每三小时一次 meaning in English

be taken at three-hour intervals

Hitherto the tropical cyclone warning for shipping is issued in english only . commencing today ( 11 august 2004 ) , the chinese version of the shipping warning is also available from the observatory s website once every three hours for use by personnel of shipping companies , mariners and members of the public who operate in chinese
船舶警告以往只以英文发放。现为方便使用中文的船公司人员、航海和公众人士，从今天( 2004年8月11日)起，天文台在网页内发放为船舶提供的热带气旋警告中文版，每三小时一次。
Hitherto the tropical cyclone warning for shipping is issued in english only . commencing today 11 august 2004 , the chinese version of the shipping warning is also available from the observatory s website once every three hours for use by personnel of shipping companies , mariners and members of the public who operate in chinese
船舶警告以往只以英文发放。现为方便使用中文的船公司人员、航海和公众人士，从今天( 2004年8月11日)起，天文台在网页内发放为船舶提供的热带气旋警告中文版，每三小时一次。