The climatology and interannual variability of landfalling tropical cyclones in the United States is examined. The analysis is based on daily gridded US precipitation data, Atlantic basin tropical cyclone track data, SST data in the tropical Pacific, and monthly mean values of the Arctic Oscillation, for the period June-November 1950-1998. Tropical cyclones originating in both the Atlantic and the northeast Pacific are considered. Studying tropical cyclone impacts is a necessary and beneficial undertaking as it relates directly to monthly and seasonal long-lead forecasts released by the CPC; the mean percentage of precipitation due to TCs often averages greater than 15% during peak months (e.g., September and October) for both the eastern United States as well as western Mexico.

The climatology provides a foundation for subsequent analysis of the interannual variability of landfalling tropical cyclones as related to the leading patterns of interannual climate variability (i.e., El Niņo-Southern Oscillation and the Arctic Oscillation). Relationships between tropical cyclone frequency and intensity and composites of 200-hPa geopotential height and wind shear anomalies are examined as a function of ENSO and AO phase.