Marion Bermuda race weather analysis

Meteorologist Ken McKinley of Locus Weather, who writes our weather email newsletter, provides us with his forecast for the Marion Bermuda Race. 

2009 Marion Bermuda Race Weather

Wednesday June 17

A difficult forecast shaping up for the Marion Bermuda Race. Computer models are having difficulty resolving a couple of lows forecast to come out of the Great Lakes region through the northeastern U.S. and into the Atlantic. The first of these looks to be fairly modest in strength, but will likely lead to less than favorable wind direction for the first day or so of the race. It appears that SE winds will prevail for the start on Friday, which will allow for a one-tack leg to get out of Buzzards Bay, but then these winds would be unfavorable for heading down the rhumb line. This first low appears that it will weaken through Friday and as the second Great Lakes low moves east and strengthens, this would pull a warm frontal boundary northeast and shift the winds into the SW. At this time it appears that SW winds will prevail for several days as the next low strengthens but also slows down. Wind speeds would be strong in the Gulf Stream in this pattern, perhaps with gusts greater than gale force, but the wind direction with the stream would mitigate the sea state. The longer range prognosis for the low is more uncertain, with some forecasts taking the low east, which would keep winds in a generally SW direction all the way to Bermuda, and some forecasts taking it more to the south, which would allow for the wind to back more toward the south close to the end of the race, and if it moved far enough south early enough, could possibly lead to an easterly component for boats that are slower.

Bottom line, after the first 18 to 24 hours, it looks like a quick race with favorable wind direction and moderate wind speeds.

Thursday June 18

My last chance to talk with clients in the race! Race rules prohibit any contact after the start of the skipper meeting at 5PM.

Computer models having even more difficulty with the forecast today, especially the second low. It appears that this low will become stronger than was indicated in yesterday’s data, but one model has a more extreme solution, carrying this low farther east more quickly, and deepening it. This scenario would produce strong gales with a northerly component along the rhumb line later in the weekend. However, it appears unlikely to me that this situation will occur. Rather, it appears that the low will remain farther to the west, which will keep the winds in a favorable direction for the large majority of the race, although with stronger speeds than appeared to be the case yesterday. In fact, it now appears that sustained winds in the Gulf Stream will be close to gale force, with frequent gusts over gale force. The stronger low would likely lead to more in the way of showers and thundershowers from the Gulf Stream south, and likely some squalls in the stream. For the start of the race, it now appears that the first low will tack a bit farther north, which would lead to south winds for the start, rather than the SE winds forecast yesterday. Moderately strong wind speeds appear likely at the start. Winds would then shift to SSW later Friday evening, and gradually veer to SW through the day Saturday. Again, it appears that the faster boats will have SW winds almost all the way to Bermuda. Early next week, it appears that the low will begin to drift slowly south along about 70° W, and this would lead to a slow backing of the winds along the southern portion of the rhumb line toward SSW Monday night and toward S later Tuesday.

Bottom line – it will likely be a heavy wind race with the wind mostly forward of the beam, but after the first 24 hours more toward the beam which should lead to some fast times to Bermuda.

Friday June 19

Race Start Day. I can’t talk to anyone anymore. Wish I could as there are a few differences in the forecast today, although the general idea of a heavy wind race with mostly favorable wind direction still seems reasonably likely.

The strong southerlies for the race start have materialized, but it now appears that the first low will maintain its strength bit longer, and the second low will be a bit slower to come out of the Great Lakes. This will allow for the possibility of some W or WNW winds this evening and much of tonight as the first low moves off to the northeast before the circulation of the second low turns the wind back to the SSW tomorrow.

Computer model differences persist with respect to the second low with some models bringing the low southeast over the race course. If this occurs there would be the possibility of northerly component winds along the course later Sunday, Sunday night and Monday. I’m not ready to buy off on this yet, but it will need to be watched. For now, it seems that the most likely scenario is still for mainly SW winds through the weekend and into early next week.

By Ocean Navigator