Please select your home edition
Edition
Predictwind - Iridium

America's Cup- Predictwind - Lighter winds initially for Day 13

by Richard Gladwell on 24 Sep 2013
The America’s Cup Race Course, framed by the Golden Gate Bridge - today the wind blows from right to left, and the ebbing tide flows from left to right against the windflow. The blue sea that can be seen behind the City to the right, is not ocean but the greater expanse of the San Francisco Bay - which exits through the relatively narrow channel under the Bridge. Richard Gladwell www.photosport.co.nz

The regular San Fransisco breeze is expected again on Day 13 of the 34th America's Cup, for Monday and Races 16 and 17 of the 2013 America's Cup. The first race is due to start at 1.15pm on Sunday, local time with the second race scheduled for 1415hrs.

Towards the bottom of this story we feature Predictwind's course routing optimised for wind and tide on the AC race course, and using an AC72 performance profile. It is included to show that the effect of the tide on the race course and race strategies. See bottom of story for the course variations.

For the official line on how the current factor is determined click here Today the tide is flooding (coming in through the Golden Gate) and will negate the previous advantage that exists with an ebbing tide.

With the first race of the day set for its regular start time of 1315hrs the wind feeds produced by Predictwind indicate that winds will be around 12kts. Both feeds produced by Predictwind are in agreement on the strength at the race start time, however the significant feature of the forecast is that just 90 minutes before the start the winds will be near calm.

The minimum breeze required to complete the course within the 40 minute time limit is 10kts (although the specified minimum breeze is 5kts), and the time limit could be an issue in the first race of the day, but for the second race, the wind should be very adequate without exceeding the maximum of 23kts plus tidal effect.

The breeze is expected to quickly build in the late morning and early afternoon to reach a strength of 15-18kts for the second scheduled race of the day.

The forecast does not take account of the influence of fog, which can have several effects on the race course winds.


The above image shows the wind speed and direction 1300hrs with breezes expected to be 12kts at the start of Race 16 - these are only average speeds and gusts will be higher.


The second image (above) shows a graphic representation of the wind build - confirming the numbers for the prognosis. The significant feature is the feed are very similar for the 90 minutes before the start of the first race of the day. They vary, but not too significantly for the second race.


The above image shows the wind speed and direction at 1400hrs still with a small increase in the breeze in the middle of the course indicated by the yellow wind arrows.


The second image (above) shows a graphic representation of the wind build - confirming the numbers for the prognosis. Reading the top line we can see the wind direction, the wind strength with winds forecast to be 15-18kts and from the SW.

The third chart (below) shows the wind expectations for Monday and Tuesday. Typically the forecast for Tuiesday is revised upwards closer to the time of the race start. Note that sea conditions described in this chart are based on open water and are not descriptive of an enclosed harbour


The courses optimised by Predictwind for an AC72 show that the optimum course only has no real variation between races. The faint purple line shows the recommended course for Race 16 and the red dotted line shows the course recommended for Race 17. The mark positions used in this projection are only very approximate - and will vary on the course set for the day. At the bottom of the upwind leg the model shows that the boats cannot use full width of the course because on the adverse, incoming tide.

The point here is that downwind is there is little variation in the options, aside from the recommendation to gybe early and get into the incoming tide. And upwind in both models the fastest course is to the south, or cityside shore, aside from allowing a short leg to Alcatraz in the first race before heading for shore. The tide is expected to be in flood (incoming) for this race, and boats will need to avoid its effects upwind by taking the city shore.



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 images 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.

