Tropical cyclone is the catch-all term for the powerful, spinning storms that feed off warm oceans and the strength of which is determined by wind speeds. The strongest are known as hurricanes in the Atlantic and typhoons in the Western Pacific and simply tropical cyclones in the South Pacific.

Alfred, Seru and Rae east of Australia in the South Pacific. (CSU/CIRA & NOAA via AP) Three tropical cyclones are spinning in the South Pacific, an occurrence that scientists say is unusual. Tropical cyclones Rae,

The unusual activity is "a lot to happen at once, but not unprecedented," an atmospheric science professor said.