Seasonality of ENSO Impacts on Hurricane Environmental Conditions

The El Niño Southern Oscillation phenomenon affects remote regions of the world through atmospheric teleconnections generated through changes in heating and/or rainfall in the Tropical Pacific. It is known that ENSO impacts the Atlantic hurricane season with more tropical cyclone activity during La Niña events, and reduced activity during El Niño events. This study seeks to characterize the evolution of ENSO teleconnections throughout the hurricane season, to better understand how ENSO and the seasonal cycle interact to influence tropical cyclone activity. Specifically, a series of composite analyses are conducted using the Oceanic Niño Index, and the ERA5 and HURDAT data sets. The analyses focus on ENSO’s role in influencing multiple atmospheric variables such as vertical wind shear, steering flow, and atmospheric stability. The composite analysis is conducted on a month-by-month basis throughout the tropical cyclone season, and results from the large-scale analyses are related to specific changes in tropical cyclone activity such as cyclone frequency, intensity, and track. Results clarify ENSO’s evolving influence on the Atlantic Hurricane season.