Marine Weather for HS 100


marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 947 am EDT Sat may 27 2017

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

There will be no warning headlines and seas will subside to below 8 ft from Sunday through the forecast period. The latest satellite images show cyclonic circulation northeast of the waters with few clouds with cold tops over nt1 zones and Baltimore Canyon. The maximum winds are 25 kt over the eastern portion of the central waters. At 1200z the NCEP map has low pressure 1000 mb just southeast of Nova Scotia with its southwest trough extending across the Maine waters and associated cold front passing east of the forecast region. High pressure with center south of 31n close to 150w extends a weak ridge into the far southern waters. The pressure gradient is well relaxed across the forecast waters.

The seas are relatively larger over the eastern portion of the central and northern waters with a peak at 10 ft. Nww3 and ecmwfwave wave models fit well the 1200z seas pattern. Both wave models have been quite consistent with the previous observations and have been in a fairly good agreement. In the short term, both wave models agree on seas subsiding to below 8 ft with small differences just on the areal coverage. The differences continue into the extended period and so will continue with just nww3 through the forecast period for seas.

The models GFS/CMC/ecmwfhr/ukmerhr/NAM have initialized well the 1200z surface observations with just small differences mostly on the wind direction. In the short term the systems are very weak and development and dissipation of small temporary features differ among the models. Otherwise the synoptic pattern remain about the same and so will just continue with GFS for winds.

----------------------------------------------------------------- Previous discussion...

At 06z NCEP surface analysis has low just se of Nova Scotia with a slow weakening trend and a trailing low pressure trough SW into the srn nt1 waters. High resolution ascat-b pass from 0140z with limited coverage appears to indicate strongest gradients and winds, up to 30 kt, have shifted east of the offshore waters with the low leaving moderately strong gradients (up to 20 or 25 kt) at least over the outer waters and also along and south of the Gulf Stream and lighter winds north of Hatteras in the inner waters. Latest 00z models are initialized well with this low and the 00z GFS looks representative. With a bit of instability along the Gulf Stream in the westerly flow south of the low noted in the GFS, will populate grids with the 00z GFS boundary later winds modified using a tool that places the higher first sigma level winds over unstable areas and the 10m winds over stable areas.

The 00z models are in good agreement through the forecast period with minor differences in placement of a slow moving warm front with waves moving off the mid-Atlantic coast Sat night into Sun night while a broad upper ridge inland moves to the coast sun and offshore Sun night. A frontal system advances toward the coast ahead of a large upper level system near the Great Lakes and southern Canada with models especially the 00z GFS/UKMET/00z gefs ensemble mean hinting at forming a weak triple point low near the New Jersey coast early Mon and moving it across the nt1 waters Mon night into Tue night while pushing a weak cold front offshore with the front stalling across the central nt2 waters Wed and Wed night with weak associated gradients. For the new forecast populated with the 00z GFS through the forecast period again using the 10m_30m stability tool. No headlines are indicated in this evolving weak zonal pattern.

Seas...the seas are highest around 10 ft over the NE nt2 waters closer to the departing low pressure area and 2 to 6 ft closer to the coast. The wave models 00z nww3 and 00z ecmwfwave have matched well the observed seas pattern and both wave models have shown consistency in the previous runs. Populated wave grids with the 00z nww3 throughout.

.Extratropical storm surge guidance...N/A.


.Nt1 New England waters... None.

.Nt2 mid-Atlantic waters... None.


.Forecaster musonda/Bancroft. Ocean prediction center.

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