Please select your home edition
Edition
Bakewell-White Yacht Design

America's Cup- Predictwind - Fresh breezes again for Day 4

by Richard Gladwell on 13 Sep 2013
The America’s Cup Race Course, framed by the Golden Gate Bridge © Richard Gladwell www.photosport.co.nz

Predictwind indicates that fresh winds winds will again prevail for Thursday, the sixth and seventh races for the 2013 America's Cup. The first race starts at 1.15pm on Thursday, local time with the second race scheduled for 1415hrs. The 18fters have the Bridge to Bridge Classic today starting at 1630hrs, which will be sailed in breezes expected to be around 22kts.

With the racing at its regular start time of 1315hrs the two feeds produced by Predictwind indicate that winds will be averaging around 17 kts, with the breeze having been up all night at around 10kts. The key point is that on the graph image the two weather feeds produced by Predictwind are very close together at race time, suggesting the the certainty of the prognosis is high. Before that there is a little disagreement as to rate of increase of the breeze strength. Today there seems to be no fog which will hold the breeze down a little, weather is also overcast restricting the inland heating which drives the Frisco 'Doctor'. When there is fog, the cold air on the sea gets angrily sucked in by the hotter inland systems, increasing the strength of the breeze. Unfortunately the fog is not easy to predict or measure and so it is a random factor in the forecast. Winds do increase 22kts, to be close to the limit of 23kts just over two hours after the conclusion of racing.


The above image shows the wind speed and direction at 1300hrs with breezes expected to be 17kts at the start of Race 6 - these are only average speeds and gusts will be higher, but not enough to exceed the wind limit. 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 close agreement between the two feeds as to the rate of build of the breeze, and around race start they are consistent in their projection.


The second image (above) shows a graphic representation of the wind build - confirming the numbers for the prognosis. If the breeze builds later than predicted, then the light winds soon one the left of the graph will extend through to the race start time.


The top image shows the wind speed and direction at 1400hrs with breezes expected to rise to 19kts at the start of Race 7 - these are only average speeds and gusts will be higher, but not enough to exceed the wind limit of 23kts.

The key feature of the forecast is agreement between the two feeds as to the rate of build of the breeze, and again around race start they are consistent in their projection.


The second image (above) shows a graphic representation of the wind build - confirming the numbers for the prognosis. If the breeze builds later than predicted, then the wind will be slightly lighter.

The third chart (below) shows the wind expectations for Tuesday and Wednesday. Note that sea conditions described in this chart are based on open water and are not descriptive of an enclosed harbour


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), www.predictwind.com!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 www.predictwind.com!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 www.predictwind.com!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.

upffront 660x82North Technology - Southern SparsT Clewring One Design

Related Articles

Rio 2016 - America's Cup champ says Paralympic racing is closest ever
Twice America’s Cup champion, Rick Dodson is extremely impressed with the standard of racing in the three man Sonar Twice America’s Cup champion, Rick Dodson is extremely impressed with the standard of racing in the three man Sonar keelboat class at the 2016 Paralympics in Rio de Janeiro. The regatta is being held in Guanabara Bay on three of the courses used for the Olympic Sailing Regatta in August.
Posted on 13 Sep
A Q&A with Peter Bresnan ONE Palma’s founder and director
Sail-World interviewed ONE Palma’s founder Peter Bresnan to learn about the company’s partnership with McConaghy Boats For the past eight years, ONE Palma (formerly OneSails Spain) has been building a strong name, first as a sailmaker and later with refit work. Recently, ONE Palma and McConaghy Boats-legendary boatbuilders who have crafted some of the planet’s fastest sailboats-entered a business partnership. I caught up with Peter Bresnan, ONE Palma’s founder and director, to learn more about this new direction.
Posted on 2 Sep
America's Cup - Emirates Team NZ train late on the Waitemata Harbour
Emirates Team NZ were out for a training session that ran into the early Thursday evening. Emirates Team NZ were out for a training session that ran into the early Thursday evening. The team were sailing their recently launched AC45 Surrogate test boat which features an articulated rudder gantry - taking the AC45 close to the geometry of the AC50 to be used in the 2017 America's Cup.
Posted on 1 Sep
Dateline Rio - Sailing Olympics review - as good as it gets?
The Rio Sailing Olympics was widely judged to have been the best of recent times. The Rio Sailing Olympics was widely judged to have been the best of recent times. The weather was better than Weymouth and Qingdao, the courses more varied, but from a working media perspective, it was the people running the Rio regatta who really made the difference.
Posted on 26 Aug
Rio 2016 - Plain speaking by triple-medalist on Olympic sailing moves
Triple Olympic medalist, Santiago Lange has been on the sharp end of changes made to Olympic classes and formats Santiago Lange, a six-time Olympian and Bronze medallist in the 2004 and 2008 Olympics, won his third medal – Gold sailing in the Nacra 17 class. With that length of experience at an Olympic level, having sailed the Laser, Tornado and now Nacra 17 classes his comments on the future shape of the Olympic regatta was one of the highlights of the Medallists Media Conferences.
Posted on 25 Aug
Rio 2016 - Images of the penultimate race in the Finns - Scott wins
Sail-World's Richard Gladwell was on the water for the final race of the Qualifying Series of the Mens Finn Sail-World's Richard Gladwell was on the water for the final race of the Qualifying Series of the Mens Finn, in what potentially could have been Giles Scott's (GBR) Gold medal winning race. In the end, the current world champion won in style.
Posted on 15 Aug
Rio 2016 - Images from the Mens RS:X Medal Race
Sail-World's NZ Editor, Richard Gladwell, was on the water at the Medal Race for the RS:X class Sail-World's NZ Editor, Richard Gladwell, was on the water at the Medal Race for the RS:X class won before the race by Dorian van Rijsselberghe (NED) without needing points from the Medal Race. Nick Dempsey (GBR) was second on a similar basis.
Posted on 15 Aug
Rio 2016 - Sailors talk of Life at the Extreme on the Atlantic Ocean
Certainly the Volvo Ocean Race catchcry of Life at the Extreme is not a phrase associated with the Sailing Olympics. The 470 crews were suffering the mixed emotions of survival of an extreme test by nature, the cold, and for some elation at their placings, after Thursday's battle for survival. In conditions that looked more out of the Volvo Ocean Race, than an Olympic sailing regatta, crews battled 20kt plus winds and Atlantic Ocean rollers that towered up to four metres.
Posted on 13 Aug
Rio Olympics - Fourth gallery of images the fearsome Niteroi course
Fourth image gallery from racing on Day 4 in the Mens and Womens 470 class on the Niteroi course in the Atlantic Ocean Fourth image gallery from racing on Day 4 in the Mens and Womens 470 class on the Niteroi course in the Atlantic Ocean - sailing in 3-4 metre swells and 20kt plus winds. believe it or not the sea conditions were worse inshore as the fleet encountered the backwashed Atlantic rollers
Posted on 12 Aug
Rio 2016 - Third image gallery of 470's braving the Atlantic Ocean
Third image gallery from racing on Day 4 in the Mens and Womens 470 class on the Niteroi course in the Atlantic Ocean Third image gallery from racing on Day 4 in the Mens and Womens 470 class on the Niteroi course in the Atlantic Ocean - sailing in 3-4 metre swells and 20kt plus winds
Posted on 12 Aug