As we approach the end of the 2013 Atlantic hurricane season and take in the media attention around the anniversary of Superstorm Sandy, it is also important to mark the 8th anniversary of Hurricane Wilma’s landfall, which occurred October 24, 2005. This was the last major hurricane to make landfall on the U.S. coastline. It has now been 2,938 days without a major landfalling hurricane – remarkable given the changes scientists said might result from warmer sea-surface temperatures in the Atlantic Ocean. The U.S. landfalling hurricane event data set is one of the best meteorological records that exist in the U.S. In looking at the historical landfall record, the longest period without a major landfalling hurricane stands at 3,316 days (August 11, 1860 – September 8, 1869). If a major hurricane doesn’t make landfall in the U.S. next year, we will surpass the longest period without one.
Unless we are in some very unusual climate state that has not been discovered, there is a growing disconnect between overall Atlantic Basin activity and landfalling named storms. While the average overall Basin numbers are higher than normal since 2006, with every passing year since then the U.S. has seen only 19 named storms make landfall, and only six hurricanes – with no major hurricanes making landfall. This translates to a landfall rate of 0.75.
Using the landfall data from 1900, in a given year the expected landfall rate of a hurricane impacting the U.S. coastline is 1.5, with a 77% probability of at least one hurricane impacting the U.S. coastline. For major hurricanes the rate is 0.5 with a 40% probability – so the U.S. landfall rate is significantly below average.
Given this landfalling hurricane drought, the United States coastline has been lucky. Although insurance companies have been suffering losses of other types over it, the average annual hurricane loss during this drought has been just $4.9 billion, according to Property Claims Services. This is below the long-term average annual loss of $6.4 billion as calculated using the insured historical loss data from Dr. Pielke Jr., a database that attempts to normalize hurricane damages in the United States. Accounting for Superstorm Sandy in 2012, which was not a hurricane at landfall, this average annual loss since 2006 would increase to $7.7 billion.
With a below normal landfall rate of only 0.75 hurricanes since 2006, in the future the trend for more landfalls should correct back closer to the long-term rate if we assume that hurricane landfalls follow a poisson distribution and we are not in some unknown climate regime. After all, the probability of not having a major hurricane make landfall over a 9-year period is a very low 1%, meaning insurance companies should expect an increase in losses from hurricanes in the future. Something to ponder as we await next year’s forecast.