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653
FXPQ60 PGUM 240815 AAA
AFDPQ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
615 PM CHST FRI OCT 24 2014

UPDATED TO INCLUDE DISCUSSIONS FOR EASTERN AND WESTERN MICRONESIA

.MARIANAS SYNOPSIS...
RELATIVELY WEAK LOW-LEVEL FLOW PATTERN CONTINUES OVER THE
FORECAST ZONES. MONSOON TROUGH PASSES SOUTH OF GUAM NEAR 11N.
TUTT STRETCHES FROM EAST TO WEST NEAR THE FAR NORTHERN CNMI ALONG
20N. CONVERGENT EAST TO SOUTHEAST WINDS ARE PRODUCING A FEW CBS
EAST OF TINIAN AND SAIPAN. 00Z SOUNDING CARRIED A PWAT OF 2
INCHES. THIS...COMBINED WITH THE LIGHT WIND REGIME...HAS ALLOWED
AFTERNOON THUNDERSTORMS TO FORM JUST TO THE NORTHWEST OF GUAM.

&&

.DISCUSSION...
ONLY SIGNIFICANT UPDATE TO THE FORECAST GRIDS WAS TO ADD ISOLATED
THUNDER THROUGH SATURDAY NIGHT. AFTER THEN...DEPTH OF LOW-LEVEL
MOISTURE SHOULD BE SHALLOW ENOUGH TO INHIBIT DEEP CONVECTION.
FORECAST CONTINUES TO FOLLOW A DRY BIAS VERSUS THE ECMWF AND
GFS40. GFS 40 APPEARS TO SUFFER FROM CONVECTIVE FEEDBACK DURING
MUCH OF NEXT WEEK AND SPINS UP SEVERAL WEAK CIRCULATIONS NEAR AND
EAST OF THE MARIANAS...WHILE THE ECMWF SEEMS TO BE TOO AGGRESSIVE
IN DEVELOPING CIRCULATIONS IN THE MONSOON TROUGH SOUTH OF GUAM.
LATEST NAVGEM RUN SUGGESTS ATMOSPHERE MAY BE MOISTER THAN EARLIER
ANTICIPATED DURING THE UPCOMING WEEK. WILL WAIT FOR SATELLITE
TRENDS TO CONFIRM A WETTER PATTERN BEFORE MAKING CHANGES TO POPS
OR CLOUD COVER. HAVE KEPT TRADE WINDS IN THE GRIDS FOR DAYS 9 AND
10. BOTH ECMWF AND GFS 40 DEVELOP A CIRCULATION EAST OF THE
FORECAST DOMAIN ON DAYS 9 AND 10.

&&

.MARINE...
MARINE SWELL GRIDS WERE INC GOOD SHAPE AND REQUIRED ONLY A FEW
COSMETIC CHANGES. BUOYS AND LATEST ALTIMETRY INITIALIZE PRIMARY
NORTHEAST SWELL BETWEEN 5 AND 6 FT FROM 045 DEGREES WITH A PERIOD
OF 13 SECONDS. STILL EXPECT MINIMAL HIGH SURF EVENT ON NORTH
FACING REEFS TONIGHT THROUGH SUNDAY.

