Hello Bill and crew -
First, regrading the route, a 39N/39W waypoint will work fine. You will miss any significant assist from the Gulf Stream along this route as you would remain south of the stream. If you want the assist from the stream, based on the latest altimetry data, you would need to head toward 40N/54W from your current position, then east to about 40N/52W, and from there you could head to 39N/39W.
Along a route toward 39N/39W, you will see SW winds veering to WSW later today with speeds of 14-18 knots. Tonight wind speeds will increase to 16-20 knots, and tomorrow speeds will increase to 18-22 knots. Seas will build to 5-7 feet later today, then to 6-8 feet tonight with similar levels tomorrow.
Tomorrow night W winds will increase to 21-25 knots with seas building to 7-9 feet, then on Thursday as you move east of 50W, winds will shift to N around daybreak and wind speeds will drop off to 17-21 knots in the afternoon. Seas will continue at 7-9 feet through the day, but will become more confused following the wind shift.
If you followed the more northern route, winds would be a little stronger, perhaps 3-4 knots from later tonight through tomorrow, and seas might be a foot or two higher, but the wind would be with the current in the Gulf Stream, and this could mean that the seas would be a bit longer. The wind shift to N would occur earlier on the northern route, probably before midnight Wednesday night, and thus the period of stronger winds ahead of the front would be shorter. Seas would still be confused after the wind shift, but likely no higher than those farther south.
By later Thursday or Thursday night, you would be in nearly the same position no matter which route is taken, perhaps 20 or 30 miles farther north on the more northern route. Winds Thursday night will back to NNW and drop off to 13-17 knots by Friday morning. Winds will back to NW later Friday and to WNW later Friday night with speeds increasing to 16-20 knots by Saturday morning. Seas will build through this period, mainly from the NW and by Friday evening will be running 9-12 feet near 39N/43W. Through the day Saturday WNW winds will ease a bit, but seas will continue at 9-12 feet before dropping off Saturday night.
It still appears that a low will be tracking east along 40N through the central Atlantic next weekend and will be centered near 41N/41W by Sunday evening. Easterly component winds will prevail to the north of this low up to about 46N or so later in the weekend. The low may intensify and head northeast early in the following week, reaching about 45N/36W by Monday evening. Increasing southwesterly winds will materialize to the south of its track early in that week, and the yacht should be able to take advantage of those on a route toward Ireland from about the 39M/39W waypoint. This is all nearly a week ahead at this point, so there is necessarily some uncertainty.
The choice of riding the Gulf Stream or staying to its south over the next day or two will probably not offer much different conditions. Slightly stronger winds, and slightly higher seas would prevail tonight and tomorrow on the northern route in the stream, but the period of strong winds prior to the wind shift would be shorter since the wind shift would occur earlier farther north. By later in the week, when higher seas are likely farther east, you would be back closer to 39N again, and conditions would not be that different compared with the southern route avoiding the stream. No real strong advice here, either option will probably work.
In the longer range, the decision about when to turn toward Ireland will depend on how the sea state develops east of 45W and the timing of the next low coming east, and also on the progress the boat makes between now and then. At this point, a turn later in the weekend when the seas drop off appears reasonable.
Email with any questions.