Thinking about wind

We were planning to deliver Karisma to Milford Haven this weekend. The boat is ready, I victualled her yesterday and, as Jenny is out of sailing action because of Eira’s arrival, our pal Julie was coming to help me get the boat west. But, as so often happens in the Bristol Channel, the weather- that is, the first real blow for a couple of weeks- forced some choices, and none of them terribly good.

Julie’s excellent suggestion to head off overnight yesterday (Friday) direct to Milford was scuppered by forecasts showing the weekend blow moving into St Anne’s Head before we could get there, making our destination a lee shore in a fair old bag of wind. So I figured we would go to Swansea today (Saturday), which was a good idea except for a couple of problems: one, it isn’t Milford and two, it has lock closures over low water this weekend. Until yesterday, the forecast suggested we’d have light winds on Monday, so it looked like we could sail to Swansea, skip Sunday and complete our delivery to Milford on the bank holiday Monday. Worth the effort to get there, then. This morning though, the forecast showed a hard westerly blow all day Monday, meaning we’d be (at the moment) indefinitely detained in Swansea. This was the story of our 2016 sailing season, and I have to admit being less than keen to repeat it. Going today also meant arriving a couple of hours before the Tawe lock would let us in, and in a southerly blow the only possible shelter being to enter the river. That would risk running aground on low springs and maybe not even finding any shelter anyway. Or sail in circles in a rising wind. Finally I took a look at the Met Office inshore waters forecast: “strong winds are forecast…. force five or six from the south….. seven later… moderate or rough”, that sort of stuff. Even though Julie is a Yachtmaster and a much better sailor than me, it’s still the sort of stuff I always say we don’t sail in. Yet I’ve sailed in that sort of stuff offshore on plenty of RORC races… and yet, that was all on pretty big yachts. Perhaps it’s the sort of stuff I just don’t skipper in; or I don’t skipper a relatively light, small boat like Karisma in. I don’t really know.

In the end I canned it for the weekend, ultimately because I wasn’t really sure getting to Swansea was a better idea than staying in Penarth. But it’s another one of those fifty-fifty weather decisions which have got me starting to loathe the inner Bristol Channel. There are no harbours of refuge and everything is a lee shore most of the time; you spend your sailing life trying to second-guess the GFS in the various chunks and snatches of time you are able to put aside for sailing. Can we get from here to there before that window closes? When can we get from there to elsewhere? Will we be stuck somewhere? With a young family and a busy life, we just can’t sit and wait for weather windows. The unfortunate truth is, we need them on the weekends. Today would have been a bit of work, but we would have got to Swansea. But I’d rather be stuck in Penarth than Swansea, and stuck for this week at least we would be. Go or stay, stick or twist, round and round and round. The boat’s still in Penarth tonight, and we will try a direct overnight delivery (so we are not constrained by the tides) as soon as we can. But when you have a pal coming as crew, you can’t expect them to keep life constantly on hold for weather windows either- it’s not fair. Round and round and round.

So how much of this is an impression about the Bristol Channel that doesn’t hold up, and how much of it is a real picture of the wind and weather here? Well, I figured I’d try and get some actual wind history and compare it to someplace which gives the impression of perpetual light winds- that, of course, is the Solent. It is the centre of British yachting and you have to suppose that the weather has something to do with it. Sometimes it seems that almost everyone is there (certainly, and at least from a BC perspective, it often seems there’s nobody else here).

A bit of internet digging quickly made it clear that if you want this sort of info from the Met Office you had better be an academic or willing to pay for it. Being neither (and proud of it), further digging found a useful site called Rensmart.com. It is aimed at the renewable energy industry and nothing to do with sailing, but it carries an archive of wind speed data, gathered hourly, for the ten years between 2000 and 2010 for a good number of locations around the UK. After downloading the data for Cardiff Airport and Southampton EGHI and fiddling about in Excel (to convert m/s bins to Beaufort forces) I got this chart.

What’s quite interesting about this is that winds above F4 are pretty rare both in the BC and the Solent; big blows are a little bit more common in the BC but not terribly so. What is striking, though, is that the wind speed is less than F3 for an astonishing 45% of the time in the Solent, versus just over 20% of the time in the BC. So while big blows in truth are relatively rare in both locations, the real difference is that light winds are very, very common in the Solent. In fact, according to the rensmart dataset, they are more common here than in any of the (generally representative) locations I looked at, across the UK.

Light winds of course open up those weather windows, and together with the density of harbours, there’s no better way to make each precious weekend count. I can’t see that we’ll ever base Karisma in the Solent- it is too far from home and too crowded, but you can see the attraction. Especially after another crappy trudge home to stare at the GFS.