 Tropical cyclones are considered to be non-frontal, low pressure systems that develop, within an environment of warm sea surface temperatures and little vertical wind shear aloft.Within the South Pacific basin to the east of 160°E, the cyclone season is defined as running between November 1 and April 30 of the following year.During the off-season a total of 90 tropical cyclones have been recorded during the off-season, with a total of 53 of these systems occurring after satellite imagery became regularly available during the 1969–70 season.