Rainfall and convective properties of tropical cyclones (TCs) are statistically quantified for different TC intensity change categories by using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2008. Four 24-h future intensity change categories are defined: rapidly intensifying (RI), slowly intensifying, neutral, and weakening. It is found that RI storms always have a larger raining area and total volumetric rain in the inner core. The maximum convective intensity in the inner core is not necessarily more intense prior to undergoing an RI episode than a slowly intensifying, neutral, or weakening episode. Instead, a minimum threshold of raining area, total volumetric rain, and convective intensity in the inner core is determined from the RI cases examined in this study. The following necessary conditions for RI are found in the inner core: total raining area > 3000 km(2), total volumetric rain > 5000 mm h(-1) km(2), maximum near-surface radar reflectivity > 40 dBZ, maximum 20-dBZ (40 dBZ) echo height > 8 (4) km, minimum 85-GHz polarization-corrected brightness temperature (PCT) < 235 K, and minimum 10.8-m brightness temperature < 220 K. To the extent that these thresholds represent all RI cases, they should be of value to forecasters for ruling out RI. This study finds that total lightning activities in the inner core (outer rainband) have a negative (positive) relationship with storm intensification.

AbstractConvective and rainfall properties of tropical cyclones (TCs) are statistically quantified by using Tropical Rainfall Measuring Mission (TRMM) data from December 1997 to December 2008. A semimanual method is used to divide the TC raining area into inner core (IC), inner rainband (IB), and outer rainband (OB) regions. Precipitation features (PFs) within these regions are compared for their convective vigor and rainfall characteristics based on passive microwave, infrared, radar, and lightning properties. Strong convective signatures are generally found more often in precipitation features in the IC region, less often in the IB region, and least often in the OB region when examining features with sizes greater than 1000 km2. However, at the very strong end of the convective spectrum, the magnitude of ice scattering signatures in OB features tends to be comparable and even stronger than that in IC features. The flash density when normalized by the raining area is about 2–3 times higher in IC features...