By John Browning
January 28, 2003
Source: www.sailtexas.com/amcupcountdown2003.html

From where will the wind blow during the race, how will it shift? Should the boat favour the left side of the course for the first beat, or the right, and what side for the legs that follow? Hauraki Gulf is compared to sailing on a lake - there are no headlands but land surrounds the race course on three sides. South-west flow produces the greatest variation, wind coming across the Tasman Sea, over the narrow neck of land to the north of Auckland and into the Hauraki Gulf. In this direction land affects wind flow every time.

In seabreeeze conditions, strange things can happen. Because the North Island is so narrow to the west of Hauraki Gulf, seabreezes tend to come from the east and west, converging over Auckland as a thin line of showers. Typically, west coast seabreezes are stronger, but may not reach the race course until 4-6pm, as they tend to get trapped around Auckland Harbour.

Excepts from Alinghi [web page]: One of the factors that has been instrumental in Alinghi's success on the race course has been our formidable weather team. Headed by Jon Bilger, the team of 8 take to the water every day in their fleet of weather boats and head for the Hauraki Gulf.

During the period between the Louis Vuitton Cup and the America's Cup the weather team will be as busy as ever, gathering data from over 40 sources and trying to predict the conditions on this capricious stretch of water. During in house training days when both SUI 64 and SUI 75 are racing each other, the weather team functions exactly as it would during a real match. After a morning briefing to the sailing team, the weather boats head out to sea, station themselves at various points on the course and relay information to the race boats up to five minutes before the start. At the preparatory signal, the flow of information stops and decisions relating to wind and weather become the sole responsibility of the afterguard, in order to recreate the conditions in which the sailors have to race normally.

According to Jon, the secret weapon of the weather team is Numerical Modeler Dr. Jack Katzfiy and the weather prediction programme Alinghi have developed. Rather than just relying on historical data where atmospheric pressure points on a given day are matched with previous similar patterns to give an estimation of the weather, the Alinghi prediction software relies completely on current weather information. Every 6 hours a global weather analysis is collated from various sources around the world. This system breaks the earth down into 60 km square chunks and predicts the forecast for each area. The Alinghi weather team are then able to predict in detail what will happen across the much smaller 20km square of the Hauraki Gulf, and in particular on the race course chosen that day.

The Hauraki Gulf is an especially tricky place to make weather predictions, due to many unique variables. As the Auckland region is such a small strip of land in between the Tasman Sea and the Pacific, the thermal winds can be unreliable and sea breezes from both a South-Westerly and a North-Easterly direction occur. The presence of hills like the Waitakere ranges in the west and the Coromandel ranges in the East throws another dice into the pot. "It doesn't matter how well you think you know the Gulf," explains Jon, "It always throws something unexpected at you which is why the short term predictions we give the sailors and being able to read the water during racing are the most important things." - Alinghi

The problem for Murray Jones the "wind spotter" for Alinghi [and others] 100 ft up the mast "reading the water", the wind may not touch the water for a considerable distance after crossing land, and until it does, there are no "ripples" to be seen.

There is also a volcano and other hills to "split" an Ocean wind, not only into slightly different directions but with different wind pressures over the racing area. This may explain why OneWorld in the LVC Repechage lost the essential win or be dropped Race 4 against Oracle USA-76.

OneWorld, 1hr 10m 19 secs into the race led at windward Mark 3. On rounding they chose the left side of the course for downwind leg 4, USA-76 rounding 48 seconds behind choose the right side. All initially went well for OneWorld, four minutes later they were still ahead [by 45 secs]. Then it all went badly wrong, unable to cover [due to an even lower wind pressure in the 3,000 ft between them], it took only four minutes for USA-76 in a stronger wind pressure, to make up the 45 seconds plus another 15 seconds to be ahead, and to go on to win by a wide margin.

At this time, USA-76 still had its "Goose," the white housing looked like a goose on the stern overhead, dock gossip was that it was a Radar target acquisition/tracking device designed for the military. It may have held nothing...!

SODAR [Sound Detection and Ranging Radar] can measure the speed and distance of particles in the wind that carries them, as can LIDAR [Light Detection & Ranging Radar] and Doppler Wind Lidar [DWL], both use a Laser beam [in place of radio waves] to measure speed. While it is possible to design a stealth fighter and bomber, car owners can stealth treat the reflective number plate on their car - to reduce the distance that it can be detected [the Police Radar Gun is LIDAR], a sailboat with its sails, like a helicopter with its rotating rotor blades, impossible to make less visible to LIDAR. This may be the rationale to ban all forms of Radar from the LVC Finals onward on AC boats, if so, it has upped the ante in cost, hand held LIDAR's are not expensive, while the necessary data over some five years for a computer to access, costs a lot of money.

OneWorld was rumored to have a computer neural network [modeled on the human brain and nervous system]. A neural network uses a set of rules to be followed in calculation in problem solving operations. For an AC weather team in their support boats, subject to the computer having the immediate weather and Hauraki Gulf weather through the last five or so years, it should supply at a touch of the keyboard, what is possible, is it likely etc etc.

According to Roger "Clouds" Badham the Team New Zealand weatherman, every syndicate during the LVC upped the ante with up to six weather boats out on the course each day in the chase for weather knowledge.

Hauraki Gulf wind patterns are unparalleled anywhere else in the world and have been closely monitored and recordered, each challenger developed their own computer modeling program to forecast for the two hours of racing, wind pressure and shifts over the three upwind legs and three legs downwind.

But such outside information is only allowed to be passed to the AC boat prior to racing, at the Pre-start, all radio equipment has to be removed from the AC boat and into a Team's waiting tender.

To read related articles on weather information used for America's Cup racing, see Decoding Auckland's Weather, or Auckland Weather.