Distinct Influences of the Pacific Meridional Mode and ENSO on Tropical Cyclone Intensity Change Rate over the eastern North Pacific

Abstract

In this study, the effects of ENSO and Pacific meridional mode (PMM) on eastern North Pacific (ENP) tropical cyclone (TC) intensity change, rapid intensification (RI) and rapid weakening (RW) rates are investigated. Based on the distribution of the mean 24-hour TC intensity change rate and the TC track density, we divided ENP into the main intensification region (MIR) and main weakening region (MWR) and examined the influence of climate factors on these two regions. The ENSO is closely related to the ocean temperature of the MIR and the vertical wind shear of the MWR. PMM is highly associated with the ocean temperature and the low-level relative humidity in the MWR. Changes in the environmental parameters of the two regions by two climate modes are significantly related to TC intensity change rate. In the positive (negative) phase of ENSO, there was an increase (decrease) in TC intensity change rate in the MIR and a decrease (increase) in the MWR, respectively. In the positive phase (negative phase) of the PMM, an increase (decrease) in TC intensity change rate is observed in the MWR, but there is no significant change by PMM in the MIR. Most RI events in the ENP occur in MIR, whereas RW occurs mostly in the MWR (except landfall). Therefore, ENSO is closely correlated with the TC intensity change rate of MIR, which showed a high positive correlation with RI rate. Conversely, the PMM associated with the TC intensity change rate in the MWR showed a negative correlation with the RW rate. It is expected that the regional tendency of TC intensity change rate and RI, RW rate according to the phase of each climate mode can be used as important information in the ENP’s TC intensity prediction.