&&

.EASTERN MICRONESIA...
THREE WEATHER FEATURES CAN BE SEEN ACROSS THE REGION THIS
AFTERNOON...A CIRCULATION SOUTHEAST OF POHNPEI...A SURFACE TROUGH
RUNNING NORTHEASTWARD FROM THE CIRCULATION...AND CONVERGENT EAST
WINDS EAST OF MAJURO. EXTENSIVE CLOUD COVER...SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS ARE ASSOCIATED WITH EACH OF THESE FEATURES.
THE CIRCULATION IS GOING TO PASS SOUTH OF POHNPEI TONIGHT. THIS
SHOULD ALLOW THE BULK OF THE INITIAL CONVECTION TO PASS TO THE SOUTH
OF POHNPEI TONIGHT AND SATURDAY. CONVECTION ASSOCIATED WITH THE
SURFACE TROUGH SHOULD REACH POHNPEI SATURDAY NIGHT. KOSRAE IS IN
LINE WITH THE CONVECTION FROM THE CIRCULATION AND TROUGH TONIGHT AND
SATURDAY. MAJURO IS LOCATED IN A WEAK RIDGE THIS EVENING...BUT
CONVERGENT SOUTHEAST AND EAST WINDS FOLLOW LATER TONIGHT. THE WEAK
SURFACE RIDGING EAST OF THE TROUGH COULD PROVIDE DRYER WEATHER FOR
MAJURO FOR THIS WEEKEND...AND KOSRAE AND POHNPEI EARLY NEXT WEEK.
AFTERWARD A TRADE-WIND CONVERGENCE ZONE CURRENTLY UPSTREAM EAST OF
THE DATE LINE MIGHT BRING MORE INSTABILITY FOR THE REGION LATER NEXT
WEEK.

LONG-PERIOD NORTH-NORTHEAST SWELLS PRODUCED BY A STRONG LOW PRESSURE
SYSTEM CURRENTLY NEAR 36N176E ARRIVED AT CHUUK AND POHNPEI
STATES TODAY. THIS WILL CAUSE HAZARDOUS SURF CONDITIONS FOR BOTH
PLACES BY TONIGHT AND SHOULD LAST UNTIL SUNDAY AFTERNOON.
HOWEVER...LATEST ASCAT IMAGERY DOES NOT INDICATE STRONG WINDS AND A
FETCH DIRECTED AT MAJURO AND KOSRAE.

&&

.WESTERN MICRONESIA...
ANOTHER SURFACE TROUGH NEAR CHUUK IS BRINGING SCATTERED SHOWERS AND
ISOLATED THUNDERSTORMS TO CHUUK TONIGHT. THIS TROUGH IS CURRENTLY
INTERACTING WITH ANOTHER SURFACE TROUGH TO THE NORTHEAST. AS THESE
TWO TROUGHS SEPARATE...THE HEAVY RAIN WENO ISLAND RECEIVED FRIDAY
AFTERNOON WILL LESSEN IN INTENSITY. ONCE THIS CIRCULATION AND TROUGH
HAVE PULLED WEST OF CHUUK ON SATURDAY NIGHT...A BRIEF IMPROVEMENT IS
POSSIBLE. HOWEVER WEATHER WILL WORSEN AGAIN ON SUNDAY AS THE TRADE
DISTURBANCE CURRENTLY OVER THE MARSHALL ISLANDS ARRIVES. AFTER THE
PASSAGE OF THIS DISTURBANCE...THINGS COULD FINALLY QUIET DOWN FOR
EARLY NEXT WEEK. REFER TO THE SECOND PARAGRAPH UNDER THE EASTERN
MICRONESIA DISCUSSION ABOVE FOR HAZARDOUS SURF CONDITIONS TONIGHT
AND SATURDAY.

ANTICIPATE A WEAK MONSOON TROUGH TO LINGER NEAR KOROR AND YAP THRU
SATURDAY. THIS TROUGH WILL COINCIDE WITH MODEST DIVERGENT FLOW ALONG
THE WESTERN HALF OF AN UPPER HIGH NEAR 7N143E...CAUSING A SLIGHT
THREAT OF THUNDERSTORMS FOR BOTH LOCALES. WITH THIS TROUGH EXPECTED
TO LIFT NORTHWESTWARD INTO THE PHILIPPINE SEA SATURDAY NIGHT AND
SUNDAY...FAIR WEATHER AND GENTLE WINDS SHOULD RETURN TO THE AREA.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 4 PM CHST SUNDAY FOR GUZ001>004.

MARIANAS WATERS...NONE.
&&

$$

MCELROY/DEVITA







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