Great Storm of 1987 from Portland Bill, Dorset to Cromer, Norfolk the return period of the respective gusts were under 10 years. Sustained winds speeds greater than 75 mph were recorded for over an hour in southern Britain. According to the Beaufort scale of wind intensities, this storm had winds of hurricane force 12 (73 mph or greater); as the term "hurricane" refers to tropical cyclones originating in the North Atlantic or North Pacific, the descriptor "great storm" has tended to be reserved for those storms in recent years reaching this velocity. Hurricanes have a very different wind profile and distribution from storms, and
Beaufort scale law relating wind velocity to Beaufort force. Wave heights in the scale are for conditions in the open ocean, not along the shore. The wind speeds in different units are not mathematically equivalent; e.g. 12–19 km/h is not equivalent to 8–12 mph, and both are not equivalent to 7–10 knots. The reason is that the Beaufort scale is not an exact nor an objective scale. It was based on visual and subjective observation of a ship and of the sea. The corresponding integral wind speeds were determined later, but the values in different units were never made equivalent. The scale