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
Burns' Day Storm the Netherlands and Belgium. The strongest sustained winds recorded were between 70 and 75 mph (110–120 km/h), comparable to a weak Category 1 hurricane or Hurricane-force 12 on the Beaufort Scale. Strong gusts of up to 104 mph (170 km/h;) were reported, and it was these which caused the most extensive damage. The Burns' Day Storm of 1990 has been given as an example of when the Met Office "got the prediction right". The model forecast hinged on observations from two ships in the Atlantic near the developing storm the day before it reached the UK. During the day of