PredictWind.comPredictWind.com 2014Predictwind - Iridium

Related Articles

An interview with Donald Weld about the 2017 J/70 North Americans
I caught up with Donald Weld, regatta chair of the 2017 J/70 North Americans, to learn more about this exciting event. The 2017 J/70 North American Championships are set to unfurl on Long Island Sound and will be hosted by the American Yacht Club from October 9-15. Given the number of sailors living in the greater region, it’s not surprising that it’s attracting the kinds of numbers that would be the swooning envy of plenty of world championships. I caught up with Donald Weld, regatta chairman, to learn more.
Posted on 9 Oct
America's Cup - New York Yacht Club makes a smart early move
New York Yacht Club's announcement of an entry in the 36th America's Cup may have seemed to some as a premature move. New York Yacht Club's announcement of an entry in the 36th America's Cup may have seemed to some as a premature move. Coming just seven days after the Protocol joint announcement, most would have expected the club with the longest involvement in the America's Cup to have at least waited until the concept drawing of the AC75 was published, at the end of November, before confirming their intentions.
Posted on 6 Oct
America's Cup - Dan Bernasconi on shaping the AC75 'Beast'
Dan Bernasconi, Technical Director of Emirates Team NZ is leading the design team charged with developing the AC75 rule Dan Bernasconi, Technical Director of Emirates Team New Zealand, has turned his hand from leading the team charged with developing the quickest America's Cup multihull on the planet to performing a similar feat with a monohull. First step in the process is coming up with a concept boat, and then writing a class rule to accommodate that type. The 75ft monohull has been given various monikers, bu
Posted on 5 Oct
A Q&A with Sam Rogers about the 2017 Melges 20 World Championship
I interviewed Sam Rogers, the Melges 20 North American fleet manager, to learn more about the 2017 Worlds (October 3-7). The 2017 Melges 20 World Championship is set to unfurl off of Newport, Rhode Island, from October 3 to 7 and will be hosted by the New York Yacht Club (NYYC) at their beautiful Harbour Court facility. I caught up with Sam Rogers, the Melges 20 North American fleet manager, via email to learn more about this exciting regatta that’s expected to draw competitors from four continents and nine nations.
Posted on 2 Oct
America's Cup - Dalton opens up on boat and options for next Cup
The Protocol for the 36th America's Cup will take place in Auckland on the morning of the 29th September Italian media are reporting that the announcement of the Protocol for the 36th America's Cup will take place in Auckland on the morning of the 29th September. Dalton confirmed the details of the yacht will be revealed two months later on November 30, but would not say if it will be a foiling monohull as speculated in the media.
Posted on 18 Sep
An interview with Rainer Muller about the International 6 Metre Worlds
I interviewed Rainer Muller, vice chair of the International 6 Metre Class Worlds, via email, to learn more. The 2017 International 6 Metre Class World Championships are set to unfurl off of Vancouver, Canada, from September 17-21 and will be hosted by the Royal Vancouver Yacht Club, so I caught up with event vice-chair Rainer Muller, via email, to learn more about this exciting biennial regatta that’s expected to draw 45-50 boats from eleven different nations.
Posted on 18 Sep
An interview with Shelia Graves about the IHYC's Classic Yacht Regatta
I interviewed Sheila Graves, co-chair of IHYC’s Classic Yacht Regatta, via email, to learn more about this upcoming even Indian Harbor Yacht Club’s eighth-annual Classic Yacht Regatta is set to unfurl the weekend of September 15 and 16, so I caught up with Sheila Graves, event co-chair (and a former winning sailor), via email, to learn more about this now-classic New England event.
Posted on 13 Sep
An interview with Katie Coleman Nicoll about the 2017 J/24 Worlds
I interviewed Katie Coleman Nicoll of the 2017 J/24 World’s organizing committee to learn more about this great event. This year’s J/24 Worlds will unfurl from September 15-23, 2017 on the waters of Canada’s Lake Ontario and will be hosted by the Port Credit Yacht Club on the lake’s northwestern shores. I interviewed Katie Coleman Nicoll, secretary/treasurer of the Canadian J/24 class and a member of the 2017 J/24 World Championship’s organizing committee, via email, to learn more about this exciting event.
Posted on 11 Sep
Pulling G’s with Beneteau – Pt II
Just a little while ago we pulled some Gs with Beneteau’s Mr Product, aka G3. Just a little while ago we pulled some Gs with Beneteau’s Mr Product, aka G3. You can go back and read Part One of the story of Gianguido Girotti, as and when you may like. However, for now we’ll push on with the incredible semi-foiler Figaro 3, and the new Oceanis 51.1, along with what they represent for the brand as a whole. It is a very interesting tale, especially as Beneteau...
Posted on 31 Aug
A conversation with Jay Keeshan about the SYC's 2017 Vineyard Race
I caught up with Jay Keeshan, vice chair for the 2017 Vineyard Race, via email, to learn more about this classic race. This year’s Vineyard Race is set to unfurl on Friday, September 1, and will likely take most boats between one and three days to complete, conditions and vessels depending, of course. I caught up with Jay Keeshan, vice chairman for the 2017 Vineyard Race, via email, to learn more about this classic New England distance contest.
Posted on 28 Aug