In support of the THORPEX Pacific Asian Regional Campaign (T-PARC) and the ONR Tropical Cyclone Structure-08 (TCS08) experiments, adaptive observing guidance for tropical cyclones will have been provided from a number of operational, academic and research institutions all over the world. At the Naval Research Laboratory, mesoscale model guidance is produced twice daily using the recently developed adjoint and tangent linear models for the atmospheric portion of the nonhydrostatic Coupled Atmosphere/Ocean Mesoscale Prediction System (COAMPS) over the Northwestern Pacific. A unique aspect of this system is that an exact adjoint to the explicit microphysics has been developed. An adaptive response function region is used to target favorable areas for tropical cyclogenesis and development. Real-time COAMPS-adjoint forecasts with lead times of 36 h and 48 h were executed twice daily during T-PARC/TCS08 using a horizontal resolution of 40 km. The characteristics of the COAMPS sensitivity patterns such as preferred altitudes, comparison of wind field to temperature and moisture field sensitivities, and sensitivity to the sea surface temperature will be summarized. Preliminary data-denial experiment results will be presented and the implications for observing system design on the mesoscale will be discussed. Implications of the adjoint-based sensitivity fields for the predictability of tropical cyclone formation will be addressed.