Tropical convection is known to self-organize under the diurnal cycle, yet is also subject to large scale convergence. In a suite of idealized numerical experiments we mimic Earth’s tropical circulation, to probe the cross talk between inherent circulation eigenmodes and the convective diurnal cycle — which generally are characterized by incommensurate oscillatory frequencies. The tropics are caricatured by a doubly-periodic domain with spatially constant surface temperature $T_S(x,y,t)$ in the “zonal” ($x$) but decreasing $T_S$ in the “meridional” dimension. Temporally, we contrast constant $T_S(x,y,t)=T_S(x,y)$ with diurnally varying $T_S(x,y,t)=T_S(x,y,t+\tau_d)$, with $\tau_d=1\,$day. We find that the diurnal forcing by no means dominates the precipitation power spectrum. Rather, the intrinsic circulation period $\tau_i$ drives temporal precipitation patterns for large and small domains. At intermediate domain sizes, where intrinsic frequencies approximately match the diurnal one, i.e., $\tau_i\approx \tau_d$, the diurnal cycle is amplified and, substantially increasing the precipitation amplitude.