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
MS Estonia starboard because of poor cargo distribution. According to the final disaster report, the weather was rough, with a wind of , force 7–8 on the Beaufort scale and a significant wave height of compared with the highest measured significant wave height in the Baltic Sea of . Esa Mäkelä, the captain of "Silja Europa" who was appointed on-scene commander for the subsequent rescue effort, described the weather as "normally bad", or like a typical autumn storm in the Baltic Sea. All scheduled passenger ferries were at sea. The official report says that while the exact speed at the time of