Area Forecast Discussion
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000
FXPQ60 PGUM 292154
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
754 AM CHST THU JUL 30 2015

.SYNOPSIS...
PGUA DOPPLER WEATHER RADAR SHOWS ISOLATED SHOWERS MOVING THROUGH
THE MARIANAS WATERS. A TROPICAL DISTURBANCE ABOUT 1160 MILES EAST
OF GUAM IS SLOWLY MOVING WEST AND COULD AFFECT THE MARIANAS EARLY
NEXT WEEK. THE VAD WIND PROFILE REVEALS MAINLY SOUTH WINDS OF 3 TO
7 KNOTS THROUGH THE LOWEST 3 THOUSAND FEET OF THE AIR.

&&

.DISCUSSION...
MOVEMENT AND DEVELOPMENT OF THE TROPICAL DISTURBANCE NEAR
ENEWETAK WAS THE MAIN FORECAST PROBLEM EARLY THIS MORNING. GFS40
HAS MOVED CLOSER TO ECMWF-HIRES AND NAVGEM OF YESTERDAY.
MEANWHILE...ECMWF-HIRES AND NAVGEM REMAINED FAIRLY CONSISTENT.
UKMET IS A LITTLE SOUTH OF THEM ACTUALLY. THEREFORE...BIASED THE
WINDS IN THE GRIDS TOWARD THE ECMWF-HIRES. USED THE DIRECTIONS
STRAIGHT OUT OF THE MODEL...JUST CAPPED THE WINDS AT 21 KNOTS FOR
NOW UNTIL WE KNOW MORE. THAT GETS US THROUGH SUNDAY NIGHT...

BASED ON MONSOON TROUGH GETTING INVOLVED WITH THE DISTURBANCE AND
LIFTING NORTHWARD...EXTENDED THE MOSTLY CLOUDY THROUGH THE END OF
THE GRIDS. ALSO ADDED SCATTERED SHOWERS NEAR THE END OF THE PERIOD
AND CHANGED SOME TEMPERATURES TO WORK TOWARD CONSISTENCY WITH WHAT
THOSE CONDITIONS SHOULD ALLOW. MODEL QPF ESTIMATES ARE 2.5 INCHES
TO 6 INCHES SO WENT AHEAD AND ISSUED A BARE-BONES HYDROLOGIC
OUTLOOK FOR SIGNICANT WIDESPREAD RAINFALL NEXT WEEK. AT THE MOMENT
THIS IS JUST AN OUTLOOK...IT MAY HAPPEN OR IT MAY NOT.

&&

.TROPICAL SYSTEMS...
THE DISTURBANCE NEAR ENEWETAK IS CONTINUING TO DEVELOP SLOWLY. IT
IS NOW THE SUBJECT OF A TROPICAL CYCLONE FORMATION ALERT FROM THE
JOINT TYPHOON WARNING CENTER. IT IS MOVING MAINLY WEST...PERHAPS
JUST A LITTLE TO THE NORTH OF WEST. IT IS EXPECTED TO CONTINUE
MOVING IN THE GENERAL DIRECTION OF THE MARIANAS AND WILL MOST
LIKELY ARRIVE IN THE SUNDAY TO MONDAY TIME FRAME.

&&

.EASTERN MICRONESIA...
WEATHER ACROSS THE REGION FROM CHUUK TO MAJURO HAS COME INTO A
LULL THIS MORNING. HEAVIEST WEATHER IS SEEN SOUTH OF CHUUK AND
MAJURO...AND NORTHEAST OF POHNPEI...NEAR THE DEVELOPING TROPICAL
DISTURBANCE. THIS DISTURBANCE WILL CONTINUE TOWARDS THE WEST OR
WEST-NORTHWEST...KEEPING NORTH OF THE MICRONESIA ISLANDS. A SECOND
CIRCULATION SOUTH OF MAJURO WILL WORK TO ANCHOR THE MONSOON TROUGH
IN PLACE...THUS MAINTAINING THE MOIST MONSOON FLOW ACROSS
CHUUK...POHNPEI AND KOSRAE A FEW MORE DAYS. THE MONSOON TROUGH AND
2ND CIRCULATION WILL SHIFT WEST BY NEXT WEEK ALLOWING FOR SOME
CALMER WEATHER TO BUILD IN FROM EAST OF MAJURO.

IN THE SHORT-TERM...THE FORECAST IS BASED ON ALL LOCATIONS REMAINING
CONVECTION-FREE THIS MORNING...BUT WITH WEATHER FIRING UP AGAIN NEAR
EACH THIS AFTERNOON IN A DIURNAL PATTERN. GFS MAINTAINS A FAIRLY WET
PATTERN AT CHUUK...POHNPEI AND KOSRAE AT LEAST THROUGH FRIDAY NIGHT.
WILL HAVE TO WATCH THIS CLOSELY...AS WELL AS A CLUSTER OF CONVECTION
BREWING JUST SOUTH OF MAJURO THIS MORNING NEAR THE CIRCULATION
THERE. IF THIS CONVECTION BUILDS NORTHWARD TODAY...FORECAST THERE
WILL NEED AN UPDATE FOR MORE SHOWERS.

WAVE WATCH MODEL CONTINUES TO SHOW A 3 TO 4 FOOT SOUTHERN HEMISPHERE
SWELL FROM THE SOUTHEAST TO SOUTH-SOUTHEAST ARRIVING 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 TODAY AND FRIDAY.

&&

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

THE MOIST MONSOON SURGE WILL CONTINUE ACROSS PALAU...BUT KEEP JUST
SOUTH OF YAP FOR TODAY. IR SATELLITE SHOWS SCATTERED SHOWERS OVER
KOROR AND TO THE EAST AND WEST THIS MORNING. THIS WEATHER HAS
REMAINED JUST SOUTH OF YAP THROUGH THE NIGHT. GFS KEEPS THESE
SHOWERS JUST SOUTH THE NEXT COUPLE DAYS...BUT SATELLITE TRENDS
SUGGEST SOME NORTHWARD SHIFT...THUS ADDED MORE CLOUDS AND A SLIGHT
CHANCE OF THUNDERSTORMS AT YAP FOR TONIGHT THROUGH SATURDAY. WHILE
THE MONSOON TROUGH WILL REMAIN IN THE VICINITY THE NEXT FEW
DAYS...SIGNIFICANT WEATHER IS NOT EXPECTED THROUGH THE WEEKEND.

&&

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

$$

STANKO/M. AYDLETT



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