The global hurricane season of 2005: was it unusual?

The Hurricane Season of 2005 in the Atlantic was unprecedented in its fury. Not only were records set for most tropical storms and hurricanes--2005 also saw three of the six most intense hurricanes on record. Was the rest of the globe also experiencing unusual levels of tropical cyclone activity? To answer this question, I have plotted in Table 1 the 2005 statistics, plus averages and all-time records, for the six ocean basins that experience tropical cyclones. Unfortunately, reliable records of tropical cyclone intensity in the Northwestern Pacific and Southern Hemisphere ocean basins begin in about 1987, so there is not much data available to do comparisons of how unusual the global hurricane season of 2005 was.


Table 1. Global tropical cyclone statistics for 2005 (in bold black, or green if a new record). Averages are given in parentheses. These averages are for the 1987-2004 period (18 years). All-time records are in red, and are for the entire time period data is available (1851-2004 for the Atlantic, 1949-2004 for the Northeast Pacific, and 1945-2004 for the other ocean basins).

Globally, the total number of tropical storms and hurricanes in 2005 was about 10% higher than average--97 were recorded, which is the second-most ever observed (the record is 101, observed in 1992). If one counts the Southern Hemisphere storms that occurred September through December 2004 as being part of the 2005 hurricane season, 2005 had 101 named storms, tying it for first place. Note that reliable records of total number of storms probably begin in the mid-1970s.

Besides the Atlantic, only the Southwest Pacific had an unusual 2005 hurricane season. There were five Category 4 and 5 storms in the ocean region east of Australia--which beat the old record of four storms. None of the 2005 cyclones caused loss of life or heavy damage. Category 5 Cyclone Meena merely brushed Raratonga in the Cook Islands, Category 4 Cyclone Ingrid hit a sparsely populated area of northern Australia, and the other three intense cyclones stayed out at sea. The other four ocean basins had rather ordinary seasons in 2005, with near average numbers of named storms, hurricanes, and intense hurricanes.

One rather amazing feature that stands out in 2005. For the first time on record, the Atlantic had more named storms than any other ocean basin. I thought I'd never see that happen! Atlantic storms, which usually make up just 11% of the global total, accounted for 28% of the global total in 2005. So while nature did indeed go berserk during the Atlantic Hurricane Season of 2005, the rest of the oceans did not, fortunately.

Next week: A 2005 paper in Science magazine presented evidence that the global number of Category 4 and 5 hurricane is increasing, due to global warming. Dr. Bill Gray of Colorado State has posted a critique of the findings, and claims there is no evidence that the global number of Category 4 and 5 hurricane is increasing. I'll present an in-depth analysis of the arguments pro and con.

Jeff Masters