Platinum Underwriters Holdings Ltd said yesterday that it expects losses from severe weather in the US to have a negative impact of almost $25 million on its first-quarter financial results.The losses relate mainly to tornadoes and hailstorms in Kentucky and Tennessee during the first quarter.The reinsurer said the $24.8 million net negative impact from these events includes preliminary estimates of losses and loss adjustment expenses, reinstatement premiums and taxes.Platinum added that it does not currently anticipate any material impact to its first quarter results from major catastrophe events that occurred in 2011 and prior years.More than 150 tornadoes touched down in two distinct systems between February 28 and March 3, with the most occurring in Tennessee, Kentucky, Indiana, Illinois, and Alabama.Last year, Platinum sustained a net loss of $224.1 million, driven by catastrophe losses, and recorded a combined ratio of 143 percent. Many Bermuda reinsurers saw their financial results hit hard last year, when the insurance industry suffered natural disaster losses of $110 billion, according to Swiss Re.