A U.S. study suggested the estimate of the number of Atlantic tropical storms occurring before the advent of aircraft and satellites is fundamentally accurate.

The counting of historic storms relies on ships logs and hurricane landfalls, resulting in the belief such historic Atlantic tropical storms might have been substantially undercounted.

The new statistical model based on climate factors that influence Atlantic tropical storm activity showed the estimates currently used are only slightly below modeled numbers, said Penn State Associate Professor Michael Mann. The new data also indicated the numbers of tropical storms in the recent past are increasing.

In the past, some researchers assumed a constant percentage of all the storms made landfall and so compared the number of tropical storms making landfall with the number of reported storms for that year. Other researchers looked at ship logs and tracks to determine how likely a tropical storm would have been missed.

However, during and before the early 1900s there were probably not a sufficient number of ships crossing the Atlantic to ensure full coverage, said Mann.

The researchers, writing in the Geophysical Review Letters, said they believe the average undercount bias was at most approximately one tropical storm annually back to 1870.  // Copyright 2007 by United Press International




Publication date: 26 November 2007   

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