Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Fri, 17 Dec 2010 00:18:39 -0600

645 
FXPQ60 PGUM 170618
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
418 PM CHST FRI DEC 17 2010

.SYNOPSIS...
SATELLITE IMAGERY REVEALS VERY DRY AIR IN PLACE WITH STRONG
SUBSIDENCE INDICATED OVERHEAD IN WATER VAPOR IMAGERY. RADAR SCAN
SHOWS VIRTUALLY NO RETURNS OVER THE FORECAST DOMAIN. ANIMATED
VISIBLE IMAGERY SUGGESTS ISOLATED SHOWERS SHOULD RETURN AROUND
MIDNIGHT. A COLD FRONT WAS SLICING BETWEEN IWO TO AND MINAMI TORI
SHIMA.

&&

.DISCUSSION...
NEAR TERM FORECAST STILL LOOKS RELATIVELY DRY. PLOT THICKENS
EARLY NEXT WEEK AS MODELS AGREE ON BRINGING A SHEAR LINE THROUGH
THE FORECAST DOMAIN BETWEEN MONDAY AND MONDAY NIGHT. GFS STILL
REMAINS THE MOST AGGRESSIVE OF THE SUITE OF MODELS IN REDUCING
SURFACE PRESSURES OVER THE MARIANAS AND VEERING SURFACE WINDS
AHEAD OF THE SHEAR LINE. GFS ENSEMBLE DOES NOT PERTURB THE WIND
FIELD OVER THE FORECAST DOMAIN AS MUCH AS THE 18Z SOLUTION...BUT
WIND SPEEDS DO BECOME WEAK. AGREE WITH PREVIOUS SHIFT IN
MAINTAINING MORE CLIMATOLOGICAL WINDS IN THE WIND GRIDS DURING
THE FIRST HALF OF NEXT WEEK UNLESS MODELS CONVERGE TO THE GFS
SOLUTION. FOR NOW...WILL INCREASE CLOUD COVER DURING MONDAY AND
TUESDAY TO ACCOUNT FOR THE PROXIMITY OF THE SHEAR LINE. MODEL
SOLUTIONS DIVERGE BEYOND MID WEEK...SO WILL ADHERE TO FORECAST
CONTINUITY AND MAINTAIN NORTHEAST WINDS...PARTLY CLOUDY SKIES AND
ISOLATED SHOWERS DURING THE SECOND HALF OF THE FORECAST PERIOD.

&&

.MARINE...
IPAN BUOY CAME IN BETWEEN 3 AND 4 FEET...SO REDUCED PRIMARY SWELL
GRID HEIGHT BY A FOOT TONIGHT AND SATURDAY. TAPERING THIS
ADJUSTMENT TO THE PREEXISTING MARINE SWELL GRIDS SUGGESTS SURF ON
NORTH AND EAST FACING REEFS WILL BUILD 1 TO 2 FEET BY SATURDAY AS
WELL. OTHERWISE...STILL EXPECT A NW SWELL TO BEGIN ARRIVING
SATURDAY AND BRING SURF ON WEST FACING REEFS TO MODERATE RIP
CURRENT RISK LEVELS.

&&

.EASTERN MICRONESIA...
LITTLE HAS CHANGED ACROSS THE REGION OTHER THAN THE DEVELOPMENT
OF A PATCH OF SHOWERS BETWEEN KOSRAE AND POHNPEI. CONVECTION HAS
BEEN SHALLOW AND RELATIVELY SHORT-LIVED. GFS PUSHES THE SHOWERS
THROUGH POHNPEI TONIGHT WITH DRIER CONDITIONS ENSUING FOR THE
NEXT 5 DAYS. EASTERLY WINDS WILL SHIFT TO THE SOUTHEAST BY MONDAY
AT ALL LOCATIONS IN RESPONSE TO A SHEARLINE DROPPING SOUTHWARD
TOWARD THE AREA BUT INCREASED SHOWER CHANCES ARE NOT EXPECTED FOR
NOW.

&&

.WESTERN MICRONESIA...
SCATTERED SHOWERS ASSOCIATED WITH A SMALL MCS ARE BEGINNING TO
ERODE AWAY AROUND KOROR AND THEY SHOULD CLEAR OUT BY MIDNIGHT. A
WEAK CIRCULATION CENTERED EAST OF YAP RAISES A LITTLE UNCERTAINTY
IN THE FORECAST FOR THE NEXT COUPLE OF DAYS. AT THE MOMENT...
MODELS ONLY PORTRAY EAST-NORTHEAST WINDS WEST OF THE CIRCULATION.
GENERAL TROUGHING APPEARS TO BE RESOLVED BY THE MODELS IN LIEU OF
THE CIRCULATION. DECIDED TO GO A LITTLE HEAVIER ON CLOUD COVER
OVER YAP FOR THE NEXT COUPLE OF DAYS. CURRENT FORECAST GIVES
WEIGHT TO MODEL GUIDANCE AND ASSUMES THE CIRCULATION WILL TROUGH
OUT QUICKLY. IF THE CIRCULATION SHIFTS TOO FAR WESTWARD BEFORE
FALLING APART...NEAR TERM WIND FORECAST FOR YAP WILL NEED TO BE
MODIFIED. UPPER-LEVEL SUBSIDENCE IS OTHERWISE KEEPING DEEP
CONVECTION OVER WESTERN MICRONESIA TO A MINIMUM. DRY CONDITIONS
WILL CONTINUE ON CHUUK...FOLLOWING THE TREND IN EASTERN MICRONESIA.
A COLD FRONT PUSHING SOUTHEASTWARD FROM JAPAN WILL GENERATE A
NORTHWEST SWELL ON KOROR AND YAP BY THE WEEKEND. THE NORTHWEST
SWELL WILL GRADUALLY BACK TO THE NORTH BY EARLY NEXT WEEK AS THE
FRONT DISSIPATES.

&&

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

$$

MCELROY/W. AYDLETT

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
To unsubscribe from WX-TROPL send e-mail to [email-masked] with
"unsub wx-tropl" in the body of your message. For help with WX-TROPL
write to [email-masked]. For more information on tropical weather products, see the NHC Homepage at http://www.nhc.noaa.gov.