| https://ocean.weather.gov/Atl_tab.shtml https://ocean.weather.gov/shtml/NFDMIMATN.txt Marine Weather Discussion for N Atlantic Ocean NWS Ocean Prediction Center Washington DC 1050 AM EDT Sat Sep 8 2018 .FORECAST DISCUSSION...Major features/winds/seas/significant .weather for the North Atlantic Ocean W of 50W from 30N to 50N. Main concerns over the offshore waters over the next few days will be gales expected to develop N of a frontal boundary, off the northern mid-Atlantic coast Sun afternoon into Mon, and then potentially tropical storm and hurricane conditions associated with what is now Tropical Storm Florence by later Wed and Wed night off the SE U.S. coast or over the southern NT2 offshore waters. For additional information on Florence please refer to the latest advisory from the National Hurricane Center. Per the 12Z NCEP surface analysis a cold front was located over the far NT1 waters with another cold front located over the northern NT2 waters. Latest GOES-16 satellite imagery along with lightning data revealed areas of showers and thunderstorms occurring over the NT1 waters, extending down into the northern NT2 waters. With the 00Z ECMWF/UKMET and 06Z GFS/NAM in good agreement through Mon night, no significant adjustments were needed through that time frame. Gales still anticipated to develop in the NW NT2 and eventually far SW NT1 waters Sun into Sun night in the strong E and NE flow between high pressure over northern New England and SE Canada, and a frontal boundary extending E from the North Carolina coast. The threat for thunderstorms will persist over the waters for the next few days, with the highest chance for strong thunderstorms near the frontal boundary. The chance for locally strong winds near or in excess of gale force and very rough seas in and near the stronger thunderstorms remains. Overall, forecast confidence for today through Mon night over the waters is slightly above average given the agreement among the GFS/NAM/ECMWF/UKMET. For Tue through Wed night over the waters, attention turns to and is dependent on the future track and intensity of what is currently Tropical Storm Florence. The latest National Hurricane Center advisory has Florence moving toward the W and NW over the next several days, with it's main impacts over southern and central NT2 offshore waters by Tue night through Wed night. Further N, we still expect a cold front to cross New England waters Tue night, and then stall near or just S of 40N Wed and Wed night as high pressure builds E over New England. For this early morning package, given the current NHC track of Florence is fairly close to the 00Z ECMWF guidance from last night, will continue to lean in that direction for now, but make adjustments to the grids and forecast once the morning NHC advisory arrives closer to forecast issuance time. Interests should monitor the forecasts for Florence for next week throughout the Atlantic offshore zones. It would be prudent to consider alternatives to planned voyages. Key messages from the National Hurricane Center include: 1. Regardless of Florence's eventual track, large swells are affecting Bermuda and will begin to affect portions of the U.S. East Coast this weekend, resulting in life-threatening surf and rip currents. 2. The risk of other direct impacts associated with Florence along the U.S. East Coast next week has increased. However, there is still very large uncertainty in model forecasts of Florence's track beyond day 5, making it too soon to determine the exact location, magnitude, and timing of these impacts. Interests near and along the U.S. East Coast should monitor the progress of Florence through the weekend and ensure they have their hurricane plans in place. Seas...The previous grids are verifying well this morning based on the latest observation. So will continue with the ongoing grids for this intermediate package for the most part, with adjustments made as needed later in the period to fit the NHC forecast for Florence as it potentially impacts the waters Tue night and beyond. .EXTRATROPICAL STORM SURGE GUIDANCE...At least a modest surge event is appearing likely just north of the front and in the persistent easterly flow Sun into Mon along the coast from North Carolina northward to around Long Island. ESTOFS guidance indicates surge values from a half-foot to just over 2 feet over this region later tonight into Mon, with conditions slowly improving beyond Mon night. The highest surge appears most likely near Delaware Bay overnight Sun, with the ESTOFS guidance only slightly higher than the ETSS at this point, and we see no need to alter the slightly higher ESTOFS forecast at this time. Tropical Storm Surge may become a significant issue especially along the SE U.S. coast toward the middle of the upcoming week as Florence tracks toward the SE U.S. coast. Please consult the latest forecasts from coastal National Weather Service offices and the National Hurricane Center for more information. |