Marine Interpretation Message
Issued by NWS

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AGPN40 KWNM 280231
MIMPAC

MARINE WEATHER DISCUSSION FOR N PACIFIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
731 PM PDT WED JUL 27 2016

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH PACIFIC N OF 30N AND E OF 150W.

THE FOCUS OF THE FORECAST REMAINS ON THE INTERACTION BETWEEN THE
HEAT LOW/TROF OVER THE INTERIOR IN CENTRAL CAL AND STRONG HIGH
PRES W OF THE NRN CAL WTRS. THE STRONGEST PART OF THE PRES GRAD IS
TO THE W OF CAPE MENDOCINO AND PT ST GEORGE...AND ASCAT FM 19Z
INDC GALES JUST OFF THE COAST...WITH A LARGE AREA OF 30 KT
EXTENDING INTO OFSHR WTRS. IN ADDITION...WIND RETRIEVALS FM A 1830
UTC ALSO INDC 30 KT...WITH SEAS ABV 14 FT...SEVL FT HIGHER THAN
THE WAVE GUID. THE 18Z GFS INDC THE CRNT PTN WL CONT OVR PZ6 INTO
SUN...WITH GALES JUST OFF THE COAST UP TO THAT TIME. THE 12Z
ECMWF/UKMET/GEM/NAM ALL AGREE FAIRLY WELL WITH THE GFS ON THE
OVERALL PTTN...AND ALL INDC GALE OR NEAR GALE FORCE WINDS INTO
SUN. THE PREV FCST HAD GALES CONSISTENT WITH THE GFS...AND CONFDC
IS MDT TO HIGH WITH THEM...SO PLANNING ON MAINTAINING PREV WRNG IN
NE PZ6/SE PZ5 IN UPDATE PKG.

ALSO...THE LTST GOES IR/VIS IMGRY INDC A STG LOW PRES SYS CENTERED
OVER THE GULF OF ALASKA....WITH A FRONTAL BNDRY EXTENDING TO THE S
THEN SW FROM THE LOW. THE IMGRY ALSO INDC A WK FRNTL WAVE CRNTLY
NR 44N149W...MOVG TO THE E TWD NRN PZ5. THE MDLS AGREE FAIRLY WELL
ON MOVING THE WK WAVE INTO NRN PZ5 THU NGT INTO FRI AND DSIPT. THE
GFS INDC THE WK CD SURGE WL ACT TO LOWER STATIC STABILITY OVR
PZ5...ALLOWING STGR WINDS ALOFT TO MIX DN. THE MDLS ALL INDC WINDS
TO 40 KT OVR THE NE WAS WTRS BY LATE FRI INTO SAT...SO THE
POTENTIAL FOR GALES TO MIX DN IS THERE. ALSO...THE MDLS INDC A
SECOND SFC TROF WL DEVELOP ALONG THE COAST OF WAS AND EXTEND OVER
VANCOUVER ISLAND...AND INTERACT WITH THE AFOREMENTIONED HIGH W OF
THE AREA. AS A RESULT...CONFDC IS MDT TO HIGH WITH GALES OVER
PZZ800 FRI NIGHT INTO SAT NIGHT...SO PLANNING ON KEEPING PREV
WARNING IN UPDATE PKG.

OTRW...THE 12Z/18Z GFS HAS BEEN CONSISTENT WITH THE OVERALL PTTN
OVER THE PAST FEW DAYS...AND INDC ANOTHER WK CD FNT WL MOV INTO
NRN PZ5 MON. THE 12Z UKMET/GEM ARE SLIGHTLY FASTER THAN THE GFS
WITH THE PROGRESSION OF THE FRONT...AND THE 12Z ECMWF IS SLOW
OUTLIER. THE GFS WAS FAVORED IN THE PREV FCST...AS IT WAS THE BEST
COMPROMISE...SO PLANNING ON STAYING WITH IT FOR THE REMAINDER OF
THE UPDATE PKG.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE ENHANCED PRES GRADIENT PERSISTS OVER THE NRN CA/SRN OR WATERS
THIS AFTN PER THE 18Z OPC SFC ANALYSIS. STRONG NLY FLOW CONTINUES
BETWEEN A 1030 MB HIGH W OF THE WATERS AND A 1010 MB THERMAL LOW
ANALYZED OVER NRN CA. A 1757Z ASCAT PASS REVEALED A LARGE SWATH OF
20-30 KT WINDS EXTENDING FROM THE SRN PZ5 WATERS INTO THE NRN AND
CENTRAL PZ6 WATERS...WITH A FEW GALE BARBS NOTED IN THE COASTAL
WATERS W OF THE CA/OR BORDER.

