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
Cyclone Kyrill Aberdaron on the Lleyn peninsula, 122 km/h (76 mph) at Mumbles near Swansea and winds of 101 km/h (63 mph) at St Athan in the Vale of Glamorgan. The German Meteorological Service had advised people to stay indoors and avoid unnecessary trips on 18 January, and wind strengths of up to 12 on the Beaufort scale were seen across the Netherlands and Germany as the storm made landfall. The storm moved across the German states of Lower Saxony, Bremen, Hamburg, Schleswig-Holstein and North Rhine-Westphalia first, then spread across the whole country in the evening hours of 18 January. Wind gusts