Small Craft Advisory 3, NWS Guam

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
523 PM CHST WED FEB 23 2011

.SYNOPSIS...A SHEAR LINE IS PUSHING SOUTHWARD THROUGH THE MARIANAS.
ONLY A FEW SMALL SHOWERS WERE SEEN ON RADAR THIS AFTERNOON AS THE
BULK OF THE PRECIPITATION ASSOCIATED WITH THE SHEAR LINE IS LOCATED
NORTH OF SAIPAN. THIS SHEAR LINE WILL MOVE FURTHER SOUTHWARD KEEPING
SKIES MOSTLY CLOUDY TONIGHT THROUGH THE WEEKEND.

&&

.DISCUSSION...
NORTHEAST WINDS EXPECTED THROUGH AT LEAST MONDAY. WIND SPEEDS
INCREASE TONIGHT THROUGH SATURDAY. TONIGHT EXPECT 15 TO 20 MPH
WINDS INCREASING TO 20 TO 25 MPH FRIDAY AND EVEN AROUND 25 MPH
SATURDAY THAN DECREASING SLIGHTLY SUNDAY.

SHEAR LINE HAS PUSHED DOWN TO NEAR ANATAHAN THIS AFTERNOON AND
WILL PUSH SOUTHWARD TO NEAR GUAM BY LATE TONIGHT EARLY THURSDAY
MORNING. SATELLITE THIS AFTERNOON SHOWS CLOUDS AND SHOWERS
ASSOCIATED WITH THE SHEAR LINE SPOTTY IN COVERAGE. WILL BANK ON
DI-URNAL EFFECTS OF SHEAR LINE AND PREDICT SCATTERED SHOWERS FOR
AT LEAST LATE TONIGHT AND THURSDAY MORNING. WHILE CONFIDENCE IS
NOT THE HIGHEST ON THIS EVENT...FEEL THAT THE CHANCES ARE AT
LEAST HIGH ENOUGH FOR A BRIEF PERIOD OF SCATTERED SHOWERS DURING
THAT TIME ALTHOUGH IT COULD PERSIST FOR A LONGER PERIOD OF TIME
AS THE SHEAR LINE WILL BE DRAPED OVER THE LOCAL AREA THROUGH THE
WEEKEND. MOSTLY CLOUDY SKIES EXPECTED THROUGH AT LEAST MONDAY
NIGHT.

&&

.MARINE...
LARGE NORTH SWELL WILL ENTER THE LOCAL AREA LATE TONIGHT AND
PERSIST INTO THE COMING WEEK. THE SWELL WILL BUILD TO AT LEAST 12
FEET IN HEIGHT AND THIS WILL GENERATE SURF UP TO 16 FEET FOR A
BRIEF TIME THIS WEEKEND. THIS HIGH SWELL COMBINED WITH LARGE WIND
WAVES WILL PRODUCE COMBINED SEAS OF UP TO 14 FEET THURSDAY NIGHT
THROUGH SUNDAY. A SMALL CRAFT ADVISORY FOR WINDS AND SEAS WILL BE
NEEDED PROBABLY BEGINNING THURSDAY NIGHT.

&&

.EASTERN MICRONESIA...
NO SIGNIFICANT WEATHER SYSTEM EXPECTED FOR THIS REGION DURING THE
FORECAST PERIOD. SATELLITE IMAGERY AND FORECAST MODELS SHOW THAT THE
WEATHER IS PRIMARILY AFFECTED BY LOW-LEVEL CONVERGENCE BETWEEN 6N
AND 9N ALONG THE ITCZ. ALTHOUGH SHOWERS ARE LIKELY THERE IS LITTLE
AGREEMENT AMONG THE MODELS FOR THESE SMALL SCALE EVENTS AND THERE
SHOULD BE PLENTY OF PARTLY CLOUDY SKIES.

