'Luna Rossa rounds mark one in the 6th race of the Louis Vuitton Cup Final on August 23, 2013 in San Francisco California.'
© Linda Wright
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Predictwind indicates that winds will build earlier than normal and are expected to be close to the limit for sailing at the start of racing at 1.10pm on Saturday for Day 7 of racing in the Finals for the Louis Vuitton Cup between Italian Challenger Luna Rossa, and Emirates Team New Zealand.
With the racing back to it regular start time of 1310hrs the two feeds produced by Predictwind indicate that winds will be averaging 16-18kts, and will be gusting higher.
The key to the day is whether the wind will build at the rate the forecast indicates. It is predicted to build much earlier than previous days.
The top image shows the wind speed and direction at 1300hrs with one feed showing winds of 22kts while the other is at 23kts - these are only average speeds and gusts will be higher. There is a little variation in the forecast indicating a higher degree of certainty as to the outcome.
The key feature of the forecast is the breeze starting to build much earlier in the day with both feeds indicating the breeze will be 18kts at 1000hrs and then buolding at varying rates over the rest of the day, before reacing a peak of around 25kts at 1500hrs.
The first image shows the wind prognosis for the scheduled start of the second race.
The second image shows a graphic representation of the wind build - confirming the numbers for the prognosis.
The next two images are showing the same style of information except for an hour later around the time of the second race for the day. Winds are creeping very close to the limit, and bearing in mind that these are only average windspeeds with no accounting for gusts, it is likely that the wind limit will be exceeded on the current wind information.
The fifth chart shows the wind expectations for the following day, Thursday, which shows a reduction in the strength of the breeze, allowing officials some scope to catch-up if required.
Two weather feeds are used by Predictwind, the key to the accuracy of the forecast lies with the graphs, as when the two lines for the two feeds are quite close together and following each other in the trend, then the likelihood of the forecast is high. If there is separation to any marked degree, then there still some issues to be resolved but usually 24 hours from the race they are well aligned.
The Predictwind model takes various weather feeds and then polishes these, part of this process is factoring in the effect of local topography on the breeze - well demonstrated by the image with the funneling of the breeze.
Developed by former Olympian, Jon Bilger (470, 1992), PredictWind application was used by the Swiss team Alinghi to win the 2003 and 2007 America's Cups, and has become the leading wind system used by racing and recreational sailors around the world. It is available on a subscription basis and also with a free forecast option.
A mobile app for Android and iPhone is available and PredictWind is probably the most used app on the Sail-World iPhone.
Real time local wind observations have been added as further functionality.
You can check the weather anywhere in the world, and get a five day forecast, plus a variety of other features and functions of PredictWind. The app is synchronised with your PC, so that your latest set of locations are always available without resetting each time you change a device.
by Richard Gladwell
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12:09 PM Sat 24 Aug 2013GMT
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