

563 

AGNT40 KWNM 040855

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

455 AM EDT SUN SEP 4 2016



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

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



THE SAT IMG INDC POST-TROPICAL CYCLONE HERMINE OVER THE CENTRAL

WATERS WITH A RIDGE JUST N OF THE WATERS. ALL THE OBSERVATIONS

INCLUDING THE ASCAT PASS AT 0250Z HAVE HIGHER WINDS OVER THE

CENTRAL WATERS. BUOY 44014 IN VIRGINIA BEACH IN THE PAST FEW HOURS

HAD WINDS 30 TO 35 KT AND GUSTS TO 40 KT WITH PEAK SEAS AT 15 FT

SEAS. AT 06Z THE NCEP MAP HAS POST-TROPICAL CYCLONE HERMINE OVER

THE CENTRAL WATERS AND WEAK HIGH PRES WITH CENTERS INLAND W AND NW

OF HERMINE AND A THIRD CENTER 1023 MB JUST NE OF THE BALT CANYON.

THE PRES GRADIENT IS VERY TIGHT OVER THE CENTRAL WATERS BUT FAIRLY

RELAXED ELSEWHERE.



THERE IS SOME ENERGY THAT STRETCHES FROM AN UPPERLELVEL TROF OVER

THE MID WEST THRU THE CENTRL WATERS AND CONTINUES E. THE MODEL

SUGGEST MORE ENERGY TO PILE IN THE TROF WHICH WILL EVENTUALLY

CLOSE UP AND PUSH THE ENERGY OVER THE CENTRAL WATERS MON AND THAT

SHOULD KEEP HERMINE OVER THE WATERS. IN THE EXTENDED PERIOD THE

UPPERLEVEL RIDGE TO THE E OF THE WATER WILL BLOCK THE ENRGY FROM

ADVANCING E AND THAT SHOULD KEEP THE ENERGY TRAPPED IN THE CLOSED

LOW LONGER OVER THE WATERS. THE RIDGE TO THE E WILL WEAKEN AND

ALLOW THE ENERGY TO SLIDE NE.



THE GLOBAL MODELS GFS/ECMWFHR/UKMETHR/CMC HAVE INITIALIZED WELL

WITH THE 06Z OBERVATIONS WITH JUST VERY MINOR DIFFERENCES IN THE

EXTENT OF THE WIND FIELD AROUND THE STORM WITH GFS SHOWING A

LARGER AREA OF WINDS IN THE WARNING RANGE. THE MODELS ALSO HAVE

SOME DIFFERENCES ON THE TRACK OF THE STORM AND THESE DIFFERENCES

ARE EVEN GREATER WHEN THE MOVEMENT OF STROM SLOWS DOWN BETWEEN

05/1200Z AND 07/0000Z. I DID NOT HAVE THE LATEST RUN OF NOGAPS BUT

THE MODEL STILL AGREE WITH THE REST IN KEEPING THE STORM OVER THE

CENTRAL WATERS. INITIALLY THE ECMWFHR IS MORE PROGRESSIVE WITH THE

SYSTEM AND IT TRIES TO KEEP IT E OF THE OTHER MODELS. GFS ALSO

KEEPS STORM W OF THE OTHER MODELS. HOWEVER...THE MODELS SHOWED A

SLIGHTLY BETTER AGREEMENT AFTER 07/0000Z AS THE SYSTEM SHOW SIGNS

OF MOVING NE. STILL TRICKY TO STICK TO ONE MODEL SOLUTION AND SO

WILL CONTINUE TO FOLLOW THE NHC TRACK OF HERMINE. WILL USE GFS AND

THE ECMWFHR BACK TO BACK AND MAKE ADJUSTMENTS TO THE WINDS

ACCORDINGLY. IN THE SHORT TERM HERMINE WILL PERSIST OVER THE

CENTRAL WATERS BUT WILL START TO MOVE NE IN THE EXTENDED PERIOD. A

RIDGE OF HIGH PRES WILL THEN MOVE INTO THE REGION.





.SEAS...THE HIGHEST SEAS ARE STILL OVER THE CENTRAL WATERS WITH

PEAKS TO 26 FT. OVER THE FAR N AND FAR S THE SEAS RANGE BETWEEN 3

AND 6 FT. NWW3 WAVE MODEL HAS INITIALIZED WELL WITH THE OBSERVED

SEAS PATTERN BUT JUST UNDERDONE BY 2 FT FOR THE PEAK VALUE. THE

ECMWFWAVE HAS ALSO INITIALIZED WELL BUT ALSO UNDERDONE BY JUST 1

FT WITH THE PEAK VALUE. THE OFFICIAL TRACK OF THE STORM MAY HAVE

SHIFTED SLIGHTLY E FROM THE PREVOIUS TRACK BUT THE SEAS HAVE NOT

SIGNIFICANTLY CHANGED AND SO WILL TRY TO STAY WITH NWW3 BUT MAKE

SOME ADJUSTMENTS ESPECIALLY OVER THE ERN PARTS.



.EXTRATROPICAL STORM SURGE GUIDANCE...WITH MODELS FORECASTING 

HERMINE TO HAVE SUCH A SLOW MOTION OFF THE NRN MID ATLC AND SRN

NEW ENGLAND COASTS THROUGH AT LEAST WED...THERE IS A HIGH

LIKELIHOOD OF SIGNIFICANT AND POSSIBLY LIFE THREATENING STORM

SURGE FROM THE DELMARVA PENINSULA TO THE SOUTHERN NEW ENGLAND

COAST TODAY INTO NEXT WEEK. FOR FURTHER DETAILS AND GUIDANCE

PLEASE SEE THE STORM SURGE SECTION OF THE NHC PUBLIC ADVISORY AND

THE NHC PROTOTYPE STORM SURGE WATCH/WARNING GRAPHIC AT:

WWW.HURRICANES.GOV/GRAPHICS_AT4.SHTML?WSURGE (ALL LOWERCASE). ALSO

SEE THE NHC KEY MESSAGES CONCERNING STORM SURGE BELOW.



