Areas of Formation

Tropical Cyclones can form in most tropical oceans of the world, although some areas exhibit noticeably more activity than others. Whilst a significant portion of storms develop in the deep tropics,some can form outside of the tropical zone, as long as sea surface temperatures are warm enough.

Image: Heatmap of all tropical cyclone activity in 2017. Some areas that didn’t see activity that year can exhibit activity in other years.

The world’s most active basin is the Western Pacific Ocean, with the statistically most active areas ofthe world being in the Philippine Sea, off the country’s eastern coast. On average, 28 storms form inthe Western Pacific each year.

The next active basin is the Eastern Pacific, featuring an average of 18 storms per year and subdividedinto two regions – the Eastern Pacific and the Central Pacific (east of the International Date Line). Thearea of ocean off the coast of western Mexico is typically the busiest, with Hawaii only seeingoccasional storm effects.

The North Atlantic ocean features an average of 12 storms per year, with its main breeding groundknown as the Main Development Region, east of the Lesser Antilles. Many long tracking storms beginin this area or further east, typically forming from tropical waves that started over Africa.

Other basins, such as the North and South Indian oceans, the South Pacific ocean, and on rare occasionsthe South Atlantic ocean, make up the rest of the numbers, with 70% of all activity occurring in thenorthern hemisphere on average.