

360 

AGNT40 KWNM 070238

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

1038 PM EDT TUE SEP 6 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 ZONE ANZ820

ABOUT 80 NM SE OF SANDY HOOK NJ WHILE A HIGH PRES RIDGE IS

DEPICTED OVER THE SRN WATERS. THE LATEST OBSERVATIONS SHOW HIGHER

WINDS OVER THE WRN PARTS OF THE CENTRAL WATERS. AT 00Z THE NCEP

MAP HAS POST-TROPICAL HERMINE NEAR 39N73W WITH A FRONT EXTENDING

NE ACROSS THE NRN WATERS. HIGH PRES 1035 MB OVER THE CENTRAL ATLC

EXTENDS A RIDGE W THAT ENDS JUST E OF THE FORECAST REGION.

ANOTHER RIDGE EXTENDS FROM THE S-ERN STATES THRU THE MID ATLC

STATES INTO NEW ENGL. THE PRES GRADIENT IS STILL TIGHT OVER THE

CENTRAL WATERS WHERE THE WINDS ARE IN THE GALE FORCE RANGE BUT

FAIRLY RELAXED ELSEWHERE. THE SEAS ARE ALSO LARGE OVER THE CENTRAL

WATERS WITH 15 FT PEAKS JUST OUTSIDE THE CENTER OF HERMINE. THE

NWW3 WAVE MODEL FITS WELL WITH THE 00Z OBSERVED SEAS PATTERN BUT

IS STILL UNDERDDONE NEAR HERMINE ESPECIALLY ON THE PEAK VALUE BY 4

FT. THE ECMWFWAVE HAS ALSO INITIALIZED WELL WITH THE OBS SEAS

PATTERN BUT ALSO UNDERDONE BY 2 FT COMPARED WITH THE OBSERVED PEAK

VALUE. OTHERWISE BOTH WAVE MODELS HAVE BEEN QUITE CONSISTENT AND

JUST NEED TO BE BUMPED UP BY A SMALL PERCENTAGE TO EQUALL THE

OBSERVATIONS AND FORECAST. I PLAN ON NOT CHANGING THE SEAS MUCH

SINCE THE FORECAST TRACK OF HERMINE AND INTENSITY OF THE WINDS ARE

VERY CLOSE TO THE FORECAST AND NO MAJOR CHANGES TO THE PREVIOUS

TRACK AND FORECAST ARE EXPECTED. WILL RETAIN THE SEAS WITH MINOR

ADJ TO FIT HERMINE.



THE MODELS GFS/ECMWFHR/UKMETHR/CMC STILL INDC SOME ENERGY IN AN

UPPERLEVEL CUT-OFF LOW OVER THE CENTRAL WATERS WITH HIGH PRES

CENTERS TO THE E AND W. IN THE SHORT TERM THE MODELS AGREE ON

WEAKENING THE HIGH PRES TO THE E AND THAT WILL FORCE THE ENERGY TO

BE SPREAD OUT AND WEAKEN THE SYSTEM. IN ADDITION MORE ENEGRY

ASSOCIATED WITH AN UPPERLEVEL TROF TO THE NW WILL SHIFT E AND

MERGE WITH THE ENERGY OVER THE WATERS. HERMINE IS NOW N OF THE

GULF STREAM AND IS EXPECTED TO REMAIN IN THE COOL WATERS. AS SUCH

WINDS ASSOCATED WITH HERMINE SHOULD CONTINUE TO DIMINISH TO BELOW

WARNING THRESHOLD ON WED NIGHT.



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

00Z SFC OBSERVATIONS ESPECIALLY THE PRESS FIELD BUT STILL HAVE

MINOR DIFFERENCES ON THE INTENSITY AND AREAL EXTENSION OF THE WIND

FIELD. ALL THE MODELS AGREE ON HIGHER WINDS IN THE SW SECTOR BUT

GFS AND CMC HAVE WINDS HIGHER THAN THE OTHER MODELS AND SIMILAR

DIFFERENCES CONTINUE IN THE SHORT TERM. OTHERWISE THE MODELS AGREE

ON MEANDERING THE SYSTEM OVER THE WRN PARTS OF THE CENTRAL WATERS

IN THE SHORT TERM AND THEN ACCELERATE IT NE AS IT WEAKENS AND

EVANTUALLY DISSIPATE. IN THE LONG RANGE A HIGH PRES RIDGE WILL

EXTEND FROM THE W INTO THE SRN WATERS WHILE A COUPLE OF FRONTS

WILL PASS E ACROSS THE NRN WATERS AND WINDS WILL REMAIN BELOW GALE

FORCE.



POST-TROPICAL CYCLONE HERMINE FORECAST POSITIONS...CENTRAL

PRESSURE...MAX WINDS



INITIAL 07/0000Z 39.3N 72.5W 1000 MB 35 KT 

12HR VT 07/1200Z 39.4N 72.7W 1001 MB 35 KT 

24HR VT 08/0000Z 39.9N 72.4W 1003 MB 35 KT 

36HR VT 08/1200Z 40.5N 71.5W 1006 MB 30 KT 

48HR VT 09/0000Z...DISSIPATED 



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

PREVIOUS DISCUSSION... 



