Excerpts from comments on "weather routing" by Brice Pryszo, founder of MaxSea International.
In 1984, when I designed the “isochrones” routing algorithm method, the only existing routing solutions required the use of powerful shore-based computers which basically tested millions of routes to choose the best one. This required power and time then not available on board sail boats. The MaxSea routing algorithm was designed to be executed on a personal computer.
The very first time that I tested the MaxSea weather routing algorithm was during the trans-Atlantic race “La Route de la Decouverte” with Philippe Jeantot onboard Credit Agricole. Philippe was late arriving at the Canary Islands due to equipment failure. The fleet leaders, 24 hours ahead, were sailing WSW in nice 10-15 Kt trade winds, south of a low pressure system (as any smart sailor would do).
Meanwhile, the MaxSea weather routing algorithm sent Credit Agricole NW, straight into unsettled weather and unstable wind, up to the cold front of a deep low pressure system. The first hours were not welcoming but behind the cold front, a 20 Kt North wind pushed the large catamaran at twice the speed of the remaining fleet. Two days later, Credit Agricole was leading the race by several hundred miles. At that time no experienced navigator would have chosen such a solution!
Another astonishing example of the power of routing occurred when we tried to optimize an Atlantic passage West to East with regular high pressure mid Atlantic. As any good sailor knows, routing should begin by passing around the high pressure using a northerly course. Instead of following the quiet sailing to the east, the weather routing plunged the course to the south, straight into the low pressure center. Before reaching ineffective wind, the MaxSea routing jibbed the boat port into an increasing breeze perfect for reaching, making her route much faster than if she had taken the northern route with a downwind slog.
These two incidents had a major effect on sail boat racing results. Today, using routing is absolutely necessary to be competitive in ocean and long distance races. Routing has also proven to be great tool for cruisers because it greatly enhances safety and comfort. Routing can exploit user-defined characteristics and create what we call “cruising” or “safety” polar curves. Utilizing such polar curves the routing will do all it can to find a path which avoids strong wind. This is beneficial because strong wind is generally surrounded by medium wind in which the boat is faster allowing her to “escape”.