User:LightandDark2000/Subtropical Cyclone Lexi

Subtropical Cyclone Lexi, unofficially named by researchers, was a highly-unusual subtropical cyclone that formed in May 2018 to the west of the Chilean coast. After the 2017–18 South Pacific cyclone season had officially ended, the system was identified in early May outside the official boundaries of the basin, near Alejandro Selkirk Island, and was unofficially dubbed Lexi by independent researchers. Lexi was one of the few tropical or subtropical systems ever observed forming in the far Southeast Pacific, outside of the official basin boundary of 120°W, which marks the eastern edge of RSMC Nadi's and RSMC Wellington's warning areas, during the satellite era. Due to the fact that this storm developed outside of the official areas of responsibility of the warning agencies in the South Pacific, the storm was not officially included as a part of the 2017–18 South Pacific cyclone season.

Meteorological history
The storm originated as a cut-off extratropical low to the west of Chile on May 4. The storm slowly moved towards the northeast, before transitioning into a subtropical cyclone of tropical storm intensity later that day. Subsequently, the storm was identified by independent researchers and unofficially named Lexi. The system transitioned into a subtropical storm at 83.7°W, a few hundred miles off the coast of Chile, well to the east of the South Pacific basin's eastern boundary of 120°W. Around this time, Lexi developed a warm, asymmetric core, according to GFS modeling. Lexi developed over waters with temperatures between 18°C to 20°C (64°F to 68°F), which are usually too cold to support the formation of thunderstorms in tropical cyclones. At the time, the storm had a highly asymmetric rainfall pattern associated with two prominent rain bands, which wrapped around the exposed center of circulation. For the next couple of days, Lexi made a clockwise loop off the coast of Chile, strengthening as it did so, and reaching its peak intensity around 00:00 UTC on May 6, with a minimum central pressure of 992 mbar and maximum 1-minute sustained winds of 95 km/h (60 mph). Around the time of its peak, Lexi developed a symmetric warm core, according to GFS phase diagrams. Afterward, the storm gradually began to weaken, while completing its loop. On May 7, Lexi turned northeastward and began to move parallel to the coastline of Chile, while continuing its weakening trend. On May 8, Lexi weakened into a subtropical depression and also shrank in size, as it encountered more hostile conditions, before degenerating into a remnant low on the next day. Lexi's remnants persisted for another day, before dissipating early on May 10.

Records
Subtropical Cyclone Lexi is unofficially the easternmost tropical or subtropical cyclone ever observed to form in the South Pacific Ocean, transitioning into a subtropical system near 80°W, a few hundred miles off the coast of Chile. This broke the previous record of around 102.9°W, set by Subtropical Cyclone Katie in May 2015. "Lexi" was also the third tropical or subtropical system to form east of the South Pacific basin's official eastern boundary of 120°W, and the second such storm observed at tropical storm intensity. Tropical cyclogenesis is extremely rare in the far southeastern Pacific Ocean, due to the cold sea-surface temperatures generated by the Humboldt Current, lack of tropical disturbance formation, and also due to unfavorable wind shear; as such, there are no records of a tropical cyclone impacting western South America. Tropical cyclone formation in this extreme part of the Southeast Pacific is so rare that no warning agencies have yet been assigned to the region east of 120°W.