Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 010059
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
859 PM EDT FRI JUL 31 2015

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.

A LOW PRES CENTER TRACKING NE ACRS THE CNTRL NT2 WTRS LKLY HAS
MARGINAL GALE FORCE ASCD WINDS OVER ITS IMMED SE QUADRANT ACRS THE
OUTER CNTRL NT2 WTRS. AN EARLIER 2232Z JASON ALTIMETER PASS
RETURNED SEAS IN THE 10-13 FT RANGE JUST E OF THE CNTRL NT2 WTRS
WHICH ARE BEING HANDLED BETTER BY THE HIGHER 18Z WAVEWATCH III VS
THE LOWER 12Z ECMWF WAM AT THE MOMENT.

OVER THE SHORT TERM...BY 01/12Z THE CONSENSUS OF THE LATEST MDLS
IS FOR THE SFC LOW TO TRACK NE TO THE VCNTY OF 39N65W WITH THE
18Z NAM/GFS AND 12Z GEM/UKMET ALL FCSTG GALE FORCE ASCD BL WINDS
CONTG OVER ITS SE QUADRANT. THEREFORE WL STAY THE COURSE WITH THE
PREVLY POPULATED STRONGER 12Z GFS 30M BL WINDS OVER THE IMMED
SHORT TERM. THEN LATER SAT THRU SUN NITE A GNRLY WEAK SWLY
GRADIENT IS FCST TO VARYING DEGREES BY ALL OF THE MDLS TO PERSIST
THRU MUCH OF THE CSTL/OFSHR WTRS. SO WITH THE 18Z NAM/GFS RMNG
CONSISTENT WL CONT TO USE THE WEAKER 12Z GFS 10M BL WINDS FOR THE
REMAINDER OF THE SHORT TERM WITH JUST SM MINOR EDITS MAINLY IN
DEFERENCE TO THE 18Z GFS/12Z ECMWF.

IN THE LONG RANGE...THE LATEST MDLS GNRLY AGREE THAT THE SSWLY
GRADIENT WL STRENGTHEN SMWHT MON/MON NITE AS AN INLAND COLD FRONT
APRCHS FM THE NW. THE 12Z GEM/UKMET AT VARIOUS TIMES IN THE LONG
RANGE BOTH LOOK TO BE HAVING CONVECTIVE FEEDBACK PROBLEMS WITH THE
SFC LOWS THEY SPIN UP IN THE SWLY GRADIENT AND HENCE WL BE
DISREGARDED. THE 12Z/18Z GFS THEN CONT TO BE SMWHT MR PROGRESSIVE
THAN THE 12Z ECMWF IN FCSTG THE COLD FRONT TO SLOWLY PUSH SE ACRS
THE NT1 AND NRN NT2 WTRS TUE/WED...BUT THEN BY WED NITE THEY COME
INTO BETTER AGRMT WITH THE FRONT STALLING W-E ACRS THE NRN NT2
WTRS. THE PREV COMPROMISE OF USING THE 12Z GFS 10M BL WINDS IN THE
LONG RANGE...BUT TIME SHIFTING THEM SLOWER MON NITE INTO WED NITE
STIL LOOKS RSNBL. THEREFORE WL CONT TO USE THESE FCST WINDS WITH
JUST SM ADDITIONAL EDITS AGAIN MAINLY IN DEFERENCE TO THE 18Z
GFS/12Z ECMWF. SO ANTICIPATE MAKING GNRLY ONLY MINOR LONG RANGE
CHNGS IN THE NEXT OFSHR FCST PACKAGE.



