In general wind speed of a tornado is not measured at all. After a tornado hits a specific area a team of surveyors from the national weather service will come access the damage and estimate the wind speeds from that damage. Sometimes there will be a mobile Doppler radar deployed and it can measure the winds at the base of the tornado or a probe can be placed by storm chasers. That's the only way to truly know how fast the winds in a tornado were blowing...
What scale is used for rating tornado intensity, based on the damage tornadoes inflict on human-built structures and vegetation?
What scale, developed by Terence Meaden as an extension of the Beaufort scale, measures tornado intensity between T0 and T11?
