Frequency of Heavy Rainfall Events in New Orleans, Louisiana, 1900 to 1991

The large number of recent heavy rainfall events in New Orleans, Louisiana, has raised concerns about change in the heavy rainfall climatology in the area. As a result, all rainfall events exceeding 125 mm were examined with respect to their generating mechanisms, seasonality, and changing frequencies through time. Two thirds of the storms were induced by frontal weather situations and tropical systems produced about a fourth. Storm seasonality was bimodal with peaks in late spring and early fall. With regard to changing frequencies through time, the entire New Orleans rainfall record suggests that storms may have a pattern of increasing occurrence. However, a temporally homogenous subset of these data were tested statistically and no significant change was found.