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
Gale force for coastal areas, between and . The definition is very non-standard. A common alternative definition of the maximum is . The most common way of measuring wind force is with the Beaufort scale which defines a gale as wind from to . It is an empirical measure for describing wind speed based mainly on observed sea conditions. On the original 1810 Beaufort wind force scale, there were four different "gale" designations whereas generally today there are two gale forces, 8 and 9, and a near gale 7: The word "gale" is derived from the older "gail", but its origin