the weathermen

ryan map 2Co-skippers Ryan Breymaier and Renaud Laplanche just broke two important ocean records this month together with their international team : Cowes-Dinard, a sprint across the English Channel and Newport to Bermuda, which is quite a bit longer, and requires a longer (therfore more unsure) weather window..

As their onboard-navigator I wanted to drop a line of acknowledgement to the guys ashore who help us pick the right weather windows and give some insights into the products/methods we employ.

We use a program called “Squid“ that, just as Ugrib, allows to download weather data. The package is very comprehensive: High resolution models, colorized satellite pictures, observations, synoptic charts and various weather models with sea temperature, waves, currents, etc… all in one place. The software as well as all the US-data is free at www.squid-sailing.com. For some models you need a subscription or special deal with “Greatcircle“ the company behind Squid. We purchased a special license to have access to the European Model (ECMWF).

Greatcircle was founded 2010 by offshore racing enthusiasts from France and Belgium. Ryan and I got to work with them in the very beginning during the preparation of our Barcelona World Race. Nowadays the company has been in the market for quite a while, and gained momentum as supplier of major ocean races like the Volvo for example. They do climatology studies (e.g. to answer what kind of sails you should bring on a round the world record), routing, consulting and a product that was really helpful for us, called: “best start“.

Not having a fixed start time or a race start imposes a question rather unusual for regatta sailors: “When should we start?“. The same question you might have delivering your boat across a long passage as the Atlantic or any other ocean.

Of course we do routing to elaborate the best possible scenario over the upcoming week or so. But the weather models change from day to day and the last thing we want is to fly 10 people in from different countries with all the associated transfers, accommodation and so on, get the huge multihull off the dock with the assistance boats to be ready at the start line to then find out the “model was wrong“ and we could not start.

A way to approach this is ensemble-routing. In addition to the “deterministic“ model run that most people use in everyday sailing the weather models like GFS and ECMWF also publish “ensemble“ results. This is a set of different results in opposite to the one deterministic result. The set is generated by slightly varying the initial set of data that starts the model and is supposed to represent the possible spread in the result due to the uncertainty of the forecast.

This allows us for instance in the case of the european model to run the routing with 51 slightly different models to “test“ the spread of the results. This approach allows us to draw a “probabilistic” conclusion like: “we would beat the record with 70 % probability on that certain departure date“.

While the GFS ensemble is freely available through Squid the ECMWF is again quite expensive. Then, one thing is to have access to them the other thing is to use them. They open an interesting angle on weather prediction – for instance to evaluate where geographically the models will be more or less reliable – but this becomes quickly a very time consuming exercise.

This is where the “best start“ product comes into play: Greatcircle’s servers do all the routings and sum up the results on a tidy pdf chart. This custom product for our specific record considers a certain wave height limit, our polar, exclusion zones and so on. (see picture / pdf: This graph established on April 12th shows the window on the 19th that we finally took: it gives a 50 % probability to be under 24 hrs for a start on the 19th at 0600z; we finally started at 0534z on the 19th)

Still, all the worlds computers and data will never render the input of experienced weather people obsolete! We had the pleasure to have Wouter Verbrak at our side for the English story with all his local knowledge about the Channel and the region. Since my first days racing on the ocean good friend and professor of meteorology Ralf Brauner from Germany has an open ear for our thirst of knowledge. Finally the great team from Greatcircle who share now many of our adventures sometimes working hard through nights and weekends to make our requests possible. They share the passion about ocean racing. – Boris Herrmann.