High Surf Advisory 3, NWS Guam

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE TIYAN GU
436 PM CHST SUN JAN 16 2011

.SYNOPSIS...
A FEW SHOWERS HAVE PERSISTED JUST WEST OF THE MARIANAS TODAY...
BUT A LOW-LEVEL RIDGE IS KEEPING SHOWER ACTIVITY LIMITED
ELSEWHERE. THE SHEAR LINE TO THE NORTHWEST CONTINUES TO DROP
SOUTHEASTWARD AND IS NOW ABOUT 400 MILES NORTHWEST OF SAIPAN.

&&

.DISCUSSION...
LATEST MODEL DATA MAINTAINS PREVIOUS FORECAST QUITE WELL SO HAVE
MADE FEW GRID EDITS. THE SHEAR LINE IS EXPECTED STALL NEAR SAIPAN
WITH ANOTHER PUSH OF STRONGER NORTHEAST WINDS PUSHING THE SHEAR
LINE SOUTHWARD ACROSS THE MARIANAS BY LATE WEEK. HAVE KEPT
SHOWERS ISOLATED FOR ALL LOCATIONS THROUGH THE WEEK...BUT
SCATTERED SHOWERS WILL CERTAINLY BE POSSIBLE FOR SOME ISLANDS IF
THE SHEAR LINE STALLS OVERHEAD. LATER IN THE WEEK...NORTHEAST
WINDS WILL INCREASE TO NEAR SMALL CRAFT ADVISORY LEVELS. TIMING
REMAINS A LITTLE FUZZY BETWEEN THE MODELS SO WILL HAVE TO WAIT A
FEW MORE DAYS UNTIL THE FORECAST OF DURATION AND MAGNITUDE CAN BE
FINE- TUNED.

&&

.MARINE...
SHIP OBSERVATIONS AND ASCAT DATA SHOW A LARGE FETCH REGION OF 30
TO 40 KNOT WINDS BEHIND THE SHEAR LINE. WAVEWATCH MODEL RUNS HAVE
BEEN CONSISTENT IN SHOWING A RAPID INCREASE IN NORTH SWELL
HEIGHTS EARLY MONDAY MORNING. THE PEAK OF THE EVENT IS EXPECTED
TO OCCUR AROUND MIDDAY TUESDAY WITH AN 11 TO 13 FOOT NORTH SWELL
AND A 12 TO 13 SECOND PERIOD. THIS WILL CREATE HAZARDOUS SURF OF
JUST OVER 15 FEET PROMPTING THE ISSUANCE OF A HIGH SURF WARNING
AND SMALL CRAFT ADVISORY MONDAY AFTERNOON VALID FOR TUESDAY. HIGH
SURF WILL ALSO LEAD TO INUNDATION OF 2 TO 4 FEET ALONG LOW-LYING
COASTAL AREAS. THE LARGE NORTH SWELL WILL GRADUALLY SUBSIDE
TUESDAY NIGHT THROUGH THURSDAY BUT WILL REMAIN LARGE ENOUGH THAT
A HIGH SURF ADVISORY WILL CONTINUE THROUGH MIDWEEK.

&&

.EASTERN MICRONESIA...
FRESH TO MODERATE TRADE WINDS AND ISOLATED SHOWERS ARE EXPECTED
TO PREVAIL ACROSS THIS AREA IN THE COMING WEEK. ASCAT ANALYSIS
SHOWS THE AXIS OF A SURFACE TROUGH WAS JUST WEST OF POHNPEI AND
DRIFTING WESTWARD. HIGH SURF ADVISORY REMAINS IN EFFECT ALONG
EASTERN REEFS OF KOSRAE. WW3 BRINGS SURF BELOW HAZARDOUS LEVELS
BY TUE...BUT ALSO SHOWS THE NNW SWELL BUILDING AT BOTH POHNPEI
AND KOSRAE AS THE WEEK PROGRESSES. MAJURO BUOY KALO SHOWS A
DOMINANT LONG-PERIOD SWELL FROM NNW NEAR 7 FT.

&&

.WESTERN MICRONESIA...
THE COLD FRONT APPROACHING NW MICRONESIA WILL GENERATE LARGE
NORTH SWELL THAT WILL QUICKLY BUILD SURF TO HAZARDOUS LEVELS LATE
MONDAY NIGHT FOR YAP AND PALAU...AND REACH CHUUK WEDNESDAY.

WEATHER WILL BE ACTIVE THIS WEEK. SAT LOOPS SHOW A WEAK MID-LEVEL
CIRCULATION BETWEEN YAP AND KOROR MOVING SLOWLY WESTWARD. ASCAT
ANALYSIS SHOWS THE COLD FRONT NEAR 13N130E AND MOVING SE.
TROUGHING ALONG WITH VARIABLE WINDS REMAINS ACROSS KOROR...AND
EAST SURFACE WINDS WERE DEVELOPING AT YAP. MODELS...MAINLY
GFS...INDICATE THE COLD FRONT WILL MOVE SE TO NEAR 10N AND
TRANSITION INTO A SHEAR LINE IN THE COMING DAYS. ASCAT WINDS SHOW
A TROUGH APPROACHING CHUUK FROM EAST AND GFS INDICATES THE TROUGH
WILL MOVE ACROSS CHUUK OVERNIGHT WITH SLIGHT CHANCE OF
THUNDERSTORMS. THE TROUGH WILL DRIFT WESTWARD TO NEAR YAP AND
PALAU BY MID WEEK. OTHERWISE...GENTLE TO FRESH TRADE WINDS WITH
MAINLY ISOLATED SHOWERS ARE EXPECTED THIS WEEK FOR WESTERN
MICRONESIA.

&&

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

W. AYDLETT/SIMPSON