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Winds and Tides in English Bay

Acknowledgements
The following descriptions of Winds and Tides on English Bay was developed by Claire Adams, former head instructor at RVYC for the 1997 J/24 Canadian Championship. Assistance in preparing the material was provided by Past Commodore Don Martin and Peter Chandler from the Institute of Ocean Sciences in Victoria. The graphics are provided courtesy of AREA51 Interactive, a website design company in Vancouver.

Winds

Generally, fair weather brings a westerly and poor weather brings an easterly. The wind rarely blows out of the north and typically out of the south when it is in a transitional state from poor to fair weather.

Westerly

This is the most hoped for wind and tends to be the most common wind in the summer months. During periods of fine weather the Fraser River valley encourages the production of thermal winds. This thermal breeze fills in the late morning at around 11 am. It will consistently increase until it hits its maximum for the day at around 2:30 pm. As it fills, it tends to bend onto the south shore. Later in the day, after thermal heating, it will blow more directly down the bay (Figure 2). This will reflect in the windward (heading west) leg of a race course by a persistent geographical back (shift to the left). The amount of this back from the leeward to the windward mark can be in the order of 10-15 degrees. As the wind builds there may be temporary oscillating shifts but once filled in, the direction seems relatively stable. Because of this; there are few to no 'passing lanes' so remember that starts and boat speed are at a major premium in a westerly. Typical wind speeds between 6-12 knots rarely rising over 20 knots.

Easterly

Easterlies are the result of a depression or bad weather and are often accompanied by rain. The water is smooth and the wind will vary from quite light up to 20 knots. It is much more shifty as you will find both geographic and oscillating shifts often appearing in a layered effect.

There are two dominant indicators to keep eye out for (Figure 3). If it is dark and raining to the left (north) side of the course, the wind will typically back (shift left). If there is a lightening low in the sky on the right (south) side of the course, then it is signalling the passage of a front. Watch out for a major veer (shift right) of up to 90 degrees. These shifts are from the median wind blowing out of the Bay.

Typically a geographic shift to the left on the left hand side of the course occurs, particularly in bad weather, which favours the left hand side of the beat. Be careful; however, the sky lightening low in the south may signify a large veer in the right hand side of the course as the front passes.

Both of those wind shifts, while they are substantially geographic, may also show up as oscillating shifts. If heading north, don't forget to tack on the oscillating shifts! The key is to be able to respond to the overlay of the two shifts which may occur at the same time.

Sailing in an easterly can be both challenging and rewarding racing. If you read the shifts right there are many opportunities to pass other boats.

Southerly

This breeze will rarely last longer than 3-4 hours and typically arises when the weather is changing from poor to fair. There will be a significant temporal veer (shift right over time). While the wind is veering, there will be lots of unpredictable oscillations through a range of 90 degrees (45 degrees either side of median). In a southerly, you're on your own! Good Luck!

Racing Area

RVYC Club racing normally takes place immediately outside of the 500 boat RVYC Jericho Marina. Longer distance races extend beyond English Bay into the Straight of Georgia. This article is about racing in the south half of English Bay 10 km (6 miles) to the west of downtown Vancouver.

English Bay is a U-shaped body of water 8 km (5 miles) long, 6.5 km (4 miles) wide and open to the west. The north/western most point is Point Atkinson (B) and the south/western most point is Point Grey (F). The eastern end of the Bay narrows through First Narrows (D) and empties into a 65 km (40 mile) inlet named Burrard Inlet (Figure 1).

The year round average wind speed is 8 knots. Be aware that as with all averages this value can be deceiving.