FORECAST CONTINUES TO SHOW LARGE NORTH SWELLS FROM ANOTHER PACIFIC
COLD FRONT...CAUSING POSSIBLE HIGH SURF CONDITIONS FOR POHNPEI
STARTING FRIDAY AFTER MIDNIGHT AND CONTINUING THROUGH THE WEEKEND.

&&

.WESTERN MICRONESIA...
THE BIG WEATHER PRODUCER FOR THIS FORECAST PERIOD IS THE EQUATORIAL
TROUGH AND THE POSSIBLE CONSOLIDATION OF A BROAD LOW PRESSURE SYSTEM
NEAR 5N142E AS IT PASSES SOUTH OF KOROR AND YAP ON FRIDAY AND
SATURDAY. STILL OPEN IS THE QUESTION OF HOW MUCH MOISTURE WILL BE
ADDED TO THIS EVENT FROM THE SYSTEM TO THE NORTH. NWP MODEL
PREDICTIONS...INCLUDING GFS...ECMWF...UKMET AND NOGAPS ARE ALL FAIRLY
CONSISTENT WITH BRINGING THE CIRCULATION THROUGH QUICKLY WHILE
AFFECTING PALAU MORE DIRECTLY. THE QUESTION FOR YAP IS A LITTLE MORE
COMPLICATED AS IT SITS ALONG THE NORTHERN PERIPHERY OF THE
CONVERGENCE INTO THE CIRCULATION. THERE IS ALSO A HINT OF A SECOND
INFLUX OF MOISTURE TYING INTO THIS CONVERGENCE FROM THE SHEAR LINE
NOW PASSING THROUGH THE MARIANAS. THIS COULD HAVE A SIGNIFICANT
EFFECT ON YAP AS WELL POSSIBLY SERVING TO EXTEND THE PERIOD OF
RAIN THROUGH THE WEEKEND FOR BOTH YAP AND PALAU.

FORECAST FOR CHUUK REMAINS THE SAME AS IT STILL IS PRIMARILY
AFFECTED BY TRADE-WIND CONVERGENCE AND THE WEATHER REGIME TO THE
EAST. THE WEAK TROUGH AND ACCOMPANYING CLOUD CLUSTER CURRENTLY
BETWEEN CHUUK AND POHNPEI IS STILL PREDICTED TO PASS THROUGH THE
CHUUK ISLANDS LATER TONIGHT...BUT IS NOT PREDICTED TO BE A SIGNIFICANT
WEATHER PRODUCER.  HOWEVER...THERE IS ALSO A POSSIBILITY THAT THE
AFOREMENTIONED SHEAR LINE DISCUSSED ABOVE MAY ALSO REACH INTO THE
CHUUK AREA BY THE WEEKEND. THIS WOULD REQUIRE A CHANGE IN THE
FORECAST FROM ISOLATED TO SCATTERED SHOWERS ONCE THIS TENDENCY
BECOMES MORE CLEAR.

WW3 WAVE WATCH MODELS CONTINUE TO BRING IN LARGE NORTHERLY SWELLS
ACROSS THE AREA FROM WEST TO EAST CAUSING HIGH SURF CONDITIONS TO
PALAU AND YAP BY FRIDAY AND TO CHUUK BY SATURDAY. A HIGH SURF
WARNING MAY BE NECESSARY FOR PALAU BY SATURDAY FOR POSSIBLE COASTAL
INUNDATIONS. THIS WILL BE UPDATED AS IT BECOMES MORE EVIDENT.

&&

.GUM WATCHES/WARNINGS/ADVISORIES...
GU...HIGH SURF ADVISORY FROM 6 PM THURSDAY TO 6 PM CHST TUESDAY FOR
     GUZ001-002.

     HIGH SURF ADVISORY FROM 6 AM THURSDAY TO 6 PM CHST TUESDAY FOR
     GUZ003-004.

MARIANAS WATERS...NONE.
&&

ZIOBRO/EDSON