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
Royal Charter Storm wind speed and a shift in its direction. There was extensive structural damage along the coasts of Devon and Cornwall. The storm drifted northwards, hitting Anglesey by about 8 p.m. and not reaching maximum force at the River Mersey until midday on 26 October, then continued northwards to affect Scotland. The winds reached force 12 on the Beaufort scale and were well over . At the Mersey a wind force of 28 lbs to the square foot (14 N per 100 mm) was measured, more than ever previously recorded. On the north coast of Anglesey, where the "Royal Charter", a