The first and third modes, and the second and fourth modes of the empirical orthogonal function (EOF) decomposition of the zonal sea surface temperatures (SST) perturbations (ZSSTP) in the Northwest Pacific are in good synchronous correlations, respectively. By synthetizing the typical phases of the two separately, the typical SST modes of the Kuroshio Extension (KE) in contraction and elongation states can be obtained. The influences of the variability of KE on the North Pacific storm track and the main mechanisms in different energy conversion processes are discussed based on the CESM1.2.0 model simulations, which are initialized with SST forcing fields in contraction and elongation modes and with climatological SST, respectively. It is found that under the KE's contraction mode, the intensity of the North Pacific storm track basically enhances, but the vortex activities weaken to the south of the center; under the KE's elongation mode, the intensity of the storm track decreases to the west of the center but the vortex activities increase to the east of the center. Diagnostic analysis of energy conversion shows that the barotropic energy conversion process makes little contribution to the change of the eddy kinetic energy (EKE). Near the center of the storm track, its major effect is to consume EKE. Under the contraction mode of the KE, the EKE consumption in the barotropic energy conversion process weakens, while it enhances under the elongation state of KE. The above differences are mainly due to different deformations of the transient eddies under different SST anomalies. The baroclinic potential energy release is one order of magnitude higher than the barotropic energy conversion. It is completed through the interaction between the meridional temperature gradients of the base flow and the meridional vortex heat transport. The atmospheric baroclinicity (meridional temperature gradient) plays a key role in this process, while the spatial distribution of the atmospheric baroclinic anomalies, the meridional temperature gradient anomalies of base flows, the baroclinic effective potential energy release anomalies and the storm tracks anomalies all have a good correspondence. This process may also be the main physical process for SST anomalies of the KE to affect the North Pacific storm track. Eddy effective potential energy needs to convert to EKE to produce transient vortex motions. The magnitude of the release of the eddy effective potential energy is approximately the same as that of the baroclinic effective potential energy, but the value is relatively small. This process is accomplished by the warm air rising and cold air falling. The changes in the negative correlation between perturbed vertical velocity and perturbed temperature also agree well with the variations of the conversion from the eddy effective potential energy to the eddy kinetic energy.