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
Storm warning is used to indicate a storm warning (the use of two such flags denotes a hurricane force wind warning or a hurricane warning). The same flag as a storm warning is used to indicate a tropical storm warning. On land, the National Weather Service issues a 'high wind warning' (Specific Area Message Encoding code: HWW) for storm-force winds, which also encompasses the lesser gale-force and greater hurricane force winds. In most cases, the warning applies to winds of 40-114 MPH for at least 1 hour; or any gusts of 58-114 miles per hour on land unless a tropical storm warning,