Marine Interpretation Message
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185 AGNT40 KWNM 191347 MIMATN Marine Weather Discussion for N Atlantic Ocean NWS Ocean Prediction Center Washington DC 847 AM EST Fri Jan 19 2018 .FORECAST DISCUSSION...Major features/winds/seas/significant .weather for the North Atlantic Ocean W of 50W from 30N to 50N. At 12z a high pressure ridge was located across the offshore NT1 and NT2 waters. Strong low pressure that had been impacting the region continued to pull away to the east and was located near 40N58W. With the 06z GFS/NAM in good agreement through the near term see no reason to make major adjustments to the ongoing forecast. Low pressure that brought warning headlines to the offshore waters continues to pull away to the east as mentioned earlier. Hence warning headlines in place in the prior forecast will be allowed to expire to start this forecast. Continue to anticipate brief period of gales in the northern NT1 waters Saturday as strong low pressure swings by to the north through Eastern Canada. Beyond that next opportunity for gales will be Tuesday night into Thursday as winds increase ahead of a strong cold front expected to move through the waters. ----------------------------------------------------------------- PREVIOUS DISCUSSION... Earlier ASCAT overpasses confirmed trends seen in Goes-16 Air Mass imagery, with strongest storm force wind returns now along the south and southeast quadrants coincident with PV anomaly and jet streak. Near term higher resolution guidance from the 00z NAM and 05z HRRR pull associated gale force winds outside of the OPC forecast area in the next couple of hours as the low continues moving quickly off to the NE at about 30 kt. This is well represented in the ongoing OPC grids, and will allow headlines to expire across the outer zones ANZ905 and ANZ910 with next forecast issuance. Sat and Sat night: as alluded to in the previous discussion, guidance initially trended stronger through the day yesterday, then remained fairly consistent in the 00z cycles with strong gradient south of approaching cold front over the far northern waters Sat afternoon. With high pressure settled over the southern zones, guidance continues to suggest a gradient supportive of minimal gale headlines generally north of about 40N. With nearly unidirectional winds and excellent agreement with the timing of the front, was able to use an even blend between the GFS first sigma level, UKMET, and NAM to produce desired coverage of winds and minimal gales. These hazards will be brief (18z to 00z). Confidence is slightly above average. Sun onwards, trended grids to previous forecast which preferred the timing of the ECMWF as another strong cold front moves across OPC waters. With the 00z run comparing favorably to the previous 12z cycle, see no reason to make changes to the ongoing forecast already in place. Gale headlines will remain in the forecast beginning around 18z Tue. Seas: opted to use the WW3 through late Sat night to better match the OPC wind grids, however did increase values to ensure seas increased to 12 ft during periods of gales. Trended forecast to previous grids / 12z ECMWF WAM thereafter. Extratropical Storm Surge Guidance...no major deviation from the latest surge guidance appears necessary through the forecast period. .WARNINGS...Preliminary. .NT1 New England Waters... .ANZ800...Gulf of Maine... Gale Saturday. Gale Possible Tuesday into Tuesday night. .ANZ805...Georges Bank west of 68W... Gale Saturday. Gale Possible Tuesday. .ANZ900...Georges Bank east of 68W... Gale Saturday. .NT2 Mid-Atlantic Waters... .ANZ920...Baltimore Canyon to the Great South Channel... Gale Possible Tuesday into Tuesday night. .ANZ905...The Great South Channel to the Hague Line... Gale Saturday. Gale Possible Tuesday night. .ANZ910...East of the Great South Channel and south of 39N... Gale Possible Tuesday night. .ANZ925...Outer Waters from Baltimore Canyon to Hatteras Canyon... Gale Possible Tuesday into Tuesday night. $$ .Forecaster Holley/Collins. Ocean Prediction Center.

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