012
AGPN40 KWNM 290241
MIMPAC
MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
741 PM PDT WED APR 28 2021
FORECAST DISCUSSION
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.
THE 00Z OPC-NCEP SURFACE MAP SHOWS A RIDGE OF HIGH PRESSURE
EXTENDING FROM JUST W OF THE CENTRAL CALIFORNIA OFFSHORE WATERS
NORTHWARD TOWARDS VANCOUVER ISLAND, WITH A LOW PRESSURE TROUGH
OVER CALIFORNIA AND A COLD FRONT WELL W OF THE OFFSHORE WATERS
ROUGHLY ALONG 140W OR SO. IT DOES APPEAR THAT THE THREAT FOR
GALES WILL INCREASE OFF THE SOUTHERN AND CENTRAL CALIFORNIA
COASTS BY SAT NIGHT AND THEN INTO EARLY NEXT WEEK, AS THE
PRESSURE GRADIENT BETWEEN THE CALIFORNIA TROUGH AND HIGH PRESSURE
BUILDING TO THE W OF THE WATERS STRENGTHENS. FOR THE EVENING
UPDATE, WE WILL NOT, HOWEVER MAKE MAJOR CHANGES TO THE ONGOING
OPC FORECAST AND WAIT FOR A FULL SET OF 00Z MODELS BEFORE MAKING
ANY MAJOR CHANGES TO THE ONGOING FORECAST, IF NEEDED.
SEAS...WAVE HEIGHT GENERALLY RANGE FROM 4 TO 6 FT OVER THE
OFFSHORE WATERS THIS EVENING PER THE LATEST OBSERVATIONS. AGAIN,
LITTLE CHANGE APPEARS NEEDED TO THE ONGOING OPC FORECAST FOR THE
EVENING UPDATE.
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PREVIOUS DISCUSSION...
A HIGH PRESSURE RIDGE WAS OVER THE CENTRAL AND NORTHERN AREAS OF
CA AND EXTENDED NE OVER THE OR AND WA OFFSHORE WATERS, THEN
INLAND. A WEAK TROF WAS ACROSS THE INTERIOR OF CA INTO OR EARLY
THIS AFTERNOON. WINDS ARE LIGHT THROUGHOUT MOST AREAS OF THE
OFFSHORE WATERS AT 15 KT OR LESS EARLY THIS AFTERNOON. WINDS WERE
TO 20 KT OVER THE WA WATERS IN ASSSOCIATION WITH A WARM FRONT
JUST N OF THE WATERS. THE HIGH PRESSURE RIDGE MOVES LITTLE
TONIGHT INTO THU WHILE A WEAKENING COLD FRONT PUSHES E INTO THE
WA/OR WATERS. ON THU NIGHT INTO FRI THE COLD FRONT MOVES SE INTO
THE N CA WATERS AND DISSIPATES OVER THE CENTRAL CA WATERS FRI AND
FRI NIGHT. WINDS PICKUP OVER THE INNER CENTRAL AND S CA WATERS
FRI NIGHT INTO SAT AS AN EXPANDING AND STRENGTHENING AREA OF HIGH
PRESSURE BUILDS IN FROM THE W AND NW OVER THE CENTRAL AREAS OF
OFFSHORE WATERS. WINDS INCREASE TO 25 KT OR 30 KT OVER THE INNER
CENTRAL CA LATE SAT AND SAT NIGHT, THEN PERSISTS TO THE W AND NW
OF THE N AND CENTRAL CA WATERS THROUGH MON BEFORE WEAKENING MON
NIGHT. A COLD FRONT MOVES E OVER THE WA/OR WATERS MON AND MOVES
SE AND INLAND MON NIGHT. BOTH THE GFS AND ECMWF ARE IN CLOSE
AGREEEMENT WITH THE TIMING OF THE FRONT AND PASSAGE OVER THE
WA/OR WATERS. FOR THE GRIDS WITH FEW DIFFERENCES EVIDENT PLAN TO
USE THE GFS THROUGH THE FORECAST PERIOD.
SEAS...GFS WAVE GUIDANCE AND ECMWF WAM ARE IN SIMILAR AGREEMENT
THROUGH MON NIGHT AND WILL USE THE GFS WAVE GUIDANCE WITH LITTLE
ADJUSTMENT ANTICIPATED.
EXTRATROPICAL STORM SURGE GUIDANCE
N/A
WARNINGS
PRELIMINARY.
PZ5 WASHINGTON/OREGON WATERS
NONE.
PZ6 CALIFORNIA WATERS
NONE.
.FORECASTER MILLS/ROWLAND. OCEAN PREDICTION CENTER.
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