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
RRS Discovery over the Christmas period the ship was blocked in by pack ice. A Norwegian whaler was met on December 29, which gifted the "Discovery" a further 50 tons of coal. On December 31 the ship was struck by a violent storm with winds of up to 70 mph (Force 11 on the Beaufort Scale). The ship was driven against the ice, while larger bergs were blown onto the ship by the wind. For eight hours the "Discovery" was repeatedly slammed into and onto thick ice and battered by bergs but MacKenzie was able to slowly work the ship offshore by