Evaluation of TRMM and SSM/I imagery in the early development of tropical cyclones

This paper examines the characteristics of the inner convective region of developing tropical cyclones as depicted in the microwave spectrum of the satellite-based TRMM and SSM/I imagery. With the launch of the TRMM satellite in late 1997, a new microwave source has become available over the tropical oceans to complement the older SSM/I imagery. With its 35-degree inclination and altitude of 350km, the TRMM Microwave Imager (TMI) has the ability to see more frequent changes and finer detail within the inner convective core of developing tropical cyclones than the higher flying SSM/I sensor. In addition, both of these sensors have the ability to capture the earlier stages of tropical cyclone development over the open oceans more frequently than from land-based or aircraft-based radar data. Initial results show earlier development and organization of pre-eyewall convection than would be expected from viewing more conventional infrared and visual imagery. It is proposed that the timing and characteristics of this inner convection will provide an early signal to the tropical cyclone forecaster for the potential and future rate of intensification of these developing tropical cyclones.