HS 100

marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 855 am EDT Mon 20 may 2013

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

Last ngts mdl runs came into better agreement with sfc low to dvlp just E of new engl waters tngt with 00z/06z GFS slightly weaker with assoc winds than previous runs...and more in line with ECMWF/UKMET. Appears that shud see winds increase to marginal gale E of offshore waters tngt. Altho in better agreement that ystrday...there remain some timing differences with cold front and any dvlpg wave alng front at weeks end. 00z UKMET was most progressive with sfc low...with GFS/ECMWF slower and in somewhat better agreement. Preferring GFS/ECMWF blend given these differences and will not be making significant changes from nt1/nt2 forecasts. 06z multigrid wavewatch iii looks reasonable this morning when compared to latest W Atlc ship/buoy obs. For Thu/Fri preference continues for a mww3/ECMWF wave mdl blend.

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

Summary...a slow-movg warm front extending from the Delmarva S and se toward far se nt2 wtrs is still fcst to lift NE ovr the off wtrs tda as high pres drifts E and se away from the NE nt2 and nt1 wtrs. The latest obs and a-scat data cont to indicate that the strongest winds currently are located from cp hat N to balt cany...or just to the N and E of the front...with winds up to 25 kt in these areas. Winds are still fcst to increase ovr wtrs mainly from hat cany northward tda as low pres dvlps and moves E-se off the New England coast. Winds to 30 kt are still lkly ovr the balt cany to the Hague ln wtrs tda with the strongest winds (psbly gale force) occurring E of these wtrs by tngt. The cold front assoc with this low will stall ovr nt1 wtrs Tue ngt...and return N as a warm front Wed as high pres builds nr Bermuda. The high nr Bermuda will then only slowly drift E late in the wk as the next cold front approaches the coast from the W and NW. This front is still expected to cross the wtrs Fri.

Models...the 00z GFS is in better agreement with the non-GFS mdl solutions ovr the off wtrs into Thu. It has weakened the low slightly as it moves E from New England tda and tngt...and maintains a moderately strong S and SW wind field ovr most of the off wtrs by late Wed into Fri ahead of the next cold front. This scenerio is supported by all available mdl guid attm. As a result...we will remain close to the GFS into Thu ovr the off wtrs or something similar to the prev opc fcst. By Fri...the 00z GFS dvlps a low E of Long Island...with another low forming along the front nr the Carolina coast by ltr Fri. Non-GFS mdls also are dvlpg lows along the front but in different locations and at different times than what is shown by the 00z GFS. As result... we feel that for now it will be best to stay the course...and remain fairly close to the prev fcst for Fri which more closely followed the 12z sun ECMWF...and the latest HPC Med range guidance.

Seas...the latest mww3 and wna versions of the wave watch iii appear to be running within a ft or so of most of the obs noted ovr the off wtrs at this time. Overall...we will not be making sig changes to the prev fcst for the early am package. The 00z wna ww3 mdl appears reasonable into Thu ovr the off wtrs. Beyond that time we will cont to trend the fcst toward the ECMWF wam WV mdl guid.

Extratropical storm surge model...N/A.

.Warnings/forecast confidence...Preliminary. Any changes will be coordinated through AWIPS 12 planet chat or by telephone:

.Nt1 New England waters... .Gulf of Maine...none. .Georges Bank...None. .South of New England...None.

.Nt2 mid Atlc waters... .Hudson Canyon to Baltimore Canyon...none. .Baltimore Canyon to Hague line...None. .Baltimore Canyon to Hatteras Canyon...None. .Hatteras Canyon to Cape Fear...None. .Cape Fear to 31n...None. $$

.Forecaster Clark/Mills. Ocean prediction center.