Quiet anchorages are becoming hard to find, but if you look at the chart and study the weather forecast you can still enjoy the real taste of cruising with the anchor down, a quiet drink in hand while you watch the sun set.
Not all sheltered bays and coves offer the same degree of protection, however. You need to choose with care, particularly if the forecast is deteriorating. So what factors are you looking for when selecting your hopefully, quiet anchorage for the night?
Obviously wind direction and strength will have a direct bearing on finding the shelter you want. If it’s not forecast to drop away during the night, you will at least want to see signs in the forecast that the wind is veering or backing towards the land so that even when it changes you will still be lying in the lee.
Where things can become uncomfortable is when the land influences the wind blowing over it – raising the wind strength and shifting its direction.
The wind can accelerate when it is running downhill. Over high ground, such as a mountain, the air is colder, and therefore heavier, at the top and wants to run downhill. It can accelerate quite dramatically on the way, so it could arrive at your location as a fierce (katabatic) squall. At best, it could make life uncomfortable, with the boat heeling and swinging; at worst the anchor could drag. These squalls can be fierce enough to stir up spray and small waves on the sheltered water and you can see them travelling across the water.
There can be a similar effect with valley winds. An offshore wind will tend to focus on the valleys rather than on the higher ground in between. Again, the colder air on the higher ground at the head of the valley wants to find the easiest path down under the warmer air, so will accelerate down along the valley floor.
It is not just the wind that you are sheltering from in an anchorage, but the waves. Just a light swell or chop is enough to mean you spend the night rolling and pitching. It is easy to think that if the waves are coming from, say, the west then you’ll find shelter if you tuck in behind a headland on its east side. Of course there will be shelter from the worst of the sea conditions on the lee side, but waves have a nasty habit of creeping around headlands and invading supposedly quiet anchorages.
The culprit here is wave refraction. Waves in the open sea tend to head in the same direction, but when they encounter shallow water they slow down. So when waves pass a headland, the inshore end slows while farther offshore it travels. This causes the whole wave to alter direction, wheeling round the headland and into the shelter behind.
These refracted waves are not likely to be dangerous – as they slow they lose energy. They are likely to be more akin to swell in the anchorage but that can be enough to make life uncomfortable for you. If you choose to anchor in the lee of an island things can get more difficult because refracted waves can come around both sides and generate quite a nasty area of crossing waves on the lee side of the island. This area is likely to be a little way downwind from the land and you might find a quiet spot close inshore if there is enough water.
No comments:
Post a Comment