Typical current speed is between 1/2 - 3/4 knot and will at times reach 2 knots. The tidal range is 5 m (15 ft). This is a salt water port where the salinity is greatly influenced by the Fraser River. The Fraser River is one of the largest melt-fed, fresh water rivers of the BC coast. You will often be able to see a definite line between the clear salt water and the silty coloured fresh water (see Figure 1). Vancouver is typically a flat water sailing venue. The average wave height seldom exceeds 1 m (3 ft). In a strong westerly wind wave height can reach up to 2 m (6 ft). In bad weather, in an off shore breeze the water is always flat. Even if the off shore wind picks up to as much as 20 knots, wave height is still typically less than 1 m (3 ft).

To the north, the Bay is bound by Coast Range Mountains which rise to 1070 metres (3500 ft). These mountains are a popular spot for local night skiing in the winter! The renowned Whistler/Blackcomb is tucked into the mountains 100 km (60 miles) further to the north. To the east, beyond the City of Vancouver, the Fraser River Valley extends 160 km (100 miles). The low lands of the Fraser River Delta extend 56 km (35 miles) southward to the USA/Canada border. 64 km (40 miles) to the west of English Bay lies Vancouver Island which prevents large ocean swells.

The commercial nature of our bay brings some interesting racing features. There are 23 freighter anchorages of which 8 are located in the typical racing area. These 'iron islands' can help as indicators to the current direction but also provide for large obstructions and wind shadows on the race course. It is important to pay attention to their infrequent comings and goings. Crab traps, identified by small floats, scattered around the Bay can bring your boat to a complete stop and can be difficult to remove so keep an eye open for these as well! Finally, a tug followed by its tow may pass through the race course which will have a submerged tow line...never sail between them!

While it seems that English Bay is riddled with many commercial hazards, we make up for it with few geographical hazards. A very large drying sandbank located on the south shore, named Spanish Banks, just west of RVYC extends 3.2 km (2 miles) east to west and approximately 0.6 km (.4 mile) out into the Bay. It is marked with large pylons but it is always important to be aware of the state of the tide when sailing close to that shore. The only other concern is the odd floating log.

Tides

Tide and current tables are notoriously unreliable because of the barometric pressure, geographic patterns and the condition of the Fraser River. The time tides turn may vary up to an hour from the predicted time. The freighters are a good indicator of the flow of the water in the Bay

Tide tables for Point Atkinson are useful for tidal height; whereas, tide tables for First Narrows are useful for current change and predicted slack water. Tide tables are available from marine retailers in the area. The current velocity at First Narrows is of no use to racers because it will always be significantly higher than what would ever occur on the race course.

Relatively speaking, the current is always rotating clockwise. The flood is harder outshore and weaker inshore due to the changing depth of the bay. Generally speaking, if you are heading west, sail along the south shore and if you are heading east, sail in the middle of the Bay.

The dominant line of flood flows from Point Grey to First Narrows heading into Burrard Inlet (Figure 5). The dominant ebb occurs north of the race course along the north shore of the Bay due to the outflow from the Burrard Inlet (Figure 6). The most important transition happens from the high flood to an ebb. This is where an often advantageous south shore, backeddie easterly current is created (Figure 5).

Two main indicators of current in the water:

1) Well defined Tideline
Normally between the fresher, silty Fraser River water and the clear salt water. This tideline is created by a vertical shear of the two waters (Figure 7). There may be a band of flotsam (floating debris) caught between the surface layers of the two different current regimes.

These tidelines often mark an abrupt change in the speed and direction of the near surface currents; therefore there is almost certainly a benefit to being on one side or another so watch the water carefully. Do not assume what you think to be happening on either side of the tide line to be true. It is essential to test your theory by watching other boats as they sail into the different water.

2) Bands of Current
Bands of ripples on the water about 23 metres (75 ft) across running parallel to wind typically occur in flood conditions. These 'tidal rivers' flow to the west so it is important to sail in the rippled water (when heading west). These are likely again the result of the mixing of fresh and salt water.

If the wind is greater than 15 knots you will not be able to see the rows of disturbed water...you will just notice that some boats will seem to have their own personal favourable water. If you do notice a band it is important to sail to it, it is not something that will ever reach you.