From the International Business Times: Report: The Ten Most Expensive Natural Disasters In 2013. It is interesting to note that none of the big 10 occurred in the U.S.
An excerpt from the article:

Last year, about 84 percent of economic losses happened outside of the United States, well above the 2003-2012 average of 65 percent. The most expensive event in the U.S. was an EF-5 tornado that hit the city of Moore, Okla., in May — it cost about $3.8 billion in economic losses.