Range and velocity ambiguities pose significant data quality challenges for the Terminal Doppler Weather Radar (TDWR). For typical pulse repetition frequencies (PRFs) of 1-2 kHz, the radar is subject to both range-ambiguous precipitation returns and velocity aliasing. Experience shows that these are a major contributor to failures of the system's wind shear detection algorithms. Here we evaluate the degree of mitigation offered by existing phase diversity methods to these problems. Using optimized processing techniques, we analyze the performance of two particular phase codes that are best suited for application to TDWRs- random and SZ(8/64) [Sachidananda and Zrnic', [1999]- in the protection of weak-trip power, velocity, and spectral width estimates. Results from both simulated and real weather data indicate that the SZ(8/64) code generally outperforms the random code, except for protection of 1st trip from 5th trip interference. However, the SZ code estimates require a priori knowledge of out-of-trip spectral widths for censoring. This information cannot be provided adequately by a separate scan with a Pulse Repetition Frequency (PRF) low enough to unambiguously cover the entire range of detectable weather, because then the upper limit of measurable spectral width is only about 2 m/s . For this reason we conclude that SZ phase codes are not appropriate for TDWR use. For velocity ambiguity resolution, the random phase code could be transmitted at two PRFs on alternating dwells. Assuming the velocity changes little between two consecutive dwells, a Chinese remainder type of approach can be used to dealias the velocities. Strong ground clutter at close range, however, disables this scheme for gates at the beginning of the 2nd trip of the higher PRF. We offer an alternative scheme for range-velocity ambiguity mitigation: Multistaggered Pulse Processing (MSPP). Yielding excellent velocity dealiasing capabilities, the MSPP method should also provide protection from patchy, small-scale out-of-trip weather. To obtain maximum performance in both range and velocity dealiasing, we suggest that information from the initial low-PRF scan be used to decide the best waveform to transmit in the following scan-random phase code with alternating-dwell PRFs or MSPP. Such an adaptive approach presages future developments in weather radar, for example electronically scanned arrays allow selective probing of relevant weather events.