NU Online News Service, Sept. 27, 3:21 p.m. EDT

The increasing frequency of low severity, rare weather events is impacting underwriting results for property and casualty insurers in the U.S., and the phenomenon is credit negative for insurers, Moody's said in its Weekly Credit Report.

Moody's noted there has not been a severe natural catastrophe in the U.S. in 2009 and so far in 2010. "However," Moody's added, "the underwriting margins of many industry players, particularly those with property coverage concentrations, have suffered significant aggregate losses because of a sharp upswing in the frequency of low-severity perils including tornados, winter storms, hail and covered floods."

First-half catastrophe losses this year in the U.S. totaled $7.9 billion, Moody's said, citing ISO Property Claims Service data. For the 2009 first half, losses were $7.7 billion. These losses outpace the first-half average over the last 10 years of $6 billion, according to Moody's.