marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 853 PM EST Tue Feb 20 2018
.Forecast discussion...Major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
There are still significant problems with getting the latest model guidance and observational data for the offshore waters and over high seas areas this evening.
Have not seen any recent ascat data over the offshore waters since earlier today over the waters.
A stationary front was located near the ME coast this evening and dying warm front was moving NE across the Gulf of ME and the outer waters. A strong high pressure area was E of the mid Atlantic waters this evening. Swly flow to 25 kt was across the New England waters into the far northern mid Atlantic waters which should continue overnight into Wed. The moderate swly flow continues and expands in areal coverage into the nrn mid Atlantic waters Wed night as a cold front moves S into the New England waters and into the nrn mid Atlantic waters late Wed night into Thu.
Will not be making any changes for now and hopefully will see model guidance and observational data coming in overnight on nawips.
----------------------------------------------------------------- Previous discussion...
Due to NWS/NCEP network problems, there are ongoing significant delays in receiving the latest model guidance platforms other than AWIPS. This discussion and this afternoons forecasts will not incorporate all of the typically available model data, including the UKMET, ECMWF, and gefs.
This mornings ascat overpasses returned winds to 25 kt across the far northern outer nt2 waters as well as just off Cape Cod. The latest guidance was reasonably well initialized with these winds. At 18z strong high pressure was centered east of the offshore waters near 36n 59w, while a weak stationary front extended east to west just off the Maine coast. This pattern will persist through Wed resulting in south to southwest return flow across the offshore waters. The latest models are then consistent in forecasting a cold front will exit the New England and northern mid Atlantic coast Wed evening and Wed night. The 12z GFS remained slightly stronger than the remaining guidance with the winds both south of the front as well as the increasing easterly winds across the northern nt2 and southern nt1 waters Thu and Thu night. The 12z NAM also supports somewhat stronger winds. Consequently, we blended in 50 percent of the 12z GFS into the previous winds grids Wed through Thu night.
The models are consistent that the stationary front across the central/northern nt2 waters will persist through midday Fri before finally lifting back north as a warm front later Fri and Fri night. Winds should again increase to 25 kt or so across the nt1 zones as this front moves northward. By the weekend, model discrepances increase as the GFS continued to be the most amplified of the global models with the upper level trough lifting northeast across the lower Great Lakes and New England, and as a result in also the strongest with the offshore surface winds associated with the approaching cold front and possible triple point development. Versus its previous run, the 12z GFS was stronger with the developing surface low. Without the 12z ECMWF or 12z UKMET, we are not inclined to make any significant changes to the medium range wind grids. However, out of deference for the stronger GFS, as was done previously will evenly blend the previous wind grids with the 12z GFS. Will cap winds at 30 kt sun and Sun night.
Seas: not surprisingly, given such a weak pattern, the 12z ww3 appears well initialized with the wave heights across the offshore and coastal waters this afternoon. To incorporate some of the recent guidance and the stronger winds seen in the 12z GFS, we will populate the wave height grids with an even blend of the previous grids and the 12z ww3.
Extratropical storm surge guidance: no major deviation from the latest surge guidance appears necessary over the few days.
.Nt1 New England waters... None.
.Nt2 mid-Atlantic waters... None.
.Forecaster Rowland/Clark. Ocean prediction center.