Stemming from the success of the third Convection and Moisture Experiment, a fourth experiment (CAMEX-4) was conducted in August and September of 2001 over the Atlantic Ocean. This experiment provided unprecedented data on the topic of tropical convection, including the first operational deployment of the High Altitude MMIC Scanning Radiometer (HAMSR), and the first dropsondes ever released from the stratosphere into a mature tropical cyclone (Hurricane Erin on 10 September). The colocation and analysis of these important data, as this project attempts, will provide an excellent resource in which the microphysical structure of tropical cyclones may be better examined.