Cumulonimbus and aviation at this altitude, updraughts with speeds that can exceed . Such an updraught speed corresponds to the wind speed of a small hurricane. The speed can even exceed . The maximum number in the Beaufort scale is 12 ("hurricane force" wind) and is assigned to wind speeds of 64 knots or greater. If the Beaufort scale were extended, these updraughts would have a Beaufort number of 14 "in the vertical direction". The turbulence is then "extreme" at this altitude. Moreover, the diameters of the updraught columns vary between 2 km (air mass thunderstorm) and 10 km (supercell thunderstorm). The height
Beaufort scale winds in hurricanes would be 23 in the scale. Today, hurricane-force winds are sometimes described as Beaufort scale 12 through 16, very roughly related to the respective category speeds of the Saffir–Simpson hurricane scale, by which actual hurricanes are measured, where Category 1 is equivalent to Beaufort 12. However, the extended Beaufort numbers above 13 do not match the Saffir–Simpson scale. Category 1 tornadoes on the Fujita and TORRO scales also begin roughly at the end of level 12 of the Beaufort scale, but are independent scales – although the TORRO scale wind values are based on the 3/2 power