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A tropical cyclone is not given a name (or, in some cases, a number) until the sustained maximum wind speed reaches a threshold of 34 Kt.

TC names are obtained from pre-designated lists maintained by the respective tropical cyclone regional bodies.

The intensity of tropical cyclones does not necessarily correspond to their size.   The images below were taken when Hurricanes Floyd and Andrew were nearly at the same location. Floyd is at least twice as large as Andrew; however, both were Category 4 storms with sustained winds around 120 kts and a central pressure of about 930 hPa.


The average annual frequency of (named) tropical cyclones (TCs) over the globe is 80 (please refer to ). Around 38% of these occur in the western North Pacific Ocean basin while only 6% occur in the North Indian Ocean. The inter-annual variability can be large for every tropical cyclone basin. You may find such information form the tropical cyclone season summaries by RSMCs for TC regional body sessions (

The most intense tropical cyclone recorded had a central pressure of 870 hPa. This was measured by dropsonde in Supertyphoon Tip over the western North Pacific in October 1979.

The highest 24-hour rainfall measured was 1,825mm (at an altitude of 2290m) on the island of La Réunion in TC Denise in January 1966.


Photos courtesy of NOAA

More information on tropical cyclones
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