How To: Understanding Rough Water: Force Three

When writing the article on how to swim in rough water, I acknowledged that it’s an area I need to do a bit more about. And the popularity of the post caught me a bit by surprise, as it always does when such happens. But I wasn’t sure what I could do next. After all while I love writing about cold swimming, and it continues to provide me new avenues of investigation and expression, rough water is just rough water.

On last Saturday’s visit to the Guillamene, a swim I didn’t want to do, because two days previously I’d had a bad asthma attack while pool training, (for the first time in two years), and I didn’t feel I was recovered. Also, though the start of the fourth week of May, the water temperatures were still down, only nine degrees the previous weekend, worse the air temperature was low, only ten degrees, with a north-easterly wind. When you live at fifty-four degrees latitude, northerly winds are always cold. It felt just like winter and when I measured the temperature at the Guillamenes, it was on a par with the air temperature, ten degrees, yes a rise over the previous week, but with the chilly wind and the lowering dull grey sky and no-one around, it was less than inviting.

And as I said, the wind was north-easterly. As this point it’s useful to show you (again) how the Guillamene is situated.

Tramore Bay

The bay faces south-west (directly up is North in this image), the Guillamenes is on the west wide, so looking out from the platform you are facing south-east. It’s sheltered from the prevailing south-westerlies, but exposed to south-easterlies, easterlies and even north-easterlies.

The bay is just under five kilometres wide from Newtown Head to Powerstown head, a not-insignificant distance. Therefore a Force Three north-easterly wind will have about four kilometers of water to blow over before it reaches the Guillamenes. You may recall we discussed this in Understanding Waves for Swimmers a long time ago. The distance of water over which water blows is called the fetch. The greater the distance over water which wind blows, the greater the waves and chop that can be pushed up.

Apart from the fetch, the strength of the wind is important. I have long thought the ability to observationally measure wind using the Beaufort Scale should be an essential skill for serious open water swimmers.

Force Three on the Beaufort Scale is also known as a “gentle breeze”, a more pleasant title. Force Three is however a critical measurement for open water swimming because at Force Three scattered whitecaps start to appear, as crests start to crumble from the wind. This means an increase in rough water to the swimmer. (If you see choppy-ish water with no whitecaps, it’s Force Two). Below is a very boring picture of all these facts! A Force Three wind, blowing onshore, across a four kilometre fetch. It’s full size if you click on it and want a better look at what Force Three looks like, but it’s pretty unexciting. If you look around you’ll see those occasional whitecaps.

You can of course swim in Force Three, but you’ll be slowed down. It took me almost twenty-five minutes to pass the pier, where it would normally take twenty. I call Force Three critical because it’s the transitional point into rough water.

And because video is better for this, here’s a short clip. (With the wind blowing across the microphone, you might want to turn your volume down first).

This second video is taken from the water. However, this was taken underneath Doneraile Head, and the fetch that wind was blowing across was less, so though the wind was the same, and blowing the same direction, the waves were less.