An America’s Cup meterologist has posted his weather prediction on the team blog

The strong w-sw sea breeze that caused the damage on Saturday moderated early in the week, but by Thursday – first race day for Dean Barker and crew – it will be back to its boat-breaking best.

Emirates Team New Zealand (ETNZ) meteorologist Roger (Clouds) Badham says that at this time of the year San Francisco weather comes in three to five day cycles. Locals say the best weather is in September/October.

I completely agree with his statement on the best weather months, but I guess I qualify as a local. Spring and Fall offer dry warm weather and moderation while the summer months bring humidity with chilly temperatures and big afternoon breeze.

As “Clouds” rightly suggests the driver of the big summer breeze is a temperature differential between the Bay Area getting cooled at night by the ocean and the heated inland area during the day.

I’ve heard it referred locally (among sailors) as proof how much Sacramento really “sucks”.

A quick look at forecasts shows nearly perfect conditions later this week, yet that’s not what ETNZ is predicting on their blog. So I downloaded a GRIdded Binary (GRIB) file to see if I could verify what “Clouds” sees.

GRIB is a format for meteorological data specified by the World Meteorological Organization’s Commission for Basic Systems. There are many choices of free software that will download, manipulate and display GRIBs. I tend to use zyGrib.

Below is a small subset of the latest images, which shows a solid wall of 30+ winds off-shore (!) but light winds of 10 knts around the Bay Area from 11am to 5pm on Thursday and on Friday. The problem when looking at these charts, however, is trying to factor in the dominant local/shore effects. The Golden Gate, for example, tends to be a funnel or convergence zone and that is where the races will be held.

Thursday morning:

Thursday afternoon:

Friday morning:

Friday afternoon:

A solid yellow can be nasty (25+ knts) to deal with. Turquoise (10 knts) is generally what you want to see. Great day to go for a sail, right? Not quite. The race venue will see some kind of variation from this high-level map. As I mentioned there’s a convergence near the Golden Gate Bridge.

When I sail in the Bay Area I know how dangerous it can be to rely on a GRIB view alone. A single day around the Bay can involve a dozen or more micro-climate areas with extremely variable and dangerous conditions at places like the “Slot” near Alcatraz, or the aptly named Hurricane Gulch and the unpredictable river of Raccoon Strait.

Fortunately there are many localized data sources. Last Saturday the wind sensor near Crissy Field (just inside the Golden Gate Bridge) posted rather high wind readings compared with the overall area. You can review it on SailFlow.com.

The AC45s will definitely be crashing if they see spikes into the 30 knt range like that. No wonder teams saw some major breakage this past weekend.

Since the Team NZ crew of six arrived in California late last week, the Bay has been dishing up 30 knot wind gusts and choppy seas, which have already claimed three of the 11 boats out practising.

Team NZ have come through the practice days unscathed, but not without a few hairy moments. Their training partner, Luna Rossa Swordfish, was not so fortunate – suffering a spectacular end-over-end capsize, destroying their AC45 wing. The Italians will need to use another wing if they are to be on the startline when racing begins in earnest on Wednesday (NZ time).

The strong sea breezes and wind against tide also flipped Artemis and Team Korea, and could cause more carnage in this first event of the 2012-13 World Series.

Photos from the team site show the boat bearing away downwind with hulls flat but the bows under heavy pressure. When you have so much spray in your face that you can’t see the sails, it’s time to reduce sail area.

Source: ETNZ

The same Crissy Pier wind sensor predicts 7-12 knts in the morning on Thursday and 10-20 knts in the afternoon. That typically means it will blow 15 knts by noon and 25 knts by 2pm. As you can see a localized prediction can be quite different from the high-level area map view that indicates 10 knts.

Source: Team Puma. Look out Jimmy! Keep clear when an AC45 has to steer in 20+ knts. You definitely don’t want to meet a carbon blade doing 30 mph.

On top of wind predictions, racers also have to factor the tide. They should see a 1-2 knt flood tide (slack at noon on Thursday, 1 pm on Friday). Given that the races start when tide is almost slack, it seems someone was planning the event date with an eye on the tide charts (Bay water can flow over 5 knts).

Sailing obviously is a sport where Big Data analysis (e.g. many sensors reading variable data in real-time) has always been an essential part of success. A team simply can’t be a top performer without a mastery of wind and water instruments.

Events this week should be a great time to see the world’s best sailors on the world’s best sailing technology racing in fast conditions, right on the edge of control.

Source: ETNZ. Helmets with radios and camera mounts, dry suits, low-profile life-vests, knives…ready for teamwork in any condition, it’s the look of high-performance sailing.

