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Bruce’s Swiftsure Forecast

by Bruce Hedrick

This could be a very interesting race because of the usual suspects: tide and wind. It maybe raining now (1100 hrs Friday) however that will pass shortly and we will be in the transition from frontal passage to a weak ridge of high pressure building over the Northwest, which will then be pushed out by another weak front on Sunday.

The good news is that with the weak ridge we’ll have breeze for the start and most of the way out the Straits. The operative phrase being most of the way. In the general overview, this will favor the fastest boats in the fleets with ability to get out and get back in with the wind.

The bad news is that even those these are still relatively small tides, the current in the Race will still be significant on Saturday and more significant on Sunday. So while there maybe breeze out at the Race, in the starting area it maybe lighter. So here are the tides for Race Passage:

Slack                           0900hrs

11:31               3.3knt Flood

Slack                           1432

17:39               3.2knt  Ebb

Slack                           2044

23:34               3.2knt  Flood


Slack                           0150

06:15               5.1knt  Ebb

Slack                           0940

12:26               4.1knt  Flood

Slack                           1535

18:55               3.3knt  Ebb

Slack                           2148


Both the PredictWind and MM5 Models have converged with the usual 5 knot variance in wind speed and the wind direction “fairly” consistent. The other constant is that while the models are converging, models may do a pretty good job of predicting what will happen they have a way more difficult problem predicting exactly when it will happen. The reason is that as fronts and pressure systems approach the coast, the speed at which they move and the direction in which they will move can and usually will change significantly. This is why you should start logging the pressure data from the NWS reporting stations as soon as the boat leaves for Victoria Harbour.

NOAA 24-hour Surface Forecast issued 05:44 UTC 23 May
NOAA 48 hour Surface Forecast issued 17:01 UTC 23 May
NOAA 48 Hour Surface Forecast Issued 05:12 UTC 23 May

The two most important stations are Forks and Bellingham as that gives you a very general idea of velocity and direction in the Straits. At 1000 hrs on Friday the pressure at Bellingham was 1016.5mb while the pressure at Forks was 1016.3. So essentially no gradient in the Straits and if you look at the surface reporting stations the velocities are less than 5 knots or calm. At the VTS buoy JA at entrance to the Straits the breeze was five knots from east which would match that breeze flows from areas of higher pressure to areas of lower pressure. The point here is that you can read this and plan all you want to however you really have to keep your head out of the boat and watch and adapt to what is actually going on.

The rule of thumb for wind speed is to subtract the difference in pressure readings in millibars and if it’s one millibar that give you 10 knots, if it’s two that’s 20 knots and if it’s three that’s 30 knots, etc etc. Then you also need to remember that the distance between to two shores in the Straits compresses in the area of Race Rocks and that is generally where you will find the highest wind velocities. If you have for instance 10-15 knots of wind from the west at Sheringham and you’re laughing and scratching under spinnaker headed towards the finish and planning your post race party you should instead be anticipating 25-30 knots at the Race. That will mean planning the drop of the kite, having the #3 ready to hoist to make the drop of the kite easier and giving you more control going through the Race. Once you clear the Race then get set to re-hoist the kite.

UW Forecast 27 hours
UW Forecast 30 hours
UW Forecast 33 hours
UW Forecast 36 hours

Back to getting around the course. The first challenge is getting a good start and finding a clear lane in which to sail. The tendency is to come off the line and then work to the west to get out of the building flood tide. The problem could be that the wind will drop as you get closer to the shore north of the Race. The closer you get to Race Passage the wind will shift from the west-southwest to west which means you can be on the beach sailing starboard tack lifts and staying out of the flood. It should be very obvious how far off the beach you can go before you have to tack back into the beach. A word of caution here if your using your tablet as your on deck navigation plotter. Remember that if you’re getting position data from the cell towers instead of direct GPS input, it will be slightly slower and that can get you into trouble with those keel  grabbing rocks that live in Race Passage.

Once you clear the Race it will pay to short tack the north shore to stay out of the flood and current models show more breeze on the north shore and as you work your way out the Straits, the breeze will continue to clock from the west to the west-northwest. So the starboard tack will be more lifted as you go out the Straits. So when do you cross over to US side? Usually somewhere closer to Sheringham however it is the safer tactic to cover your fleet and don’t let too much separation occur.

You would also like to make the US shore west of Slip Point at Clallam Bay as the breeze will begin to drop from 15-20+ knots after about 1600-2000 hours and the closer you get to the entrance of the Straits it will begin to back to the west and west-southwest.

After about 2200-0000 hours the breeze will drop significantly with the US side holding breeze longer than the Canadian side. The next problem is making sure you are near a beach after 0200 hrs on Sunday morning as that will be the start of the big ebb of the day and the breeze will continue to drop except in the area of Race Rocks where it will hold in the 8-15 knot range. You really want to have your navigator monitoring the wind and pressure readings as you fight your way back down the Straits.

After about 0300 to 0600 the breeze in the Straits will become light and flukey but generally from the west, By 0900 to 1200 on Sunday it will be very light and if the pressure begins to drop you should anticipate the breeze coming in, the very light breeze, from the east-southeast.

Welcome to Swiftsure.

I’ll try and get another post up later today as the ridge begins to set up. As always, if you have questions or comments don’t hesitate to send them to me and I’ll get back to you.

Be safe, don’t take unnecessary chances. Also, if you have a new crew get a big meal into them in the morning because it may be pretty uncomfortable to cook or eat late in the afternoon or early evening. Don’t let anyone get too wet or too cold as that is always tough to fix.

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