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

CRNT GOES VIS IMGRY INDC A CDFNT OVR NT1 AND NRN NT2...AND ALSO
AN AREA OF LOW PRES ABOUT 90 NM NE OF CAPE HTRS WITH A TROF
EXTENDING TO THE SSW. THE IMGRY AND THE LGTNG DENSITY PROD BOTH
INDC AN AREA OF SHOWERS AND TSTMS ALNG THE TROF IN THE UNSTABLE
EVRNMT OVR THE GLF STRM...AND ALSO A FEW ALNG THE FRNTL BNDRY. WL
MAINTAIN MENTION OF TSTMS AND SHOWERS IN THE FCST...BUT MAIN
CONCERN IS GALES IN SW FLOW OVR NT2 ZONES. ASCAT FM 1520 UTC INDC
25 TO 30 KT AHD OF THE TROF AND FRNTL BNDRY...WITH A VRY SML AREA
OF GALES OVR NRN NT2. RECENT SFC RPRTS INDC WNDS UP TO 25 KT OVR
NT2...AND TO 35 KT JUST SE OF NRN NT2 WTRS. THE 12Z GFS 30M WNDS
ARE INIT JUST A TAD LOW AHD OF THE BNDRY...SO PLANNING ON BOOSTING
WNDS INITIALLY INVOF THE FRNT TO MATCH CRNT DATA. OTRW WL CONT
WITH 30M OVR THE GULF STRM AND SE...AND 10M WNDS TO THE N OF THE
GULF INTO 18Z SAT...AS THE 12Z ECWMF/UKMET ARE INIT LOW...THO
SYNOP FEATURES MATCH GFS.

THE 12Z MDLS RMN IN GENLY GUD AGRMT ON THE OVERALL PTTN INTO
MON...AND ALL INDC THE CRNT BNDRY WL STALL OVR NT2 WHILE WKNG. THE
12Z GEM SEEMS TO HAVE SOME FEEDBACK ISSUES...AS IT OVR DVLPS A
LOW ALNG THE FRNT. ATTM PLANNING ON USING 10M GFS WNDS INTO 00Z
TUE...AS A RESULT OF THE DECENT MDL AGRMT. HOWEVER...12Z MDL SOLNS
START DVRGING AT 00Z TUE...WITH THE GFS BCMG FASTER WITH THE NEXT
SYS THRU THE W ATLC. THE 12Z ECWMF IS ABT 12 HOURS SLOWER BY 12Z
WED...AND IT SEEMS TO HAVE A BIT MORE CREDIBILITY WITH THE UPR LVL
PTTN INDCG A SLGTLY AMPLIFIED RDG IN THE ERN ATLC THAT SHUD SLOW
DN THE FLOW A BIT. THE 12Z UKMET AND GEM ARE MUCH DIFF...AND INDC
ANTHR STG LOW WL DVLP IN THE EXTENDED...AND BOTH SEEM TO HAVE
FEEDBACK PRBLMS. FOR THE FCST...PLANNING ON USING A CMPRMS BTWN
THE 12Z GFS AND ECMWF...AND WL TIMESHIFT THE GFS 6 HOURS SLOWER.

SEAS...THE 12Z MWW3 AND ECMWF WAM HV BOTH INIT SEAS A TAD LOW
OVER THE FAR E NT2 WTRS E OF CAPE HTRS...BUT ELSWHR LOOK RSNBL.
THE MDLS SEEM RSNBL INTO 00Z TUE...BUT TMG ISSUES WITH ASSOC WX
MDLS CREATE DIFFS WITH THE WAVE MDLS. FOR THE FCST...PLANNING ON
USING A SMLR STRATEGY AS WITH THE WX MDLS...AND TIMESHIFT 12Z MWW3
SEAS 6 HOUR SLOWER. THIS BRINGS WAVE MDLS CLOSE...SO WL
SUBSEQUENTLY USE A 50/50 BLEND OF THE TIMESHIFTED MWW3 GRIDS WITH
THE 12Z ECWMF WAM GRIDS FOR THE FCST FROM 00Z TUE ONWARD.

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


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...
     GALE TONIGHT.

$$

.FORECASTER VUKITS/KELLS. OCEAN PREDICTION CENTER.


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