Exploring Decadal Predictability of Tropical Cyclones using CESM Decadal Prediction Large Ensemble (CESM-DP-LE)

Studies have shown that variability of North Atlantic tropical cyclones (TCs) is substantial on decadal timescales. In particular, a “shift” to more active tropical cyclone period occurred in the mid-1990s, coincided with a change in phase of the Atlantic multidecadal oscillation (AMO). The NCAR CESM decadal prediction large ensemble (CESM-DP-LE) has been shown to be skillful in predicting AMO-related SST on pendatal-to-decadal timescales, and thus it is of interests to investigate if this skillful prediction in North Atlantic SST can be translated to useful skills in predicting the decadal TC shift in the North Atlantic. To address this issue, we analyzed TC-related environmental changes in CESM-DP-LE. Five-year predictions with lead year two to six were investigated before and after the shift, and the difference in pentadal TC activity was estimated based on TC-related environmental variables. The results of this study give an assessment of the potential skill of the CESM-DP-LE in predicting TC variations on decadal timescales, especially on the mid-1990 shift, and suggest the potential value in downscaling the CESM-DP-LE for TC simulations.