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What are jetstreams?

At high altitudes, very strong winds are found, conventionally (for aviation forecasts) with speeds of 80 knots (40 m/s) or more, but most often with speeds in the range 120 to 160 knots (60-80 m/s), and in extreme cases, over 200 knots (100 m/s). These very strong winds are found in relatively narrow horizontal, and even narrower vertical space, and are known to meteorologists as jetstreams: named by Carl-Gustav Rossby in 1947, following research in the USA. However, the existence of jetstreams had been suspected theoretically for many years before, and, though not recognised as such, had been picked up by Zeppelin flights in the Great War (1914-1918) flying at 20000 ft/6 km on return to Germany.