Crossing oceans in a sailboat is a complex dynamic problem with the boat’s progress depending on the evolving wind field and the current. In the past, sailors have had to plan voyages based on pilot charts which indicate the prevailing conditions and for the prudent sailor the range of expected conditions. Unfortunately, prevailing or climatological patterns never occur . On a given day, the variety of conditions across an ocean are defined by the weather for that day - the individual highs, lows, clouds, rain etc. This daily weather does not look like the pilot chart climatology which is the aggregation of these weather events. As another thing that Mark Twain probably didn’t say "climate is what you expect - weather is what you get".

Climate statistics were put together as a means to summarize expected conditions and are invaluable in understanding the distribution of weather conditions at a point. In sailing, however, you are never at one point long enough to enjoy the climatology for that point. You sail in the evolving daily wind field. In the past, pilot chart type climate statistics were the only way one could comprehend the thousands of hours of different weather events. Today, however, relatively powerful computers available to most sailors at home coupled with a sail boat simulator allow the sailor to experience the historical weather data from a quite different but practical point of view.

The following describes what appears to be the first sailboat simulator tied to a 40 year world weather data set that allows the sailor to sail across an ocean experiencing actual winds as the boat sails through the evolving wind field. For example, a sailor planning to sail from Boston to Gibraltar in late May can select a year, a weather window to start the voyage, then sail through the weather systems experiencing the head winds, following winds, calms, gales etc. that all occur that year on the voyage. The sailor may make this sail forty different years, if he desires, to see the best and worst the Atlantic has to offer. This is a totally different way of viewing the climatology of a voyage.

In the relatively recent past, accessing large volumes of weather data required big computers and special archival techniques that were only available to government agencies or universities. Even in these environments consistent true global data sets spanning many years were difficult to find. In the past ten years, however, due to concerns about global climate change, scientists have made a tremendous effort to consolidate and reanalyze in a consistent manner weather data through several past decades. The weather data set used in this software package was derived from one of these reanalysis data sets. In the sailboat simulation system this voluminous data has been reduced to only the data of interest to sailors.

The sailboat simulator in this package was designed to replicate the characteristics of a sailboat important to a transoceanic crossing. That is, details about acceleration are largely irrelevant. The sailboat dynamics are based on a set of four differential equations that incorporate such factors as wetted surface area, heeling moments, gravity wave drag etc. Actual hull hydrodynamics are ignored except through keel and waterline length considerations.

A variety of sail boat types can be selected from heavy displacement cruisers to light racing sled designs. Factors such as stability, hull speed, drag etc. are derived from the selection of the boat. Spinnaker sets and reefs can be accomplished. Rudimentary sail trim is provided to allow the sailor experience the range of beating, reaching and downwind sailing encountered.

Graphical depictions of windexes and compasses are provided to give a realistic feel for the sailing. The sailor can sail by the relative wind on the windex and see the response on a compass of turning the boat and of the changing wind conditions.

Graphical representations of angle of heel and sail trim are provided.

The interaction of the boat and the weather is accomplished through a primary window that provides the:

• Boat Location

• Boat and Sail Attributes

• Weather Field Depictions,

• Wind Speed and Direction

• Current Speed and Direction

• Heading and Speed

• Actual Direction and Speed

• Sky Depictions

•  Wave Heights

•  Tropical Cyclone Positions and Winds

Four panels of weather information are available:

• Wind Vector Fields and Color Contours of Wind Speed

• Clouds and Precipitation

• Surface Pressure Map

• Sea Surface Temperatures and Seasonal Current Data

Each of these images can be zoomed.

For the sailor planning an offshore passage - take trial voyages in different years to explore the range of conditions likely to be encountered and length of voyage.

For the racer planning an offshore race - explore different race strategies, learn to respond to the evolving wind field, test running to the Stream versus the rhumb line. Race the disastrous 1979 Fastnet. Race the Whitbread or BOC and try to beat the winning boats.

For the sailor trying to learn about weather and forecasts - use the forecast mode to learn how weather evolves. Probably the best and most practical way to learn meteorology - not boring.

For the armchair sailor - this is probably the ultimate armchair experience - round the Great Capes of the World - even the Horn. Reenact Sir Francis Chichester’s and his Gypsy Moth around the world voyage in 1966 or even the Jack Aubrey and Stephen Maturin adventures (using 20th Century data)

For the computer gamer - race against a friend - try to beat their elapsed times around the world or across oceans.

• Windows 95/98

• 32 Mbytes Memory

• CD ROM Drive (12x or higher preferred)

• 50 Mbytes Hard Disk Space (10Mb minimum running from CD)

• 100 Mhz Processor or higher