With the approach of peak tornado season, it is timely that Risk Management Solutions (RMS) released a report analyzing the impact of the 2008 U.S. severe convective storm season. Last year's season, which included nearly 1,700 tornadoes, was the costliest in the last decade, causing more than $10.5 billion in insured losses. It was also the deadliest in a decade, with more than 125 fatalities.

In the paper, RMS highlights the precipitating factors that lead to active U.S. severe storm seasons. The Newark, Calif.-based catastrophe modeler notes that storms in the severe category include tornadoes, hail, straight-line winds, lightning strikes, and flash flooding. Hail storms account for more than 60 percent of the average annual loss, compared to 25 percent for tornadoes and 15 percent for straight-line winds, primarily because hail storms cover a larger area and occur more frequently and in coordination with tornadoes.

Almost half of last year's total insured losses were caused by five events, which RMS examines in relation to its convective storm model and methodology to offer insight. Although there has not been such a severe season for a number of years, RMS' analysis reveals that a season similar could be right around the corner.