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America's Cup Rialto: AC75's dodge a bullet - surprise 70kt squall hits Auckland on Friday

by Richard Gladwell Sail-World NZ 18 Sep 13:45 BST 19 September 2020
American Magic - Waitemata Harbour - September 18, 2020 - 36th America's Cup © Richard Gladwell / Sail-World.com

Both AC75's were out sailing in Auckland on Thursday, sailing once again in fresh breezes offshore breezes of 18-20kts, gusting 22kts.

These conditions are getting close to the racing wind limit for the AC75's but they seem to have little difficulty with the conditions - doing the usual mix of race training around laid marks and speed runs.

Both boats left their docks at the same time - 1000hrs, and towed out - both on their foils. That was as close as they got all day, with Emirates Team NZ heading for the boondocks in The Paddock, or Course E, and along the western side of Motuihe Island.

Defiant turned left at North Head, at the entrance to the inner Waitemata Harbour and headed for the old America's Cup course off the East Coast Bays.

They stayed there for a marathon seven hour training session in the tough conditions. Eventually the posse of reconnaissance boats either started running out of gas or got bored, and left American Magic to their own devices. We'll never know if the New York Yacht Club's challenger tried something new, in the absence of the recon teams - or if they just liked the sailing.

Defiant's crew sailed home arriving on the dock at 1720hrs - two and a half hours after the Kiwis - and a marathon session.

On Friday, Auckland was thrown into chaos when a 70kt squall, lasting 10 minutes, and shifting 100 degrees, ripped down the harbour causing a container to be blown off a truck on the Auckland Harbour Bridge and another to bounce off the centrespan The incidents caused the centre lanes of the bridge to be closed and remain that way for several weeks.

Fortunately none of the AC75's were on the water, with Friday's forecast being a little on the high side for America's Cup training.

All week the wind has been up and down, with Tuesday also being a no-sail day due to strong winds. However Friday's freak weather event is a warning to all sailors.

An hour before the squall, conditions were only about 20kts, increasing to 25kts in the occasional rain squall, interspersed with blue skies. They increasing suddenly to 45kts average at Northern Leading Beacon gusting 55kts. A few minutes earlier it was recorded at average 40kts gusting 70kts on the Harbour Bridge, lasting for 10 minutes before dropping back to 20kts average and changing direction by around 100 degrees.

Similar readings gusting to 55kts were recorded at the Royal New Zealand Yacht Squadron clubhouse, adjacent to the Harbour Bridge.

No wind warnings were issued for the Harbour Bridge. Later checking of wind data on Predictwind, it transpired that the wind had been gusting at 70kts on Auckland's West Coast all morning - and it seemed that one squall popped over the top of the Waitakere ranges which lie between Auckland and the Tasman Sea.

The wind gusted to 63kts at Bean Rock, and 55kts at Northern Leading beacon reckoned to be the most accurate indicator of windspeed/direction for the America's Cup courses. Been Rock and Northern are at an elevation of 8metres and 12metres respectively. America's Cup race management readings are taken at a level of 5.5 metres.

In other key points around the Cup courses, winds gusted to 45kts at Rangitoto Light, and 70kts at the top of Browns Island. The weather was short lived at just 10 minutes, with the the breeze dropping away across the area accompanied by a 100 degree windshift, before coming back at 20-25kts average - quite sailable and certainly within the band used by the teams for training.

Auckland's weather is notorious for being "four seasons in one day", or "if you don't like the weather now, wait ten minutes and it will be different".

Earlier in the week, on Monday the two AC75's did get caught in a serious rain squall - when there had been several others move down the course. Emirates Team New Zealand had stopped sailing and towed home through the 33-35kt squall. American Magic's Defiant hitched up to a chase boat, kept her mainsail up and rode it out. That strategy would have been impossible in Friday's situation, and underlines yet again why wingsailed catamarans are not a viable option for Auckland. The AC75's can drop their mainsails if required in these situations, and often fast tow to and from the race areas with all sails lowered.

The AC75 can quickly exit a dangerous situation, unlike the AC72 and AC50 which had to be extracted at pedestrian pace, using a technique known as "sideslipping" where the chase boat and the wingsailed catamaran were lashed side by side and stern to bow, with the catamaran always having to point its bow into the wind. The trip home with a nose dived AC50 alongside the ETNZ tender took over 40 minutes to travel a mile or so, including some difficult maneuvering to avoid the AC50's wingsail taking control in the Royal Dockyard - home to the team bases.

America's Cup boats have been caught by freak weather situations while training in Auckland. In 2012, in the buildup to the 2013 America's Cup Emirates Team NZ's AC72 was badly caught when a sudden weather system hit West Auckland , killing three people. ETNZ's AC72 was out off the East Coast Bays where the AC75's have been training this Cup cycle. ETNZ's AC75 took refuge behind an island, but in the end had no option but to take their chances and sail home in winds over 30 kts.

Fortunately for this America's Cup Auckland has been ringed with a series of new real time wind recording stations - and monitoring these should provide a lot higher warning accuracy than previously.

Predictwind, developed originally by Alinghi meteorologist and 470 Olympic representative, Jon Bilger, has excellent web and mobile applications to display forecasts and real time wind information, and Predictwind staff have played an integral role in the installation and maintenance of the new weather stations.

Readings on Friday's weather incident, while brief was very serious, and could be tracked in realtime on over 20 points around the Auckland marine area, on both the east and west coasts. Predictwind also has other functionality including weather routing, all from a mobile phone and using the latest forecast in quick and detailed formats.

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