5 expert tips: A professional’s guide to weather routing

Highly successful professional navigator Simon ‘Si Fi’ Fisher gives Andy Rice his five top tips for race-winning weather routing.

Whether you’re preparing for a race or even just a leg of a longer race, there’s always a process for planning your routing, says Si Fi. “I’ll start looking at the forecast and the different weather models about five to six days out from the start. It’s vital to do some wide-ranging research, taking a look at the overall weather pattern and where the models agree or disagree, but it’s also important not to get to the point of paralysis by analysis.”

He uses a range of technology to plan the routing, but advises a KISS (Keep It Simple, Stupid) approach. “Most of what I do is based around Expedition and Adrena. I think one or the other will serve most people’s needs very well. Ultimately it is better to know the tools you’re using well as opposed to trying to use every software tool available.”

The ever-accelerating advance of AI will doubtless revolutionise weather routing at some point but he warns of becoming too reliant on the latest technology as good seamanship and sailing skill will still often trump the technology.

Fisher still has the skills to navigate with sextant and stars, although he admits: “I haven’t tried it on the new generation of high-speed foilers like the IMOCA. I suspect trying to get a steady reading while you’re bouncing along at 25 knots could be quite challenging!” he laughs.

Choose weather models

There’s a huge range of weather models, but the two main ones for the global stuff are the EC (European) model, and the GFS (American) model. Then there are the UK and French models to consider too. These are the best models for looking at routing when you’re well offshore, but when you get closer to shore, and closer to race start day, there’s a whole range of higher resolution local models worth looking at.

Most people tend to lean on the EC and the GFS models because they’re the most available and relevant over a period of longer than 24 hours. GFS is completely free and runs four times a day. The EC also runs four times a day but is typically available to download only twice a day.

I’d normally use these two models initially to understand how the weather is working and the main features in play. Then in the last 24 hours before a start I’ll look to the higher resolution models for more detail and fine tuning of the strategy.

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Do the models agree?

When you’re preparing for a race, look closely at what the different models are saying. How much do they agree or disagree? If you’re five days out and each model has multiple different answers, you can be pretty confident the forecast is going to change significantly in the coming days. But that uncertainty can be useful in determining what to focus on.

In the days preceding a race I run different models through routing software to see how the answer changes both from run to run and also day to day. Is one model trending towards another, or are they converging on the same answer? You can be most confident where all the models agree, but if they aren’t in agreement you can often draw a little more confidence from the model which is moving the least from day to day. Consistency can often indicate more accuracy for that particular scenario.

Ensemble modelling

Ensemble modelling is another useful weapon to have in your armoury, particularly for ocean races. GFS and EC have ensemble forecasts where they start with an initial ‘control’ model, and then tweak the initial conditions very slightly. What you end up with is 30 different model forecasts in the case of the GFS, or 50 in the case of the EC.

It’s a useful tool to see when and where the forecast diverges over time. Running multiple routes, and seeing how tightly packed or spread out the routes are, provides valuable insight into how many strategic options are possible and how consistent the deterministic forecasts are likely to be.

Often you’ll see one or two groups of tightly packed routes, which gives an idea of where the most likely options are going to be. Where the ensemble forecasts or associated routes descend into chaos after a certain number of days will at the very least tell you things are going to change and that you’ll need to keep your options open and not be too radical.

Talk it through

Besides looking at scenarios in more than one way, at a human level it’s always good to discuss routing with a wider group of people. On The Ocean Race programme, we tend to work with a bigger team on the shore side, with assistance from professional meteorologists and other navigators.

But there’s always a certain amount of chat between the guys in the race – whether it’s your teammates or rivals – because you’re all in a similar position. Of course at some level everyone wants to keep their cards close to their chest, but it’s good to share ideas and get a feel for what other people might be looking at or worrying about.

Manage your risk

Good routing comes down in large part to good risk management. A big part of that is how much risk you place on the weather forecast or a routing option, versus what the rest of the fleet is doing. It’s a strategy versus tactics trade-off.

Some decisions and routing options might give you a big win if they work out, but if they don’t then you lose everything. There’s often a safer option, or one where you can cover the fleet better. Very often it’s prudent in races to give up a few miles if you’re ahead, to make sure the fleet can’t get past you.

I can’t stress enough how important it is to always keep your head out of the boat when you’re on the race course. You always need to be prepared to modify your strategy based on what’s going on around you, whether it’s the weather, your boat’s performance or your competitors. The race winning strategy will have to factor in all those things.

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