SLOWLY WEST-NORTHWESTWARD. IT IS THE SUBJECT OF A TROPICAL  
CYCLONE FORMATION ALERT FROM THE JOINT TYPHOON WARNING CENTER.  
 
THIS SYSTEM IS EXPECTED TO DEVELOP OVER THE NEXT FEW DAYS. WHILE  
THERE IS STILL UNCERTAINTY IN THE MODELS AND THINGS COULD STILL  
CHANGE OVER THE NEXT FEW DAYS, GUIDANCE HAS BEGUN TO CONVERGE  
TOWARD A SOLUTION WHICH BRINGS THE SYSTEM NEAR OR NORTH OF SAIPAN  
WEDNESDAY OR THURSDAY. THE GFS, ECMWF, CMC AND NAVGEM ALL SUPPORT  
THIS SOLUTION. HOWEVER, THERE ARE DIFFERENCES AS TO HOW FAR NORTH  
OF SAIPAN THE SYSTEM GETS AND OBVIOUSLY, THESE DIFFERENCES ARE  
CRITICAL. THERE ARE STILL SOME OTHER MODELS WITH DIFFERENT  
SOLUTIONS AS WELL.  
 
EVEN THOUGH THE MODELS HAVE CONVERGED ON A SOLUTION, IT IS STILL  
POSSIBLE THAT THE MODELS MAY MAKE ADDITIONAL CHANGES IN EITHER  
TRACK, STRENGTH OR TIMING OVER THE NEXT FEW DAYS.  
 

 
   
EASTERN MICRONESIA AND CHUUK
 
 
A TROPICAL DISTURBANCE, CENTERED NEAR 8N159E, IS THE THE SUBJECT OF  
A TROPICAL CYCLONE FORECAST ALERT BY THE JOINT TYPHOON WARNING  
CENTER. THIS SYSTEM IS MOVING TOWARD THE WEST-NORTHWEST AND IS  
GENERATING CLOUDY SKIES WITH SCATTERED TO NUMEROUS SHOWERS ACROSS  
POHNPEI STATE. THIS INCLEMENT WEATHER WILL CONTINUE ACROSS POHNPEI  
THROUGH MONDAY NIGHT AS THE SYSTEM SLOWLY MOVES FARTHER WEST-  
NORTHWESTWARD. CHUUK WILL BEGIN TO SEE THE AFFECTS OF THE  
DISTURBANCE MONDAY NIGHT, AS CLOUDS AND SCATTERED SHOWERS MOVE IN TO  
THE STATE. WINDS AND SEAS ARE NOT EXPECTED TO BE A CONCERN AT  
POHNPEI AS THE DISTURBANCE IS ALREADY NORTH OF THE ISLAND AND MOVING  
AWAY. WINDS WILL BEGIN TO INCREASE AS WELL AT CHUUK THROUGH MIDWEEK  
DUE TO INCREASING MONSOON FLOW INTO THE DEVELOPING SYSTEM. THIS  
SYSTEM IS EXPECTED TO STRENGTHEN OVER THE NEXT FEW DAYS, THOUGH IT  
IS EXPECTED TO REMAIN NORTH OF EASTERN MICRONESIA AND CHUUK. DRIER  
CONDITIONS ARE MOVING IN TO KOSRAE AS THE SYSTEM PULLS FARTHER AWAY  
FROM THE STATE.  
 
FARTHER EAST, A BAND OF WEAK CONVERGENCE IS GENERATING PATCHY  
SHOWERS AND THUNDERSTORMS NEAR MAJURO. THIS IS EXPECTED TO CONTINUE  
THROUGH MIDWEEK BEFORE A DRIER PATTERN MOVES IN TO THE REGION.  
 

 
   
WESTERN MICRONESIA YAP AND KOROR
 
 
A MONSOON TROUGH STRETCHES EASTWARD ACROSS PALAU THROUGH A WEAK  
CIRCULATION CENTERED SOUTH OF GUAM. SHOWERS AND THUNDERSTORMS  
ASSOCIATED WITH THE TROUGH ARE LOCATED OVER SOUTHERN KOROR WATERS  
AND LOOK TO REMAIN THERE FOR THE NEXT FEW DAYS. A DEVELOPING  
TROPICAL SYSTEM IN EASTERN MICRONESIA, NORTH OF POHNPEI, WILL BEGIN  
TO LIFT THE TROUGH NORTHWARD AROUND MIDWEEK. THIS WILL MAINTAIN  
CONVECTION OVER KOROR THROUGH AT LEAST THE END OF THE WEEK.  
MAINTAINED ISOLATED SHOWERS FOR NOW, THOUGH PERIODS OF SCATTERED  
SHOWERS ARE A POSSIBILITY, DEPENDING ON THE LOCATION AND STRENGTH OF  
THE TROUGH. A FAIR WEATHER PATTERN IS EXPECTED TO CONTINUE OVER YAP  
THROUGH MIDWEEK. SHOWERS AND CLOUD COVER WILL BEGIN TO INCREASE AS  
THE MONSOON TROUGH DRIFTS NORTH.  
 

 
   
GUM WATCHES/WARNINGS/ADVISORIES
 
 
GU...NONE.  
MARIANAS WATERS...NONE.  

 
 

 
 
NIERENBERG/KLEESCHULTE  
 
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