Recent increases in U.S. heavy precipitation associated with tropical cyclones

Precipitation time series for 935 long-term U.S. climate stations were analyzed to identify daily extreme events associated with tropical cyclones (TCs). Extremes were defined as daily amounts exceeding a threshold for a 1 in 5-yr occurrence. TCs account for 30% or more of all such extreme events at a number of stations and about 6% of the national annual total. During 1994-2008, the number of TC-associated events was more than double the long-term average while the total annual national number of events was about 25% above the long-term (1895-2008) average. Despite the limited spatial area and portion of the annual cycle affected by TCs, the anomalous number of events associated with TCs accounted for over one-third of the overall national anomaly for 1994-2008. While there has been a recent increase in the number of landfalling U.S. hurricances, the increase in TC-associated heavy events is much higher than would be expected from the pre-1994 association between the two.