Area Forecast Discussion
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FXPQ60 PGUM 300912 AAA
AFDPQ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
712 PM CHST THU JUL 30 2015

UPDATED FOR TD 13W AND TO ADD MICRONESIAN DISCUSSION

.SYNOPSIS...
PGUA RADAR SHOWS ISOLATED LIGHT SHOWERS OVER THE COVERAGE AREA.
TROPICAL DEPRESSION 13W IS ABOUT 985 MILES EAST OF GUAM MOVING WEST
AND COULD BECOME A TROPICAL STORM BY FRIDAY MORNING. A WEAK MID-
LATITUDE LOW REMAINS FAR TO OUR NORTH...AFFECTING THE FARTHEST NORTH
MARIANA ISLANDS.

&&

.DISCUSSION...
TD 13W WILL BE OUR MAIN FORECAST PROBLEM THROUGH THIS WEEKEND. FOR
THE NEAR TERM...MUCH LESS ISLAND CONVECTION DEVELOPED TODAY AND
MAINLY FAIR WEATHER IS EXPECTED ACROSS THE MARIANAS UNTIL SATURDAY
EVENING. LATER FORECAST MAY NEED TO SEPARATE THE NORTHERN ZONES OF
SAIPAN AND TINIAN TO ACCOUNT FOR STRONGER WINDS AND LARGER WAVES
THAT WILL DEVELOP THERE IF TD 13W FOLLOWS THE CURRENTLY FORECAST
TRACK. IN THE LONGER TERM...SIGNIFICANTLY MORE SHOWERS ARE EXPECTED
ACROSS THE FORECAST ZONES NEXT WEEK.

&&

.MARINE...
GENTLE WINDS AND COMBINED SEAS OF 2 TO 4 FEET WILL PERSIST TONIGHT
THROUGH SATURDAY. ONLY MINOR CHANGES WERE MADE TO WIND AND WAVE
GRIDS AT THIS TIME...BUT WIND GUSTS TO 30 KT FOR THE SAIPAN AND
TINIAN WATERS WERE MENTIONED FOR SUNDAY AND SUNDAY NIGHT. LATER
FORECASTS WILL LIKELY NEED ADJUSTMENTS TO ACCOUNT FOR ANY CHANGES
IN THE TRACK OR INTENSITY OF TD 13W.

&&

.TROPICAL SYSTEMS...
SPECIAL WEATHER STATEMENT FOR WHAT IS NOW TD 13W WAS RE-ISSUED AND
THE HYDROLOGIC OUTLOOK FOR SHOWERY WEATHER NEXT WEEK WAS ALSO RE-
ISSUED. MODEL SOLUTIONS ARE AGAIN SIMILAR ENOUGH AND TRACK 13W WEST
THEN NORTHWEST AND EVENTUALLY TOWARD ANATAHAN...NORTH OF SAIPAN...
AS A TROPICAL STORM BY SUNDAY AFTERNOON. A TROPICAL STORM WATCH FOR
SOME ISLANDS OF THE MARIANAS WILL BE REQUIRED BY FRIDAY AFTERNOON.

&&

.EASTERN MICRONESIA...
MONSOON TROUGH RUNS EASTWARD FROM WESTERN MICRONESIA ALONG 12N...
NORTH OF CHUUK AND POHNPEI THROUGH TD 13W CENTERED NEAR 14N159E
SOUTHEASTWARD SOUTHEAST OF MAJURO TO ABOUT 5N170E. UNSETTLED WEATHER
IS FOUND SOUTH OF 10N FROM CHUUK THROUGH KOSRAE TONIGHT. A WEAK
CICULATION SOUTHWEST OF MAJURO WILL SERVE TO ANCHOR THE MONSOON
TROUGH IN PLACE...THUS MAINTAINING THE MOIST MONSOON FLOW ACROSS
CHUUK...POHNPEI AND KOSRAE A COUPLE MORE DAYS. THE MONSOON TROUGH
AND WEAK CIRCULATION WILL SHIFT WEST BY NEXT WEEK ALLOWING FOR SOME
CALMER WEATHER TO BUILD IN FROM EAST OF MAJURO.

WAVE WATCH MODEL CONTINUES TO SHOW A 3 TO 4 FOOT SOUTHERN HEMISPHERE
SWELL FROM THE SOUTHEAST TO SOUTH-SOUTHEAST ON POHNPEI AND KOSRAE.
SWELL WILL PERSIST A COUPLE MORE DAYS. SURF IS EXPECTED TO REMAIN
BELOW ADVISORY LEVELS. SURF WILL BUILD ON WEST-FACING REEFS FOR THESE
LOCATIONS AND CHUUK TONIGHT AND FRIDAY.

&&

.WESTERN MICRONESIA...
CHUUK DISCUSSION IS INCLUDED ABOVE WITH EASTERN MICRONESIA.

THE MONSOON TROUGH STRETCHES EASTWARD FROM 10N130E THROUGH A WEAK
CIRCULATION NORTH OF KOROR AT 9N134E...OVER YAP AND NORTH OF CHUUK
AND POHNPEI...THROUGH TROPICAL DEPRESSION 13W CENTERED NEAR 14N159E.
MODELS INDICATE TD 13W WILL STRENGTHEN AND INTERACT WITH THE MONSOON
TROUGH...KEEPING KOROR SOUTH OF THE TROUGH IN MOIST UNSETTLED
WESTERLIES. YAP IS EXPECTED TO REMAIN IN THE VICINITY OF THE TROUGH
IN LIGHT WINDS. SIGNIFICANT WEATHER IS NOT EXPECTED FOR YAP THROUGH
THE WEEKEND.

&&

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

$$

SIMPSON/DEVITA



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