marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 1032 PM EDT Thu Sep 18 2014
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
Most of the conv is still confined to the srn wtrs and E of the region along frntl bndry. Lghtng is more concentrated ovr the areas spanning from inland to the wtrs adj to GA and SC states. At 19/00z inland low pres ovr the mid atl states has trof xtndg NE and SW. A wkng cld frnt strtches from low pres ovr Canada and passes acrs the Maine wtrs. E of the cntrl region is another low pres 1009 mb with a trof xtndg W into the balt cynyn wtrs. The pres grdnt is very slack and Max obs winds are 20 kt. The last ascat pass was at 1507z and had no winds above 20 kt acrs the region. The seas range btwn 3 and 6 ft acrs the fcst wtrs. The last Jason pass at 1842z went thru the cntrl rgion and missed the rst of the nrn and srn wtrs and it indctd seas with 6 ft peaks. The nww3 multi grid WV mdl fits well with the obsvd seas pattern and is close to the ecmwfwave...so will stay with nww3. The glbl mdls seem to agree on most of the features in the short term but hv a problem on the path of the low pres that will approach the region from the S sun. Depending on the path each mdl takes that will dictate the winds strength ovr the wtrs. GFS and CMC hv both kept the low path ovr the wtrs and hv winds reaching gale force while the ecmwfhr and UKMET are quite weak and do not even hv a closed low but a trof. With the mdl discrpcies at the sfc we seek to explore the enrgy sources. There is an upperlevel trof just W of the region that has locally indcd energy that will help the frntl bndry curr W of the region to move E acrs the wtrs in the short term. Mdls show that there will be some more energy that will slide over area of hgh pres and combine with some sigfcnt energy frm the NW early next week ovr the region. This senario supports strengthening of the synop sys ovr the region. So in the short term a weak cld frnt will pass ovr the nrn wtrs while low pres moves E acrs the cntrl region. The pres grdnt will remain slack and winds will remain below gale force. In the xtndd prd wrngs will be introduced as the low pres from the S passes ovr the ern wtrs.
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Summary...IR Sat imgry still shows some convection over the ern nt2 wtrs this aftn with the lightning product showing isoltd shwrs/tstms over the srn nt2 zones. Latest avail ascat passes at 1502z thru 1506z show 5 to 15 kt winds with a few higher gusts to 20 kt in N to NE flow over the nrn nt2 wtrs. Hurcn Edouard was at 39.9n 42.7w and movg ENE 22 kt at 18/15z today based on latest NHC advisory...which puts it well E of the mim area. A stg hi pres rdg will build in from the NW tonight into Fri night...then move E Sat and sun while maintaining a wkng rdg W into nt1 and nrn nt2 wtrs. Another low is expctd to form off the GA/SC CST Sat night...move NE over the nt2 ofshr wtrs sun and Sun night...then pass NE of nt2 area Mon. Next cold front will approach the new eng and New Jersey coasts from the W later sun into sun nite...then move E across the ofshr wtrs late sun nite into Mon nite. Another rdg will bld in from the NW Tue and Tue nite.
Models...the 12z Med rng mdls are all in gud overall agreemnt thru the fcst prd...except there is some disagreemnt with speed/timing and strength of the low which is expctd to form off the se CST by sun. The 12z Gem/GFS are stgr and farther W with this low while the 12z ECMWF/UKMET are wkr and farther E...and the 12z GFS is faster than all of the mdls except the 12z NOGAPS. So will use a 50/50 blend of 12z ECMWF/GFS 10m for populating the wind grids to reach a representative soln until the picture becomes clearer. Blending the ECMWF with the GFS 30m wld result in gales over the nt2 wtrs on sun and sun nite.
Seas...multigrid ww3 mdl and ECMWF wam are in gud overall agreemnt across the ofshr wtrs thru Sat...but the mww3 becomes svrl feet higher with the seas in the nt2 areas during the sun thru Mon nite timeframe...due to stronger low fcst by GFS. Will use a 50/50 blend of ECMWF wam/mww3 mdl thru fcst prd.
Extratropical storm surge guidance...N/A.
.Nt1 New England waters... .anz900...Georges Bank east of 68w... gale possible Sun night.
.Nt2 mid Atlc waters... .anz920...Baltimore Canyon to the great South Channel... gale possible sun into Sun night. .Anz905...The great South Channel to the Hague line... gale possible Sun night. .Anz910...East of the great South Channel and south of 39n... gale possible Sun night. .Anz925...Outer waters from Baltimore Canyon to Hatteras Canyon... gale possible sun. .Anz930...Outer waters from Hatteras Canyon to Cape Fear... gale possible Sat night into sun.
.Forecaster musonda/Scovil. Ocean prediction center.