marine weather discussion for N Atlantic Ocean NWS ocean prediction center Washington DC 930 PM EDT Sat 27 Aug 2016
.Forecast discussion: major features/winds/seas/significant .Weather for the North Atlantic ocean W of 50w from 30n to 50n.
This mornings 1450z ascat overpass indicated 25 to 30 kt winds across the N quadrant of the surface low which at 00z was invof 31n68w and is moving WNW at around 10 kt. Ascat winds were at least 5 to 10 kt higher than 12z models initialized. Latest models are in good agreement that the low will approach the srn nt2 waters sun and slowly move WNW across the area sun evening through Mon night...approaching the NC coast Tue. Bumped up the previous associated winds...now up to 25 kt sun into Sun night. Later in the week 12z UKMET was a strong outlier as it strengthens low into a gale across central nt2 waters Wed. Later Wed and Thu the past few runs of the GFS are closer to the ECMWF with a developing low near NE FL Wed and then tracking NE across srn nt2 zones along the cold front Wed night into Thu night. Am leaning more toward the more consistent ECMWF from Wed Onward.
The 12z/18z wavewatch iii and 12z ECMWF were both well initialized with wave heights across offshore and coastal zones this evening...however seas were 4 ft or less. The long period E to se swell associated with Tropical Storm Gaston has yet to reach buoy 41048 W of Bermuda...or Georges Bank buoy 44011. The wavewatch iii has been very consistent with this swell over the past several runs. Will get better idea of how the ww3 is handling the timing over the next few hours as swell should arrive at buoys noted above. Seems reasonable that swell should top out at 6 or 7 ft across outer offshore waters.
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The Sat img still indc a high pres ridge to the NW building into the region. All the observations including ascat pass show Max winds 20 kt mainly over nt1 waters and min winds 5 to 10 kt over the central region. At 18z the NCEP map has high pres 1025 mb centered over the central Atlc with its ridge extending W into most of the central and srn regions and the pres gradient is fairly slack across the region. A cold front also extends SW from complex low pres 1004 mb just E of new foundland Canada into the Balt canyon waters then through the central waters into srn VA. Another low pres 1012 mb is slowly approaching the S-ern waters from the E. The models have generally continued to initialize well with these few synop features. The models GFS/ukmethr/CMC/ ecmwfhr/NOGAPS/jma have a decent agreement in the short term pushing the cold front farther E and dissipate it. The models also agree on building a high pres ridge behind the front across the region. In the extended period there are minor differences mainly on the timing and track of the low pres that will develop inland and then move E across the srn waters. The winds will remain below gale force threshold and the models have differences in wind speed within 5 kt thru most of the preiod. So will just stay with GFS like in the previous forecasts.
.Seas...The seas range between 2 and 4 ft over the nt1 waters and they range between 3 and 6 ft over the nt2 waters. Nww3 wave model fits well with the observed seas pattern and has been quite consistent in the previous runs with the forecast and has also been in good agreeemnt with the ecmwfwave espcially in the short term with just minor differences in the extended period. Will stay close to nww3 for the seas. Long period swell generated by Gaston will affect the waters thru Wed.
.Extratropical storm surge guidance...N/A.
.Nt1 New England waters... None.
.Nt2 mid Atlc waters... None.
.Forecaster Clark/musonda. Ocean prediction center.