Energetic Perspectives on U.S. Tropical Cyclone Activity

We introduce an extended tropical cyclone climatology using accumulated cyclone energy (ACE) to investigate intra- and interseasonal variability and trends in tropical cyclone activity over the continental U.S. and in the Atlantic basin. In terms of intraseasonal variability, our findings suggest that the first tropical cyclone activity is trending earlier in the year, with implications on U.S. coastal preparedness for early and out-of-season impacts. In terms of interseasonal variability, landfall activity scaled by basin-wide activity since 1950 exhibits a statistically significant downward trend. The extremely active 2017 Atlantic hurricane season concluded an extended period of quiescent continental U.S. tropical cyclone landfall activity that began in 2006, commonly referred to as the landfall drought. The drought years between 2006 and 2016 recorded an average value of total annual ACE over the U.S. that was less than 60% of the 1900-2016 average, with the percentage of total Atlantic ACE expended over the continental U.S. at a series minimum. These results support the recently advanced idea that there is an inherent tension between conditions most likely to direct hurricanes towards the U.S. and the environmental conditions most favorable for tropical cyclone development.