Puget Sound is one of the most beautiful and challenging places you will ever sail. This is because as weather systems come across the Pacific, the first landmass they encounter is usually the Pacific Northwest.
When these systems begin to interact with the land, the speed at which they move usually slows down, and the winds associated with these systems change direction. This makes weather forecasting very interesting and as we say, the National Weather Service sends their forecasters to the Pacific Northwest to teach them humility.
The sailing conditions described below were prepared by Bruce Hedrick, who compiles pre-race weather predictions for all major northwest sailboat races.
September is a great time of the year to sail here, as it is when we transition from summer to fall. It also means just about all options are on the table for weather. There are generally three possibilities for weather systems in September. The first is that the Pacific High-pressure system which resides off the West Coast through most of the summer will remain in place bringing beautiful weather and a perfect sailing breeze to Puget Sound. This breeze usually starts to fill from the northwest sometime after about 1000 hours. It will come down Puget Sound at 5-8 knots starting from a direction around due north and then back to 335° to 350° and building to 8-12 knots. In the Worlds sailing area, the oscillations will tend to be less than 10° once the breeze has settled.
The other conditions involve the fact that in September we may get the first fall low-pressure systems and their attached fronts. As these systems come onshore, remember that warm fronts always lead cold fronts, and cold fronts move faster than warm fronts.
The second of these possibilities is that you may be sailing in a pre-frontal condition. This will mean that the barometer is dropping, the cloud ceiling is lowering, and the wind will be out of the southeast anywhere from 10-25+knots. However, conditions do change quickly in Puget Sound.
The third possibility is sailing in the post-frontal condition, which tends to last longer than the pre frontal situation. When the front has passed, the rain will tend to ease, the wind will clock from southeasterly to south/southwesterly, and generally ease in velocity.
We also have to deal with tidal currents in the sailing area, and while they tend to be less than a knot, you will find that the velocity will vary slightly over the racecourse and can make mark roundings as well as tack and gybe locations interesting. Don’t think of this as a body of water moving at a uniform velocity over the racecourse. Instead, think of a series of small streams that are moving at different speeds. You will want to watch for tidelines that mark the interaction between these bodies of water and work to stay on the more favorable escalator.
Remember also that Puget Sound is one cold body of water with the water temperatures in the race area averaging 55°F (12.8°C) in September.