

189 

AGNT40 KWNM 050247

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

1047 PM 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 THAT POST-TROIPICAL CYCLONE HERMINE IS OVER THE

ERN PARTS OF THE CENTRAL WATERS WHILEA HIGH PRES RIDGE IS OVER THE

FAR NRN PART S AND ALSO OVER THE S-WRN PARTS. THE CURRENT

OBSERVATIONS INCLUDING THE ASCAT PASS AT 1430Z SHOW HIGHER WINDS

OVER THE CENTRAL WATERS. A SHIP LOCATED NEAR 37N 66W REPORTED 50

KT WINDS AT 22Z. THE 00Z NCEP MAP HAS POST-TROPICAL CYCLONE

HERMINE OVER ZONE ANZ910 WITH A SERIES OF HIGH PRES CENTERS TO THE

N WITH A RIDGE STRETCHING FROM HIGH PRES CENTER 1029 MB NEAR

44N58W THRU THE FAR NRN WATERS TO THE GREAT LAKES AND BEYOND. THE

PRES GRDIENT IS VERY TIGHT OVER THE CENTRAL WATERS BUT VERY

RELAXED OVER THE SRN AND FAR NRN WATERS. THE SEAS PEAK AT 30 FT

OVER THE CENTRAL WATERSAND THEY RANGE BETWEEN 5 AND 12 FT OVER

MOST OF THE WATERS OUTSIDE THE WARNING AREA AND ARE EVEN SMALLER

AT THE FAR NRN AND FAR S-WRN WATERS. NWW3 WAVE MODEL FITS WELL

WITH THE SEAS PATTERN BUT IS UNDERDONE ON THE PEAK VALUE BY 6 FT.

THE ECMWFWAVE ALOS FITS WELL WITH THE SEAS PATTERN BUT IS ALSO

UNDERDONE ON THE PEAK VALUE. WILL STILL USE THE NWW3 FOR THIS

UPDATE BUT WILL HAVE TO MAKE SOME MINOR ADJUSTMENTS TO MATCH THE

PEAK VALUES NEAR HERMINE. 



THE GLOBAL MODELS HAVE INITIALIZED FAIRLY WELL WITH THE 00Z

OBSERVATIONS BUT STILL HAVE DIFFERENCES ON THE MAX WINDS. GFS HAS

ITS STRONGEST WINDS IN THE NW SECTOR WHILE THE ECMWFHR HAS THAT IN

THE N SECTOR AND THAT THE ECMWFHR WINDS ARE LOWER THAN GFS. THE

CMC WINDS ARE HIGH IN BOTH THE N AND NW SECTORS AND ARE ABOUT THE

SAME AS MAGNITUDE AS THE GFS AND THE UKMETHR WINDS ARE AS WEAK AS

THE ECMWFHR AND ITS COVERAGE OF HIGHER WINDS IS SIMILAR TO THE

CMC. DIFFERENCES IN WINDS AREAL COVERAGE AND MAGNITUDE ARE SIMILAR

THRU THE SHORT TERM BUT THESE DIFERENCES ARE LESS IN THE EXTENDED

PERIOD AS HERMINE WEAKENS AND MOVES TWD NE. THE MODELS SUGGEST

THAT HERMNE WILL MOVE NE AS IT WEAKENS AND WILL EITHER GET

ABSORBED OR JUST DISSIPATE IN THE EXTENDED PERIOD. MOST OF THE SRN

HALF WILL HAVE A VERY RELAXED PRES GRADIENT AND WINDS WILL REMAIN

BELOW WARNING THRESHOLD THRU MOST OF THE PREIOD.



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

PREVIOUS DISCUSSION... 



THIS MORNINGS ASCAT OVERPASSES MISSED CENTER OF HERMINE AS WELL 

AS THE HIGHEST WINDS. HOWEVER THE EDGE OF THE 1430Z PASS 

SUGGESTED THAT GALES OVER THE W QUADRANT OF HERMINE EXTEND 

SLIGHLY FURTHER W THAN INITIALIZED BY THE 12Z MODELS. ALSO THE 

GALES N OF THE WARM FRONT EXTENDED AS FAR E AS 63W. OVER THE 

NEAR TERM THE 12Z MODELS ARE IN GOOD AGREEMENT THAT HERMINE 

SHOULD DEEPEN OVER THE NEXT 12 TO 24 HOURS...WITH THE MODEL 

CONSENSUS ON ORDER OF 7 TO 10 MB...AT WHICH TIME SHOULD SEE A 

SLIGHT INCREASE IN WINDS TO HURCN FORCE. AS FAR AS THE TRACK 

MODELS CONTINUE TO HAVE DIFFICULTY AND SHOW LITTLE RUN TO RUN 

CONSISTENCY. THE 12Z ECMWF MOVES THE SYSTEM WITHIN MUCH FURTHER 

N AND WITHIN 30 NM OF NANTUCKET AND CAPE COD...ALTHOUGH AS A 

WEAKER SYSTEM THAN SHOWN BY PREVIOUS RUNS. OVER PAST DAY OR SO 

MODELS HAVE GENERALLY TRENDED WEAKER WITH HERMINE FROM TUE 

ONWARD. HOWEVER THE 12Z GFS BUCKED THIS TREND AND NOW INDICATES 

WINDS UP TO 50 OR 55 KT AS HERMINE TRACKS NE NEAR GEORGES BANK 

AND S OF THE CANADIAN MARITIMES. IF THE NEXT NHC ADVISORY 

REMAINS CONSISTENT AND IS STRONGER LIKE THE 12Z GFS...WILL BE 

ABLE TO BETTER UTILIZE THE 12Z WAVEWATCH III FOR WAVE HEIGHT 

GRIDS AT LATE TUE THROUGH THU. 



