Marine Weather for HS 100


marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 808 am EST Fri Nov 24 2017

.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.

The latest model guidance indicates that low pressure currently east of northern Florida will track northeast across the southern nt2 waters today into Saturday. Minimal gales are still expected across the southern nt2 waters today and then should remain just east of the nt2 waters tonight into Saturday night. Northwest flow will then increase across the northern portion of the offshore waters by Sunday with winds still expected as high as 30 knots or so. Mainly light winds are then expected across most of the offshore waters by Monday night as strong high pressure moves off the mid Atlantic coast. A cold front will then approach the New England coast by Tuesday night with minimal gales possible across the far northern nt1 waters. The front will then move across the nt1 waters by Wednesday night. For wind grids will continue to use the current grids throughout the forecast period. Current warnings look reasonable and few changes should be needed on the next offshore waters forecast.

For wave height grids will also continue to use the current grids throughout the forecast period.

Extratropical storm surge guidance...N/A.

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Geocolor satellite images still show cold clouds over most of the region with lightning density map showing tstms moving northeast across Florida and now entering the far southern waters. Satellite images also continue to show fewer clouds across New England and the mid Atlantic states which is in line with the observed surface features. At 06z the NCEP weather map has a cold front to the east of the region that turns into a nearly stationary front as it enters and lies across the far southern waters. High pressure 1019 mb over waters adjacent to Virginia has ridges into the northern and central waters. Pressure gradient is still very relaxed across most of the region except near the frontal boundary over the southern waters. Winds are mainly from the west over the north waters and from the north and northeast over the rest of the region. Higher winds in gale force range are confined to the southern waters in the vicinity of the stationary front.

In the upper levels, an upper level ridge extends northeast from the southwestern states while an upper level trough lies just west of the forecast waters across the Great Lakes into the southeastern states. There is some energy embedded in the upper level trough that will pass east over the waters in the short term. Another upper level trough will approach the waters and bring some energy especially to the northern waters Sunday. Currently there is energy associated with surface Storm Warning in the Gulf of Alaska that will eventually track through Canada and reach the northern waters toward the end of the period and both ecmwfhr and GFS are in a good agreement on timing of this energy. So with moderate confidence, will initiate gale warnings over the far northern waters in the extended period.

Models GFS/CMC/NOGAPS/ukmethr/ecmwfhr/NAM have initialized the 06z surface observations fairly well especially over the forecast waters. In the short term, models generally agree on low pressure moving northeast from the Gulf of Mexico into the southeastern portion of the southern waters but differences are on the actual track of the low center. The models have difficulty in locating the center as low pressure moves into the waters. More models suggest a complex low over the southeastern waters. The position of the low center will help to determine if winds will reach gale force over the waters. For this issuance, I plan to just retain the previous models choice which is using GFS initially then switch to ecmwfhr.

.Seas...Seas are generally small across the region with a peak at 8 ft over the Baltimore Canyon. Seas range between 3 and 6 ft over the western half north of 34n while they range between 6 and 7 ft over the rest of the area. Nww3 and ecmwfwave models agree well with the observed 06z seas pattern. The wave models agree in the short term on keeping seas less than 8 ft across the region but will be relatively higher over the northern waters. Will just use the nww3 guidance in the short term and extend seas 5 through 7 days with ecmwfwave.

.Extratropical storm surge guidance...Storm surge from Georgia to North Carolina will be positive but less than a foot. This is in response to the gales in the vicinity of the front and so the surge will quickly subside by tonight.


.Nt1 New England waters... .anz800...Gulf of Maine... gale possible Tuesday night.

.Nt2 mid-Atlantic waters... .anz930...outer waters from Hatteras Canyon to Cape Fear... gale today. .Anz935...Outer waters from Cape Fear to 31n... gale today.


.Forecaster nolt/musonda. Ocean prediction center.

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