| Abstract from DBPedia | A subtropical cyclone is a weather system that has some characteristics of both tropical and an extratropical cyclone. As early as the 1950s, meteorologists were uncertain whether they should be characterized as tropical or extratropical cyclones. They were officially recognized and titled by the National Hurricane Center in 1972. Beginning in 2002, subtropical cyclones received names from the official tropical cyclone lists in the North Atlantic, South-west Indian Ocean, and South Atlantic basins. There are two definitions currently used for subtropical cyclones depending on their location. Across the north Atlantic and southwest Indian Ocean, they require some central convection fairly near the center surrounding a warming core existing in the mid-levels of the troposphere. Across the eastern half of the northern Pacific however, they require a mid-tropospheric cyclone to be cut off from the main belt of the westerlies and with only a weak surface circulation. Subtropical cyclones have wider wind fields with the maximum sustained winds located further from the center than typical tropical cyclones, and have no weather fronts linked into their center. Since they form from initially extratropical cyclones which have colder temperatures aloft than normally found in the tropics, the sea surface temperatures required for their formation are lower than the tropical cyclone threshold (around 26.5°C (79.7°F)) by 3°C (5°F), lying around 23 °C (73 °F). This also means that subtropical cyclones are more likely to form outside the traditional bounds of the North Atlantic hurricane season and at higher latitudes. Subtropical cyclones are also observed to form in the South Atlantic, where subtropical cyclones are observed in all months.亜熱帯低気圧（あねったいていきあつ、英: subtropical cyclone）とは、熱帯低気圧と温帯低気圧の中間的な性質をもった低気圧のこと。 対流圏下層では熱帯低気圧と同じ性質がみられるが、上層では寒気を伴っていて温帯低気圧の特徴を有している。基本的には熱帯低気圧のように暴風を伴い、湿った空気と大雨をもたらす。しかし熱帯低気圧と違って、北半球で発生した場合、雲の塊は回転する中心の北側または東側に偏って存在（南半球では西または南側）し、暴風の最も強い部分も中心から約500kmほど離れた辺縁部にあるほか、構造上気象やトラフとつながっていてそれらと関連性が強い。 現在、亜熱帯低気圧を低気圧の大分類として採用しているのはNOAA・NHCなど限られた機関のみである。NHCが管轄する大西洋海域や管轄の南西インド洋では、熱帯低気圧と同様に亜熱帯低気圧にも命名を行っている。一方、日本の気象庁では、一般に馴染んでいないことなどから予報用語として採用しておらず、公式には使用していない。 (Source: http://dbpedia.org/resource/Subtropical_cyclone) |
