We have developed a deep-atmosphere extension within the GMCORE (Grid-Model dynamical CORE) using a dry terrain-following mass-based coordinate. The new dycore retains the full three-dimensional Coriolis force, accounts for the height dependence of gravity, and introduces radial metric corrections into the discrete operators, while preserving the main structure of the original solver. Two idealized test cases are used for evaluation: a baroclinic wave test and a tropical cyclone test. In the standard Earth-radius baroclinic wave experiment, the deep- and shallow-atmosphere solutions are similar, whereas in the reduced-radius X20 configuration the GMCORE deep-atmosphere dycore reproduces the clear separation reported in earlier studies. In the tropical-cyclone experiment, the deep-atmosphere configuration has little effect on storm intensity and warm core structure, but leads to a systematic south-westward trajectory shift relative to the shallow-atmosphere simulation. The trajectory difference is linked to an organised inner asymmetry. This includes a dipole-like pattern connected to 2<em>&Omega;</em>cos<em>&Phi;</em> <span style="border-bottom: 1px solid #000; vertical-align: 70%; font-size: .7em; color: #000;"><em>&part;w</em></span><span style="margin-left: -1.3em; margin-right: .5em; vertical-align: -15%; font-size: .7em; color: #000;"><em>&part;y</em></span> and a low-level easterly anomaly. These results demonstrate that GMCORE can be extended to a deep-atmosphere dycore and provide a useful work for idealized tropical cyclone trajectory sensitivity and deep-atmosphere dynamics.