Abstract Author: Kathy Pegion, Philip Pegion and Mihai Sirbu
Abstract Title: Simulation and Forecast of Subseasonal Variability of Hurricane Activity
Abstract: It is well known that tropical cyclones tend to cluster in both time and space. Specifically, tropical cyclones tend to occur during 1-2 weeks periods separated by periods when little to no activity occurs. Due to the subseasonal nature of tropical cyclone formation, it has been suggested that there is a relationship between the phase of the Madden-Julian Oscillation (MJO) and the formation of tropical cyclones. Several studies have found that the MJO impacts the large-scale atmospheric environment and can influence whether conditions are more or less favorable for hurricane development in specific regions.
In this study, we investigate the relationship between the MJO and hurricane activity in terms of the Seasonal Genesis Parameter (SGP; Gray 1979) and Genesis Potential Index (GPI, Emanuel and Nolan 2004) calculated from daily NCEP/NCAR Reanalysis data and a 52-year simulation of the NCEP Climate Forecast system. The ability of the model to simulate the observed relationship between MJO phase and hurricane activity is evaluated. Furthermore, we evaluate which terms in the SGP and GPI contribute most to this relationship in both the model and reanalysis. The skill of the CFS in forecasting observed SGP and GPI associated with the phase of the MJO is also investigated in a series of subseasonal re-forecast experiments.