

405 

AGNT40 KWNM 031221

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

821 AM EDT WED AUG 3 2016



.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT

.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.



UPDATE...06Z NCEP SFC ANALYSIS SHOWS A STATIONARY FRONT EXTNDG E

TO W ACROSS THE CENTRAL AND SRN NT2 WTRS TO CAPE LOOKOUT...WITH A

HI PRES RIDGE BUILDING S OVER THE NT1 AREA...AND A COUPLE OF

DEVELOPING LOWS CENTERED ABOUT 300 NM SE OF ZONE 900 IN THE

GEORGES BANK WTRS. LATEST AVAIL ASCAT HI-RES AND RAPIDSCAT PASSES

FROM LAST NITE SHOW SHOW 20 TO 25 KT WINDS IN SW FLOW OVER THE

INNER OFSHR ZONES OFF THE NORTH CAROLINA COAST...BUT ELSEWHERE IN

THE OFSHR WTRS MAINLY 15 TO 20 KT WINDS. LIGHTNING DENSITY DATA AT

1100Z SHOWS ISOLATED SHOWERS AND TSTMS IN THE ERN PART OF ZONES

905 AND 910 AND ALSO IN THE OUTER CENTRAL NT2 WTRS...WITH

SCATTERED SHOWERS AND TSTMS S OF THE STATIONARY FRONT AND ACROSS

MOST OF THE SRN NT2 ZONES.



MAIN WEATHER FEATURES...A WEAK LOW WILL MOVE OFF THE CAROLINA

COAST TODAY...PASS E OVER THE NT2 WTRS TONITE INTO THU...THEN MOVE

OFF TO THE E LATER THU AND THU NITE. A COLD FRONT WILL APPROACH

THE COAST FRI NITE AND SAT...MOVE OFFSHORE LATE SAT INTO SAT

NITE...THEN SWEEP SE OVER THE OFSHR WTRS SUN AND SUN NITE.



MODELS...THE MED RNG MDLS ARE IN GUD OVERALL AGREEMNT ACROSS THE

OFSHR WTRS THRU THE FCST PERIOD...WITH THE ECMWF/GFS STILL IN VRY

GUD AGREEMNT. MAIN DIFF AMONG THE MDLS IS THE GEM/UKMET ARE JUST A

BIT SLOWER WITH THE COLD FRONT OVER THE SAT NITE THRU SUN NITE

TIMEFRAME. THE GFS 10M SOLN LOOKS REPRESENTATIVE ENUF TO BE USED

FOR THE WIND GRIDS THRU THE ENTIRE FCST PERIOD...EXCEPT WILL BE

USING A 50/50 BLEND OF THE GFS 10M/30M SOLNS OVER THE GULF STREAM

DUE TO STRONGER SW FLOW EXPECTED THERE DURING MUCH OF THE FCST

PERIOD. AM NOT PLANNING TO MAKE ANY SIGNIF CHANGES TO THE CURRENT

FCST TREND.



SEAS...BOTH THE WNA WAVEWATCH III AND ECMWF WAM INITIALIZED A FOOT

OR TWO LOW OFF THE SC/GA COAST...SO THE SEA HTS ARE ADJUSTED

UPWARDS IN THE SHORT RANGE. OTHERWISE THE MDLS ARE IN GUD OVERALL

AGREEMNT THRU THE FCST PERIOD WITH ONLY MINOR DIFFERENCES

NOTED...SO WILL USE A 50/50 BLEND OF THE WNA WAVEWATCH III/ECMWF

WAM TO SMOOTH OUT THE MDL DIFFERENCES.



EXTRATROPICAL STORM SURGE GUIDANCE...N/A.



-----------------------------------------------------------------

PREVIOUS DISCUSSION...



THE LTST GOES IR IMGRY INDC DVLPG LOW PRES E OF THE NE NT2

WATERS...WITH A FRONTAL BNDRY EXTENDING TO THE SW INTO THE CENTRAL

NT2 WATERS...THEN INLAND NEAR CAPE HATTERAS. CRNT SFC RPRTS INDC

WINDS UP TO 25 KT OVR SRN NT2 IN THE SW FLOW AHD OF THE

FRONT...ALONG WITH SOME TSTM ACTIVITY ALONG THE FRONT IN THE UNSTABLE

ENVIRONMENT AHEAD OF IT...AS INDC BY THE LGTNG DENSITY PROD. THE

PREV FCST HAD TSTMS OVR NT2...SO PLANNING ON KEEPING THEM IN THE

NEXT FCST PKG. AS FAR AS THE WINDS ARE CONCERNED...ASCAT FM 02Z

IN C NT2 IN THE SW FLOW INDC 20 KT...THO THE PASS MISSED WHERE

CRNT RPRTS INDC 25 KT. THE 00Z GFS/ECMWF WINDS ARE INIT 5 TO 10 KT

LOW WHEN COMPARED WITH THE CRNT DATA OFF THE COAST OF SC...SO

PLANNING ON BOOSING WINDS INITIALLY...WHILE STARTING OFF WITH THE

GFS.



THE 00Z MDLS AGREE SOMEWHAT WELL THRUT THE FCST...AND ALL SOLNS

INDC THE FRNTL BNDRY CRNTLY ACRS NT2 WL STALL TDA...AND CONT OVR

NT2 WHILE SLOWLY WKNG. THE 00Z GFS/ECMWF BOTH INDC A WK SFC LOW WL

MOVE ALONG THE FRONT OVR SE NT2...AND THEN MOVE E OF THE AREA BY

THU NGT. THE PREV RUNS OF THE ECMWF/GFS HAD BEEN INCONSISTENT ON

THE DVLPMT OF THE LOW...BUT NOW SEEM TO BE SETTLING INTO THIS CRNT

SOLN. THE 00Z UKMET/GEM BOTH AGREE WELL WITH THE GFS/ECWMF WITH

THE TRACK...THO ARE A BIT STGR. THE PREV FCST FAVORED THE GFS

SOLN...WHICH HAS BEEN CLOSE IN THE PREV FEW RUNS...SO PLANNING ON

STAYING NR IT THE SHORT TERM. ALSO...PLANNING ON USING A 50/50

BLEND OF THE 10M/30M GFS WINDS OVR THE GULF STREAM...TO ACCT FOR

THE LOWER STATIC STABILITY AND SLIGHTLY DEEPER MIXING.



IN THE EXTENDED...THE 00Z GFS/ECMWF/GEM/UKMET REMAIN IN GUD AGRMT

WITH THE NEXT FRNTLY BNDRY TO MOVE OFF THE NEW ENGLAND COAST ON

SAT...ALTHO THE 00Z ECMWF/UKMET ARE SLIGHTLY SLOWER THAN THE 00Z

GFS/GEM SOLNS. AS A RESULT...PLANNING ON USING THE 00Z GFS...BUT

WL SLOW IT BY 3 HOURS AS A COMPROMISE.



SEAS...THE 00Z WAVEWATCH III AND ECMWF WAM BOTH INITIALIZED A FT

OR TWO LOW OFF THE SC COAST...SO WL NEED TO ADJUST SEAS HIGHER IN

THE SHORT RANGE TO ACCT FOR IT. OTRW THE MDLS AGREED FAIRLY WELL

THRUT THE FCST PD...SO PLANNING ON USING A 50/50 BLEND OF THE TWO

SOLNS AS A CMPRMS TO THE MINOR DIFFS.



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



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

     NONE.



.NT2 MID ATLC WATERS...

     NONE.



$$



.FORECASTER SCOVIL/KELLS. OCEAN PREDICTION CENTER.