THE 12Z MODELS CONTINUED TO SHOW SIGNIFICANT TIMING DIFFERENCES 

FROM LATE MON NIGHT THROUGH THU NIGHT WITH THE ECMWF STILL A 

FULL TWO DAYS FASTER THAN GFS/UKMET IN WEAKENING THE UPPER LOW 

AND THEN EJECTING THE OPEN TROUGH NE OF GEORGES BANK. THE 

PREVIOUS NHC FORECAST RELIED ON A COMPROMISE BETWEEN THE GFS AND 

ECMWF. AM NOT ANTICIPATING THAT THERE WILL BE MAJOR CHANGES WITH 

NEXT NHC ADVISORY...AND AS A RESULT WILL NOT BE MUCH CHANGE IN 

THE WARNINGS FROM THE PREVIOUS NT1/NT2 FORECASTS. FORECAST 

CONFIDENCE REMAINS WELL BELOW AVERAGE AFTER ABOUT 24 TO 36 

HOURS. SURPRISINGLY BY LATE FRI/FRI NIGHT THE GFS AND ECMWF ARE 

IN DECENT AGREEMENT IN MOVING A WEAK COLD FRONT OFF THE NEW 

ENGLAND COAST.   



SEAS...LAST EVENINGS ASCAT OVERPASS RETURNED 50 TO 55 KT ACROSS 

THE GULF STREAM FROM ABOUT 36.5N TO 38N...JUST NW OF THE 

OCCLUDED FRONT. WITH HERMINE FORECAST TO SLOWLY MEANDER N THE 

STRONGEST N TO NE WINDS WILL CONTINUE TO BE COUNTERFLOW TO THE 

GULF STREAM TONIGHT INTO EARLY TOMORROW CREATING A PERILOUS SEA 

STATE NEAR THE STREAM. WE BELIEVE THE HIGHER ECMWF WAM HAS A 

MUCH BETTER HANDLE THAN THE WAVEWATCH III WITH WAVE HEIGHTS THIS 

AFTERNOON.  1445Z CRYOSAT AND 16Z JASON-2/3 ALTIMETER OVERPASSES 

RETURNED 20 TO 27 FT ACROSS THE GULF STEAM AND WAVE HEIGHTS ARE 

LIKLEY SOMEWHAT HIGHER BETWEEN THESE TWO OVERPASSES. GRIDS WILL 

LIKELY AGAIN NEED A GREAT DEAL OF MANUAL EDITS TO ADJUST FOR THE 

TIMING AND INTENSITY FORECAST FROM NHC.  



.EXTRATROPICAL STORM SURGE GUIDANCE...WITH MODELS FORECASTING 

HERMINE TO HAVE A SLOW MEANDERING N AND THEN NE MOTION OFF THE 

NRN MID ATLC AND SRN NEW ENGLAND COASTS THROUGH AT LEAST 

WED...STORM SURGE WILL CONTINUE TO IMPACT THE COAST FROM THE 

DELMARVA PENINSULA TO LONG ISLAND THROUGH EARLY THIS 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 (FROM 11AM NHC ADVISORY): 



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 AND INTO MIDWEEK. 



2. TROPCIAL STORM CONDITIONS WILL SPREAD NORTHWARD WITHIN THE 

WARNING AREA ALONG THE ATLANTIC COAST THROUGH MON. TROPICAL 

STORM CONDITIONS ARE POSSIBLE IN THE WATCH AREA BY MON.



3. THERE IS A DANGER OF LIFE-THREATENING INUNDATION WITHIN THE 

NEXT 36 HOURS FROM CAPE CHARLES, VIRGINIA, TO SANDY HOOK, NEW 

JERSEY. THERE IS ALSO THE POSSIBILITY OF LIFE-THREATENING 

INUNDATION DURING THE NEXT 48 HOURS AT NAMY COASTAL LOCATIONS 

BETWEEN SANDY HOOK, NEW JERSEY AND BRIDGEPORT, CONNECTICUT, 

INCLUDING LONG ISLAND.



4. 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. 



.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED NIGHT. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED NIGHT. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED. 

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

     TROPICAL STORM TONIGHT INTO TUE. 



.NT2 MID ATLC WATERS...

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

     TROPICAL STORM MON INTO TUE. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED NIGHT. 

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

     TROPICAL STORM TONIGHT INTO TUE. 

     TROPICAL STORM POSSIBLE TUE NIGHT.

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

     TROPICAL STORM TONIGHT INTO MON NIGHT. 



$$



.FORECASTER MUSONDA/CLARK. OCEAN PREDICTION CENTER.

