Fastest jet stream on Earth
5 Feb 2004 jet stream near Yonago, Japan
115.7 metre(s) per second
Not Applicable ()

Based on data collected by the Integrated Global Radiosonde Archive, the fastest jet stream ever recorded on Earth by a weather balloon is 115.7 m/s (416.5 km/h; 258.8 mph). The strength of the jet stream is commonly measured by its speed at a pressure of 250 millibars, which corresponds to an altitude of around 10,400 metres (34,120 feet), and that was the measure used in this case. The reading was taken near Yonago in Tottori, Japan, from where the balloon launched on 5 February 2004.

A jet stream is a narrow channel of very fast-moving air found at high elevations in the atmosphere. They are caused by naturally occurring heat and pressure differentials between the equator and the poles, with air rushing in a (typically) west-to-east direction in response to the imbalance. Both the northern and southern hemispheres experience jet streams, though those in the former are more powerful on average; each hemisphere has two primary streams (polar and subtropical).

Climate change may be altering the intensity of jet streams, though for now this remains an active area of research still undergoing investigation by climatologists and meteorologists.

The record was discovered by analysing weather balloon data from 2,788 stations stored in the Integrated Global Radiosonde Archive (IGRA) dating back to 1905. The data were first screened to remove any very fast wind speeds that were likely to be errors resulting from, for example, faulty sensors or reception problems when radioing the measurements back to ground.

A weather balloon is a package of electronic measuring devices (called a radiosonde) attached to a helium-filled balloon. Measurements are constantly radioed back to a ground receiver as the balloon ascends through the sky; eventually, the balloon bursts and falls back to ground, attached to a parachute. Satellites can also measure jet-stream speed, but historically this has been possible only by tracking the movement of clouds through consecutive satellite pictures. This approach requires clouds to be present, whereas weather balloons can operate in clear or cloudy skies. Furthermore, satellite cloud-tracking reveals the wind speed only at the altitude of the cloud, whereas weather balloons measure the speed all the way from the ground up. The next generation of satellites will be much better at measuring the jet stream, but for now weather balloons remain a vital source of information.