Cowes Week navigation tips part 1

Jim Saltonstall looks at the winds and tides in the eastern Solent

See tomorrow for navigational tips for the central Solent.
Eastern Solent - north

Wind Direction

340-070 degrees: The north-north-east sector is the shifty sector for this race area. Although the wind is blowing over relatively low land, the shifts are still quite significant. As with any offshore wind, the shifts will be more frequent and over a wider arc the closer you get to the shore. There are possible lifts on port tack near the apex of the beat, if the mark is within half a mile of the shoreline. Remember the wind shifts to the right as it leaves land and comes on to the surface of the sea. When the wind is coming from this sector, the advice is to get out to the race track in good time to identify the wind shift pattern - a great card to have up the sleeve of your drysuit, especially for the first beat. And don’t forget the basic theory in these conditions - work the shifts more up the middle and don't get to the laylines too early. Also watch out for the tidal wind shift as you sail in towards the shore.

070-150 degrees: The breeze is now blowing at an angle off, or parallel to, the shoreline. So it will pay to go left up the beat, due to the convergence band of wind along the mainland shore. There is also the possible header as you go in on starboard tack, with lifts along the shoreline on port tack. The only thing stopping you going left up the beat is the tide, which we will look at later.

160-230 degrees: With the wind in this sector it is coming over the Isle of Wight to the south. How shifty the wind is will depend on how much the island has mixed it up as it blew over the top. A rough rule is that the stronger the wind and the hotter the day, the less shifty it will be. It's another day for getting out there early to determine the shift pattern. The chances are that you will be sailing across the tide - as for the northerly wind direction - so watch out for the tidal wind shift.

230-270 degrees: With the wind from anywhere in this sector the race area will be affected to some extent by the wind blowing down the western Solent. These effects will be more noticeable the further west you go in the race area. When the breeze is blowing up the western Solent the island shore has the convergent wind zone, and this band of stronger breeze will continue as it rolls into the eastern Solent. Try to find and stay in this band of strong breeze as you tack upwind or run downwind. There may well be lighter breeze to either side of it. To the west it is created by the divergent wind band on the mainland shore of the western Solent, and to the east it can be created by the wind shadow of the island.

270-320 degrees: With the wind in this sector, the most important influence is the mix of land and water to windward. The western shore of Southampton Water will be creating a zone of stronger convergent breeze that will blow downwind into the eastern Solent. While the land south of that shore, from Calshot down towards Stansore Point, will be creating an area of shifty lighter wind that you want to stay out of. But both of these effects will recede as you go east down the Solent.

320-340 degrees: Once the wind is round this far towards the north, the primary influence will be the fact that the eastern shore of Southampton Water and the north shore of the Solent are both divergent wind shorelines, creating zones of light air near them. For the best breeze you will want to look offshore.


Sea Breeze

The eastern Solent is an area which can struggle to get the sea breeze, as it tries to fill in from the south-east and/or the south-west. The right conditions for a good sea breeze are a light north-westerly gradient wind in the early morning, a clear blue sky and a hot sunny day. Towering cumulus clouds by mid or late morning are a good sign, after which the south-west sea breeze should start coming up the Solent. It often rolls in a line from the south-west and it can blow hard at 20 knots. But if the gradient wind is anywhere in the eastern sector, then we normally get the south-east sea breeze coming up the eastern Solent. This is never as strong as the south-westerly sea breeze, as it is local to the eastern Solent - maybe 8-10 knots maximum. As the day gets older, the south-east sea breeze will normally veer with the sun, and collapse by about 1800. The south-west sea breeze also tends to veer slightly later in the afternoon (more in the eastern Solent than the western Solent) but as it is normally stronger, it lasts later into the evening before dying.

Tide

The critical factor in the Solent, there is always a fair amount of water sloshing around, even during neap tides. Consult the guides, but the basic situation is that for the Lee-on-Solent and Stokes Bay race courses, the flood tide runs parallel with the shoreline to the east-south-east, stronger offshore, with the ebb running west-north-west. The change round is fairly quick, about two and a half hours before high water Portsmouth.

Racing on the island side, the flood tide runs east-south-east along the island shore, and west-north-west on the ebb. It runs more strongly in the channel and changes inshore first. Always look at any boats on moorings, or the flow round buoys in the water for indications of the tidal direction and strength.

See page two for Eastern Solent (south)