

071 

AGNT40 KWNM 080122

MIMATN



MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN 

NWS OCEAN PREDICTION CENTER WASHINGTON DC

925 PM EDT SUN 7 AUG 2016 



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

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



A STATIONARY FRONT EXTENDED W TO E ACROSS THE MID ATLC OFFSHORE 

WATERS FROM JUST S OF CAPE HATTERAS AT 00Z. SHIP REPORT ABOUT 60 

NM E OF CAPE HATTERAS WITH 1012 MB SUGGESTS THERE IS A WEAK 

SURFACE LOW ALONG THE FRONT IN THIS VICINITY. THIS SHIP HAS BEEN 

REPORTING HOURLY OVER THE PAST SEVERAL DAYS AND IS AN EXCELLENT 

OBSERVER WITH MEAN SLP ERROR NEAR ZERO AND MEAN WIND SPEED ERROR 

 + 1.6 KT. THE LATEST MODELS DO NOT PRESENT ANY SIGNIFICANT 

SHORT TERM DIFFERENCES ACROSS THE W ATLC. SCATTERED TSTMS ARE 

CONTINUING ALONG THE STATIONARY BOUNDARY THIS EVENING AND SHOULD 

PERSIST OVER THE NEXT 24 TO 36 HOURS GIVEN OFFSHORE SB AND ML 

CAPE VALUES GREATER THAN 2000 J/KG. SREF PROBABILITIES SUGGEST 

THAT ENVIRONMENT SHOULD BECOME MORE STABLE MON NIGHT. BOTH THE 

12Z ECMWF AND 12Z UKMET TRENDED WESTWARD WITH THE WEAK 

DEVELOPING SURFACE LOW TO APPROACH AND MOVE INTO THE SRN NT2 

WATERS THIS WEEK. PAST THREE RUNS OF GFS REMAINED CONSISTENT 

WITH PREVIOUS RUNS WITH NO DEVELOPMENT SHOWN. AFTER TAKING 

LATEST GUIDANCE INTO CONSIDERATION THE PREVIOUS OPC GRIDS 

CONTINUE TO LOOK REASONABLE SO WILL NOT BE MAKING ANY 

SIGNIFICANT ADJUSTMENTS WITH THIS EVENINGS UPDATES. THE 18Z 

WAVEWATCH III AND 12Z ECMWF WAM WERE BOTH WELL INITIALIZED WITH 

COASTAL/OFFSHORE WAVE HEIGHTS THIS EVENING. 



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

...PREVIOUS DISCUSSION...



THE LTST GOES VIS IMGRY INDC A FRONTL BNDRY ACRS THE NRN AND 

CENTRAL NT2 WTRS. THE LGTNG DENSITY PROD INDC A FEW SCATTERED 

SHOWERS AND TSTMS ALONG THE FRONT...MAINLY IN THE UNSTABLE 

ENVIRONMENT OVER THE GULF STREAM. THE PREV FCST GRIDS INDC 

SHOWERS AND TSTMS IN NT2 ASSOC WITH THE FRONT AS IT MOVES SLOWLY 

S...SO ATTM PLANNING ON MAINTAINING MENTION IN THE NEXT FCST PKG.



OTRW...15Z ASCAT WIND RETRIEVALS INDC UP TO 25 KT IN THE SW FLOW 

AHD OF THE FRONTAL BNDRY IN THE UNSTABLE ENVIRONMENT OVER THE 

GULF STREAM. THE 12Z GFS WINDS ARE INIT OK WHEN COMPARED WITH 

THE DATA...AND INDC 20 KT OVR NT2...WITH 25 KT JUST E OF THE 

OFSHR WTRS. THE 12Z MDLS AGREE FAIRLY WELL ON THE TMG AND 

INTNSTY OF THE FRONT...AND INDC IT WL SLOWLY WKN WHILE MOVG TO 

THE SRN NT2 WTRS AND STALLING NR CAPE HTRS TNGT. THE PREV FCST 

STAYED NR THE GFS WITH THIS SYS...AND WITH THE GFS NOT CHANGING 

MUCH...PLANNING ON STAYING NR IT FOR THE NEXT FCST WITH THIS 

SYS. ALSO...THE AREA OF TSTMS IN THE GULFMEX HAVE STAYED OVER 

WATERS...AND DECOUPLED FROM A LOW CTR THAT HAS MOVED INLND OVER 

NRN FLORIDA. THE 12Z MDLS ALL INDC THAT THE LOW WL MOVE SLOWLY 

TO THE W...UNDER AN UPR RDG THAT IS NOT PROVIDING MUCH IN THE 

WAY OF STEERING. AS A RESULT...ATTM NOT XPCTG THIS SYSTEM TO 

IMPACT THE NT2 WTRS. 



THE GFS HAD BEEN A FAST OUTLIER WITH THE NEXT FRONT TO MOVE OFF 

THE NEW ENGLAND COAST WED NIGHT INTO THU...AND THE 12Z RUN HAS 

NOT SLOWED DOWN MUCH. IN FACT...THE 06Z GFS HAD SLOWED 

SLIGHTLY...AND WAS A LITTLE CLOSER TO THE SPEED OF THE 00Z 

ECMWF/UKMET/GEM SOLNS. HOWEVER...THE 12Z GFS REVERSED 

COURSE...AND IS NOW TAKING THE FRONT OFF THE NEW ENGLAND COAST 

AT THE SAME SPEED AS THE 00Z GFS...SO GFS IS AGAIN THE OUTLIER 

SOLN WITH THIS FRONT...SO CONFDC IS LOW WITH IT. IN 

ADDITION...THE 12Z ECWMF/UKMET/GEM ALL DVLP A WK LOW TO THE E OF 

THE BAHAMAS...FROM THE AREA OF TSTMS CRNTLY S OF THE AREA. THE 

12Z MDLS ALL KEEP THE LOW FAIRLY WK...BUT THE GFS IS AGAIN AN 

OUTLIER SOLN AS IT DOES NOT DVLP THE LOW AT ALL. IN 

ADDITION...THE WPC MED RANGE GUID INDC THE LOW ON THE LTST FCST 

PROG CHARTS...AND FAVORS THE 12Z ECMWF SOLN...SO ATTM PREFERRING 

TO SWITCH TO THE 00Z ECMWF SOLN FOR THE FCST FM ABT 00Z WED 

ONWARD. 



.SEAS...THE 12Z MULTIGRID WAVEWATCH-III AND ECMWF WAM MDLS ARE 

INIT WITHIN A FT OR TWO OF THE CRNT DATA...AND SEEM RSNBL AND 

AGREE WELL THRU THE FIRST 48 HOURS OF THE FCST PD. MINOR DIFFS 

START APPEARING AFTER THAT PT...MAINLY AS THE RESULT OF THE 

DIFFS BTWN THE ASSOC WX MDLS. ATTM PLANNING ON USING THE 12Z 

INTO 00Z WED...THEN USING TO THE 12Z ECMWF WAM THEREAFTER TO 

REFLECT PREFERRED WX MDL TRENDS. 



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



.WARNINGS...PRELIMINARY. 



.NT1 NEW ENGLAND WATERS... 

     NONE. 



.NT2 MID ATLC WATERS... 

     NONE. 



$$ 



.FORECASTER CLARK/KELLS. OCEAN PREDICTION CENTER.

