

283 

AGNT40 KWNM 030335

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN

NWS OCEAN PREDICTION CENTER WASHINGTON DC

1135 PM EDT FRI SEP 2 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 A RIDGE ACROSS THE NRN WATERS WITH TROPICAL

CYCLONE HERMINE STILL INLAND BUT CLOSE TO THE COAST APPROACHING

VA. BUOY 41004 SE OF CHARLESTON SC HAD WINDS 40 KT WITH GUSTS TO

55 KT AT 22Z WITH 19 FT SEAS. ALL THE OBS INCLUDING ASCAT PASS

SHOW HIGHER WINDS OVER THE S-WRN PARTS. AT 000Z THE NCEP MAP HAS

HERMINE OVER THE CAROLINAS WHILE A STATIONARY FRONT LIES ACROSS

THE CENTRAL WATERS. THE PRES GRADIENT IS VERY RELAXED OVER THE

WATERS N OF THE FRONT BUT VERY TIGHT OF COURSE OVER THE S-WRN

PARTS. THE NCEP WAVEHEIGHTS MAP HAD HIGHER SEAS WITH PEAKS TO 21

FT OVER THE S-WRN WATERS. SEAS ARE LESS THAN 8 FT OVER THE CENTRAL

AND NRN WATERS WITH MAINE HAVING SEAS BETWEEN 2 AND 4 FT. THE

NWW3 WAVE MODEL FITS VERY WELL WITH THE OBSVERVED SEAS PATTERN

AND MATCHES THE PEAK VALUE OVER THE S-WRN WATERS. NWW3 IS ALSO

VERY CLOSE TO THE ECMWFWAVE AND BOTH WAVE MODELS HAVE BECOME

BETTER AT MATCHING THE PEAK SEAS. WILL STAY WITH NWW3 FOR SEAS.



THE GLOBAL MODELS HAVE INITIALIZED WELL THE 00Z OBSERVATIONS WITH

JUST MINOR DIFFERENCES IN WIND SPEEDS OVER THE SRN WATERS. THE

MODELS STILL HAVE SOME DIFFERENCES IN THE SHORT TERM REGARDING THE

TRACK OF HERMINE AND THESE DIFFERENCES HAVE INCREASED WITH TIME.

THE MODELS DIVERGE MOSTLY IN THE EXTENDED PERIOD. WILL STAY WITH

THE OFFICIAL TRACK AND WILL USE BOTH GFS AND THE ECMWFHR TO ADJUST

WINDS ACCORDINGLY. I PLAN ON NOT MAKING ANY MAJOR CHANGES TO THE

REST OF THE FORECAST WATERS AND SO WILL USE THE FRCST WINDS AND

RETAIN MOST OF THE FORECAST. IN THE SHORT TERM THE CENTRAL AND SRN

WATERS WILL CONTINUE TO BE HEAVILY IMPACTED BY HERMINE WHILE A

RIDGE WILL PERSIST OVER THE NRN WATERS.



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

PREVIOUS DISCUSSION... 



BUOYS JUST OFF THE GEORGIA AND SOUTH CAROLINA COASTS HAVE BEEN 

REPORTING TROPICAL STORM FORCE WINDS FOR SEVERAL HOURS...AND 

BUOY 41008 SE OF SAVANNAH HAS REPORTED PEAK GUSTS IN 50 TO 55 KT 

RANGE. AS WAS MENTIONED IN THE PREVIOUS DISCUSSION THE OVERNIGHT 

MODEL RUNS NAMELY THE 00Z/06Z GFS AND 00Z ECMWF TRENDED 

SIGNIFICANTLY STRONGER WITH HERMINE SAT THROUGH TUE PART OF THE 

TIME WHICH IT IS FORECAST TO BE POST-TROPICAL. THE 12Z GFS/ECMWF 

WERE NEARLY AS STRONG AS THEIR RESPECTIVE PREVIOUS RUNS. THE 

LATEST GUIDANCE ALSO SUGGESTING THAT BY LATE MON HERMINE COULD 

AGAIN ACQUIRE TROPICAL CHARACTERISTICS OFF THE NRN MID ATLC 

COAST. THERE THEN IS STILL SUBSTANTIAL MODEL DISCREPANCY WITH 

THE TRACK OF HERMINE BEGINNING SUN MAINLY AROUND THE TIME THAT 

THE MODELS WANT TO MOVE THE SYSTEM AROUND CYCLONIC LOOP ACROSS 

THE NRN MID ATLC WATERS. THE 12Z ECMWF IS FURTHER W AND CLOSER 

TO COAST MOVING THE CENTER OF HERMINE WITHIN ABOUT ABOUT 30 NM 

OF THE DELAWARE COAST SUN NIGHT. ALSO VERSUS ITS PREVIOUS RUNS 

THE 12Z ECMWF IS MUCH QUICKER TO OPEN UP THE UPPER LOW INTO A 

TROUGH AND KICK IT NE OF THE NT1 WATERS LATE WED AND WED NIGHT. 

THE 12Z GFS IS E OF THE 12Z ECMWF AND ALSO IS MUCH SLOWER THAN 

THE 12Z ECMWF IN MOVING HERMINE ACROSS AND E OF THE NT1 WATERS. 

IN FACT THE 12Z GFS STILL INDICATES HERMINE WILL BE OVER THE NRN 

OUTER NT2 WATERS FRI. WITH THAT SAID FORECAST CONFIDENCE BEYOND 

DAY2 IS WELL BELOW AVERAGE.      



