Tropical cyclone

As its own name indicates, it is the cyclone that forms within the tropical realm, although only the cyclonic system sufficiently developed to acquire the singular characteristics distinguishing it from a tropical depression and a tropical storm is given this name. That pair of low-pressure systems are also cyclones, but do not reach the status of tropical cyclone. It is very common to use the term hurricane as a synonym for tropical cyclone, but only those forming in the tropical band of the Atlantic basin and in the eastern part of the Pacific should be so named. Those forming in the rest of the ocean basins receive other generic names (typhoons, cyclones), apart from some local terms. The tropical cyclone always forms over warm waters located between the two tropics or, sporadically, in the subtropical realm. It reaches several hundred kilometers in diameter, its size varying greatly from one to another. Seen from satellite, it takes on a very characteristic spiral shape, with a cloud-free central area, called the "eye," of a few dozen kilometers in diameter, where atmospheric pressure reaches its lowest value (below 900 hPa in many cases) and winds are light. The eye is surrounded by a first ring of large cumulonimbi, forming a thick cloud wall in which torrential rains occur. That first ring is followed by others, separated from each other by concentric corridors in which very intense sustained winds blow. The strongest gusts are reached in the outer part of the eyewall. Throughout that outer area there is strong lightning activity. Depending on the intensity of the sustained winds generated by a tropical cyclone, it is assigned one of five possible categories. Hurricane status is reached when the intensity of those winds equals or exceeds 119 km/h (Saffir-Simpson scale).