Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 27 Dec 2010 14:42:33 -0600

579 
FXPQ60 PGUM 272042
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
642 AM CHST TUE DEC 28 2010

.SYNOPSIS...A FEW SHOWERS COULD BE SEEN ON RADAR THIS MORNING OVER
THE LOCAL AREA. SATELLITE SHOWS MAINLY HIGH LEVEL CLOUDS COVERING
THE MARIANAS. EXPECT MOSTLY CLOUDY SKIES TODAY WITH ISOLATED
SHOWERS. A SHEAR LINE WILL ENTER THE AREA THIS WEEKEND.

&&

.DISCUSSION...LITTLE CHANGE MADE TO FORECAST. GFS...GFSE AND
UKMET KEEP THE WINDS NORTHEAST DURING THE DAY BECOMING EASTERLY BY
TONIGHT. GFS AND UKMET BOTH SHOW A TROUGH OF LOW PRESSURE IN THE
WIND FIELD JUST TO THE WEST OF THE MARIANAS TONIGHT. GFSE KEEPS
SOME RELATIVE VORTICITY OVER THE AREA TONIGHT...SO PERIODS OF
SHOWERS ARE POSSIBLE. MODEL 700 MB RH GREATER THAN 70 PERCENT ARE
PREDICTED TO BE NORTH AND WEST OF THE MARIANAS TONIGHT SO ANY
SCATTERED SHOWERS THAT DO DEVELOP WILL PROBABLY BE THERE WHILE
ISOLATED WILL PREVAIL ACROSS THE ISLANDS.

MODELS STILL DEPICT A SHEAR LINE MOVING SOUTHWARD AND PASSING
ACROSS THE LOCAL AREA ON SATURDAY. THE PASSAGE WILL BE DURING THE
DAY FOR TINIAN AND SAIPAN AND THE NIGHT FOR GUAM AND ROTA. WINDS
WILL TURN NORTHEAST. GFS DEPICTS THAT THE SHEAR LINE WILL MAKE IT
ONLY AS FAR SOUTH AS GUAM. IT REMAINS OVER THE SOUTHERN MARIANAS
WITH CLOUDINESS PERSISTING THROUGH AT LEAST THROUGH TUESDAY. IT
IS POSSIBLE THAT PERIODS OF SCATTERED SHOWERS ARE POSSIBLE
SATURDAY THROUGH TUESDAY ASSOCIATED WITH THE SHEAR LINE...BUT WILL
LEAVE IT OUT OF THE FORECAST FOR NOW UNTIL MORE IS KNOWN.

&&

.MARINE...
THE NORTHWEST SWELL AND EAST SWELL WILL PERSIST THROUGH THE
FORECAST. THE EAST TRADE-WIND SWELL WILL DECREASE DURING THE
FORECAST FROM 6 FEET TODAY TO 5 FEET ON SATURDAY. THE NORTHWEST
SWELL WILL BECOME THE MORE INTERESTING SWELL BY THE WEEKEND. THE
NORTHWEST SWELL WILL BE ABOUT TWO FEET TODAY INCREASING BRIEFLY
TO FIVE FEET WEDNESDAY NIGHT THEN DROP TO THREE FEET THURSDAY
NIGHT. THIS LULL WILL BE SHORT LIVED AS THE SWELL WILL INCREASE
TO FOUR FEET AGAIN ON FRIDAY. A MAJOR INCREASE WILL OCCUR BY THE
WEEKEND AS STRONG WINDS OVER THE NORTHWEST PACIFIC WILL PUSH LARGE
SWELLS SOUTHEASTWARD. THE LARGER SWELLS WILL ENTER THE AREA
SATURDAY NIGHT BECOMING 11 FEET ON SUNDAY NIGHT. IF THE MODELS
ARE ACCURATE AND THIS 11 FOOT SWELL DOES IN-FACT OCCUR THAN SURF
MAY REACH 15 FEET ON SOME NORTH FACING REEFS SUNDAY NIGHT AND
MONDAY. THIS SITUATION WILL BE WATCHED AND IF THIS PANS OUT THAN
ADVISORIES WILL BE NEEDED. 

&&

.EASTERN MICRONESIA...
THE LINE OF CONVECTION HAS SHIFTED NORTHWARD SLIGHTLY AND NOW
SITS NORTH OF KOSRAE EASTWARD ACROSS KWAJALEIN AND MAJURO AND
ONWARD TO THE DATELINE. HAVE EXTENDED SCATTERED SHOWERS AT MAJURO
INTO TONIGHT FOLLOWING MODEL GUIDANCE OF SHOWERS LINGERING IN THE
AREA BEFORE DISSIPATING. SHOWERS CONTINUE TO PROGRESS TOWARD
POHNPEI AND SCATTERED SHOWERS SHOULD ARRIVE AROUND NOON TODAY.
GFS INDICATES DIMINISHING CONVECTIVE ACTIVITY LATER TONIGHT. AT
THE MOMENT ONLY GFS40 POINTS TO A REDEVELOPED TRADE-WIND TROUGH
BETWEEN POHNPEI AND THE MARSHALLS LATER THIS WEEK SO WILL KEEP
ONLY ISOLATED SHOWERS IN THE FORECAST FOR NOW.

&&

.WESTERN MICRONESIA...
NOW THAT THE TROUGH NEAR CHUUK IS BEGINNING TO PASS
WEST...SHOWERS ARE BECOMING BETTER DEVELOPED WEST OF CHUUK. TODAY
SHOULD SEE JUST ISOLATED SHOWERS BEFORE SCATTERED SHOWERS MOVE IN
LATE TONIGHT AS A TRADE-WIND TROUGH APPROACHES FROM THE EAST.
SHOWERS SHOULD DROP BACK TO ISOLATED WEDNESDAY AS THE FOCUS OF
CONVECTION DROPS SOUTH OF CHUUK. DEEP CONVECTION HAS SUBSIDED
NEAR YAP AND PALAU OVERNIGHT BUT LOW-LEVEL CONVERGENCE NORTH OF A
NEAR- EQUATORIAL TROUGH WILL BEGIN TO TRIGGER ANOTHER ROUND OF
SHOWERS FOR WEDNESDAY NIGHT AND THURSDAY AT BOTH LOCATIONS.

&&

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

$$

ZIOBRO/W. AYDLETT

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