Sea breeze city


 
We speak to Alinghi meteorlogist Jack Katzfey about what makes the America's Cup venue tick
"It's not normally like this" is a phrase we hear regularly when attending windless/gale bound/torrential rain ridden regattas about the globe. The light winds that caused seven days of racing to be cancelled at the beginning of the Louis Vuitton Cup's Round Robin 1 are an unfortunate and extreme case of this, caused, we are told, by a meteorological 'block', where the typical weather systems in our part of the northern hemisphere invert - ie a high pressure system over northern Europe bringing July-like conditions to the UK and torrential rain to North Africa, with little Valencia caught in between (see below). At a presentation earlier in the week, provided kindly but perhaps slightly oddly by Alinghi (rather than ACM or one of the challengers), we were shown just how unusual this meteological phenomenon was as the charts immediately below shows. These figures are based on the hours of 12-1500 for winds of of 7-23 knots, typically the range in which sailing can take place, and show that in April 2007 only 50% of days have been sailable compared to on average around 85% for previous years, with seven consecutive sailing cancelled compared to the typical mean of around two. Interestingly, using the same criteria, it compares with 35-55% of days that can be sailed during the summer months in Auckland. A block is effectively a meteorological brick wall that spans the atmosphere from ground level up to around 10km (ie most of it). We are told it is not uncommon particularly over Europe, but what is unusual this April has been that the block has lasted for more than a month. Absolutely this has nothing to do with global warming, or nothing provable at least, oh no. Given that a low pressure system is now over mainland Spain and heading

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