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463
FXPQ60 PGUM 192143
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
743 AM CHST SAT DEC 20 2014

.MARIANAS SYNOPSIS...EAST TRADE-WINDS AND ISOLATED SHOWERS PREVAILED
ACROSS THE MARIANAS THIS MORNING.

&&

.DISCUSSION...
LITTLE CHANGE MADE TO FORECAST. STRONG HIGH PRESSURE BUILDING OUT
INTO THE NORTHWEST PACIFIC WILL KEEP WINDS ELEVATED ACROSS THE
MARIANAS THROUGH TONIGHT. MODELS SHOW THAT WIND SPEEDS MAY
DECREASE SLIGHTLY SUNDAY THROUGH MONDAY NIGHT BUT WILL AGAIN RISE
BY MID-WEEK AS ANOTHER HIGH PRESSURE AREA BUILDS OUT OF ASIA.
MODELS DEPICT A FEW TRADE-WIND DISTURBANCE PASSING ACROSS THE
LOCAL AREA. THIS WILL PRODUCE PERIODS OF CLOUDS AND SHOWERS
THROUGH AT LEAST SUNDAY NIGHT.

&&

.MARINE...
AN EAST TRADE-WIND SWELL AND A NORTH TO NORTHWEST SWELL WILL
PERSIST THROUGH THE FORECAST. RITIDIAN BUOY SHOWS THE NORTHWEST
SWELL AROUND 6 FEET AT 13 SEC THIS MORNING.THIS IS PREDICTED TO
PRODUCE A SURF HEIGHT OF AT LEAST 9 FEET. WENT WITH SURF OF 8 TO
10 FEET ON NORTH FACING REEFS AND 7 TO 9 FEET ON WEST FACING
REEFS THROUGH AT LEAST SUNDAY MORNING. THIS IS ABOVE HAZARDOUS
LEVELS SO ISSUED A HIGH SURF ADVISORY. MODELS SHOW THIS SWELL
DECREASING BY SUNDAY MORNING SO ADVISORY IS ONLY OUT UNTIL SUNDAY
MORNING. RITIDIAN AND IPAN BUOYS SHOW SEA HEIGHTS OF 10 TO 12
FEET. VAD WIND PROFILE SHOWS 2KFT WINDS ABOVE 30 KNOTS.
SCATTEREOMETER DATA SHOWS WINDS OF 20 TO 25 KNOTS OVER THE AREA.
A SMALL CRAFT ADVISORY IS IN EFFECT FOR WINDS AND SEAS THROUGH AT
LEAST WEDNESDAY. ADDED GUST TO 30 KNOTS IN FORECAST BECAUSE OF
THE VAD AND SCATTEROMETER DATA AS WELL AS SURFACE OBS. THERE HAVE
ALREADY BEEN A FEW PEAK WINDS OBSERVED ACROSS THE MARIANAS THIS
MORNING WHICH SEEMS TO VERIFY GUST TO 30 KNOTS.

&&

.EASTERN MICRONESIA...
THE LEADING EDGE OF SURGING NORTHEASTERLY TRADES WILL TRIGGER A
FEW SHOWERS NEAR CHUUK AND POHNPEI TODAY. OTHERWISE...FAIR TRADE
WEATHER IS GOING TO PREVAIL ACROSS CHUUK THRU SUNDAY NIGHT AND
POHNPEI UNTIL SUNDAY EVENING. LATEST ASCAT SATELLITE IMAGERY
INDICATES EVEN STRONGER SURGING TRADES SOUTHEAST OF HAWAII HAVE
DISPLACED THE TRADE CONVERGENCE ZONE SOUTHWARD TO SOUTH OF 5N. ON
THE OTHER HAND...THESE TRADES HAVE ENHANCED A DISTURBANCE
APPROACHING THE MARSHALL ISLANDS THIS MORNING. SOUNDING DATA FROM
WSO MAJURO LAST NIGHT REVEALS STRONG VERTICAL WIND SHEAR OF 15 TO
25 KT BETWEEN 500 AND 350MB... CAUSED BY THE ADVANCING ELEMENT OF
THE SAME SURGING TRADES ALOFT. THIS HAS PREVENTED CONVECTION TO
MATERIALIZE NEAR MAJURO LAST NIGHT DESPITE THE PRESENCE OF A
DISTURBANCE. AS TRADES INCREASE NEAR THE SURFACE TODAY...VERTICAL
WIND SHEAR WILL DIMINISH WHICH SHOULD ALLOW CONVECTION TO FLARE
UP NEAR MAJURO. THIS DISTURBANCE IS GOING TO GRADUALLY PROGRESS
WESTWARD AND AFFECT KOSRAE BY SUNDAY MORNING. IT COULD EVENTUALLY
REACH POHNPEI AND CHUUK AROUND MONDAY. A FEW MORE DISTURBANCES
CAN ALSO BE SEEN UPSTREAM EAST OF THE DATE LINE. THESE SYSTEMS
WILL PROBABLY PROLONG OFF AND ON SHOWERS FOR MAJURO THRU
MONDAY...KOSRAE...POHNPEI AND CHUUK UNTIL MIDWEEK. AS THE LARGE
DOME OF HIGH PRESSURE CURRENTLY SOUTH OF JAPAN DRIFTS EASTWARD
OVER THE NEXT FEW DAYS...IT WILL CROSS THE DATE LINE BY EARLY
NEXT WEEK. IN RESPONSE...A THIRD WAVE OF SURGING TRADES IS
SCHEDULED TO ARRIVE AT THE MARSHALLS. THESE DRIER TRADES MIGHT BE
ABLE TO USHER IN NICER WEATHER FOR MAJURO.