THE SIGNIFICANT DEEPENING SHOWN BY THE GFS DOES NOT SEEM 

UNREASONABLE AS HERMINE IS FORECAST TO SLOWLY MOVE ACROSS THE 

GULF STREAM WHERE SST ANOMALIES ARE ON THE ORDER OF +3 TO +5 C 

AND WITH THE DEVELOPING BAROCLINICITY OVER THE SW SEMICIRCLE OF 

LOW. SO POTENTIAL REMAINS THAT SYSTEM COULD VERIFY STRONGER AS 

POST TROPICAL CYCLONE THAN WHAT IS CURRENTLY FORECAST. THE LAST 

NHC ADVISORY INDICATED WINDS WILL REACH HURCN FORCE EARLY MON. 





.SEAS...BUOY 41004 SE OF CHARLESTON REPORTED 17 FT AT 19Z WHICH 

WAS JUST A FT OR TWO HIGHER THAN THE 12Z WAVEWATCH III. AS IS 

THE CASE WITH THE LATEST GFS AND ECMWF...THE 12Z WAVEWATCH III 

AND 12Z ECMWF WAM ARE IN PRETTY GOOD AGREEMENT THROUGH SUN. AS 

GFS/ECMWF DIVERGE WITH THE TRACK OF HERMINE RESPECTIVE WAVE 

GUIDANCE DOES AS WELL. THE MAX WAVE HEIGHTS SHOWN BY THE 12Z 

WAVEWATCH III LOOK REASONABLE BUT WILL HAVE TO TIME SHIFT WAVE 

HEIGHT GRIDS TO BETTER MATCH NHC FORECAST TIMING AND TRACK. 





.EXTRATROPICAL STORM SURGE GUIDANCE...WITH ALL OF THE 12Z MODELS 

FCSTG HERMINE TO SLOW AND NEARLY STALL OFF THE NRN MID ATLC AND 

SRN NEW ENGLAND COASTS SUN INTO TUE...THERE IS A HIGH LIKELIHOOD 

OF SIGNIFICANT AND POSSIBLY LIFE THREATENING FROM THE DELMARVA 

PENINSULA TO THE SOUTHERN NEW ENGLAND COAST LATE TOMORROW 

POSSIBLY THROUGH MIDWEEK 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).





NHC KEY MESSAGE: 



1. HERMINE IS EXPECTED TO BECOME A POST-TROPICAL CYCLONE WHILE 

STILL PRODUCING HAZARDOUS WINDS AND STORM SURGE OVER LAND. NWS 

POLICY ALLOWS NHC TO WRITE ADVISORIES ON AND ISSUE TROPICAL 

STORM WATCHES AND WARNINGS FOR POST-TROPICAL CYCLONES, WHEN THE 

SYSTEM CONTINUES TO POSE A SIGNIFICANT THREAT TO LIFE AND 

PROPERTY. NHC AND THE NWS EASTERN REGION HAVE DECIDED THAT THIS 

OPTION WILL BE INVOKED FOR HERMINE. AFTER HERMINE BECOMES A 

POST-TROPICAL CYCLONE, NHC WILL CONTINUE TO ISSUE ITS FULL SUITE 

OF ADVISORY AND WARNING PRODUCTS FOR AS LONG AS THE SYSTEM 

REMAINS A SIGNIFICANT THREAT TO LAND. 





.WARNINGS...PRELIMINARY.



.NT1 NEW ENGLAND WATERS...

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

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED NIGHT. 

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

     TROPICAL STORM POSSIBLE WED.

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

     TROPICAL STORM SAT NIGHT.

     TROPICAL STORM POSSIBLE SUN INTO WED NIGHT. 

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

     TROPICAL STORM SAT NIGHT.

     TROPICAL STORM POSSIBLE SUN INTO WED NIGHT. 



.NT2 MID ATLC WATERS...

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

     TROPICAL STORM SAT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO SUN NIGHT. 

     HURRICANE POSSIBLE MON INTO MON NIGHT. 

     TROPICAL STORM POSSIBLE TUE INTO WED. 

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

     TROPICAL STORM SAT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO SUN NIGHT. 

     HURRICANE POSSIBLE MON INTO MON NIGHT. 

     TROPICAL STORM POSSIBLE TUE INTO WED NIGHT. 

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

     TROPICAL STORM SAT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO SUN NIGHT. 

     HURRICANE POSSIBLE MON INTO MON NIGHT. 

     TROPICAL STORM POSSIBLE TUE INTO TUE NIGHT. 

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

     TROPICAL STORM POSSIBLE TUE NIGHT INTO WED NIGHT. 

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

     TROPICAL STORM TONIGHT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO TUE. 

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

     TROPICAL STORM TONIGHT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO MON NIGHT. 

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

     TROPICAL STORM SAT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN INTO TUE. 

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

     TROPICAL STORM TONIGHT INTO SAT NIGHT. 

     TROPICAL STORM POSSIBLE SUN.

.ANZ833...INNER WATERS FROM CAPE HATTERAS TO CAPE FEAR...

     TROPICAL STORM TONIGHT INTO SAT. 

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

     TROPICAL STORM TONIGHT INTO SAT NIGHT. 

.ANZ835...INNER WATERS FROM CAPE FEAR TO 31N...

     TROPICAL STORM TONIGHT INTO SAT. 



$$



.FORECASTER MUSONDA/CLARK. OCEAN PREDICTION CENTER.