Recently the NYT described some of the reasons the America’s Cup has changed.

Two years ago the officials who run the America’s Cup made an important decision: they were going to change professional sailing into a sport that was actually fun to watch.

That has meant bringing Big Data, surveillance and real-time analysis into the picture.

Honey’s team has to measure the position of every boat to within an inch at all times, while also measuring the position and angle of every helicopter-mounted television camera. The team is also collecting data on wind and water conditions, which play heavily into sailing strategy, and looking for ways to incorporate that into the television display.

By collecting this data, Honey’s team has ended up changing how the races operate. Race officials now watch the sailing on monitors from a control room on the shore, and any decision that relies on the objective knowledge of a boat’s position is made using the same positional data used to create the graphics.

[…]

The America’s Cup is designing an augmented reality smartphone app, which will allow spectators on shore to hold their phones up to the water and get the type of information available on television.

Obviously another change to the sport has been to bring the thrill of racing within view of people on shore. The big boats used to disappear and sail in light wind and steady seas, where only a few could see, but now everyone can enjoy watching in city-front weather conditions.

We’ve had some windy days recently and the forecast is starting to look like 10-20 mph through next week. Inside Bay Area gives an exciting prediction of the event.

“Hold on for dear life!”

That’s the warning from sailors aboard the 45-foot racing catamarans that you’ll see slicing through whitecaps next week, when the America’s Cup World Series brings the thrills and spills of the world’s most exciting racing to San Francisco Bay.

Imagine a white-knuckle drag race on the back of a bucking bronco — with winds whipping up at nearly 20 mph and a fire hose of salt water battering over the bow. The signature America’s Cup races are still a year away, but 11 catamarans from eight countries will be on the bay next week offering a taste of the drama that’s to come.

[…]

Four Olympic medalists fresh from London will compete next week, including four-time gold medalist Ben Ainslie, who carried the British flag into closing ceremonies. His credentials are impressive, but his experience on the temperamental AC45 is limited.

“I think he’ll be a little bit scared,” said Kimball Livingston, an editor-at-large for Sail Magazine. “I think all these guys as they get into it are a little bit scared — and for good reason. You can hurt yourself.”

They’re not just scared of being hurt, they’re scared of losing control. Ainslie won his gold medals by sailing a 1949 design called the Finn that plods along at about 7 mph. The AC45 will give him a state-of-the-art racing machine that tops out around 30 mph.

It’s like the difference between driving a 1950s Studebaker at 50 mph versus racing a 2012 LeMans race car at 200 mph. You can get hurt in either. Doing everything four times faster than ever before is the real issue, which is why they’re scared. After racing for a while at higher speed they become used to it and stop feeling scared, despite the risk of being hurt.

Does 30 mph sound slow to you? It actually is about the fastest a sailboat can go using current technology. The AC72, which will be far more powerful than the AC45, is expected to go only about 40 mph. For reference, driving a car over 30 mph usually requires a very smooth surface. These boats are bigger than a bus, navigating a very rough and unpredictable surface (waves), with no brakes and balancing one hull up in the air. Personally, I think it’s the best feeling in the world.

Photo:(c)2011 Gilles Martin-Raget, americascup.com

With only a few days before things start there have been numerous helicopters flying overhead, presumably to help prepare the races and to take photos like those found on SF Gate.

As you can see the races will be held in front of the Marina Green, giving land spectators an easy and free view of everything. The America’s Cup Village opens Tuesday the 21st at 10am.

A US Sailing Farallones Panel Report has been posted with detailed analysis of the Low Speed Chase Capsize on 14 April 2012.

Four safety issues are explained. The first is that the crew sailed too close to shore.

As a result of the panel’s investigation, it became clear that the cause of the capsize was that Low Speed Chase sailed a course which took them across a shoal area over which breaking waves could be expected to occur several times per hour (see Appendix D) and encountered a breaking wave, which capsized the boat.

[…]

With a forecast for swells up to 15 feet, a maximum wave height of 30 feet would be expected, and 1% of waves (two or three per hour) would be expected to average 25 feet in height. The forecast wind waves would add two or three feet to the maximum wave. (See Appendix D)

The remaining three issues are related to adequate safety gear, communication and incident response procedures. Other sailors are also called out in the report for the decision to not assist.

Of the seven other race boat crews interviewed who witnessed the incident, all deemed the conditions too dangerous to physically stand by and attempt to render assistance. All continued racing.

[…]

22 boats heard the radio traffic concerning the LSC incident and five respondents saw Low Speed Chase on the shore, while one actually saw the capsize.