Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Sun, 19 Dec 2010 02:22:44 -0600

309 
FXPQ60 PGUM 190822
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
622 PM CHST SUN DEC 19 2010

.SYNOPSIS...
A WELL DEFINED SHEAR LINE CONTINUES SINKING SOUTHWARD AND IS
CURRENTLY NEARING PAGAN. AN INVERTED SURFACE TROUGH IS LOCATED
EAST OF THE MARIANAS ALONG 149E. SHOWERS WERE CONCENTRATING ALONG
THE TROUGH AXIS AND WESTWARD AS FAR AS THE MARIANAS. VERY DRY AIR
WAS EVIDENT EAST OF THE TROUGH FOR A COUPLE OF HUNDRED MILES.

&&

.DISCUSSION...
NO SIGNIFICANT CHANGES TO FORECAST REASONING. MODEL GUIDANCE
CONSENSUS STILL SUGGESTS INVERTED SURFACE TROUGH JUST EAST OF THE
MARIANAS WILL ENHANCE CLOUD COVER OVER THE FORECAST ZONES THROUGH
MONDAY. MODELS ARE NOT BACKING WINDS ENOUGH AHEAD OF THE TROUGH SO
HAVE ADJUSTED SHORT TERM WIND GRIDS ACCORDINGLY. MODEL GUIDANCE
CONSENSUS ALSO SUGGESTS SHEAR LINE WILL SINK INTO THE FORECAST
ZONES ON MONDAY AND TUESDAY. WEAKNESS OF SHEAR LINE BY THIS TIME
SUGGESTS WIND FIELD TO THE NORTH OF THE BOUNDARY WILL BE
RELATIVELY WEAK. IF NOT...MAGNITUDE OF THE WIND GRIDS OVER THE
FORECAST ZONES MAY NEED TO BE BEEFED UP DURING AND JUST AFTER THE
TIME FRAME OF THE SHEAR LINE PASSAGE. INHERITED FORECAST MAINTAINS
MOSTLY CLOUDY SKIES THROUGH TUESDAY...WHICH LOOKS LIKE A PRETTY
GOOD GUESS FOR NOW. MODEL QPFS AND SATELLITE IMAGERY STILL SUGGEST
SHOWER COVERAGE SHOULD REMAIN ISOLATED THROUGH TUESDAY...THEN A
DRYING TREND IS EXPECTED. HOWEVER...WOULD NOT BE SURPRISED TO SEE
SHOWERS BRIEFLY CONCENTRATE ABOVE THE SCATTERED COVERAGE THRESHOLD
ON THE MESOSCALE UNTIL THE DRIER AIR ARRIVES.

&&

.MARINE...
IPAN BUOY INITIALIZES WITH A MAXIMUM SIGNIFICANT SWELL HEIGHT
BETWEEN 3 AND 4 FEET FROM 050 DEGREES AT 12 SECONDS. HAVE BACKED
THE SWELL FROM 060 TO 050 DEGREES AND SHAVED A FOOT FROM THE SWELL
HEIGHT. WILL TAPER THESE CHANGES INTO THE EXISTING SWELL GRIDS.
BASED UPON THIS EXPECT SURF TO BUILD ON NORTH AND EAST FACING
REEFS A BIT DURING THE NEXT DAY OR SO IF WAVE WATCH GUIDANCE IS
CORRECT. OTHERWISE...NO BIG CHANGES TO THE MARINE SWELL GRIDS.
STILL EXPECT MODERATE RIP CURRENT RISK LEVEL SURF TO PREVAIL ON
NORTH AND EAST FACING REEFS FOR AT LEAST THE NEXT SEVERAL DAYS.

&&

.EASTERN MICRONESIA...
LIGHT SURFACE WINDS ASSOCIATED WITH THE NEUTRAL POINT OF AN
UNSEASONAL TROUGH EXTENDING NORTHEASTWARD FROM THE MARSHALLS TO
BEYOND THE DATE LINE WILL CONTINUE TO PROMOTE FAIR WEATHER OVER
MAJURO INTO TUESDAY. GENTLE NORTHEAST TO EAST WINDS SOUTHEAST OF A
STRONG SHEAR LINE NEAR THE MARIANAS ARE ALSO SUPPORTING DRY
WEATHER FOR BOTH KOSRAE AND POHNPEI THRU MONDAY EVENING. AS THE
TROUGH NEAR THE MARSHALLS GRADUALLY LIFTS NORTHWARD DURING
MIDWEEK...THE SURFACE RIDGE EAST OF THE DATE LINE WILL STRETCH
WESTWARD AND PROLONG DRY WEATHER FOR THE ENTIRE REGION.

&&

.WESTERN MICRONESIA...
A WEAK SURFACE TROUGH IS EXPECTED TO BRING A FEW CLOUDS AND
SHOWERS OVER CHUUK THRU MONDAY. BY TUESDAY...THE SAME DRY PATTERN
OVER EASTERN MICRONESIA WILL ALSO DOMINATE CHUUK AS WELL. FARTHER
WEST...A SHEAR LINE FRAGMENT IS GENERATING SOME WETNESS FOR BOTH
YAP AND KOROR. WITH THIS FEATURE SLOWLY SHIFTING WESTWARD...
IMPROVEMENT SHOULD BEGIN ON TUE AND LAST INTO AT LEAST FRI.

NW-N SWELLS PRODUCED BY NEAR-GALE WINDS NORTH OF THE SHEAR LINE
AND COLD FRONT ARE GOING TO CAUSE HIGHER SURF ALONG THE NORTH
SHORES OF BOTH THE REPUBLIC OF PALAU AND YAP STATE FOR THE NEXT
FEW DAYS...AND FOR CHUUK BY MIDWEEK. SURF HEIGHTS ACROSS PALAU AND
YAP SHOULD STAY BELOW ADVISORY LEVELS...BUT COULD REACH ADVISORY
CRITERIA ON CHUUK AND NEEDS TO BE MONITORED.

&&

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

$$

MCELROY/CHAN

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