Beaufort scale the extension to 17 noted above. China also switched to this extended version without prior notice on the morning of 15 May 2006, and the extended scale was immediately put to use for Typhoon Chanchu. Hong Kong and Macau retain force 12 as the maximum. In the United States, winds of force 6 or 7 result in the issuance of a small craft advisory, with force 8 or 9 winds bringing about a gale warning, force 10 or 11 a storm warning ("a tropical storm warning" being issued instead of the latter two if the winds relate to a tropical
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