Area Forecast Discussion
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000
FXPQ60 PGUM 300803
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
603 PM CHST TUE JUN 30 2015

.SYNOPSIS...
SATELLITE AND RADAR SHOW ISOLATED SHOWERS OVER THE MARIANAS. IPAN
BUOY SHOWS COMBINED SEAS TO BE AROUND 4 TO 5 FT. ACROSS
MICRONESIA...CONVECTION ALONG THE MONSOON TROUGH HAS BECOME MORE
CONSOLIDATED AROUND 3 CIRCULATIONS. THE FIRST IS NW OF KOROR NEAR
12N131E. THE SECOND...INVEST 94W...IS BETWEEN GUAM AND CHUUK NEAR
9N148E. THE THIRD...INVEST 95W...IS NNE OF POHNPEI NEAR 10N159E
AND IS THE SUBJECT OF A TROPICAL CYCLONE FORMATION ALERT.

&&

.DISCUSSION...
MADE SOME SIGNIFICANT CHANGES IN BOTH MARINE AND WIND GRIDS TO
BETTER ALIGN WITH MODEL GUIDANCE IN BRINGING A TROPICAL CYCLONE
TOWARD THE MARIANAS OVER THE WEEKEND. THERE IS STILL SOME QUESTION
AS TO WHAT PATH 95W WILL TAKE AS IT NEARS THE MARIANAS AND HOW
STRONG IT WILL BE. GFS AND ECMWF BOTH SHOW RAINFALL INCREASING
AS EARLY AS FRIDAY SO HAVE ADDED IN SCATTERED SHOWERS BEGINNING
FRIDAY NIGHT. HEAVIEST RAINFALL IS STILL EXPECTED SATURDAY AND
SUNDAY AND WILL LINGER INTO THE BEGINNING OF NEXT WEEK.

&&

.MARINE...
COMBINED SEAS OF 4 TO 5 FEET WILL CONTINUE THROUGH THURSDAY THEN
BUILD TO BETWEEN 6 AND 8 FEET FRIDAY. SEAS WILL BUILD FURTHER AS
THE DEVELOPING CIRCULATION NEARS THE MARIANAS OVER THE WEEKEND.

.TROPICAL SYSTEMS...
MODELS HAVE SHOWN BETTER AGREEMENT TODAY IN SHOWING 95W HEADING
TOWARD THE WNW...ABSORBING 94W AROUND THURSDAY...THEN PROCEEDING
TOWARD THE MARIANAS. THERE IS STILL QUESTION ON HOW STRONG THE
SYSTEM WILL BE AS IT AFFECTS THE MARIANAS AND EXACTLY WHERE IT
WILL PASS. SATELLITE IMAGERY SHOWS THAT 95W HAS BEGUN TO MOVE
TOWARD THE WNW. AS FUTURE MODEL RUNS PICK UP ON THIS MOTION...
FORECAST UNCERTAINTY WILL DECREASE.

&&

.EASTERN MICRONESIA...
A COMPLEX WEATHER PATTERN CONTINUES ACROSS MICRONESIA FROM
CHUUK TO THE MARSHALL ISLANDS. JTWC INVEST 94W CONTINUES TO SPIN
WEST-NORTHWEST OF CHUUK AT 9N148E...WHILE 95W REMAINS NORTH-
NORTHWEST OF KOSRAE NEAR 10N159E. A WEAK CIRCULATION IS LOCATED
JUST SOUTHEAST OF MAJURO NEAR 6N174E. A MONSOON TROUGH RUNS FROM
WESTERN MICRONESIA THROUGH 94W TO 95W TO THE WEAK CIRCULATION NEAR
MAJURO THEN EASTWARD. INVEST 95W IS THE SUBJECT OF A TROPICAL
CYCLONE FORMATION ALERT. GFS AND ECMWF INDICATE THAT THE MONSOON
TROUGH WILL LIFT SLOWLY NORTHWARD WHILE 95W MOVES WEST-
NORTHWESTWARD AND MERGES WITH 94W SOMEWHERE NORTH OF CHUUK-POHNPEI
AROUND THURSDAY. IN THE COMING DAYS POHNPEI AND KOSRAE WILL BE IN
UNSETTLED CONDITIONS WITH OCCASIONAL STRONG TO NEAR-GALE WESTERLY
WINDS SOUTH OF THE MONSOON TROUGH.

HIGH SURF ADVISORIES REMAIN IN EFFECT FOR KOSRAE AND POHNPEI. SURGING
WESTERLY WINDS WILL CAUSE HAZARDOUS SURF AND SEA CONDITIONS FOR MUCH
OF MICRONESIA THIS WEEK...ESPECIALLY ON THE SOUTH SIDE OF THE
MONSOON TROUGH.

&&

.WESTERN MICRONESIA...
ASCAT ANALYSIS SHOWS AN ACTIVE MONSOON TROUGH RUNS EASTWARD FROM A
CIRCULATION NORTHWEST OF KOROR NEAR 11N132E TO ANOTHER CIRCULATION
NORTHWEST OF CHUUK AT 9N149E...THEN CURVES OVER THE NORTHERN ISLANDS
OF CHUUK STATE AND THROUGH THE DEVELOPING CIRCULATION NORTHEAST OF
POHNPEI AT 9N161E. A HIGH SURF ADVISORY WAS ISSUED FOR CHUUK AND HSA
REMAINS IN EFFECT FOR KOROR. YAP MAY ALSO NEED A HIGH SURF ADVISORY
LATER IN THE WEEK. SOUTHWEST TO WEST MONSOON WINDS ARE STILL SURGING
ACROSS THE REPUBLIC OF PALAU AND EASTWARD TOWARD EASTERN MICRONESIA
AND THIS MONSOON WEATHER PATTERN IS EXPECTED TO PERSIST ACROSS
WESTERN MICRONESIA THROUGH THE COMING WEEKEND. MODELS STILL DIFFER
SIGNIFICANTLY ABOUT DEVELOPMENTS OF THE MONSOON TROUGH AND THE
DIFFERENT CIRCULATIONS...AND THE SITUATION WILL NEED TO BE MONITORED
CLOSELY IN THE COMING DAYS.

&&

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

&&

$$

W. AYDLETT/DEVITA/SIMPSON



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