Abstract: By using the WKB method, the similar and different conditions of the development of symmetric wavepacket and inertia-gravitational wavepacket in the moment nondivergent mouel arc discussed. The development symmetric wavepacket depended not only on the external parametric nonstationary but also on the thermal wind deviations mainly. If thermal wind balance was zssumed, a conservation quantity ωE was obtained, but it was not so about the inertia-gravitational wave. If the vertical coordinate axis was rotated to the direction in whirl: the develepment of smmetric perturbation was maximum, the condition of the development of symmetric wavepachet was similar to that of inertia-gravitational wavepaket.