Maximum sustained wind 50% of the geostrophic wind speed aloft; while over open water or ice, the reduction is between 10% and 30%. In most basins, maximum sustained winds are used to define their category. In the Atlantic and northeast Pacific oceans, the Saffir–Simpson scale is used. This scale can be used to determine possible storm surge and damage impact on land. In most basins, the category of the tropical cyclone (for example, tropical depression, tropical storm, hurricane/typhoon, super typhoon, depression, deep depression, intense tropical cyclone) is determined from the cyclone's maximum sustained wind. Only in Australia is this quantity not used to
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