Typhoon

A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern (North America to 140°W), central (140°W to 180°), and western (180° to 100°E). The Regional Specialized Meteorological Center (RSMC) for tropical cyclone forecasts is in Japan, with other tropical cyclone warning centers for the northwest Pacific in Hawaii (the Joint Typhoon Warning Center), the Philippines and Hong Kong. While the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year. A hurricane is a gale-force tropical cyclone that occurs in the Atlantic Ocean or the northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a tropical cyclone occurs in the South Pacific or the Indian Ocean. A typhoon is a mature tropical cyclone that develops between 180° and 100°E in the Northern Hemisphere. This region is referred to as the Northwestern Pacific Basin, and is the most active tropical cyclone basin on Earth, accounting for almost one-third of the world's annual tropical cyclones. For organizational purposes, the northern Pacific Ocean is divided into three regions: the eastern (North America to 140°W), central (140°W to 180°), and western (180° to 100°E). The Regional Specialized Meteorological Center (RSMC) for tropical cyclone forecasts is in Japan, with other tropical cyclone warning centers for the northwest Pacific in Hawaii (the Joint Typhoon Warning Center), the Philippines and Hong Kong. While the RSMC names each system, the main name list itself is coordinated among 18 countries that have territories threatened by typhoons each year. A hurricane is a gale-force tropical cyclone that occurs in the Atlantic Ocean or the northeastern Pacific Ocean, a typhoon occurs in the northwestern Pacific Ocean, and a tropical cyclone occurs in the South Pacific or the Indian Ocean. Within the northwestern Pacific, there are no official typhoon seasons as tropical cyclones form throughout the year. Like any tropical cyclone, there are a few main requirements for typhoon formation and development: (1) sufficiently warm sea surface temperatures, (2) atmospheric instability, (3) high humidity in the lower to middle levels of the troposphere, (4) enough Coriolis effect to develop a low pressure center, (5) a pre-existing low level focus or disturbance, and (6) a low vertical wind shear. While the majority of storms form between June and November, a few storms do occur between December and May (although tropical cyclone formation is at a minimum during that time). On average, the northwestern Pacific features the most numerous and intense tropical cyclones globally. Like other basins, they are steered by the subtropical ridge towards the west or northwest, with some systems recurving near and east of Japan. The Philippines receive the brunt of the landfalls, with China and Japan being impacted slightly less. Some of the deadliest typhoons in history have struck China. Southern China has the longest record of typhoon impacts for the region, with a thousand-year sample via documents within their archives. Taiwan has received the wettest known typhoon on record for the northwest Pacific tropical cyclone basins. The term typhoon is the regional name in the northwest Pacific for a severe (or mature) tropical cyclone, whereas hurricane is the regional term in the northeast Pacific and northern Atlantic. Elsewhere this is called a tropical cyclone, severe tropical cyclone, or severe cyclonic storm. The Oxford English Dictionary cites Urdu ṭūfān and Chinese tai fung giving rise to several early forms in English. The earliest forms—'touffon', later 'tufan', 'tuffon', and others—derive from Urdu ṭūfān, with citations as early as 1588. From 1699 appears 'tuffoon', later 'tiffoon', derived from Chinese with spelling influenced by the older Urdu-derived forms. The modern spelling 'typhoon' dates to 1820, preceded by 'tay-fun' in 1771 and 'ty-foong', all derived from the Chinese tai fung. The Urdu source word توفان ṭūfān ('violent storm'; cognate to Hindi तूफ़ान (tūfān)) comes from the Persian tūfān (Persian: توفان/طوفان‎) meaning 'storm' which comes from the verb tūfīdan (Persian: توفیدن/طوفیدن‎), 'to roar, to blow furiously'. The word طوفان (ṭūfān) is also derived from Arabic as coming from ṭāfa, to turn round. The Chinese source is the word tai fung or taifeng (simplified Chinese: 台风; traditional Chinese: 颱風; pinyin: táifēng). The modern Japanese word, 台風 (たいふう, taifuu), is also derived from Chinese. The first character is normally used to mean 'pedestal' or 'stand', but is actually a simplification of the older Chinese character 颱, which means 'typhoon'; thus the word originally meant 'typhoon wind'. The Ancient Greek Τυφῶν (Typhôn, 'Typhon') is related and has secondarily contaminated the word. The Persian term may originally have been influenced by the Greek word. A tropical depression is the lowest category that the Japan Meteorological Agency uses and is the term used for a tropical system that has wind speeds not exceeding 33 knots (38 mph; 61 km/h). A tropical depression is upgraded to a tropical storm should its sustained wind speeds exceed 34 knots (39 mph; 63 km/h). Tropical storms also receive official names from RSMC Tokyo. Should the storm intensify further and reach sustained wind speeds of 48 knots (55 mph; 89 km/h) then it will be classified as a severe tropical storm. Once the system's maximum sustained winds reach wind speeds of 64 knots (74 mph; 119 km/h), the JMA will designate the tropical cyclone as a typhoon—the highest category on its scale. From 2009 the Hong Kong Observatory started to further divide typhoons into three different classifications: typhoon, severe typhoon and super typhoon. A typhoon has wind speed of 64-79 knots (73-91 mph; 118–149 km/h), a severe typhoon has winds of at least 80 knots (92 mph; 150 km/h), and a super typhoon has winds of at least 100 knots (120 mph; 190 km/h). The United States' Joint Typhoon Warning Center (JTWC) unofficially classifies typhoons with wind speeds of at least 130 knots (67 m/s; 150 mph; 241 km/h)—the equivalent of a strong Category 4 storm in the Saffir-Simpson scale—as super typhoons. However, the maximum sustained wind speed measurements that the JTWC uses are based on a 1-minute averaging period, akin to the U.S.' National Hurricane Center and Central Pacific Hurricane Center. As a result, the JTWC's wind reports are higher than JMA's measurements, as the latter is based on a 10-minute averaging interval.