Climatological relationships between tropical cyclones and rainfall

Flooding from tropical cyclone (TC) precipitation has lead in recent years to massive death and loss of property. The identification of climatological linkages between rainfall and TC parameters through study of longterm records would be useful in (i) identifying seasonal predictive climatic parameters to TC development, (ii) producing better precipitation estimates for affected areas, and (iii) developing better parameterizations between storm intensity, latent heat release, and rainfall in hurricane models. This study uses a daily satellite-derived oceanic precipitation record from 1979 to 1995 to determine the rainfall associated with the Atlantic and North Pacific basins over that time period (877 TCs). These data, categorized into 2.5°x 2.5°ocean grid cells, were used to create two precipitation databases. The first uses the surrounding nine grid cells marked from the average position of the tropical cyclone on the day of observation, while the second uses only the center grid cell for the day (representative of only the inner-core precipitation). Strong relationships were found to exist between daily rainfall accumulation and a TC's daily maximum surface wind speeds. The precipitation associated with the inner core is generally representative of the cyclone's total rainfall. The relationship between the ratio of inner-core rainfall and the total storm rainfall with maximum surface winds demonstrates a U-shaped pattern. The inner-core precipitation accounts for nearly 35% of the total rain of the weakest TCs and also of the strongest hurricanes but less than 25% of the total rainfall for weak hurricanes. Forecasters can used rainfall relationships such as these to aid in heavy rainfall and flooding warnings for affected land areas.