Tropical cyclone scales barometric pressure is low compared with its surroundings. Other classifications historically used include: cyclonic storm where the winds did not exceed force 10 on the Beaufort scale and a Cyclone where the winds are either force 11 and 12 on the Beaufort scale. Between 1924 and 1988, tropical cyclones were classified into four categories: depression, deep depression, cyclonic storms and severe cyclonic storms. However, a change was made during 1988 to introduce the category "severe cyclonic storm with core of hurricane winds" for tropical cyclones, with wind speeds of more than . During 1999 the categories Very Severe Cyclonic Storm
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