Marine Interpretation Message
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000 AGNT40 KWNM 271925 MIMATN .Marine Weather Discussion for N Atlantic Ocean .NWS Ocean Prediction Center Washington DC 325 PM EDT TUE 27 JUN 2017 .FORECAST DISCUSSION...Major features/winds/seas/significant .weather for the North Atlantic Ocean W of 50W from 30N to 50N. A 14Z Ascat overpass across the outer NT2 zones south of Hatteras Canyon west to southwest winds to 20 kt associated with the low and stationary front. The 12Z GFS/ECMWF/CMC were well initialized with these winds while the 12Z NAM/UKMET were slightly weak. The 12Z GFS/ECMWF are in good agreement across the west Atlantic over the next few days in forecasting the weak frontal wave to move northeast through the NT2 waters tonight with associated southerly 20 kt winds shifting east of the waters by evening. The 12Z models are consistent that the cold front will pass east of the offshore zones by early Wednesday. As high pressure builds toward the coast tonight and Wednesday, then moves offshore Wednesday evening, the 12Z GFS/UKMET both advertise post frontal winds to reach 20 kt across the NT2 outer waters after midnight tonight, and then transition southward across the waters, becoming northeast to east across the southern NT2 zones Wednesday through Thursday. Models then all forecast the high pressure center to shift east of the waters Thursday, while a series of sheared upper level shortwaves pass east across New England through the end of the week. Over the past few days, the models have generally trended weaker with these upper shortwaves. At the surface, whereas the GFS/ECMWF from a couple days ago was consistently moving an associated cold front to near Georges Bank, more recent runs are only moving the front as far south as the Maine coast and maintaing southerly winds across the all the offshore waters at least through Sunday. Versus the GFS/ECMWF the 12Z UKMET moves the front further offshore. The 12Z models are mostly consistent that a moderately strong southwest gradient will persist across the New England waters Thursday night into Friday night as low pressure passes across New England and a zonally oriented cold front drifts south toward the Maine coast. Front should stall along the Maine coast and then lift back north as a warm front Saturday night/Sunday. The 12Z GFS/ECMWF/UKMET then have come into much better agreement with the cold front forecast to approach the New England and northern Mid Atlantic coasts and move just offshore Sunday night. For wind grids through Friday, will be populating with the 12Z GFS winds but using the tool which places the 10m winds across stable areas (as defined by the GFS low level static stability) and first sigma level winds across unstable areas, which are really only across the NT2 waters behind the cold front tonight and over the southern NT2 waters through Thursday. Beginning Friday night, transitioned to the 12Z ECMWF mainly to keep continuity. .Seas...The 12Z Wavewatch III and 12Z ECMWF WAM are well initialized with the offshore wave heights (4 ft or less) this afternoon. These models continued to be within a ft or so of each other across the offshore waters through the forecast period. Will continue to populate the wave height grids with a 50/50 blend of the two models through the period. .Extratropical Storm Surge Guidance...N/A. .WARNINGS...Preliminary. .NT1 New England Waters... None. .NT2 Mid-Atlantic Waters... None. $$ .Forecaster Clark. Ocean Prediction Center.

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