Cowes Week navigation tips part 3

RYA training guru Jim Saltonstall looks at the winds and tides for the western Solent

Wind Direction
340-020 degrees: When the wind comes from this northern sector, it's blowing over relatively low land with lots of trees. As you would expect, the wind is fairly shifty, more so as you get closer to the shore. As with any offshore wind, the further you get away from the land, the less frequent the shifts become and the range or arc of shift narrows - in this case to about 10 degrees. The closer you get to the land, the more frequent they become and over a wider arc - up to 30 degrees or more in the light winds. It's important to know the high and low headings on the compass. If the windward mark is within half a mile of the shore, look for lifts on port tack as you approach the land, because of the wind shift from land to water - always to the right as it blows offshore in the northern hemisphere.

020-090 degrees: The mainland shore is typically favoured in this sector, with more breeze. On the beat go left for the wind, with more pressure on the port side of the course, as well as the headers on starboard tack as you sail that way. There are possible lifts on port tack, especially if you are within half a mile of the mainland shoreline - which is the convergent shore.

090-180 degrees: The wind is now blowing over the Isle of Wight and will be shifty as a result. It likes to line up with the various valleys that open onto the island shore of the western Solent. A look at the Ordnance Survey map will help you figure out where these are in relation to your race course. It will also blow stronger down these valleys, than where there is high land close to the water. Generally though, the mainland shore will be favoured with more wind, as it is further away from the shadow of the island.

180-220 degrees: The wind is still blowing over the Isle of Wight. The island shore now has a band of convergent breeze that provides stronger pressure down that shoreline. The backed wind blowing over the island will also funnel out of the valleys along this shore. The wind coming out of these valleys will be stronger, and will be shifted to the left, compared to the wind blowing down the middle of the Solent. So expect port tack lifts and gusts when sailing upwind to the west, along the island shore. The island side is usually favoured in these conditions. If you’re beating west against a flood tide, normally the mainland shore is preferable because it's easier to duck out of the tide (see below). But with the gradient wind left of 220, the better wind on the island shore usually over-rides this. Unfortunately, the wind also has a tendency to try to swing to the right during the day. The western Solent is effectively a flooded valley, and once it gets around 220, the wind will try to line up and blow straight down this valley - which also happens to be the sea breeze direction. So watch for a right hand swing in early afternoon if there's a hint of sea breeze conditions (see below)

220-250 degrees: This is the most common summer wind direction in the western Solent. There’re two good reasons, one is that it’s the sea breeze direction. The second is that once the breeze is to the right of 220, it likes to blow straight down the Solent. In these conditions it’s not usually that shifty, and tidal concerns will often over-ride any wind shifts. The Isle of Wight shoreline still has the band of convergent breeze down it that we described above. If you are racing close to Hurst Point in this wind direction watch out for the wind funnelling through the Narrows. It will accelerate through the gap, and then fan out once inside the Solent. So expect a right-hand wind shift on the island shore west of Yarmouth, and a left-hand shift along the mainland shore west of Lymington.

250-340 degrees: The mainland shore is now a divergent wind zone, and so left-of-middle should pay for the wind, with more pressure away from the shore line.

Sea Breeze

The signs for a good sea breeze in the western Solent are a clear blue sky in the morning, with little or no gradient wind or a light north-westerly offshore wind. As the day gets older, cumulus clouds develop over the mainland, and by late morning or early afternoon a light sea breeze should develop from the south-west. On a hot summer's day, the sea breeze will often try to fill even when the underlying gradient wind doesn't favour it. One useful indicator is the horizon looking towards Hurst Narrows and the Isle of Wight. If this goes clear the chances are that something will happen in the next hour. The sea breeze tends to move in a line down the Solent from Hurst Narrows towards Cowes, and it's common to be sitting becalmed with spinnakers running towards you from the west. It will usually blow harder on the mainland shore first. It also cranks pretty hard, over 20 knots by the time it's got going mid-afternoon. When there's four knots of ebb tide running out against it, you'll know all about a day's racing in a Solent sea breeze.

Tide

This is often the win or lose factor in the Solent. And you cannot buy enough of the reference books we've recommended below. Knowing where the shallow and deep sections are, and using the tide effectively, is critical to gaining the advantage, so make sure that you are familiar with the race area. The basic deal is that the flood tide runs parallel to the shoreline, going to the north-east. It changes direction against the shore first, about 1.5 hours before high water at Portsmouth, and ebbing to the south-west. Shallow water will always provide relief, and as a general rule, it's easier to sail against the tide on the mainland shore. The reason is that the shoreline shelves much more slowly on this side and it's mud - you can get in further, and stay in for longer, than on the rock strewn island shore. The tide runs strongest in the shipping channel which is on the island side of the Solent. It can run at over four knots out there on a spring tide, and that puts a real premium on accurate layline calls.

There are plenty of wrinkles in the tide around the western Solent, most of which are covered in Boldre Marine's Solent Tides and various guide books, which are particularly good on this area. The change of the tide is also difficult to get right. It changes at the shore first, and then moves quickly out to the middle of the Solent, the whole process taking about half an hour. But the right place to be can turn into the wrong place to be in the space of ten minutes. A couple of the better-known tidal wrinkles include the strong tidal push off Yarmouth and by the Black Rock buoy; and the back eddy that curls around Hurst on a flood tide. But there are plenty more - buy the books.