All good questions. To be as to the point however, radar is one additional tool that for tropical cyclones, may assist Meteorologists determine overall rotation, or in fact if there is a clear and obvious center. Often times, in a weak system, especially at night time, it is diffucult to determine a "fix" or center point of a low pressure area. Well, with satellite............and given a well developed eye within a hurricane, there is no doubt as to the location and motion of that system. Recon flights offer different diverse information. One being a center fix - pretty much a where is it, how strong is it, barometric pressure, wind speed, and other readings specific to the current state of the storm. Perhaps more importantly however, are observations and samplings done of surface conditions ( sea surface temp, wave heights, etc ) to wind and pressure readings of the different levels of the atmosphere. This data, when fed into computers, further help scientists by providing the necessary information to assist in analyzing steering conditions and influences on future intensity.. The planes are basically flying laboratories that gather information for hundreds of miles around, within, and in advance of an approaching storm.