Inside an America's Cup team: Alinghi's weather team

For the third installment of our "Inside an America's Cup team" special section we visit the base of Alinghi, the America's Cup defender, in order to talk to Jon Bilger and Jack Katzfey, head of the weather team and meteorologist respectively. Both men were also part of Alinghi in the previous America's Cup in Auckland where they played an important role in the Swiss challenger's defeat of the New Zealand defender.

Most of the basic terms used in this article have been defined in the first installment on weather in the America's Cup and can be found here.

Meteorological data gathering

A very important aspect we didn't address in our first article was the question of weather data. In order for meteorologists to build their models they need a detailed set of data on current weather situation. How does an America's Cup team gather all the detailed data needed to follow and forecast the wind in Valencia?

A great novelty in this America's Cup, as far as the weathermen are concerned, is the existence of MDS, the Meteorological Data Service. MDS is a set of 21 purpose-built buoys spread around the north and south race courses as well as 6 inland base stations providing almost real-time weather information to all 12 teams. Every 15 seconds each buoy and station records and transmits wind direction, speed, barometric pressure and humidity and each team instantly receives this data.

Even for the Defender of the America's Cup this does make a difference. During the 31st America's Cup in Auckland Alinghi had 7 boats that crisscrossed the Hauraki gulf to get valuable weather data, while in comparison here in Valencia they use three of them, mainly to gather data from specified positions in the race area not covered by the buoys or further afield. Prior to the creation of the MDS the most efficient way to collect such data was the deployment of as many as possible weather boats. Each team, even the ones with the smallest budgets, has now access to an incredible wealth of accurate meteorological data without the need of dedicated weather boats.

Alinghi's "weaponry" in gathering meteorological data. On the left, one of the 21 yellow buoys of the MDS spread around the south and north race course. In the center, the large weather boat whose antenna is 24 meters high and on the right one of the two smaller weather boats. Photo copyright Ivo Rovira / Alinghi

Still, Alinghi can gain a compettitive advantage by deploying their weather boats and gathering data from spots not covered by the MDS or by using more sophisticated instruments. An important tool is their largest weather boat with a 24-meter high antenna. The mast of a typical America's Cup yacht is approximately 32 meters high and it is not rare to observe considerable variations in wind speed and direction between the sea level and the top of the mast. As a result the top of the 24-meter antenna is much closer than the 6-meter high antenna of the buoy and can provide much more accurate data.

Another advantage the MDS gives is the ability for any team to have real-time weather data on the race course during an official race. According to the America's Cup rules all weather boats must leave the course before the start of the race. As a result, up to the 31st America's Cup it was impossible to have an exact view of what happened during the race as far as weather was concerned since no detailed gathering of data was possible. On the contrary, thanks to the MDS, all teams have now the ability to see the real-time wind conditions in various positions throughout the race course even during official races. This data cannot be used by the racing yacht but still the weather team can check the validity of their forecast and, equally important, the sailing team can analyze it at the end of the day and discuss their tactics during the race.

The Spanish national port authority has also set an additional 2 seawatch buoys to provide wave and current information for the race course area. On the left-hand column of our website and under the "Valencia Guides" section you can click on the link and see the buoy's data real-time. Last but not least, the city of Valencia has provided a wind profiler that provides wind shear information every 50-metres up to an altitude of two-kilometres, located at the entrance of the new canal.

Alinghi's weather model

Alinghi uses a weather model developed by CSIRO (Commonwealth Scientific and Industrial Research Organisation), Australia's national science agency and one of the largest research agencies in the world. The relationship between the Swiss team and the Australian national research body dates back to 2001 when Bilger, head of the weather team of then challenger Alinghi, was looking for a weather model to use in order to forecast wind. Katzfey was then a researcher at CSIRO's Atmospheric Research department and a promiment specialist in regional weather modelling. The two decided to join forces and as a result Katzfey moved to Alinghi where he is now in charge of building and running the weather model.

According to Katzey, the CSIRO model has proved to be very successful both in Auckland and here in Valencia. Through the 5 years it has now been in use it has been optimized and improved and is now capable of producing a 24-hour forecast with a resolution down to 1km in approximately 2 hours. Alinghi doesn't rely on any external computing power (as far as the weather team is concerned) and its model runs on a cluster of computers located right inside the base in Valencia. The model was originally developed to study climate change in Australia and as a result it had to be extremely efficient and fast as it would have taken a prohibiting amount of time to make large-scale forecasts. This is the reason it runs so fast (compared to other weather models).

Alinghi's weather team briefing the sailors on the day's forecast. One of the most important moments in the workday of any America's Cup team is the daily morning briefing. Photo copyright Ivo Rovira / Alinghi

The Alinghi weather team doesn’t need to go too far afield geographically in its model. In general Alinghi’s weathermen study the patterns up to central Spain, the south of France and the Balearic islands. A system in nortwestern Spain, 400km away, will not necessarily have influence over Valencia and for the America’s Cup there is no necessity to have such a geographically expanded view of the weather, it’s more at the local level that differences matter.

Concerning the time frame of their forecast, Alinghi’s weathermen start with a 8-day forecast in order to get a “general idea” of developing weather patterns and then focus on the first 2-3 days. Still the most important task is to correctly predict the following day. Sea breeze being the primordial factor to watch it is very difficult and unstable to predict it further into the future. It all comes down to the precise knowledge of wind direction and speed.

A non-specialist could naturally wonder why the Swiss team doesn't refine its model even further in order to be able to forecast changes in a scale smaller than the current 1km. According to the Alinghi weather specialists there are two main reasons why this isn't feasible. First of all, as its geographical precision increases, the number of mathematical equations rises exponentially, making it extremely time-consuming and impossible to obtain results in a reasonable period. Secondly, the model cannot be more precise than the input data it uses. Since the input data for the model are raw weather measurements, an America's Cup team would need to have them more densely collected which would also become impractical and expensive.

Valencia compared to Auckland

Being the first time an America’s Cup is held in the Mediterranean sea, let alone in Valencia, and given the presence of both weathermen in Auckland in the last America's Cup it was an obvious question for us to ask them to compare wind patterns over the two cities.

In Auckland the weather is subject to many variations, with wind speed increasing from light to strong in a short time and big directional changes during the day. There is a relatively small land mass with weather systems going across it very quickly and the local geography is also complicated, particularly due to the fact it’s a bay. Having said that, both men were quick to add that Valencia’s weather was by no means much easier to predict. It is true it’s an enormous land mass with smaller variations, especially in summer, but still many local factors have an important role in shaping wind patterns.

In Auckland when you woke up in the morning you didn’t know what direction the wind would come from while the only thing that is almost certain in Valencia during summer is that wind comes from the east and extremely rarely from the west. Nevertheless, when you forecast wind for an America’s Cup campaign this is too rough an approximation, what you really want to know is exact wind speed and direction, still very difficult to precisely predict even in Valencia.

When asked whether Valencia lives up to its promises as far as wind speed is concerned, Katzey did not hesitate to qualify local conditions as “spot on what we anticipated”. Having taken part in the selection process he thinks there is a “common perception” Valencia would turn out to be windier than what it really is but he always knew the mean would be around 12 knots and that is what we have been getting so far.

Closeup picture of one of the 21 weather buoys. Their mast is 6 meters high and this particular one on the north race course is the closest one to Valencia's main beach. Photo by Pierre Orphanidis / Valencia Sailing