Post-tropical cyclone
A post-tropical cyclone is a former tropical cyclone that no longer possesses enough tropical qualities to be considered a tropical cyclone.[1] The word may refer to a former tropical cyclone undergoing extratropical transition or a tropical cyclone degenerating into a remnant low. A tropical cyclone degenerating into a trough or wave, or having its low level circulation dissipate overland, lacks a cyclonic circulation and is referred as remnants instead of a post-tropical cyclone. However, post-tropical cyclones or remnants can continue producing high winds and heavy rains.[2]
Formation[edit]
A post-tropical cyclone is formed when the typical characteristics of a tropical cyclone are replaced with those of extratropical cyclones, otherwise known as extratropical transition.[23] After the initial formation, a post-tropical cyclone has the potential to gain strength and intensity by forming an extratropical storm.[23] If a post-tropical cyclone does become an extratropical storm, it will eventually decay through the process of occlusion.[24]
Impacts[edit]
The re-intensification of a post-tropical cyclone can cause dangerous conditions in North Atlantic shipping routes with high seas and winds comparable to those of hurricanes.[23]
Origin[edit]
The terminology was initiated by Meteorologist Peter Bowyer of the Canadian Hurricane Centre in 1998 during Tropical Storm Bonnie.[25] In 2008, the National Hurricane Center used this term for Tropical Storm Laura to address the limitation of the two classes (extratropical/remnant low) mentioned above.[26] The term was later adopted by the National Weather Service on May 15, 2010.[7]
Synonym[edit]
The Bureau of Meteorology in Australia refers to a former tropical cyclone as an "ex-tropical cyclone".[27] An example is ex-tropical cyclone Oswald.