NORTHWEST SWELL PRODUCED BY STRONG WINDS BEHIND THE COLD FRONT TO
THE NORTH ALONG WITH LARGE TRADE-WIND SWELL AND WIND WAVES WILL
CAUSE SEAS TO RISE FROM CHUUK STATE EASTWARD TO THE MARSHALL
ISLANDS OVER THE NEXT FEW DAYS. THEREFORE...SEAS WILL BECOME
HAZARDOUS FOR SMALL CRAFT NEAR KOSRAE BY TUESDAY AND THE REST OF
THE LOCATIONS BY MONDAY. TRADE-WIND SWELL WILL ALSO CAUSE
HAZARDOUS SURF FOR ALL THE LOCATIONS AS WELL. IN CONJUNCTION WITH
THE SPRING HIGH TIDE CYCLE STARTING MONDAY...COASTAL INUNDATIONS
ARE LIKELY ON MAJURO AND NEARBY ATOLLS. RESIDENTS OF CHUUK STATE
EASTWARD TO THE MARSHALL ISLANDS WILL NEED TO STAY ALERT ON THIS
DEVELOPING SITUATION OVER THE NEXT SEVERAL DAYS.

&&

.WESTERN MICRONESIA...
REASONING FOR THE CHUUK FORECAST IS INCLUDED UNDER THE EASTERN
MICRONESIA SECTION ABOVE DUE TO A SIMILAR TRADE-WIND PATTERN.

A STRONG HIGH PRESSURE SYSTEM SLIDING EASTWARD FROM SOUTH OF
JAPAN WILL DIRECT FRESH TO STRONG TRADE WINDS TOWARD THE REPUBLIC
OF PALAU AND YAP STATE FOR THE NEXT SEVERAL DAYS. A SERIES OF
TRADE-WIND DISTURBANCES CAN BE SEEN UPSTREAM ALONG
8N...STRETCHING EASTWARD FROM 140E TO 170E. EXPECT THESE
DISTURBANCES TO BRING PERIODIC SHOWERS AND EVEN A THUNDERSTORM OR
TWO TO YAP THRU MONDAY...AND TO KOROR BY SUNDAY EVENING. TOWARD
MIDWEEK...A STRENGTHENING UPPER-LEVEL HIGH OVER THE PHILIPPINE
SEA COULD PROVIDE ENOUGH SUBSIDENCE TO INTRODUCE A DRIER PATTERN
FOR BOTH PLACES.

HAZARDOUS SURF WILL PERSIST ACROSS THE REPUBLIC OF PALAU AND YAP
STATE THRU TONIGHT AS RESIDUAL NORTH SWELL LINGERS IN THE REGION.
COMBINING WITH BUILDING TRADE-WIND SWELL AND WIND WAVES...SEAS
WILL ALSO REMAIN HAZARDOUS FOR SMALL CRAFT UNTIL AT LEAST SUNDAY
AFTERNOON.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY UNTIL 6 AM CHST SUNDAY FOR GUZ001>004.

MARIANAS WATERS...SMALL CRAFT ADVISORY UNTIL 6 AM CHST WEDNESDAY FOR PMZ151>154.

&&

$$

ZIOBRO/CHAN






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