Preview: The Atlantic Trade Winds leg to Rio de Janeiro, Brazil

The 12 teams will start their ocean odyssey and the 5,186 nautical mile Atlantic Trade Winds leg to Rio de Janeiro, Brazil, at 12.30pm today off Southend, UK.

The fleet will be starting in light to moderate conditions of 8-10 knots of wind from generally north as they travel south on a deep run from the Thames Estuary.

The wind will pick up a little more into the low teens, gusting a little more occasionally, down the English Channel, according to Simon Rowell, the Clipper Race meteorologist .

The fleet will face the likelihood of more north to north west winds to pass Ushant at the North West corner of France. Then the notorious Bay of Biscay must be swiftly crossed, with a favourable forecast hopefully giving the fleet a fast passage to Cape Finisterre.

Skippers will then be watching for developing incoming low pressure systems heading across the Atlantic Ocean.

The Canary Islands are on the direct route to Rio. The decision whether to leave them to the east, sail through the middle or pass on the west delivers a major tactical headache. Get it wrong and you are caught in the wind shadow of the huge mountains that extend for more than 100 miles out to sea.

Spinnakers are likely to be set for as much as two weeks on this leg. The spinnakers have to last another 40,000 nautical miles, so it’s a fine balance between pushing hard in the early stages and risk suffering damage to kit or taking it too easy and missing a podium place.

Next up is the dreaded Doldrums (Inter Tropical Convergence Zone), where wind holes, squalls, humidity and unpredictable conditions will try the patience of even the most stoical crew members. And a visit to the Court of King Neptune as crews cross the Equator and go from the Northern to the Southern Hemisphere is a highlight of the leg.

Dual nationality Brazilian and Dutch Unicef crew member Eduard Braga Rettich will be sailing into Rio for the first time on Race 1. He said: "The race is going to be a very big and demanding challenge with a lot of lows and highs. To get into the bay of Guanabara will be wonderful with friends and family waiting for me there.

"It is going to be very emotional."

The Race Viewer will go live here at 12.30pm when the race starts and will update every hour with real time updates on the fleet's positions. A story with information on other ways to follow the race will be posted shortly.