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20:06 Tuesday 2 Aug 2016 Rupert HolmesCowes Week tidal streams and heights 2016

This year’s Aberdeen Asset Management Cowes Week is a week later than usual to avoid spring tides. The opening day is only two days after the peak of the spring tide cycle, while the smallest neap tide is on Friday. The start sequence gets closer to low water as the week progresses, with the first starts happening on a falling tide from Thursday onwards.

High water Portsmouth on the first Saturday is in the early afternoon, so the scheduled start times for most classes will see a consistent east-going flood tide. However, by midday the west-going eddy close inshore will start to come into play for the later starters on the Royal Yacht Squadron line. Getting into this eddy can give a big boost to speed if you’re heading west, but it’s also important to avoid the big holes in the wind that are often found directly in front of the RYS in an offshore breeze. Therefore, if you will be short-tacking towards the west immediately after the start it’s rarely worth starting closer to the shore than one-third of the length of the start line.

Towards the end of the week, the situation will be reversed, with the main stream ebbing to the west for classes in the very earliest part of the start sequence from Thursday onwards, although an inshore east-going eddy will be active. By this stage of the regatta racing will be taking place over low water, although the neap tides mean the height of tide isn’t predicted to fall below 1.8m at Cowes from Thursday onwards. Nevertheless, it’s worth noting that high atmospheric pressure will depress this figure by 0.1-0.2 metres.

Work on the outer breakwater has now been completed, but boats entering and leaving Cowes harbour via the main channel need to be aware of a strong west going cross tide in the area just to the north of the Yacht Haven, especially between two and a half hours before high water to an hour before high tide. This tends to set vessels towards the western shore of the channel.

It’s worth getting along to the skippers’ briefings at the Events Centre in Cowes Yacht Haven on Friday 5 August. These are at 1730 for Sunsail class yachts, at 1830 for White Group Classes and at 1930 for Black Group competitors.