THE 12Z MODELS CONTINUE TO DEPICT AN EXTENDED PERIOD OF GALES
BEGINNING OVER THE NRN CA WATERS LATER THIS AFTN...EXPANDING INTO
THE FAR SE OR WATERS ON FRI AS THIS PATTERN PERSISTS FOR THE NEXT
FEW DAYS. POPULATED WITH A BLEND OF THE 10/30M GFS WINDS THRU SAT
TO ACCOUNT FOR THE 10M GFS/ECMWF WINDS RUNNING A BIT TOO LOW AS
NOTED IN THE PREVIOUS FCST. THEN TRANSITIONED TO THE 10M GFS WINDS
THROUGH MON NIGHT...WHICH REFLECTS LOWERED CONFIDENCE FOR GALES
LATER IN THE PERIOD AND MATCHES UP WELL WITH THE 12Z ECMWF AND OUR
NEIGHBORING WFOS. AS A WEAK AREA OF LOW PRES RIDES OVER THE SFC
RIDGE SUN THRU EARLY MON...SFC HIGH PRES WILL WEAKEN AND THE
GRADIENT SHOULD RELAX ENOUGH FOR THESE GALES TO SUBSIDE BY SUN
NIGHT.

A SECOND AREA OF GALES IS EXPECTED TO DEVELOP OVER THE NE WA
WATERS LATE FRI/EARLY SAT. THE 12Z GFS/ECMWF SHOW ANOTHER SFC
TROUGH DEVELOPING OVER THE NRN PZ5 WATERS FRI INTO SAT...WITH
ENHANCED N/NW FLOW PRIMARILY BETWEEN 00Z-12Z SAT OVER THE NE
PORTION OF PZ800. THERE WAS ENOUGH SUPPORT WITH THE 12Z GUIDANCE
TO WARRANT KEEPING THIS BRIEF PERIOD OF GALES IN THE FCST ATTM.

.SEAS...A JASON-2 ALTIMETER PASS FROM 1828Z INDICATES THAT BOTH
THE NWW3 AND ECMWF WAM GUIDANCE ARE STILL RUNNING 1-2 FT TOO LOW
WITHIN THE STRONG NLY FLOW OFF NRN CA. USED PREVIOUS WAVE GRIDS
FOR THE NEAR TERM AND MANUALLY EDITED THEM TO BOOST SEAS AND REFLECT
THE 14 FT MAX SHOWN IN THE LATEST ALTIMETER DATA. THEN POPULATED
WITH THE 12Z NWW3 THU THROUGH MON NIGHT TO MATCH THE WIND GRIDS.

.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...PRELIMINARY.

.PZ5 WASHINGTON/OREGON WATERS...
.PZZ800...INNER WATERS FROM CAPE FLATTERY TO CAPE SHOALWATER...
     GALE POSSIBLE FRI NIGHT.
     GALE POSSIBLE SAT NIGHT.
.PZZ815...INNER WATERS FROM FLORENCE OR TO POINT ST. GEORGE...
     GALE FRI.
     GALE POSSIBLE FRI NIGHT.

.PZ6 CALIFORNIA WATERS...
.PZZ820...INNER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE TONIGHT INTO FRI.
     GALE POSSIBLE FRI NIGHT INTO SUN.
.PZZ920...OUTER WATERS FROM POINT ST. GEORGE TO POINT ARENA...
     GALE POSSIBLE FRI NIGHT.

$$

.FORECASTER KELLS/REINHART. OCEAN PREDICTION CENTER.


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