.Marine weather discussion for N Atlantic Ocean .NWS ocean prediction center Washington DC 1015 PM EDT Fri 24 Mar 2017
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
The ship which reported 30 kt south of Block Island at 00z has a mean wind speed error of +11 kt. After taking this error into consideration and as suggested by the surrouding buoy observations, southwest 20 to 25 kt appears more representative of the present conditions. The 18z NAM/GFS/gefs were generally consistent with their respective previous runs and overall the guidance is in above average agreement across the west Atlantic for the next several days. The cold front will move off the New England coast tonight, continue to drop south across the waters Saturday and Saturday night, and stall off the Delmarva coast early Sunday. The previous opc wind and wave height grids look reasonable and will not be making any significant changes in this evenings forecast updates. Wave heights across the Gulf of Maine are already up to 8 to 9 ft this evening. We adjusted the previous wave height grids upward by a ft or so across the nt1 waters for the near term to better match the current buoy observations.
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There was an ascat pass at 14z with a swath across the wrn areas of the mid Atlantic into the New England waters. Winds were to 20 kt over the wrn sections of the nrn mid Atlantic into the New England waters which was close to the 15z GFS winds over this region. At 17z buoy observations close to the ME coast had winds to 30 kt.
At 18z strong high pressure was situated over the ern areas of the central mid Atlantic waters. The high pressure area moves S through tonight while becoming weaker. A warm front should move NE over the nrn New England waters later this afternoon into early tonight...then briefly stall as low pres develops and moves E along the frontal boundary. Models show developing low pressure moving along the frontal boundary and E of the New England waters later tonight while strengthening. The GFS is a bit stronger with winds than other guidance with winds near gale force just E of the waters. Will keep Max winds to 30 kt over the New England and nrn mid Atlantic waters. Associated cold front moves S across the New England waters later tonight and Saturday...then crosses into the nrn mid Atlantic by late Saturday afternoon/early Saturday night into Sunday...then stalling along and E of the Delmarva coast before returning to the N as a warm front Sunday night. Some models such as the Gem/GFS/ECMWF do Show Low pressure moving E along the front over the New England waters Monday and Monday night. The GFS/Gem models seem too strong with the winds N of the low and prefer the weaker winds with ECMWF. By Tuesday and Tuesday night model guidance is not in good agreement. The 12z UKMET/ECMWF are much weaker than the GFS with low pressure that moves off the NJ coast and strengthens into Wednesday and Wednesday night. Prefer the GFS which seems more likely to be correct considering the strong upper shortwave that moves offshore into the New England waters Wednesday night. Will go no stronger than 30 kt due to the disagreement among the models.
Seas...at 18z the multigrid wwiii and ECMWF wam were in close agreement with observed seas across the offshore waters. Will use a 50/50 blend of the wwiii and ECMWF wam through Tuesday morning...then favor the wwiii for the remainder of the forecast period.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid-Atlantic waters... None.
.Forecaster Clark/Rowland. Ocean prediction center.