Marine Interpretation Message
Issued by NWS

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AGNT40 KWNM 270113
MIMATN

MARINE WEATHER DISCUSSION FOR N ATLANTIC OCEAN
NWS OCEAN PREDICTION CENTER WASHINGTON DC
913 PM EDT THU MAY 26 2016

.FORECAST DISCUSSION: MAJOR FEATURES/WINDS/SEAS/SIGNIFICANT
.WEATHER FOR THE NORTH ATLANTIC OCEAN W OF 50W FROM 30N TO 50N.

CRNT SFC RPRTS AND 15Z ASCAT DATA INDC WINDS 15 KT OR LESS OVER
THE OFSHR WTRS ATTM...AND THE GOES WV IMGRY INDC AN UPR RDG OVR
THE WRN ATLC. THE GOES IR IMGRY ALSO INDC AN AREA OF DISTURBED
WEATHER SE OF THE OFSHR WTRS. NHC HAS AN 80 PERCENT CHANCE OF
TROPICAL DEVELOPMENT WITH THIS LOW...WHICH IS CRNTLY MOVING TO THE
NW. THE 18Z GFS IS INIT OK WHEN COMPARED WITH THE CRNT DATA...AND
INDC THE LOW TO SE WL MOVE NE TWD THE SRN OFSHR WTRS...AND MOVE
OVER THEM WITHIN THE NEXT 48 HOURS. THE GFS IS SLIGHTLY FASTER
THAN THE 12Z ECMWF/UKMET SOLNS...BUT ESSENTIALLY TAKE THE SAME
TRACK. THE PREV FCST FAVORED THE 12Z ECMWF SOLN IN THE SHORT TERM...BUT
INCREASED THE WINDS TO ACCT FOR THE LOW BIAS. ALSO...THERE IS SOME
MODEL DIVERGENCE ON THE TRACK AS IT MOVES UNDER THE RIDGE
SUN...BEFORE AN UPR TROF MOVES INTO THE ERN CONUS MON. THE
ECMWF/UKMET HINTS AT THE LOW DRIFTING INTO THE UPR TROF...THO
DOES NOT INDC IT WL GET COMPLETELY DRAWN INTO IT. THE 12Z
GFS/ECMWF KEEP IT UNDER THE RDG...AND DRIFT THE SFC LOW TO THE
WSW. FOR NOW WL CONT WITH PREV FCST GRIDS...PREFERRING TO SEE THE
00Z GUID BEFORE MAKING ANY CHANGES.

OTRW...THE 18Z GFS AND 12Z ECMWF ARE IN RSNBLY GUD AGRMT OVR THE
REMAINDER OF THE FCST AREA. THE MDLS INDC A PAIR OF CD FRONTS WL
PASS THRU THE NRN WATERS DURING THE FCST PERIOD. THE GFS AND ECMWF
BOTH INDC THEY WILL BE FAIRLY WK...WITH WINDS UP TO 25 KT. THE
FIRST CD FNT IS XPCTD ON SAT AND SAT NIGHT...AND LOOKS A LTL WKR
THAN THE SECOND ONE ON MON NGT. THE TMG IS SIMILAR ON BOTH
FRONTS...THO THE 12Z UKMET/GEM ARE A LTL SLOWER WITH THE SECOND
SYS. THE PREV FCST STAYED WITH THE 12Z ECWMF...WHICH AGREES WITH
THE 18Z GFS...SO PLANNING ON STAYING WITH IT FOR THE UPDATE FCST.
ALSO...PLANNING ON MAINTAINING WINDS UP TO 25 KT.

-----------------------------------------------------------------
PREVIOUS DISCUSSION...

