Wind Speed - Highest Speed

Highest Speed

During the passage of Tropical Cyclone Olivia on 10 April 1996, an automatic weather station on Barrow Island, Australia, registered a maximum wind gust of 408 km/h (220 kn; 253 mph; 113 m/s). The wind gust was evaluated by the WMO Evaluation Panel who found that the anemometer was mechanically sound and the gust was within statistical probability and ratified the measurement in 2010. The anemometer was mounted 10 m above ground level and so 64 m above sea level. During the cyclone, several extreme gusts of greater than 300 km/h (160 kt; 83 m/s) were recorded, with a maximum 5-minute mean speed of 176 km/h (95 kt; 49 m/s), the extreme gust factor was in the order of 2.27–2.75 times the mean wind speed. The pattern and scales of the gusts suggests that a mesovortex was embedded in the already strong eyewall of the cyclone.

The second-highest surface wind speed ever officially recorded is 372 km/h (231 mph; 103 m/s) at the Mount Washington (New Hampshire) Observatory in the US on 12 April 1934, using a heated anemometer. The anemometer, specifically designed for use on Mount Washington, was later tested by the US National Weather Bureau and confirmed to be accurate. The highest surface wind speed ever officially recorded in Afghanistan on 14 August 2008: 328 km/h (204 mph; 91 m/s) in Ab-Paran, Ghowr.

Wind speeds within certain atmospheric phenomena (such as tornadoes) may greatly exceed these values but have never been accurately measured. The figure of 486 km/h (302 mph; 135 m/s) during the F5 tornado in Bridge Creek, Oklahoma on May 3, 1999 is often quoted as the highest surface wind speed.

In 1991, a chase team from the University of Oklahoma chased a tornado in Red Rock, Oklahoma and used a portable Doppler weather radar to measure a wind speed of 460 km/h (286 mph; 128 m/s).

According to Alan F. Arbogast ("Discovering Physical Geography") wind direction and speed are affected by three main factors:

1. Pressure gradient - the difference in barometric pressure between adjacent zones of high and low pressure.
2. Frictional forces - features on the Earth's surface which oppose the wind; e.g.: mountains, trees, buildings, etc.
3. Coriolis effect - the Earth's rotation causes winds to be deflected to the right in the Northern Hemisphere, and in the Southern Hemisphere to the left.

All three of these combined result in the spiral motion of air in both high and low pressure systems.