Tropical Cyclone Climatology
Global Tropical Storm Formation
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Approximately 85 tropical storms annually develop over the world's warm tropical oceans.
Cyclone, Hurricane, and Typhoon Development
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More than half (45) of these storms intensify into tropical cyclones, also regionally known as hurricanes or typhoons.
Geographical Distribution
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72% of these tropical storms form in the Northern Hemisphere.
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The remaining 28% develop in the Southern Hemisphere.
The diagram below illustrates the seasonal tropical cyclone activity across various basins.
mean_ann_cycle_all.jpg (638×657) (ucar.edu)
Average annual cycle of tropical cyclone occurrence for each ocean basin. The abscissa spans the 13 months, December through January of the following year; the ordinate is the number of storms per hundred years. For each day, the graph shows the number of years that a cyclone was present (normalized per 100 years). The blue line represents all tropical cyclones (surface winds greater than 17 m s-1 or 34 knots); shading represents tropical cyclones of hurricane strength (surface winds greater than 33 m s-1 or 64 knots).