It is found that a strong tropical cyclone tends to weaken at the edge of the baroclinic zone, while a weak tropical cyclone intensifies for a relative long time in the baroclinic environment. Stronger tropical cyclones tend to influence the upper troposphere at greater distances. Therefore, the interaction between the upper-level jet and a strong tropical cyclone can be significant enough to impact the evolution of the tropical cyclone even when the cyclonic vortex is only at the edge of a baroclinic area. In addition, when the beta effect is taken into account, the vertical shear is composed of the environmental westerly shear and the beta shear. In the case that a tropical cyclone is strong, the beta shear is usually conspicuous. The resultant shear over the tropical cyclone is large and unfavorable for further intensification of the cyclone.
As a tropical cyclone moves poleward, the baroclinic flow is greatly modified. One prominent feature is a jet streak forming in the region where the outflow of the tropical cyclone impinges on the jet. As the decaying tropical cyclone moves into the right entrance region of the jet streak, rapid re-development of the system usually takes place. The numerical results indicate that, under the condition that the straight jet is strong enough, a PV anomaly may form downstream of the poleward-moving tropical cyclone. If the PV anomaly happens to lie beneath the right entrance region of the jet streak, surface cyclogenesis may happen. In this case, the new cyclone rapidly develops and the original cyclone associated with the tropical cyclone cannot undergo the re-development process and finally dissipates.