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Late-starting hurricane seasons

By: Dr. Jeff Masters, 2:01 PM GMT on July 29, 2009

Late-starting hurricane seasons--ones where the first named storm of the year doesn't occur until August--have happened in eleven of the fifty years between 1960 - 2009 (a 22% occurrence.) Only two of these eleven seasons ended up with more hurricanes than average (seven or greater). The record for the latest starting hurricane season since 1851 was set in 1914, when the only storm of the season formed on September 15. The year 1941 was also late starting, with the season's first storm arriving on September 11. Of course, we didn't have satellites back then, so it's a good bet there were storms earlier in these seasons that got missed. However, there's a good possibility that 1914 really did have only one storm. A re-analysis of the hurricane activity in the decade 1911-1920 (Landsea et al., 2008) found 1.3 missing tropical cyclones per year, thanks to the inclusion of a new database of ship weather reports called COADS. However, 1914 was not one of those years. Various authors have estimated that we missed an average of between one and three tropical cyclones per year during that time period, so it is quite possible 1914 had only one storm.

Figure 1. The hurricane season of 1914 featured only one tropical storm, and was the latest-starting hurricane season on record (September 15).

The latest dates for the first named storm of the season in the recent past, followed by the number of named storms, hurricanes, and intense hurricanes that year are:

2009 (August 15) 9,3,2
2004 (August 1) 15,9,6
2000 (August 4) 15,8,3
1988 (August 7) 12,6,3
1987 (August 9) 7,3,1
1984 (August 18) 13,5,1
1983 (August 15) 4,2,1
1977 (August 30) 6,5,1
1967 (August 30) 8,6,2
1963 (August 2) 9,6,2
1962 (August 22) 5,3,1

We can also add 1992 to the list if we ignore the unnamed subtropical storm that formed in April of that year. That year had the notorious Hurricane Andrew as its first named storm. Andrew formed on August 17 of that year, and was the only major hurricane in a year that had only seven named storms and four hurricanes. For comparison, an average Atlantic hurricane season has 10 named storms, 6 hurricanes, and 2 intense hurricanes. So, it is a good bet that 2009 will be a below-average season.

Landsea, C. W. , D. A. Glenn, W. Bredemeyer, M. Chenoweth, R. Ellis J. Gamache, L. Hufstetler, C. Mock, R. Perez, R. Prieto, J. Sanchez-Sesma, D. Thomas, and L. Woolcock, 2008, A Reanalysis of the 1911-20 Atlantic Hurricane Database", Journal of Climate, 21, p.2138-2168.

Jeff Masters


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