Area Forecast Discussion
Issued by NWS

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FXPQ60 PGUM 290802 AAA
AFDPQ

AREA FORECAST DISCUSSION...UPDATED
NATIONAL WEATHER SERVICE TIYAN GU
600 PM CHST WED JUL 29 2015

.SYNOPSIS...
RADAR SHOWS A FEW AREAS OF HEAVY SHOWERS DEVELOPED OVER GUAM THIS
AFTERNOON. HEAVY SHOWERS WERE OVER THE SOUTHERN MOUNTAINS AND THE
FAR NORTHERN PARTS OF GUAM. A WEAK MID-LATITUDE LOW WAS CENTERED
TO OUR NORTH AT ABOUT 22N147E AND AFFECTING THE FARTHEST NORTH
MARIANA ISLANDS. THE TROPICAL DISTURBANCE ASSOCIATED WITH INVEST
AREA 93W IS ROUGHLY 500 MILES NORTH OF KOSRAE AND DRIFTING
WESTWARD...AND IT COULD AFFECT OUR FORECAST ZONES THIS WEEKEND.

&&

.DISCUSSION...
A NOWCAST WAS ISSUED FOR LOCALLY HEAVY RAINFALL ON GUAM THIS
AFTERNOON. ISLAND CONVECTION WILL CAUSE SHOWERS DURING THE NEXT
FEW AFTERNOONS AND ISOLATED THUNDERSTORMS ARE EXPECTED BY SUNDAY.
SOME ADJUSTMENTS WERE MADE TO THE FORECAST MAINLY TRENDING TOWARD
MORE SHOWERY WEATHER DEVELOPING THIS WEEKEND THROUGH EARLY NEXT
WEEK AS INVEST AREA 93W MOVES TOWARD THE MARIANA ISLANDS.

&&

.MARINE...
GENTLE WINDS AND COMBINED SEAS OF 2 TO 4 FEET ARE EXPECTED
TONIGHT THROUGH SATURDAY. REFRESHED WIND GRIDS WITH GFS 29/00Z
OUTPUT AND ONLY MINOR CHANGES WERE MADE TO WAVE GRIDS.

&&

.TROPICAL SYSTEMS...
SPECIAL WEATHER STATEMENT WAS ISSUED FOR INVEST AREA 93W CENTERED
NEAR 12N165E. IT HAS BEEN UPGRADED TO A MEDIUM POTENTIAL FOR THE
DEVELOPMENT OF A TROPICAL CYCLONE WITHIN 24 HOURS. MODEL SOLUTIONS
ARE SURPRISINGLY SIMILAR AND INDICATE 93W WILL CONTINUE TO DEVELOP
AS A CIRCULATION AND MOVE TOWARD WEST OR WEST-NORTHWEST THROUGH
FRIDAY...THEN TURN TOWARD NORTHWEST POSSIBLY AS A TROPICAL STORM
BY SATURDAY OR SUNDAY. THIS FORECAST TRACK WOULD TAKE IT ACROSS
THE MARIANAS JUST TO THE NORTH OF SAIPAN LATE SUNDAY OR MONDAY.
THIS SYSTEM IS OF COURSE STILL DEVELOPING...AND ITS EXACT TRACK
AND STRENGTH AND POSSIBLE EFFECTS ON THE MARIANAS WILL NEED TO BE
WATCHED CAREFULLY.

&&

.EASTERN MICRONESIA...
LITTLE CHANGE TO THE SHORT TERM SYNOPTIC PATTERN OF THE LAST FEW DAYS.
MONSOON TROUGH RUNS WEST TO EAST ACROSS THE REGION BASICALLY ALONG 10N
UNTIL IT COMES TO THE DEVELOPING TROPICAL DISTURBANCE NEAR 12N166E THEN
TURNS SOUTHWARD TO A WEAK CIRCULATION SOUTHWEST OF MAJURO. SATELLITE
IMAGERY SHOWS MAJURO IS IN PARTLY TO MOSTLY CLOUDY WEATHER NORTH OF THE
MONSOON TROUGH. POHNPEI AND KOSRAE ARE IN THE CLOUD SHIELD SOUTH OF THE
TROUGH IN UNSETTLED WEATHER. CHUUK ON SATELLITE HAS SCATTERED SHOWERS
APPROACHING THEM. IN THE LONGER TERM...UNCERTAINTY REMAINS WITH RESPECT
TO THE CIRCULATION NORTH OF MAJURO BUT MODEL SOLUTIONS HAVE BECOME
SIMILAR AND INDICATE 93W WILL LIKELY TRACK NORTH OF SAIPAN...BUT LEAVING
CHUUK...POHNPEI AND KOSRAE IN AN UNSETTLED PATTERN.

WAVE WATCH MODEL CONTINUES TO SHOW A 3 TO 4 FOOT SOUTHERN HEMISPHERE
SWELL FROM THE SOUTHEAST TO SOUTH-SOUTHEAST ARRIVING ON CHUUK...POHNPEI
AND KOSRAE. ALTIMETRY VERIFIES THE SWELL. SWELL WILL PERSIST THE NEXT
SEVERAL DAYS...BUT SURF IS EXPECTED TO REMAIN BELOW ADVISORY LEVELS.
SURF WILL BUILD ON WEST-FACING REEFS FOR THESE LOCATIONS BY THE END OF
THE WEEK AS UPSTREAM WEST WINDS INCREASE.

&&

.WESTERN MICRONESIA...
CHUUK DISCUSSION IS INCLUDED ABOVE WITH EASTERN MICRONESIA DUE TO
A SIMILAR SYNOPTIC PATTERN.

ONLY MINOR CHANGES WERE MADE TO THE YAP AND KOROR FORECASTS THROUGH
THE END OF THE WEEK. SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS AT
KOROR TONIGHT. AT YAP...GENERALLY DRY CONDITIONS TONIGHT WITH MOST
CLOUDS AND WEATHER DISPLACED TO THE SOUTH. LIGHT TO MODERATE WESTERLY
MONSOON FLOW WILL PERSIST THE NEXT SEVERAL DAYS AT BOTH LOCATIONS.

&&

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

$$

SIMPSON/DEVITA



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