Geographical distribution of weather catastrophes in the United States

In the 1949-2008 data period, the nation experienced 1,506 storm catastrophes (each causing losses of $1 million or more), and these caused insured losses totaling $368.1 billion. Catastrophes were most frequent in the eastern half of the nation, as were their losses, with 82% of catastrophes there and 91% of the nation's losses. The highest regional loss for 1949-2008 was $147.5 billion in the Southeast. Regional ranks based on average losses differed from those based on the 60-year frequency of catastrophes. The distributions of catastrophes and their losses were examined for the three 20-year periods during 1949-2008. The first period, 1949-1968, had fewer catastrophes in most regions than the two later periods, with less than 20% of the total catastrophes. In six regions, average losses per catastrophe were highest in the period 1949-1968, while average losses were highest in 1989-2008 in the Central, Southeast, and Southwest regions. In all but the Southwest region, average storm losses were lowest in the 1969-1988 period. The results reflect spatial and temporal differences in the atmospheric conditions that cause catastrophic storm events. The shift to much higher losses in the Southeast since 1990 reflects recent enhancement of intense tropical storms. The nation's eastern half also had its greatest number of catastrophes in this recent period. There is also evidence that these recent increases are a result of enhanced societal vulnerability to storm damages.