In this paper a comparison is presented between simulations of the diurnal and semidiurnal tides in the middle and upper atmosphere from the thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIMEGCM) and satellite observations from the Upper Atmosphere Research Satellite (UARS) high-resolution Doppler imager (HRDI). Reasonable agreement is found between the model and observations for a March condition when a strong diurnal tide was observed. The model is able to reproduce many tidal features at altitudes between 65 and 110 km as observed in the HRDI wind measurements. Of interest in these features is the shortening vertical wavelength of the (1,1) tide in the upper mesosphere and lower thermosphere, which appears in both model simulations and the wind observations. The HRDI data also show large longitudinal variations in the diurnal tide, of which the amplitude can be as high as ~50% of the migrating tide. The wavelike structures in latitude and altitude dimensions suggest that the longitudinal variations are likely due to the presence of propagating nonmigrating tides in the upper mesosphere and lower thermosphere. For further investigations of the observed tidal variability the model demonstrates great potential with the use of more realistic heating/cooling and wave forcing schemes. ¿ American Geophysical Union 1996