page_title: 2017–18 South Pacific cyclone season
section_title: Other systems
hierarchical_section_title: 2017–18 South Pacific cyclone season / Systems / Other systems
caption_attribution_description: English: This satellite image from the Suomi-NPP satellite shows what is possibly a rare subtropical depression off the coast of Chile
context_page_description: The 2017–18 South Pacific cyclone season was a slightly below-average season that produced 6 tropical cyclones, 3 of which became severe tropical cyclones. The season officially began on November 1, 2017 and ended on April 30, 2018; however, a tropical cyclone could form at any time between July 1, 2017 and June 30, 2018 and would count towards the season total. During the season, tropical cyclones were officially monitored by the Fiji Meteorological Service, MetService and the Australian Bureau of Meteorology, while the United States Joint Typhoon Warning Center also monitored the basin and issued warnings for American interests. The FMS attaches a number and an F suffix to significant tropical disturbances that form in or move into the basin, while the JTWC designates significant tropical cyclones with a number and a P suffix. The BoM, FMS and MetService all use the Australian Tropical Cyclone Intensity Scale and estimate wind speeds over a period of ten minutes, while the JTWC estimates sustained winds over a 1-minute period, which are subsequently compared to the Saffir–Simpson hurricane wind scale.
context_section_description: During December 16, Tropical Disturbance 02F developed within a trough of low pressure, about 25 km (15 mi) to the northeast of the island of Futuna. During the following day, Tropical Disturbance 03F developed along the same trough of low pressure about 45 km (30 mi) to the southeast of the island of Wallis. Over the next couple of days, the disturbances moved southeastwards into areas of high vertical wind shear, before they were last noted during December 18 and 19 as they dissipated to the southeast of Samoa.
  On January 28, the JTWC issued a tropical cyclone formation alert on a tropical disturbance, which was located near the French Polynesian island of Rapa Iti. The system had a well defined low-level circulation, and was located within an area of warm sea surface temperatures and marginal vertical wind shear. The system subsequently peaked with 1-minute sustained wind speeds of 65 km/h (40 mph), which made it equivalent to a tropical storm. The alert was subsequently cancelled during the next day, after the system's low level circulation center became ragged, while atmospheric convection was displaced to the east of the circulation center.
  On May 4, 2018, a system identified as a subtropical cyclone formed east of 120°W, just a few hundred miles off the coast of Chile, with researchers unofficially naming the storm Lexi. The cyclone formed in an area without a Regional Specialized Meteorological Center, so it was not officially classified. On May 9, the satellite services division of the NOAA classified the system as a weak subtropical storm, despite occurring in cooler (below 20°C) sea surface temperatures.
caption: Subtropical Cyclone "Lexi" near Chile on May 7
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