NHC KEY MESSAGES: 



1. THE SLOW MOTION AND LARGE WIND FIELD ASSOCIATED WITH HERMINE

WILL RESULT IN A LONG DURATION OF HAZARDOUS CONDITIONS ALONG MUCH

OF THE MID-ATLANTIC COAST EXTENDING INTO SOUTHERN NEW ENGLAND

THROUGH THE HOLIDAY WEEKEND.



2. ALTHOUGH HERMINE HAS BECOME A POST-TROPICAL CYCLONE, NHC WILL

CONTINUE TO ISSUE ITS FULL SUITE OF ADVISORY AND WARNING PRODUCTS

AS LONG AS THE SYSTEM REMAINS A SIGNIFICANT THREAT TO LAND AREAS.



3. P-SURGE, THE MODEL THAT DRIVES THE POTENTIAL STORM SURGE

FLOODING GRAPHIC, IS DESIGNED FOR A WIND FIELD TYPICAL OF A

TROPICAL CYCLONE. THE WIND FIELD OF HERMINE IS VERY POORLY

REPRESENTED BY THE P-SURGE MODEL AND AS A RESULT, RECENT FLOODING

GRAPHICS HAVE UNDERSTATED THE INUNDATION RISK FROM THE CAROLINAS

NORTHWARD. NHC WILL BE DISCONTINUING RUNS OF THE P-SURGE MODEL FOR

HERMINE WITH THIS ADVISORY. THE NWS IS ATTEMPTING TO SUBSTITUTE

THE GFS ENSEMBLE SYSTEM FOR P-SURGE FOR THE NEXT ISSUANCE OF THE

POTENTIAL STORM SURGE FLOODING GRAPHIC, TO PROVIDE A MORE

REALISTIC DEPICTION OF THE THREAT. IF THIS EFFORT IS UNSUCCESSFUL,

ISSUANCE OF THE POTENTIAL STORM SURGE FLOODING GRAPHIC FOR HERMINE

WILL ALSO BE DISCONTINUED.



4. THE PROTOTYPE STORM SURGE WATCH/WARNING GRAPHIC DOES ACCOUNT

FOR THE CURRENT WIND STRUCTURE OF HERMINE, AND THEREFORE

ACCURATELY IDENTIFIES THOSE AREAS AT RISK FOR LIFE-THREATENING

STORM SURGE. THIS GRAPHIC WILL CONTINUE TO BE PRODUCED FOR

HERMINE.







.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

.ANZ805...GEORGES BANK WEST OF 68W...

     TROPICAL STORM TODAY INTO TONIGHT. 

     TROPICAL STORM POSSIBLE WED INTO THU NIGHT. 

.ANZ900...GEORGES BANK EAST OF 68W...

     TROPICAL STORM POSSIBLE WED NIGHT INTO THU NIGHT. 

.ANZ810...SOUTH OF NEW ENGLAND...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE MON NIGHT INTO THU. 

.ANZ815...SOUTH OF LONG ISLAND...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE MON NIGHT INTO WED NIGHT. 



.NT2 MID ATLC WATERS...

.ANZ820...HUDSON CANYON TO BALTIMORE CANYON...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE MON NIGHT INTO WED. 

.ANZ915...HUDSON CANYON TO THE GREAT SOUTH CHANNEL...

     TROPICAL STORM EARLY TODAY INTO TONIGHT. 

     HURRICANE MON.

     HURRICANE POSSIBLE MON NIGHT.

     TROPICAL STORM POSSIBLE TUE INTO THU. 

.ANZ920...BALTIMORE CANYON TO THE GREAT SOUTH CHANNEL...

     TROPICAL STORM EARLY TODAY INTO TODAY. 

     HURRICANE TONIGHT INTO MON. 

     HURRICANE POSSIBLE MON NIGHT.

     TROPICAL STORM POSSIBLE TUE INTO WED NIGHT. 

.ANZ905...THE GREAT SOUTH CHANNEL TO THE HAGUE LINE...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE WED INTO THU NIGHT. 

.ANZ910...EAST OF THE GREAT SOUTH CHANNEL AND SOUTH OF 39N...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE WED INTO WED NIGHT. 

.ANZ825...INNER WATERS FROM BALTIMORE CANYON TO CAPE CHARLES LIGHT...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE MON NIGHT INTO TUE. 

.ANZ828...INNER WATERS FROM CAPE CHARLES LIGHT TO CURRITUCK BEACH LIGHT...

     TROPICAL STORM EARLY TODAY INTO MON. 

.ANZ925...OUTER WATERS FROM BALTIMORE CANYON TO HATTERAS CANYON...

     TROPICAL STORM EARLY TODAY INTO MON. 

     TROPICAL STORM POSSIBLE MON NIGHT INTO TUE. 

.ANZ830...INNER WATERS FROM CURRITUCK BEACH LIGHT TO CAPE HATTERAS...

     TROPICAL STORM EARLY TODAY INTO TODAY. 

.ANZ930...OUTER WATERS FROM HATTERAS CANYON TO CAPE FEAR...

     TROPICAL STORM EARLY TODAY INTO TODAY. 



$$



.FORECASTER MUSONDA. OCEAN PREDICTION CENTER.

