Weather Update: 000 FXZS60 NSTU 310240 AAA AFDPPG AREA FORECAST DISCUSSION FOR AMERICAN SAMOA AND INDEPENDENT SAMOA...UPDATED NATIONAL WEATHER SERVICE PAGO PAGO AS 340 PM SST MON DEC 30 2013 .SHORT TERM... .TONIGHT THROUGH WEDNESDAY NIGHT...AN ACTIVE MONSOONAL TROUGH OVER TOKELAU IS PROGGED TO DESCEND OVER THE SAMOAN ISLANDS STARTING TONIGHT INTO TUESDAY AFTERNOON. THE LEADING EDGE OF THE SOUTH PACIFIC CONVERGENCE ZONE (SPCZ) IS NOW DRIVING UP CLOSE TO MANUA THIS EVENING WHICH HINTS THE EARLY ARRIVAL OF HEAVY RAINFALL AND POSSIBLE TSTMS NEAR AMERICAN SAMOA TONIGHT. THE ASCAT SWATHE FROM THIS AFTERNOON SHOWS MODERATE TO FRESH NORTHEAST WINDS UPSTREAM. THE GFS MODEL INSINUATE WET WEATHER CONDITIONS AND POSSIBLE TSTMS OVER THE SAMOAN ISLANDS DURING THE NEXT 24 TO 36 HOURS. ALTHOUGH THE COMPUTER MODEL MATERIALIZES A DEVELOPING LOW PRESSURE SYSTEM NEAR SAMOA...THE TWO MAIN CONCERNS FOR THE AREA ARE WIND SPEED AND SHOWER COVERAGE. THE SPCZ AXIS IS EXPECTED TO DIVE SOUTHWESTWARD HENCE A STRONG AREA OF HIGH PRESSURE WILL HINDER THIS LOW FROM DREDGING FARTHER SOUTH UNTIL DURING THE NEW YEAR/S DAY. THE DEVELOPING LOW PRESSURE IS EXPECTED TO LINGER NEAR SAMOA WITH MINIMAL TO NO IMPACT OVER THE SAMOAN ISLANDS. THE SPCZ WILL BE THE MAIN WEATHER PRODUCER...AND ITS LOCATION AND MOVEMENT WILL BE MONITORED OVER THE NEXT COUPLE OF DAYS. IF MODELS ARE CORRECT...HEAVY RAINFALL AND GLOOMY WEATHER CONDITIONS WILL LINGER OVER THE FCST ZONES THROUGH THE NEW YEAR/S DAY. AS A RESULT...HAVE UPDATED THE PREVIOUS FORECAST FOR AMERICAN SAMOA TO INCLUDE ISOLATED TSTMS OVER WATERS AND A CHANCE OF TSTMS OVER ZONES...AND UPDATE THE WIND SPEED AND DIRECTION FROM THE NORTHEAST AT 10 TO 15 KT TONIGHT...THEN INCREASING TO 15 TO 20 KT TUESDAY WITH HIGHER GUSTS. THE RAIN SHOWERS ARE EXPECTED TO WIND DOWN DURING WEDNESDAY NIGHT...BUT FOR NOW...WILL KEEP THE SCATTERED WORDING UNTIL THIS SITUATION UNWINDS DEPENDING ON FUTURE FORECAST MODELS. .LONG TERM... .THURSDAY THROUGH MONDAY...A MONSOONAL TROUGH OVER THE SAMOAN ISLANDS WILL TRIGGER OCCASIONAL SHOWERS AND ISOLATED TSTMS BEFORE THE END OF THE WEEK. A SURFACE RIDGE CENTERED A FEW HUNDRED MILES NORTHEAST OF PAGO PAGO IS EXPECTED TO SUPPRESS THE SPCZ SOUTHWESTWARD OF THE REGION UNTIL SUNDAY OR MONDAY. ALTHOUGH THE SPCZ IS PROGGED TO DIG SOUTH SOUTHWESTWARD...A BROAD AREA OF HIGH PRESSURE WELL SOUTHEAST OF SAMOA WILL NOT BE EASILY REMOVED FROM ITS POSITION. INCREASING RAINFALL AND CLOUD COVERAGE ARE ANTICIPATED OVER THE NEXT SEVERAL DAYS INTO THE NEW WEEK...BUT FOR NOW...WILL KEEP THE PREV FCST THE SAME EXCEPT TO UPDATE THE SUNDAY AND MONDAY FORECAST PERIODS BY REDUCING THE SHOWER COVERAGE TO ISOLATED WORDING. && .MARINE...LOCALLY STRONG WINDS ASSOCIATED WITH THE MONSOONAL TROUGH OR THE SPCZ WILL GENERATE A NEW NORTHEAST SWELL OF 6 TO 8 FEET TO ARRIVE TUESDAY AFTERNOON. ISSUANCE OF A SMALL CRAFT ADVISORY TUESDAY MORNING OR EARLIER IS MANDATORY TO REFLECT THIS SITUATION. && .PPG WATCHES/WARNINGS/ADVISORIES... .A SMALL CRAFT ADVISORY IS NOW IN EFFECT. && $$
Posted on: Tue, 31 Dec 2013 21:31:07 +0000
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