The wind was up and down
Wind gusts that would go virtually unnoticed by those walking around on land can play havoc to those traveling on a sailboat. This we know from experience! As I wrote in the last post, it was a big wind gust that caused the damage to our boat on Friday. We had an equally gusty day on the water yesterday, making for a sometimes exhilarating, and other times frustrating, sail.
When wind increases in velocity, the force exerted on a boat’s sails increases exponentially. As an example, a 20 knot wind applies four times the force that a 10 knot wind does. Yesterday, we frequently saw the wind drop to less than five knots. In fact, we were stopped dead in the water on multiple occasions, drifting with the current. Just as often though, the wind would suddenly jump to over 20 knots, the highest we recorded was 29.2 (true, not apparent). Fortunately, after the trouble we had the previous day, we had the foresight to begin the day with our mainsail reefed and only our little jib flying.
Although this is the lowest wind velocity I snapped a pic of, there were several times when we had no wind at all!
Our gauge recorded 29.2 knots as the highest but both Rebecca and I both saw it gust to 29.8 for a few seconds.
Why is the wind so gusty here? I’m nowhere near an expert on weather conditions but I’m going to speculate a bit. If I’m wrong, feel free to call me on it.
The high mountains along the coast no doubt have an effect on the wind here. Even though we were sailing on the protected side of the island (the trade winds blow from the east and we were sailing on the west side of Guadeloupe), they say that the wind on the lee side is effected by the land for a distance of seven times the height of the land mass. In other words, if the hills along the coast were 500m high, and many of them here are quite a bit higher than that, we would need to be 3500m offshore before we would have wind free of the land’s effect. At times strong winds can flow down off a mountain slope, much like a stream of water runs downhill. The name for this effect is Katabatic and my guess is that at times, this is what we were experiencing.
In addition to the land effect, the sky yesterday was littered with big, puffy cumulous clouds, some of which were quite dark and carrying rain. We have learned from past experience that the wind often increases sharply when passing underneath clouds like this. Yesterday proved to us again that this can be true.
Rain in the distance as we tack in towards the shore. We tacked again to avoid all but a sprinkling.
As I said, gusty conditions are definitely not favorable for the cruising sailor. Sails can be set for either light winds or strong winds but when the wind velocity changes abruptly, especially when it increases due to the effects I described or for other reasons, it can cause problems. In our case yesterday, it meant that we had to hand steer for the entire trip, and consistently be on our guard. It was not a relaxing day of traveling.