Area Forecast Discussion
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FXPQ60 PGUM 310748
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
548 PM CHST FRI OCT 31 2014

.MARIANAS SYNOPSIS...
TROPICAL DEPRESSION 20W HAS FORMED IN THE PHILIPPINE SEA AND IS
CENTERED ABOUT 550 MILES TO THE WEST OF GUAM. THE MONSOON TROUGH
EXTENDS EAST-SOUTHEASTWARD FROM 20W TO BETWEEN GUAM AND CHUUK.
CONVECTION ASSOCIATED WITH THE TROUGH IS DISPLACED TO THE NORTH AND
SOUTH OF THE TROUGH AXIS...WHERE THE STRONGEST LOW-LEVEL CONVERGENCE
IS OCCURRING. AT PRESENT...THESE AREAS LIE OVER TINIAN AND SAIPAN
AND BETWEEN GUAM AND YAP...RESPECTIVELY.

&&

.DISCUSSION...
MODELS HAVE COME INTO BETTER AGREEMENT IN NOT DEVELOPING A SECONDARY
TROPICAL SYSTEM TO THE SOUTHEAST OF 20W. BASED UPON THIS...FAVORED
FORECAST SCENARIO REVOLVES AROUND THE BEHAVIOR OF THE MONSOON TROUGH
TO THE EAST OF 20W. BOTH THE ECMWF AND GFS40 MAINTAIN THE STRONGEST
TRADE-WIND CONVERGENCE OVER THE TINIAN AND SAIPAN ZONES THROUGH
SATURDAY NIGHT...THEN MONSOON TROUGH BEGINS TO SLOWLY RETREAT TOWARD
THE SOUTHWEST...ALLOWING SCATTERED SHOWERS TO OVERSPREAD ALL OF THE
FORECAST ZONES SUNDAY AND SUNDAY NIGHT. TROUGH CONTINUES TO WEAKEN
AND HEAD SOUTHWEST EARLY NEXT WEEK...ALLOWING DRIER TRADES TO
INFILTRATE BY MID WEEK.

&&

.MARINE...
LATEST ALTIMETRY AND BUOY READINGS ONLY INDICATE 3 TO 5 FT SEAS IN
THE MARINE ZONES. TRIMMED TRADE SWELL A FOOT TO AGREE WITH THE
LATEST READINGS. LATEST ASCAT ANALYSIS INDICATES A LARGE FETCH
GENERATION AREA FORMING ON THE SOUTH SIDE OF 20W. WAVE WATCH MODEL
IS PICKING UP ON THIS...SO HAVE BEEFED UP WEST TO WEST-NORTHWEST
SWELL IN THE MARINE GRIDS BEGINNING WITH NEXT TUESDAY. WOULD NOT BE
SURPRISED TO SEE HIGH SURF ON WEST-FACING REEFS BY THE MIDDLE OF
NEXT WEEK. IT IS TOO EARLY TO TELL IF LONG PERIOD SWELL WILL BE HIGH
ENOUGH TO BRING COMBINED SEAS TO SMALL CRAFT ADVISORY HEIGHTS DURING
THIS TIME FRAME.

&&

.EASTERN MICRONESIA...
SATELLITE IMAGERY INDICATES A SURFACE RIDGE IS DOMINATING KOSRAE
WEATHER AND IS ALSO AFFECTING POHNPEI WEATHER. MODELS INDICATE
THIS WILL CONTINUE THROUGH SATURDAY NIGHT. THEN THE BULK OF THE
CONVECTION PASSES NORTH OF KOSRAE AND POHNPEI. CONVERGENT EAST
WINDS CONTINUE TO TRIGGER CONVECTION EAST OF MAJURO AS A WEAK
CIRCULATION CONTINUES TO WEAKEN TO A SURFACE TROUGH. SHOWERS AND
THUNDERSTORMS ARE EXPECTED TO STAY MAINLY NORTH OF MAJURO AND THE
OTHER FORECAST LOCATIONS AS THE TROUGH MOVES WESTWARD. ANOTHER
WEAK CIRCULATION NEAR THE DATE LINE IS ALSO EXPECTED TO DISSIPATE
INTO AN OPEN TROUGH LATER IN THE WEEKEND BUT COULD BRING A FEW
MORE CLOUDS AND SHOWERS TO MAJURO EARLY NEXT WEEK.

A LARGE STORM SYSTEM AFFECTING NEW ZEALAND WILL GENERATE A SOUTH
SWELL THAT MAY AFFECT MAJURO OVER THE WEEKEND. GLOBAL WAVE MODEL
INDICATES A SMALL SWELL WITH A LONG PERIOD COULD REACH THE MARSHALL
ISLANDS BEGINNING LATE SATURDAY. FOR NOW...SWELL STILL APPEARS TO BE
SMALL AND TIDE CYCLES ARE NOT AT HIGHEST LEVEL ABOVE MLLW DURING
THIS TIME FRAME. WILL HAVE TO WATCH THIS EVENT CLOSELY BUT FOR NOW
APPEARS SWELL HEIGHT WILL BE BELOW THAT WHICH COULD CAUSE
SIGNIFICANT INUNDATION.

&&

.WESTERN MICRONESIA...
NEWLY FORMED TD 20W IS LOCATED NEAR 13N137E NORTHWEST OF YAP AND
NORTH OF KOROR AND IS PRESENTLY MOVING WESTWARD AT 8 MPH. TD 20W
WILL GRADUALLY TURN TOWARD NORTHWEST AWAY FROM WESTERN MICRONESIA.
THE MONSOON TROUGH EXTENDS SOUTHEASTWARD FROM TD 20W TO JUST
NORTH AND EAST OF CHUUK. TD 20W IS EXPECTED TO MOVE ALONG A
WESTWARD TO NORTHWESTWARD TRACK AND HELP MAINTAIN SOUTHWEST TO
SOUTH WINDS AT YAP AND KOROR THE NEXT SEVERAL DAYS. SHOWERS AND
THUNDERSTORMS WILL PERSIST AT YAP THROUGH TONIGHT. AT
KOROR...CONVECTION HAS JUST REACHED THE AREA LATE THIS AFTERNOON.
MODELS SHOW THE SHOWERS AND THUNDERSTORMS GRADUALLY PULLING AWAY
TO THE NORTHWEST SATURDAY...BUT WILL STILL HAVE TO KEEP AN EYE ON
CONDITIONS IN CASE MODELS ARE BEING TOO QUICK PUSHING CONVECTION
OUT OF THE AREA. AT CHUUK ISOLATED SHOWERS AND THUNDERSTORMS ARE
SUBSIDING OVERNIGHT AS THE MONSOON TROUGH PULLS OUT OF THE AREA.

WITH THE MONSOON TROUGH JUST NORTH OF YAP AND PALAU...AND TD 20W
SLOWLY DEVELOPING...HAVE FURTHER INCREASED COMBINED SEAS FOR THE
AREA. IF THE CIRCULATION DEVELOPS FASTER THAN MODELS CURRENTLY
SHOW...THEN WINDS AND SEAS WILL HAVE TO BE INCREASED FURTHER.

&&

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

$$

MCELROY/DEVITA





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