420
AGPN40 KWNM 290753
MIMPAC
MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
1253 AM PDT THU APR 29 2021
FORECAST DISCUSSION
MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.
THE MAIN FORECAST CONCERN OVER THE NEXT 5 DAYS WILL BE THE
POTENTIAL FOR NORTH AND NORTHWESTERLY GALES DEVELOPING OVER THE
EASTERN PORTIONS OF THE INNER CALIFORNIA OFFSHORE WATERS. BASED
ON THE 00Z GUIDANCE, WHICH IS IN GOOD AGREEMENT OVER THE REGION
RIGHT INTO EARLY NEXT WEEK, WE WILL GO AHEAD AND ADD MARGINAL
GALES TO THE FAR EASTERN INNER CENTRAL AND SOUTHERN CALIFORNIA
OFFSHORE WATERS FOR SUN NIGHT, FOR THE EARLY MORNING OPC
FORECAST PACKAGE. THE 00Z GUIDANCE FROM THE GFS, ECMWF, UKMET AND
GEM ALL BRING WINDS TO AT LEAST 30 KT OVER THE ABOVE MENTIONED
WATERS BY SUN NIGHT, AND WE WILL USE AN EVEN BLEND OF THE BIAS-
CORRECTED 00Z ECMWF WINDS AND 00Z GFS WINDS FOR LATER SUN AND SUN
NIGHT INTO MON FOR THE EARLY MORNING PACKAGE, WHICH WILL LEAD TO
THE POSSIBLE GALES AS NOTED BELOW IN THE PRELIMINARY WARNINGS
SECTION. THERE IS SOME POTENTIAL FOR GALES DEVELOPING A LITTLE
SOONER THAN CURRENTLY FORECAST, AND ALSO EXTEND A LITTLE LONGER
INTO EARLY NEXT WEEK, BUT FOR NOW, THE SUN NIGHT TIME FRAME
APPEARS TO BE THE MOST LIKELY TIME FOR GALES OVER THE INNER
SOUTHERN AND CENTRAL CALIFORNIA OFFSHORE WATERS. FORECAST
CONFIDENCE IS CLOSE TO AVERAGE ACROSS THE WATERS FOR THE NEXT FEW
DAYS.
ASCAT FROM LAST EVENING INDICATED N AND NW WINDS TO 25 KT JUST
OFF MUCH OF THE CALIFORNIA COAST, WITH WINDS 20 KT OR LESS
ELSEWHERE OVER THE REGION AND HIGH PRESSURE DOMINATES WATERS FROM
SOUTHEASTERN WASHINGTON WATERS S AND SW TO W OF THE CENTRAL
CALIFORNIA WATERS. THE 06Z OPC-NCEP PRELIMINARY SURFACE ANALYSIS
ALSO SHOWS A COLD FRONT W OF THE OFFSHORE WATERS, EXTENDING
ROUGHLY ALONG 138W. THE FRONT WILL MOVE E AND CROSS PZ5 WATERS
TONIGHT INTO FRI, REACH NORTHERN CALIFORNIA WATERS DURING FRI,
CENTRAL CALIFORNIA WATERS FRI NIGHT INTO SAT, AND THEN SOUTHERN
CALIFORNIA WATERS AS IT DISSIPATES LATER SAT INTO SUN, AS A LOW
PRESSURE TROUGH NEAR THE CALIFORNIA COAST STRENGTHENS. A RATHER
STRONG PRESSURE GRADIENT BETWEEN THE TROUGH AND HIGH PRESSURE
BUILDING W OF THE REGION WILL DOMINATE MAINLY CALIFORNIA WATERS
BY SUN INTO MON BEFORE THE HIGH SLOWLY WEAKENS BY MON NIGHT AND
TUE.
MODELS...AS THE 00Z MODELS REMAIN IN VERY GOOD AGREEMENT, WE SEE
NO REASON NOT TO POPULATE GRIDS WITH THE 00Z GFS WINDS FOR TODAY
INTO SUN. FOR LATER SUN INTO MON WE WILL THEN POPULATE GRIDS WITH
AN EVEN BLEND OF THE GFS WINDS AND 00Z ECMWF-BIAS CORRECTED
WINDS, AND THEN TREND GRIDS CLOSER TO THE MORE CONSISTENT ECMWF
WINDS BY MON NIGHT INTO THE MIDDLE OF NEXT WEEK, AND CAP WINDS
BELOW GALE FORCE DURING THAT EXTENDED TIME PERIOD.
SEAS...BOTH THE 00Z GFS WAVE GUIDANCE AND ECMWF WAM HAVE
INITIALIZED FAIRLY WELL OVER THE REGION EARLY THIS MORNING. FOR
TODAY INTO MON, WE WILL USE AN EVEN BLEND OF THESE TWO WAVE
MODELS, AND THEN TO MATCH WINDS TREND WAVE HEIGHT GRIDS CLOSER TO
THE WAM BY MON NIGHT INTO THE MIDDLE OF NEXT WEEK.
EXTRATROPICAL STORM SURGE GUIDANCE
N/A
WARNINGS
PRELIMINARY.
PZ5 WASHINGTON/OREGON WATERS
NONE.
PZ6 CALIFORNIA WATERS
PZZ825...INNER WATERS FROM POINT ARENA TO PIGEON POINT
GALE POSSIBLE SUNDAY NIGHT.
PZZ830...INNER WATERS FROM PIGEON POINT TO POINT PIEDRAS BLANCAS
GALE POSSIBLE SUNDAY NIGHT.
PZZ835
INNER WATERS FROM POINT PIEDRAS BLANCAS TO SANTA CRUZ ISLAND, CA...
GALE POSSIBLE SUNDAY NIGHT.
.FORECASTER MILLS. OCEAN PREDICTION CENTER.
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