The Impact of Anthropogenic Climate Change on North Atlantic Tropical Cyclone Tracks

The authors examine the change in tropical cyclone (TC) tracks that results from projected changes in the large-scale steering flow and genesis location from increasing greenhouse gases. Tracks are first simulated using a Beta and Advection Model (BAM) and NCEP-NCAR reanalysis winds for all TCs that formed in the North Atlantic Ocean's Main Development Region (MDR) for the period 1950-2010. Changes in genesis location and large-scale steering flow are then estimated from an ensemble mean of 17 models from phase 3 of the Coupled Model Intercomparison Project (CMIP3) for the A1b emissions scenario. The BAM simulations are then repeated with these changes to estimate how the TC tracks would respond to increased greenhouse gases. As the climate warms, the models project a weakening of the subtropical easterlies as well as an eastward shift in genesis location. This results in a statistically significant decrease in straight-moving (westward) storm tracks of similar to 5.5% and an increase in recurving (open ocean) tracks of similar to 5.5%. These track changes decrease TC counts over the southern Gulf of Mexico and Caribbean by 1-1.5 decade(-1) and increase counts over the central Atlantic by 1-1.5 decade(-1). Changes in the large-scale steering flow account for a vast majority of the projected changes in TC trajectories.