Roaring Forties

The Roaring Forties are strong westerly winds that occur in the Southern Hemisphere, generally between the latitudes of 40° and 50° south. The strong eastward air currents are caused by the combination of warm air being displaced upward from the Equator towards the South Pole, Earth's rotation, and the scarcity of landmasses to serve as windbreaks at those latitudes. On average, winds speeds in the region measure around 10 m/s (22 mph) with peak gusts of over 25 m/s (56 mph). The Roaring Forties were a major aid to ships sailing the Brouwer Route from Europe to the East Indies or Australasia during the Age of Sail, and in modern times are favoured by yachtsmen on round-the-world voyages and competitions. The boundaries of the Roaring Forties are not consistent: the wind-stream shifts north or south depending on the season. The strong and continuous winds in the Roaring Forties make this zone advantageous for wind power in places such as New Zealand and Tasmania. Similar winds that occur at more southerly latitudes are called the Furious Fifties and the Shrieking or Screaming Sixties, with the greatest winds near the former. These prevailing winds have been moving farther south over time due to climate change.