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
Night of the Big Wind warm air over land, bringing strong winds and heavy rain. First reports of stormy weather came from western County Mayo around noon, and the storm moved very slowly across the island through the day, gathering strength as it moved. By midnight the winds reached hurricane force. Contemporary accounts of damage indicate that the Night of the Big Wind was the most severe storm to affect Ireland for many centuries. It is estimated that between 250 and 300 people lost their lives in the storm. Severe property damage was caused, particularly in Connacht, but also in Ulster and northern Leinster. Between