Winds will continue to back through the late afternoon, likely running S by evening with speeds in the 16-20 knot range. Seas may actually subside a little bit through this period as the increase in seas you have seen has probably been running into old swells from the “second low” now well to your northwest.
Conditions will deteriorate fairly quickly overnight tonight as the occluded front approaches from the west. Winds will back to SSE and increase to 26-30 knots by midnight with seas building to 7-9 feet. A period of 4-6 hours of even stronger winds appears likely after midnight, probably 29-33 knots with higher gusts (maybe some over 40 knots), and seas will build to 9-12 feet during this period with locally higher seas possible. Also during this time some fairly heavy rain is likely.
Based on your current position, and assuming SOA of 8 knots, it appears that the front will pass the yacht shortly after daybreak tomorrow around 49N between 22W and 23W. Winds will shift to WSW with the frontal passage, and speeds will drop off to 23-27 knots. Seas will be confused following the frontal passage, but will generally drop off to 6-9 feet.
WSW winds will continue through the day tomorrow, easing a bit toward evening, then tomorrow night winds will back to SW as you move east of 20W with speeds in the 17-21 knot range. A secondary cold front will pass the yacht on Saturday with winds shifting to WNW by afternoon at 19-23 knots. Winds will become a bit lighter through Saturday night, then will back to SW and perhaps S Sunday morning ahead of another front approaching southwestern Ireland before shifting to W later Sunday after the front passes. Seas will remain in the 6-8 foot range from later tomorrow through the weekend along the route.
Again, the main message today is that conditions will become rather gnarly through tonight with near gale winds, and gusts above gale force along with quickly building seas. After the frontal boundary passes early tomorrow, winds will quiet down a bit, but seas may remain uncomfortable for a good portion of the day due to their confused nature.
At this point, there is little difference between a GC route and a rhumb line route. The heading at any given time can be dictated by wind and sea considerations. There is no particularly large scale tactical advantage to one route over another, although moving farther north tonight will delay the passage of the frontal boundary, and thus delay the easing of the wind. If you find yourselves being pushed farther north than you like if there is more of an easterly component to the wind than anticipated, then heaving to might be better to just wait for the front to pass. Once the front passes, winds will have a significant westerly component for the rest of the passage.
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Latest Grib file at Current Time showing Newfie low to the boats west with the front running N-S
24 hrs later, front has just passed boat which will have moved about 200nm to the eat. Low has turned north and will pass behind boat, leaving them moderated SW winds.