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Subject: A19) What does ATCF stand for and how are tropical cyclones numbered?

Contributed by Neal Dorst

The Automated Tropical Cyclone Forecast (ATCF) system was developed for the Joint Typhoon Warning Center in 1988. This is a software package used to plot tropical cyclone information and assist in the generation of forecast messages. In order to distinguish different tropical cyclones that might be occurring simultaneously, a distinct alphanumeric code is assigned to each cyclone as it develops. This code system was adopted by other warning centers in order to facilitate the passing of storm information and reduce confusion.

The code designation consists of two letters designating the oceanic basin ("AL" for Atlantic, "EP" for Eastern Pacific, "CP" for Central Pacific and "WP" for Western Pacific), a two-digit number designating the sequential number of that particular cyclone for that basin in the year, and lastly a four-digit year number. So the first depression to form in the Atlantic for 2001 would be AL012001, the third depression for the Central Pacific in 1999 would be CP031999.

A cyclone retains its ATCF code designation as long as it remains a distinct tropical vortex. Even if it becomes a named Tropical Storm or Hurricane the software will still track it by its ATCF code.

References

Miller, R.J., J. Schrader, C.R. Sampson, and T.L. Tsui, 1990, "The Automated Tropical Cyclone Forecasting Sytem (ATCF)",Weather and Forecasting, Vol. 5, (Dec. 1990), p. 653-660


Revised August 14, 2009

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