Quantifying the contribution of tropical cyclones to extreme rainfall along the coastal southeastern United States

Abstract

Analysis of a unique satellite precipitation dataset coupled with an extensive database of storm tracks are used to develop a parameter called the “millimeter‐day (MD).” MD analysis in 4 mini‐basins near coastal southeastern United States reveals that September and October account for the largest number of extreme rainfall days (e.g. “wet millimeter‐days” or MD > 0) during the 1998–2006 Atlantic hurricane seasons. Tropical cyclone (TC) days are more likely to produce “wet millimeter days” than non‐TC days, and category 3–5 hurricane days (e.g., major hurricanes) produce the wet millimeter‐days of largest magnitude. Major hurricanes produce the most extreme rainfall days, but tropical depression/storm days contribute most significantly to cumulative seasonal rainfall (8–17%, basin‐dependent) due to frequency of occurrence. Thus, the influence of major hurricanes on rainfall may be most apparent in extreme daily events while weaker storms may be more critical for assessing trends in cumulative seasonal rainfall.