Subject: Western Pacific: Synoptic Discussion For The Marianas

From: LDM Weather <[email-masked]>
Date: Mon, 18 Oct 2010 16:14:44 -0500

746 
FXPQ60 PGUM 182114
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
714 AM CHST TUE OCT 19 2010

.SYNOPSIS...LIGHT WINDS AND ISOLATED SHOWERS ARE PRESENT ACROSS
THE MARIANAS THIS MORNING. A SURFACE TROUGH OF LOW PRESSURE IS
LOCATED JUST TO THE EAST OF THE ISLANDS WHILE AN UPPER-LEVEL
TROUGH LIES JUST WEST OF THE LOCAL AREA.

&&

.DISCUSSION...
EXPECT LIGHT WINDS TO PREVAIL TODAY THROUGH WEDNESDAY AS A SURFACE
TROUGH MOVES ACROSS THE MARIANAS. DIFFERENT MODELS HAVE VARIOUS
VIEWS ON WHAT TO DO WITH THE SURFACE TROUGH JUST TO THE EAST OF
THE MARIANAS. WHILE IT IS TRUE THAT THERE IS A CIRCULATION ON THE
TROUGH...FIGURE THAT IT IS TOO FAR NORTH AND IF IT MOVES OVER THE
AREA IT WILL BE NORTH OF SAIPAN. IN THE FORECAST TRIED TO DEPICT
A SURFACE TROUGH MOVING ACROSS THE MARIANAS THROUGH WEDNESDAY.
THIS WILL KEEP WINDS LIGHT TODAY AND TONIGHT. LIGHT WINDS AND
DAYTIME HEATING COMBINED WITH THE UPPER-TROUGH OVER THE AREA WILL
LEAD TO THE POSSIBILITY OF THUNDERSTORMS THIS AFTERNOON.
THUNDERSTORMS MAY LINGER INTO TONIGHT. ONLY ISOLATED SHOWERS
EXPECTED THROUGH THE FOR EAST.

&&

.MARINE...
EAST TRADE-WIND SWELL WILL PERSIST THROUGH THE FORECAST. THE
SWELL BRIEFLY INCREASES TO FIVE FEET WEDNESDAY THROUGH THURSDAY.
THIS WILL CAUSE A SHORT TIME PERIOD OF MODERATE RIP CURRENT RISK
ON EAST FACING SHORES. AT THIS TIME IT IS BELIEVED THAT NO
SIGNIFICANT SWELLS WILL ENTER THE AREA FROM TYPHOON MEGI.

&&

.EASTERN MICRONESIA...
WITH THE EXCEPTION OF SOME MINOR ADJUSTMENTS TO WINDS AND CLOUD 
COVER...NO CHANGES WERE MADE TO THE EXISTING FORECAST. MODELS PRETTY 
WELL AGREE THAT ALL THREE LOCATIONS WILL REMAIN FAIRLY DRY WITH 
SOUTHEAST FLOW SPREADING WESTWARD FROM MAJURO. WINDS AT POHNPEI WILL 
BE VARIABLE TODAY BEFORE TURNING SOUTHEAST...BUT EXACT TIMING 
DEPENDS ON HOW QUICKLY THE NEARLY-STATIONARY TROUGH AND WEAK 
CIRCULATION NORTH OF KWAJALEIN NEAR 12N169E...JTWC INVEST AREA 
96W...PUSHES WEST-NORTHWESTWARD. A MID- AND UPPER-LEVEL LOW JUST 
SOUTH OF WAKE ISLAND HAS ALSO HELPED TO DEEPEN CONVECTION FROM 
KWAJALEIN NORTH...BUT CONVECTION SHOULD REMAIN NORTH OF POHNPEI AND 
MAJURO THROUGH THE WEEK. ANOTHER SURFACE TROUGH WILL APPROACH THE 
MARSHALLS AROUND THURSDAY LEADING TO INCREASED CLOUD COVER...BUT FOR 
NOW IS NOT EXPECTED TO SIGNIFICANTLY INCREASE THE CHANCE FOR SHOWERS.

&&

.WESTERN MICRONESIA...
A LINE OF SHOWERS SEEN IN SATELLITE IMAGERY JUST WEST OF KOROR 
PROMPTED THE ADDITION OF SCATTERED SHOWERS FOR TODAY. THE SHOWERS 
WILL LIKELY BE ACCOMPANIED BY WEAK WEST WINDS. ONLY GFS HINTS AT THE 
EXISTENCE OF THESE SHOWERS AND KEEPS THEM IN PLACE VERY BRIEFLY 
TODAY BEFORE ERODING THEM OUT OF THE PICTURE. A FEW CONVECTIVE CELLS 
HAVE RECENTLY DEVELOPED EAST OF YAP ALONG A TROUGH THAT STRETCHES 
NORTHEASTWARD TO A CIRCULATION EAST OF THE MARIANAS NEAR 17N154E. 
MODELS PROG THE CIRCULATION TO DROP WEST-SOUTHWESTWARD THE NEXT 
SEVERAL DAYS WHILE THE SOUTHERN END OF THE TROUGH MOVES VERY SLOWLY 
WESTWARD. FOR NOW...MODELS SUGGEST THE MAIN EFFECT THE TROUGH WILL 
HAVE ON YAP AND KOROR WILL BE LIGHT AND VARIABLE WINDS. LITTLE 
CHANGE IS EXPECTED AT CHUUK AS DRY SOUTHEAST WINDS PERSIST THROUGH 
THE REST OF THE WEEK.

&&

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

$$

ZIOBRO/W. AYDLETT

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