THE 14Z AND 15Z OFFSHORE ASCAT OVERPASSES RETURNED WINDS 15 KT
OR LESS...WITH WINDS LESS THAN 10 KT IN THE IMMEDIATE VICINITY
OF THE COLD FRONT EXTENDING FROM CAPE COAD ACROSS GEORGES BANK.
OVERALL THE 12Z MODELS ARE IN ABOVE AVERAGE AGREEMENT ACROSS THE
W ATLC FOR THE NEXT SEVERAL DAYS...PARTLY DUE TO WEAK ZONAL
UPPER LEVEL FLOW AS UPPER LEVEL RIDGE PERSISTS OFF THE MID ATLC
COAST AND GRADUALLY MIGRATES NE ACROSS NEW ENGLAND. THE WEAK
COLD FRONT ACROSS THE NEW ENGLAND WATERS WILL STALL THIS EVENING
THEN LIFT NE AS A WARM FRONT FRI AND FRI NIGHT. MEANWHILE OVER
THE MID ATLC WATERS THE 12Z MODELS CONTINUED IN AGREEMENT THAT
THE DEVELOPING SURFACE LOW (TROPICAL DISTURBANCE) NEAR 27N70W
WILL TRACK NW AND APPROACH THE FAR SOUTHERN WATERS FRI NIGHT.
NHC HAS INCREASED THE FORMATION CHANCE TO MEDIUM (60 PERCENT)
OVER NEXT 48 HOURS...AND TO HIGH (70 PERCENT) OVER NEXT FIVE
DAYS. THE 12Z ECMWF AND 12Z UKMET ARE SLIGHTLY S OF THE 12Z GFS
TRACK FRI NIGHT INTO SUN BUT DIFFERENCES ARE ON ORDER OF ABOUT
50 TO 60 NM. ALSO OF NOTE IS THE 12Z ECMWF WAS SLIGHLY STRONGER
WITH WINDS COMPARED TO ITS PREVIOUS RUN. 12Z HWRF WAS ALSO
STRONGER THAN ITS PREVIOUS RUN BUT NONE OF THE MODELS ARE
INDICATING SIGNIFICANT STRENGTHENING OVER NEXT FEW DAYS. HOWEVER
MARINERS SHOULD STILL PAY CLOSE ATTENTION TO NHC
OUTLOOKS/FORECASTS AND NWS MARINE FORECASTS/ DISCUSSIONS TO
MONITOR THIS SITUATION. DID BUMP UP WIND GRIDS TO 30 KT ACROSS
SOUTHERN WATERS S OF CAPE FEAR SAT INTO SUN NIGHT. THE FORECAST
BECOMES MORE UNCERTAIN EARLY NEXT WEEK AS THE MODELS DIVERGE AS
TO WHETHER SURFACE LOW WILL MOVE NORTHWARD INLAND... ALONG THE
COAST AHEAD OF AN APPROACHING COLD FRONT LIKE THE GEM OR REMAIN
QUASI STATIONARY ALONG OR JUST OFF THE COAST AS SUGGESTED BY
ECMWF/GFS/UKMET. THERE IS LITTLE ENSEMBLE SUPPORT AND WITH THE
EXCEPTION OF THE 12Z HWRF LITTLE SUPPORT IN GENERAL FOR GEM
SOLUTION SO WILL BE DISREGARDING IT. AS FOR THE REMAINING
DETERMINISTIC MODELS AM FAVORING A SOLUTION CLOSER TO THE 12Z
ECMWF WHICH SHOWS SOME NORTH AND NORTHEASTWARD DRIFT MON/TUE. IN
SUMMARY FOR WIND GRIDS USED A 50/50 BLEND OF THE 12Z GFS 30M AND
12Z GFS 10M WINDS THROUGH FRI...THEN THE 12Z ECMWF THROUGH THE
REMAINDER OF THE FORECAST PERIOD WITH ONLY MINOR EDITS S OF CAPE
HATTERAS TO EXPAND AREAS OF 25 KT FRI NIGHT THROUGH SUN NIGHT.

.SEAS...THE 12Z WAVEWATCH III AND 12Z ECMWF WAM ARE WELL
INITIALIZED ACROSS THE W ATLC THIS AFTERNOON...ALTHOUGH OVER
OFFSHORE WATERS WAVE HEIGHTS ARE CURRENTLY 4 FT OR LESS. THESE
MODELS ARE IN PRETTY GOOD AGREEMENT ACROSS NT1/NT2 WATERS OVER
THE NEXT SEVERAL DAYS. USED A 50/50 BLEND OF THE ABOVE GUIDANCE
TONIGHT BEFORE TRANSITIONING TO THE 12Z ECMWF WAM AS IT IS
SLIGHLY HIGHER OVER THE SOUTHERN NT2 WATERS FRI NIGHT THROUGH
THE WEEKEND. AS WAS DONE WITH WIND GRIDS ALSO BUMPED UP WAVE
HEIGHT GRIDS 15 PERCENT OR SO S OF CAPE HATTERAS FRI THROUGH MON
NIGHT.
.EXTRATROPICAL STORM SURGE GUIDANCE...N/A.


.WARNINGS...PRELIMINARY.

.NT1 NEW ENGLAND WATERS...
     NONE.

.NT2 MID ATLC WATERS...
     NONE.

$$

.FORECASTER KELLS/CLARK. OCEAN PREDICTION CENTER.



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