Sunday, 15 November 2009

LVT: Unravelling the Weather

Veteran meteorologist Roger 'Clouds' Badham reveals the secrets of Nice's weather

Emirates Team New Zealand Meterologist, Roger "Clouds" Badham. Image copyright Chris Cameron.

by Chloe Daycard

While many of the world class sailors competing at the Louis Vuitton Trophy Nice Côte d’Azur know the conditions well along this magnificent coast line during the summer months, it is rare for them to be competing here this late in the season, when the weather is wholly different. Why, for example, does the wind seem to shut down for a while at 11am each day during this regatta?

The man with the answers is meteorologist, Roger ‘Clouds’ Badham. Working here in Nice with Emirates Team New Zealand, Clouds has been involved with the weather side of the America’s Cup since 1987, along with Whitbreads/Volvo Ocean Races, Olympics, records and countless other regattas.

Having studied the weather in Nice for a couple of weeks now, Clouds reckons he has a reasonable handle on how the weather here works.

Pretty much the whole of the south of France, all the way around to Genoa, Italy, he says is affected by the ‘Mistral’, the fierce northwesterly that is funnelled between the Alps and Pyrenees. “That will give you anything from 30-100 knots,” says Badham. This wind either wraps around the coast from Marseille and the Golfe de Lyon or from the opposite way from Genoa, but, usually, it never quite reaches Nice, tucked away in the lee of the Alps.

What does affect Nice directly is a secondary effect of the Mistral – a small localised depression that forms in the lee of the Alps. Unfortunately this has a tendency to move around and can be hovering over Nice, over Corsica or anywhere between – its positioning vital to determining the wind direction. Hence why a strong Mistral can result in SSEerly or northeasterly wind off Nice.

While this is the ‘big picture’ weather scenario, of a more local nature is the unpleasant-sounding ‘drainage flow’, the cold air that floods down from the at present snow-covered Alps every night and is the reason why the weather mark for the early morning races is usually closest to the coast.

“The cold air drainage at night is quite deep and quite strong, but it doesn’t go offshore a long way,” says Badham. “It flows down from the hills, across the airport and the town but it is channelled more according to the topography.” For example the flow is more consistent and strong on the flatter, western, airport side of the bay in the morning.

Racing early morning is good, but sadly this wind packs up mid-morning as the land begins to heat up – the exact time depends upon how cold the night was and how quickly the land warms up the following morning. Today, due to the cloud cover, the ‘drainage flow’ lasted until around midday.

With the heating of the land, convection occurs and with it a ‘sea breeze’, wind blowing on to the shore, typical of racing in the Mediterranean, only at this time of year the difference in temperatures between land and sea are not great enough for this to be strong. According to Clouds this has been the situation for the last few days and will continue into next week, with the sea breeze typically from the southeast rather than the more robust southwest, typical of what we experienced on Tuesday when the sea breeze peaked at 13 knots and a full afternoon of racing could be held.

“Generally the sea breeze is a pretty minor sort of creature and it will last for 3-4 hours at best and might reach 12 knots or it be struggling at 6-7 knots. So it comes in different disguises.”

And his forecast for next week? A number of fronts are coming across France but they are all quite weak and won’t prompt a Mistral to blow. This is the case, reckons Badham, until Wednesday-Thursday, with the northerly drainage flow in the morning followed by a shut-down until a soft easterly establishes itself in the afternoon. “Friday the flow wanted to go into the east but it was sick trying to do it and it’ll be like that for the next couple of days and gradually it might get more robust,” concluded Badham.

Louis Vuitton Trophy

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