Rapid Intensification of North Atlantic Tropical Cyclones in a Changing Climate

Tropical cyclones (TCs) are becoming increasingly harder to forecast due to the influences caused by climate change. Since 1980, we have noticed an increase in the number of North Atlantic (NATL) storms and the occurrences of rapid intensification (RI). RI is defined as an increase in the maximum sustained wind by at least 30 knots in a 24-hour period. RI adds to forecasting uncertainty, causing more damages due to lack of preparation. Comparing NATL TCs over the 1980-2000 and 2001-2021 periods, RI is occurring more frequently, and at higher intensities. By analyzing the environmental conditions within a 0.5 degree radius centered on each RI location with a lead of 2-days, 1-day, and the moment of RI we are able to investigate which environmental variables are related to RI. The variables include sea-surface temperature (SST), relative humidity (RH) at 600 hPa, relative vorticity at 850 hPa, and wind shear. RI occurs in environments of warmer SSTs, more moist mid-levels, and stronger low-level vorticity than typical summertime environments. Perhaps counterintuitively RI occurs in environments of stronger vertical wind shear. We hypothesize that this could be related to the ventilation effect of storms under strong upper level flow. Here, the flow acts to strengthen the outflow out of the top of the storm that in turn accelerates the inflow leading to RI. Moving forward, the study will use climate model projections to explore potential future changes in RI behavior and its environmental drivers.