A 1530Z ASCAT OVERPASS S OF LONG ISLAND RETURNED MAX WINDS OF 35 

KT ASSOCIATED WITH POST-TROPICAL HERMINE...AND ONLY OVER ITS W 

QUADRANT. WITH COASTAL WINDS LESS THAN TROPICAL STORM FORCE NHC 

JUST ISSUED THE LAST ADVISORY FOR HERMINE. AS A RESULT THE 

PREVIOUS TROPICAL STORM WARNINGS ACROSS THE S OF NEW ENGLAND 

OFFSHORE WATERS AND WRN NT2 ZONES N OF BALTIMORE CANYON WILL BE 

CONVERTED TO GALE WARNINGS. 12Z MODELS ALL CONTINUED WITH THE 

WEAKENING TREND...A CONSISTENT TREND OVER THE LAST COUPLE DAYS. 

THE 12Z ECMWF AND 16Z RAP APPEAR TO BE THE BEST INITIALIZED WITH 

WINDS THIS AFTERNOON. REMAINING GUIDANCE NAMELY THE 12Z GFS AND 

16Z HRRR ARE SOMEWHAT OVERDONE WITH WINDS ASSOCIATED WITH 

POST-TROPICAL HERMINE. FOR THIS REASON AM FAVORING THE QUARTER 

DEGREE 12Z ECMWF FOR WINDS OVER THE NEAR TERM. 12Z GUIDANCE IS 

ALSO IN GOOD AGREEMENT THAT HERMINE WILL DISSIPATE JUST E AND NE 

OF CAPE COD AHEAD OF THE APPROACHING COLD FRONT THU EVENING. WE 

WILL BE PROVIDING SOME FORECAST POINTS AND MAXIMUM WINDS WHILE 

POST-TROPICAL HERMINE MAINTAINS AT LEAST GALE FORCE WINDS. THIS 

FORECAST INFORMATION IS PROVIDED BELOW.



IN THE EXTENDED THE 12Z GFS AND 12Z ECMWF ARE IN DECENT 

AGREEMENT WITH THE WEAK COLD FRONT FORECAST TO MOVE OFF THE NEW 

ENGLAND COAST FRI. THIS FRONT SHOULD STALL NEAR 1000 FM OR JUST 

S OF GEORGES BANK EARLY SAT BEFORE LIFTING BACK N ACROSS THE NT1 

WATERS AS A WARM FRONT LATER SAT AND SAT NIGHT. OPC PREFERENCE 

WILL CONTINUE WITH THE 12Z ECMWF THROUGH 09Z/11. THEN BY SUN/SUN 

NIGHT PREFER THE TIMING OF THE SLIGHTLY LESS PROGRESSIVE 12Z GFS 

WITH THE NEXT COLD FRONT...SO WILL POPULATE ITS WINDS BEGINNING 

12Z/11 THROUGH THE REMAINDER OF THE FORECAST PERIOD.    





POST-TROPICAL CYCLONE HERMINE

FORECAST POSITIONS...CENTRAL PRESSURE...MAX WINDS



INITIAL 06/1800Z    39.4N 72.3W  1000 MB  35 KT 	

12HR VT 07/0600Z    39.2N 72.2W  1001 MB  35 KT

24HR VT 07/1800Z    39.7N 72.1W  1003 MB  35 KT

36HR VT 08/0600Z    39.8N 71.5W  1006 MB  35 KT

48HR VT 08/1800Z    41.1N 70.0W  1007 MB  25 KT

72HR VT 09/1800Z...DISSIPATED





.SEAS...THE 12 WAVEWATCH III AND THE 12Z ECMWF WAM BOTH APPEAR A 

COUPLE FT UNDERDONE WITH WAVE HEIGHTS INVOF POST-TROPICAL 

HERMINE THIS AFTERNOON. THE 14 FT SHIP REPORT ACROSS THE NWRN 

PART OF THE GULF STREAM AT 18Z LOOKED GOOD. USED A 50/50 BLEND 

OF THE 12Z WW3 AND 12Z ECMWF WAM THROUGH THU...AND BASED ON 

MODELS CURRENT PERFORMANCE BUMPED UP THE HIGHER WAVE HEIGHTS BY 

ABOUT 10 PERCENT. LIKE PREFERENCE FOR WINDS USED THE 12Z ECMWF 

WAM THROUGH SAT NIGHT...THEN TRANSITIONED TO THE 12Z WW3.  



.EXTRATROPICAL STORM SURGE GUIDANCE...WITH POST-TROPICAL HERMINE 

CONTINUING TO WEAKEN THE DIMINISHING TRENDS SEEN IN THE LATEST 

ETSS AND ESTOFS ALONG LONG ISLAND LOOK REPRESENTATIVE. BOTH THE 

12Z ETSS AND 12Z ESTOFS INDICATE SURGE DROPPING BELOW 1 FT THIS 

EVENING INTO TONIGHT...WITH WATER LEVELS ALONG THE NRN MID ATLC 

AND NEW ENGLAND COASTS REMAINING BELOW MAX ASTRONOMICAL TIDE 

LEVELS FOR THE NEXT FEW DAYS. 





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

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

     GALE WED NIGHT.

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

     GALE TONIGHT INTO WED NIGHT. 



.NT2 MID ATLC WATERS...

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

     GALE TONIGHT INTO WED. 

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

     GALE TONIGHT INTO WED NIGHT. 

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

     GALE TONIGHT.



$$



.FORECASTER MUSONDA/CLARK. OCEAN PREDICTION CENTER.

