TRANSPAC 2001
During Transpac 2001 "Local Knowledge" will post updates of wind and weather conditions, boat positions and routing analysis. Prior to the first start, we will post weekly weather shots and routing computations based on the forecast for that week. All routing computations are performed with our "Force 4" offshore tactical program. For further information about Force 4, last year's Pacific Cup and this year's program, see www.goflow.com/pacific.htm. |
EXAMPLES OF ROUTING ANALYSIS: FOR ACTUAL RACE ANALYSIS, CLICK HERE
| Pacific Wind & Weather Forecast for 4/17 at 00 UTC. This web satellite image was converted into an electronic "chart" with Force 4's "Chartmaker" utility. The rhumbline (red line) and great circle route (blue line) are shown start to finish. |
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| "Best Course" Routing computation by Force 4 for ILC 46 polars and MRF wind grib file. The program calculates a fastest route (red) and several alternatives for comparison (total times in box are color-coded to route). There are a number of options for defining alternative courses. In this case they are constrained to sectors around the rhumbline for the first 40% of the distance, after which they can take the optimal route from there to the finish. There are normally 5 alternatives, but in this case the "magenta" route coincides with the "red." Wind vectors are shown at the start (1900 UTC on 4/16) drawn from the grib file. |
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| The graphic below shows the same solution 3 days after the start. The black dots on the various routes show boat location at the common time (22:29) indicated in the bottom of the box. Note that the high to the NW at the time of the start has moved SE, impinging on the red route, and the high originally to the SE has moved further south, replacing the "hole" there with stronger winds. One thing a good "router" can do for you is to balance wind conditions over the entire period of the race to come up with the best overall solution. |
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| Same solution a couple of days later. Note that the red route, which took advantage of the strong winds associated with the low northwest of the start, has managed to stay below the NW high and is well-positioned to reach to the finish. At this point the "red" boat is some 951 nm from the finish, compared to 1313 for the "green" (last column of box). Were it not for the stronger winds now in the SE, the "green" route would be even slower. |
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| The "Chartmaker" can build many alternative "charts," each a lot more informative than a bare "lat-lon" grid. The graphic below shows the routing solution overlaying an infrared satellite weather image (GOES IR) from the web. |
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| Routing solutions depend on weather
forecast (grib) files and the performance characteristics of your boat. A fast boat may
get through an area before a high arrives there, while a slower boat may have to
anticipate that and route around the area. With Force 4 you can calculate a route tailored
specifically to your boat (for the computer-phobic, we can do the computation for you and
deliver a routing solution to you at the start). FOR MORE
INFO, CONTACT: David
Brayshaw - Local Knowledge Marine Software -
Or, check our website: www.goflow.com |