No Changes in US Hurricane Landings
The parade of hurricanes hitting the United States has not grown faster and more furious over the last century. An investigation into the frequency and intensity of hurricanes making landfall since 1900 concludes that the storms have continued striking the continental US at the steady average rate of two per year.
It's certainly true that hurricanes landed 15 times in the US during 2004 and 2005, making these two particularly disastrous years in a row. That period is balanced out by three years, 2000, 2001 and 2006, when no hurricanes reached the US coast, while one storm did hit in 2002 and two in 2003.
Altogether, the country had hurricane-strength storms make landfall 214 times between 1900 and 2006. The count includes repeated landings from several storms, such as the three by Hurricane Charley in August 2004, and two by Hurricane Andrew in August 1992.
Although the most notorious of storms to batter the US is Hurricane Katrina, which devastated the Gulf states in August 2005, it is not the most powerful. The strongest storm reaching the country since 1900 was the Labor Day Hurricane that swept the Florida Keys in September 1935. It struck land with winds of 185 miles per hour (160 knots or 300 kilometres per hour) and a central pressure estimated at 892 millibars (mb).
Probability calculations predict the chances of a storm with 185 mph winds appearing again is once in 265 years. Winds on land the magnitude of Katrina's 125 mph occur about every four years, and her central pressure of 920 mb resurfaces on average every 13 years.
The Labor Day Hurricane was well over the threshold for a category 5 storm on the Saffir-Simpson Hurricane Scale. Category 5 hurricanes have winds topping 155 mph and less than 920 mb pressure. Since 1900, hurricanes of category 5 severity have landed in Florida on average once every 23 years and in the Gulf states of Texas, Louisiana, Mississippi and Alabama once every 37 years.
The east coast from Georgia to Maine at worst gets a category 4 storm about every three decades. Overall, a major hurricane of category 3 or greater makes landfall every two years in the continental US.
While another Katrina-sized storm arriving on the US coastline in the near future is quite probable, there are few places where people need to fear another storm with the strength of the 1935 Labor Day Hurricane. The authors of this study believe such an intense storm would only make landfall on the two southernmost shores of the country: the Florida Keys or near Brownsville Texas.
Francis Parisi and Robert Lund. 2008. Return Periods of Continental U.S. Hurricanes. Journal of Climate. 21(2) 403-410.