Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Fri, 11 Jan 2008 01:58:21 -0600

127 
FXPQ60 PGUM 110758
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
558 PM CHST FRI JAN 11 2008

.SYNOPSIS...ONLY A FEW SMALL TRADE-WIND SHOWERS WERE VISIBLE ON
RADAR THIS AFTERNOON AS DRY AIR MOVED ACROSS THE MARIANAS. MODERATE
TO FRESH TRADE WINDS AND A FEW WIND GUSTS IN THE 20 TO 30 KNOT
RANGE WERE OBSERVED. 

&&

.DISCUSSION...LITTLE CHANGE TO THE CURRENT FORECAST. MODERATE TO
FRESH NORTHEAST TRADE-WINDS WILL PREVAIL THROUGH THE FORECAST.
LITTLE IN THE WAY PRECIPITATION EXPECTED ALSO. EARLIER FORECAST
HAD SOME CLOUDS ON SUNDAY AND SUNDAY NIGHT. THE GFS AND UKMET HINT
AT THE POSSIBILITY OF SOME CLOUDS DURING THIS TIME SO LEFT THEM IN.
NGPS AND ECMWF HAD SOME CLOUDS SATURDAY BUT FELT IT WAS NOT STRONG
ENOUGH OF A PATTERN TO PUT IN.

&&

.MARINE...THIS FORECAST WAS BASICALLY LEFT AS IS. EASTERLY SWELL
AND TRADE-WIND INDUCED WIND WAVES DOMINATE THE FORECAST. BY
SATURDAY A SECONDARY NORTHERLY SWELL PUSHES THROUGH THE MARIANAS.
NONE OF THESE SWELLS APPEAR LARGE ENOUGH AT THIS TIME TO GENERATE
HAZARDOUS SURF. COMBINED SEAS REACH 10 FEET BY TUESDAY AND AS A
RESULT A SMALL CRAFT ADVISORY MAY BE NEEDED BY MID-WEEK.

&&

.EASTERN MICRONESIA...
THE EXACT POSITIONING OF THE NARROW BAND OF STRONG TRADE-WIND 
CONVERGENCE WILL BE KEY FOR FOR THE AMOUNT OF RAINFALL EXPECTED 
FOR EACH PARTICULAR ISLAND DURING THIS FORECAST PERIOD. ALL
MODELS...AS WELL AS THE SATELLITE IMAGERY AND WIND DATA...SHOW THE
EXISTENCE OF THIS STRONG BAND. HOWEVER...A SLIGHT PUSH NORTH OR 
SOUTH MAKES A BIG DIFFERENCE AS THE WEATHER TENDS TO DRY OUT FAIRLY 
QUICKLY IN THIS TRADE-WIND REGIME THE FURTHER ONE GETS AWAY FROM THE 
CONVERGENCE ZONE.  THE MODELS...SUCH AS GFS...NOGAPS...UKMET...AND 
ECMWF ALL HAVE A SLIGHT VARIATION IN THIS POSITIONING...THUS LITTLE 
AGREEMENT FOR ANY SPECIFIC ISLAND FORECAST.  IN GENERAL...I TRIED 
NOT TO CHANGE EXISTING FORECAST TOO MUCH WITH THIS LOW CONFIDENCE 
SCENARIO...EXCEPT FOR THE NEAR TERM PORTION OF THE FORECAST. A CASE 
IN POINT IS FOR MAJURO WHERE THE WEATHER SEEMS TO HAVE REPOSITIONED 
FURTHER TO THE SOUTH DURING THE DAY.

AS DISCUSSED IN THE PREVIOUS AFD...HIGH SURF IS EXPECTED TO REACH 
ALL THREE ISLANDS DURING THE UPCOMING WEEKEND.  ALTHOUGH THE LATEST 
WW3 MODELS ONLY SHOW THE 8 FOOT HIGH SURF CRITERIA REACHING KOSRAE 
BY TONIGHT...IT IS LIKELY THAT 12 FOOT CRITERIA FOR MAJURO AND 
POHNPEI ARE STILL ABOUT 24 TO 36 HOURS AWAY. TO AVOID ANY CONFUSION 
ON THE TIMING AND THE EVENTUAL EXISTENCE OF THIS EVENT...I LEFT 
THE ADVISORY UNCHANGED.

&&

.WESTERN MICRONESIA...
LITTLE CHANGE FROM THE PREVIOUS FORECAST. FAIR WEATHER WILL PREVAIL 
ACROSS CHUUK STATE TONIGHT THROUGH THE WEEKEND. AFTER THIS THE 
PARTICULARITY OF THE SPECIFIC FORECAST WILL ALSO DEPEND UPON THE 
EXACT POSITIONING OF THE AFOREMENTIONED NARROW TRADE-WIND 
CONVERGENCE ZONE. CURRENT WEATHER OVER YAP AND PALAU IS EXPECTED TO 
CONTINUE TO PUSH FURTHER TO THE WEST AND SOUTH OVER THE NEXT COUPLE 
OF DAYS...BRINGING AT LEAST A SHORT PERIOD OF FAIR WEATHER. DURING 
THE PAST 24 HOURS...MODERATE TO HEAVY RAINFALL IN EXCESS OF TWO 
INCHES WAS REPORTED PRIMARILY DUE TRADE-WIND CONVERGENCE. 

AS DISCUSSED IN THE PREVIOUS AFD...COMBINED SEAS STAY IN THE 7 TO 9 
FOOT RANGE FOR MOST AREAS THROUGH THE FORECAST PERIOD. THE EXCEPTION 
IS CHUUK STATE. SEAS WILL RISE TO NEAR 10 FEET BY SUNDAY. BY THIS 
TIME...HIGH SURF IS EXPECTED TO HAVE REACHED THESE ISLANDS.

&&

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

$$

ZIOBRO/EDSON

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