Weather
conditions

An anticyclone is an area of high pressure. When the pressure rises above 1015 hPa (hectoPascal), this heralds fine weather.
Under the effect of this increased pressure, the winds drop, fostering the arrival of better weather, but this is not necessarily helpful for speed.

The Doldrums are a zone dreaded for its changeable climate. Also known as the Intertropical Convergence Zone (ITCZ), the Doldrums encircle the Earth at the Equator. Skippers thus cross them twice during their round-the-world voyage.
As they approach this zone, the trade winds, which carry yachts with south-westerly winds in the northern hemisphere and north-westerly winds in the southern hemisphere, suddenly rise vertically, depriving sailors of horizontal wind.

This is a very unstable area: in very calm seas, the winds can suddenly become violent and bring torrential rain as well.

Particularly unstable and energetic, the Saint Helena High forces skippers to sail well off the coast of Africa.
The skippers' goal is to get as close as possible to the anticyclone to “capture” the anti-clockwise winds without getting trapped in this large zone of high pressure, which can cause major delays.

Do you know ?
St Helena is also an island at the heart of the anticyclone, 2,000 kilometres from the African coast and over 3,000 kilometres from Brazil. It was home to a very famous Frenchman: Napoleon I, who was exiled here in 1815 until his death in 1821.

Between the 40th and 50th parallels in the Southern Hemisphere, all around Antarctica, there are no obstacles or continents to impede a crazy series of depressions created by the meeting of warm and cold air. This area is known for its strong winds and raging seas.
These lows create impressive waves, increased by the force of winds blowing continuously over very long distances. This area is dreaded by skippers for its storms and fearsome waves.
 

This is a climatic anomaly that occurs every 3 to 7 years. The name "El Niño", meaning "baby Jesus" in Spanish, comes from the fact that this event occurs at Christmas in Peru. El Niño is a warm sea current that heats up the waters off the coasts of Chile and Peru and prevents the "normal" rising of deep cold water. 

Consequences : 

- The warm water prevents plankton from reproducing, and fish become scarce and die. This leads to frequent famines in coastal countries

- The northern part of South America experiences severe drought, while torrential rains fall on the west coast of South America.

In the depths, currents are slower than at the surface.
This is due to differences in the temperature and salt content of the water. Cold, salty water sinks to the bottom, while warmer, less salty water is lighter and rises to the surface. This is known as thermohaline circulation.

These are caused by winds that carry the surface layers of seawater along with them.

Some currents arising in the tropics are warm, like the Gulf Stream, which is the reason for our mild climate in Europe. Others, coming from the polar regions, are cold. These currents turn clockwise in the Northern Hemisphere and anti-clockwise in the Southern Hemisphere.

Like oceans, the atmosphere is full of air currents. The Jet Stream, for example.
These winds follow the Gulf Stream current in the ocean and reach speeds of 200 to 300 kph.