Conditions favour Dee - approaches Agulhas Current

by Aviva Challenge on 31 Mar 2006 Dee is now 650 miles from the Cape of Good Hope, averaging around eight-nine knots in relatively warm strengthening winds from the northeast. She is approaching the waters affected by the Agulhas Current, a notorious spot where a clash between westerly winds and the current can cause boat-breaking conditions.

'Thankfully the conditions are not conspiring to create the particularly foul seas associated with this area,' said Aviva Challenge weather forecaster Mike Broughton. 'The northeasterly breeze looks set to carry Dee through, allowing a run downwind when we would normally expect to see her beating to windward, but I have still told her to shut the hatches. Just because it won’t be as bad as normal and the sun is likely to be out, with 20 knots from the northeast she could still see steep-sided breaking waves.'

The useful northeasterly winds are being generated by a high-pressure system to the south of Dee’s position, which is heading directly for the Agulhas Bank, a shallow water plateau that extends 100 miles south of the Cape of Good Hope. 'The depth of the ocean rises abruptly here from 4000m to just 68m and the current moves fast down its eastern bank, bringing hot water down from the Madagascar channel,' continued Mike. 'The main core is 26° Celsius while just a short time ago Dee was fighting with water temperatures of around 6°. It attracts a huge amount of wildlife and is a favourite feeding place for Great White Sharks.

'The current can be very strong, up to three or four knots, and is actually the second fastest ocean current in the world. The fastest is the Gulf Stream close to Florida, but the difference at the Cape of Good Hope is the tendency for the Agulhas Current to run directly against the strong prevailing westerly winds, which creates the problems for sailors. Not generally well understood, the returning Agulhas Current branches off to the east around 200 miles south of the main flow, and was responsible for giving Dee three knots of adverse current for a short while earlier in the week.'