Area Forecast Discussion
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000
FXPQ60 PGUM 180841
AFDPQ

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
641 PM CHST SAT APR 18 2015

.SYNOPSIS...
A WEAK TRADE-WIND DISTURBANCE IS OVER THE MARIANA ISLANDS THIS
EVENING. WIDELY SCATTERED SHOWERS ARE PRESENT OVER GUAM WATERS.
ANOTHER SLIGHTLY BETTER ORGANIZED DISTURBANCE IS FARTHER EAST NEAR
151E. A BROAD NEAR-EQUATORIAL TROUGH STRETCHES ACROSS EASTERN
MICRONESIA NEAR 6N.

&&

.DISCUSSION...
BASED ON THE LATEST RADAR AND VISIBLE SATELLITE IMAGERY...SHOWERS
AND CLOUDS NEAR GUAM ARE THINNING OUT. THEREFORE SHOWERS SHOULD
STAY AT WIDELY SCATTERED CATEGORY AND SKIES WILL BE MAINLY PARTLY
CLOUDY TONIGHT. THE DISTURBANCE UPSTREAM IS LITTLE MORE ROBUST AND
WILL PASS SOUTH OF TINIAN...OVER ROTA AND GUAM SUNDAY EVENING
BASED ON ITS TRAJECTORY. HAVE INCREASED CLOUDINESS FOR THESE TWO
ISLANDS AND RAISED POP TO JUST BELOW SCATTERED. OTHERWISE A
RELATIVELY DRY TRADE PATTERN WILL CONTINUE THRU MONDAY NIGHT. THE
MAJORITY OF THE MODEL OUTPUTS ARE STILL GRADUALLY LIFTING THE
NEAR-EQUATORIAL TROUGH NORTHWESTWARD STARTING TUESDAY. THE
LIKELIHOOD FOR THIS TO HAPPEN DEPENDS ON HOW A FRONTAL SYSTEM
CURRENTLY OVER EASTERN CHINA WILL INTERACT WITH THE SUB-TROPICAL
RIDGE NORTH OF WAKE ISLAND BY MIDWEEK. UNDER THIS SCENARIO...
CONVECTION INDUCED BY TRADE-WIND CONVERGENCE NORTH OF THE TROUGH
AXIS WILL CREEP TOWARD THE MARIANAS BY MIDWEEK. HAVE KEPT MOSTLY
CLOUDY IN THE MID-RANGE FORECAST BUT STILL TOO EARLY TO UPGRADE
SHOWER COVERAGE AT THIS POINT.

&&

.MARINE...
A STEADY TREND OF TRADE-WIND WAVE AND SWELL HEIGHTS WILL MAINTAIN
SEAS AT 5 TO 7 FEET THRU MONDAY. AFTERWARD THE POTENTIAL FOR
INCREASING PRESSURE GRADIENT BETWEEN THE NEAR-EQUATORIAL TROUGH
AND THE SUB-TROPICAL RIDGE COULD STRENGTHEN TRADE WINDS ACROSS OUR
AREA. IF SO...SEAS WILL BEGIN TO BUILD ON TUESDAY NIGHT AND PEAK
AFTER MIDWEEK. NEED TO MONITOR FOR THE POSSIBILITY OF SMALL CRAFT
ADVISORY CONDITIONS.

&&

.EASTERN MICRONESIA...
ASCAT WIND ANALYSIS INDICATES A VERY WEAK CIRCULATION IS NEAR KOSRAE
AT ABOUT 5N164E. ALSO..THE COMBINATION OF LOW-LEVEL CONVERGENCE AND
AN UPPER-LEVEL TROUGH IS TRIGGERING SCATTERED SHOWERS AND A FEW
THUNDERSTORMS IN LARGE AREAS FROM MAJURO TO THE DATE LINE AND
NORTHWEST ACROSS THE NORTHERN MARSHALL ISLANDS TO NEAR WAKE ISLAND.

MAJURO WILL REMAIN WITHIN THIS SHOWERY WEATHER PATTERN TONIGHT
THROUGH SUNDAY AT LEAST. MOST MODELS INDICATE THE AREAS OF HEAVIER
SHOWERS WILL EVENTUALLY MOVE SLOWLY TOWARD THE WEST...BUT MODELS
ALSO INDICATE THAT A RELATIVELY WET TRADE-WIND FLOW WILL CONTINUE
FOR MAJURO THROUGH THE NEXT SEVERAL DAYS.

KOSRAE WILL HAVE VARIABLE WINDS AND A FEW SHOWERS AT TIMES WHILE THE
WEAK CIRCULATION/DISTURBANCE REMAINS NEARBY DURING THE NEXT DAY OR
TWO. WINDS SHOULD GRADUALLY BECOME MORE EASTERLY WITH JUST
ISOLATED SHOWERS AND THUNDERSTORMS FOR MOST OF THE COMING WEEK.

POHNPEI AND CHUUK...A FAIRLY DRY TRADE-WIND FLOW WILL CONTINUE FOR
POHNPEI THROUGH SUNDAY AND FOR CHUUK THROUGH MONDAY OR TUESDAY. MOST
MODELS INDICATE THE WEAK CIRCULATION NEAR KOSRAE THIS AFTERNOON WILL
MOVE WESTWARD...AND THE SHOWERY WEATHER OVER THE NORTHERN MARSHALL
ISLANDS WILL ALSO MOVE TOWARD WEST. THE AREAS OF HEAVIER SHOWERS ARE
EXPECTED TO REMAIN NORTH OF POHNPEI AND CHUUK...BUT CONDITIONS COULD
BECOME CHANGEABLE AND UNSTABLE FOR POHNPEI AND CHUUK DURING THIS
COMING WEEK...ESPECIALLY FOR POHNPEI.

&&

.WESTERN MICRONESIA...
CHUUK DISCUSSION INCLUDED ABOVE WITH POHNPEI DUE TO SIMILAR WEATHER.

YAP AND KOROR...
ONLY MINOR CHANGES WERE MADE TO THESE FORECASTS. A RELATIVELY DRY
TRADE-WIND FLOW WILL CONTINUE ACROSS YAP AND KOROR THROUGH THE NEXT
SEVERAL DAYS. SOME CLOUDS AND SHOWERS COULD ARRIVE FROM THE EAST
LATER IN THE COMING WORK WEEK.

&&

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

$$

CHAN/SIMPSON



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