Rainfall Hazard from Tropical Cyclones

The assessment of rainfall hazard from tropical cyclones (TCs) typically relies on empirical models, which estimate the rainfall field for a given TC intensity and motion category as the ensemble average over the historical storms in that category. The coarseness of the classification, the exclusion of other relevant storm parameters (most notably the radius of maximum winds), and the paucity of the historical data make the estimates rather inaccurate. Moreover, ensemble averaging suppresses the all-important fluctuations due to rainbands and local convection and severely underestimates the rainfall maxima. We have developed an alternative approach to evaluate the probability distribution of the maximum rainfall intensity in a period d at a geographical point due to passage of a tropical cyclone. This maximum rainfall intensity, Imax(θ, r, d), depends on the duration d, the distance r of the point from the storm center, and several storm parameters θ. The calculated distributions of Imax(θ, r, d) are in good agreement with maximum rainfall intensities estimated from TRMM measurements.