000
FXPQ60 PGUM 160746
AFDPQ 

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
546 PM CHST WED MAY 16 2012

.SYNOPSIS...
PGUA WSR-88D SHOWS ISOLATED TRADE-WIND SHOWERS MOVING THROUGH THE
MARIANAS WATERS. THE VAD WIND PROFILE SHOWS GENTLE TO MODERATE
TRADE WINDS THROUGH THE LOWEST SIX THOUSAND FEET.

&&

.DISCUSSION...
DRY SEASON TRADE-WIND REGIME HAS REMAINED FIRMLY ENTRENCHED UP TO
NOW. A TRADE-WIND DISTURBANCE TO THE EAST WILL LIKELY BRING SOME
INCREASED CLOUDINESS. MOST OF THE SHOWER ACTIVITY SHOULD PASS TO
THE SOUTH. THE INHERITED GRIDS DID A FINE JOB OF DESCRIBING THESE
SHORT TERM TRENDS...SO NO CHANGES WERE NEEDED THROUGH THE
WEEKEND.

FOR THE LONG TERM...NO CHANGES WERE MADE FOR A DIFFERENT REASON.
WHILE THE GFS40 HAS GOOD RUN-TO-RUN CONSISTENCY AND SO DOES THE
ECMWF-HIRES...THEY HAVE RATHER POOR MODEL-TO-MODEL CONSISTENCY
WITH EACH OTHER. THIS IS LEADING TO A LOW CONFIDENCE FORECAST FOR
THE LONGER TERM NEXT WEEK. THE ECMWF-HIRES SETS UP A SOUTHEAST
FLOW OVER THE MARIANAS...WHILE THE GFS40 TAKES A MINIMAL TROUGH
AND SPINS UP A CIRCULATION TO THE EAST OF THE MARIANAS WITH A
WEST FLOW SETTING UP. THE ECMWF-HIRES LOOKS MORE LIKELY GIVEN
PAST TRENDS THIS YEAR...BUT THE GFS40 SCENARIO CANNOT BE
COMPLETELY RULED OUT.

&&

.EASTERN MICRONESIA...
JUST AS WITH THE LAST FORECAST...SHORT TERM FORECASTS WERE
ADJUSTED FOR MAJURO AND KOSRAE AS WEATHER CONDITIONS IMPROVED
THROUGH THE DAY. PLEASANT WEATHER WILL PERSIST OVERNIGHT FOR
THESE TWO LOCATIONS. A TRADE-WIND DISTURBANCE OVER POHNPEI WILL
KEEP SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS IN THAT STATE
OVERNIGHT. VIS SATELLITE SHOWS A WEAK NEARLY CONVECTION-FREE
CIRCULATION CENTERED CLOSE TO THE EQUATOR WITHIN A DRY TRADE-WIND
TROUGH THAT IS CURRENTLY APPROACHING KOSRAE. MODELS AGREE WELL
WITH SATELLITE TRENDS WHICH INDICATE LITTLE WEATHER OVER KOSRAE
AS THIS SYSTEM PASSES. LONG TERM REMAINS CONSISTENT WITH PREVIOUS
FORECAST. MODELS SHOW A ZONE OF INCREASED SHOWER COVERAGE
CONCENTRATING BETWEEN 7N AND 10N FROM WEST OF KWAJALEIN TO WEST
OF POHNPEI THURSDAY NIGHT THROUGH SATURDAY AS MOIST...CROSS-
EQUATORIAL FLOW DEVELOPS. MEANWHILE...MODELS PROG A TRADE SURGE
TO BRING MORE SHOWERS TO THE CENTRAL MARSHALLS BY SATURDAY.

&&

.WESTERN MICRONESIA...
FAIR WEATHER HAS SET UP OVER CHUUK WHILE A TRADE DISTURBANCE
LOOMS TO THE EAST NEAR POHNPEI. MODELS BRING UNSETTLED CONDITIONS
TO CHUUK STATE BY THURSDAY AND INTO THE WEEKEND AS THE
DISTURBANCE SLOWLY MOVES THROUGH. A FEW PERIODS OF SCATTERED
SHOWERS ARE POSSIBLE...BUT TIMING IS HARD TO DISCERN THIS FAR IN
ADVANCE. FARTHER WEST...A BROAD WEAK CIRCULATION IS CENTERED
SOUTHEAST OF KOROR WITHIN A NEAR-EQUATORIAL TROUGH. SCATTERED
SHOWERS AND A FEW THUNDERSTORMS WILL CONTINUE OVERNIGHT ON
KOROR...WHILE JUST A SLIGHT CHANCE OF THUNDERSTORMS EXISTS OVER
YAP. LIGHT AND VARIABLE WINDS IN KOROR METARS INDICATE THE TROUGH
HAS LINGERED OVER THE ISLAND MUCH OF THE DAY. MODELS SHOW THIS
FEATURE WILL DRIFT SLOWLY WEST...BUT THE TROUGH AXIS WILL REMAIN
CLOSE TO KOROR DURING THE NEXT COUPLE OF DAYS. ECMWF MAINTAINS A
WETTER TREND ON FRIDAY AND SATURDAY THAN DOES THE GFS...WHICH
STILL SHOWS A WEAK CIRCULATION CENTERED JUST NORTHWEST OF
KOROR...BUT WITH RELATIVELY DRY WEATHER OVER BOTH KOROR AND YAP.
LIGHT AND VARIABLE WINDS OVER THE WEEKEND COULD SIGNAL ISLAND
THUNDER ON KOROR. THEREFORE...SHORT TERM ADJUSTMENTS MAY BE
REQUIRED FOR THE KOROR FORECAST THIS WEEKEND.

&&

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

$$

STANKO/M. AYDLETT