Area Forecast Discussion
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000
FXPQ60 PGUM 170807
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
607 PM CHST WED SEP 17 2014

.MARIANAS SYNOPSIS...ISOLATED SHOWERS AND THUNDERSTORMS AND
SOUTHEAST WINDS PREVAIL ACROSS THE MARIANAS THIS AFTERNOON.

&&

.DISCUSSION...
A DEVELOPING TROPICAL DISTURBANCE WAS LOCATED FAR TO THE WEST OF
GUAM THIS AFTERNOON. WEAK CONVERGENCE TO THE EAST OF THE
DISTURBANCE WILL GENERATE A FEW SHOWERS AND THUNDERSTORMS ACROSS
THE MARIANAS FOR PART OF THE NIGHT. HIGH PRESSURE WILL BUILD INTO
THE LOCAL AREA LATE TONIGHT. THE CENTER OF THE HIGH WILL PASS
OVER THE MARIANAS ON THURSDAY. SOUTHEAST WINDS THIS EVENING WILL
GRADUALLY BACK TO NORTHEAST BY THURSDAY. NORTH WINDS CAN BE
EXPECTED OVER THE LOCAL AREA THURSDAY NIGHT AND FRIDAY AS THE
CENTER OF THE HIGH PRESSURE MOVES WEST OF THE MARIANAS.

MODELS SHOW AN AREA OF WIND FLOW-CONVERGENCE...WHICH IS NOW EAST
OF THE MARIANAS NEAR 155E... AND MOVE IT WEST AND OVER THE
MARIANAS FRIDAY AND SATURDAY. TEMPTED TO ADD ISOLATED
THUNDERSTORMS TO THE FORECAST FOR BOTH DAYS...ESPECIALLY SINCE
THERE ARE THUNDERSTORMS ASSOCIATED WITH THIS AREA NOW . MODELS
HOWEVER KEEP THE DEEP LAYER MOISTURE AT A MINIMUM SO WILL LEAVE
OUT FOR NOW.

MODELS SHOW A CIRCULATION PASSING SOUTH OF THE AREA SATURDAY. A
TROUGH WILL TRAIL BEHIND THE CIRCULATION AND WILL BE DRAGGED
ACROSS THE MARIANAS SUNDAY NIGHT. IT WILL REMAIN IN THE AREA THE
FIRST HALF OF THE COMING WEEK. BECAUSE OF THE UNCERTAINTY OF
WHERE THE TROUGH AXIS WILL BE LOCATED WIND DIRECTIONS HAVE A HIGH
DEGREE OF UNCERTAINTY.

&&

.MARINE...
A SOUTHWEST SWELL AND A EAST SWELL ARE PRESENT THIS AFTERNOON
OVER THE LOCAL AREA. WW3 GUIDANCE SHOW THE SOUTHWEST SWELL
GRADUALLY BECOMING WESTERLY SATURDAY NIGHT THAN NORTHWEST BY
MONDAY. THIS IS PROBABLY SWELL FROM THE TROPICAL DISTURBANCE NOW
TO THE WEST OF THE MARIANAS. MODELS DO DEVELOP IT INTO A TROPICAL
CYCLONE IN THE PHILIPPINE SEA.

&&

.EASTERN MICRONESIA...
THE MCS THAT DEVELOPED LAST NIGHT AT MAJURO HAS STRATIFIED OUT. THE
MODELS INDICATE THAT HIGH PRESSURE WILL TRY TO BUILD IN TONIGHT THEN
MOVE WESTWARD TO AFFECT KOSRAE AND POHNPEI. MODELS INDICATE A BROAD
TROUGH WILL MOVE IN FIRST OVER KOSRAE. THIS TROUGH DOES NOT HAVE
MUCH WEATHER ASSOCIATED WITH IT...AND THE  GFS STILL SHOWS A DRYING
TREND OVER THE NEXT 24 HOURS ACROSS THE REGION AS THE BROAD TROUGH
OVER THE MARSHALL ISLANDS SHIFTS WEST.  EXPECT MOSTLY CLOUDY SKIES
AND ISOLATED SHOWERS AND THUNDERSTORMS AT LEAST THROUGH THURSDAY
NIGHT AT BOTH MAJURO AND KOSRAE. WEATHER APPEARS TO BE A BIT MORE
BENIGN AT POHNPEI IN THE NEAR TERM. BY FRIDAY...MODELS SHOW A BROAD
MONSOON-TYPE TROUGH DEVELOPING ALONG 10N BRINGING WINDS AT ALL
LOCATIONS TO SOUTH OR SOUTHWEST. ADDITIONALLY...A WETTER PATTERN IS
PROGGED TO BEGIN WITH THIS FEATURE.

&&

.WESTERN MICRONESIA...
IR SATELLITE SHOWS ISOLATED SHOWERS AND THUNDERSTORMS REACHING CHUUK
FROM THE EAST AS FORECAST. THIS WEATHER WILL CONTINUE THROUGH
THURSDAY NIGHT. DRIER WEATHER WILL RETURN FOR THE END OF THE WEEK.
AS MENTIONED IN THE EASTERN DISCUSSION...A MONSOON-TYPE PATTERN IS
PROGGED TO DEVELOP BY SATURDAY ALONG 10N. WILL HAVE TO WAIT A COUPLE
MORE DAYS TO SEE HOW IT INFLUENCES THE WEATHER.

THE BROAD MONSOON CIRCULATION IS CENTERED NORTH-NORTHWEST OF YAP
NEAR 12N136E. THIS CIRCULATION IS THE SUBJECT OF A TROPICAL CYCLONE
FORMATION ALERT BY THE JOINT TYPHOON WARNING CENTER. SCATTERED
SHOWERS HAVE PULLED AWAY FROM YAP AND KOROR WITH THE BULK OF THE
WEATHER NOW NORTHWEST OF BOTH LOCATIONS. HOWEVER...IR SATELLITE
SHOWS A SWATH OF SHOWERS NEARLY UPON YAP BETWEEN 139E AND 141E. GFS
PICKS UP ON THIS...SHOWING SHOWERS UPON YAP AT 6Z AND IN ISOLATED
SHOWERS BY MIDNIGHT. CONDITIONS WILL DRY OUT THROUGH THURSDAY AND
FRIDAY. WEEKEND FORECAST FOR BOTH YAP AND KOROR LOOKS ERRATIC IN THE
MODELS WITH LIGHT TO GENTLE WIND FLOW SWITCHING FROM THE SOUTHWEST
DIRECTION TO COMING FROM THE NORTH DIRECTION...BUT GENERALLY DRY.

AS THE MONSOON CIRCULATION GRADUALLY STRENGTHENS...WINDS WILL
MAINTAIN HIGHER SWELL ACROSS THE REGION.

&&

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

$$

ZIOBRO/DEVITA






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