Abstract
El Niño‐Southern Oscillation (ENSO) influences global climate variability, including Atlantic tropical cyclone activity. The Niño‐3.4 index has long been used to characterize ENSO. However, new ENSO indices have been proposed in recent years. Here, in the context of Atlantic tropical cyclone activity, we compared Niño‐3.4 to three modern ENSO indices: the relative Niño‐3.4 index, the ENSO Longitudinal Index (ELI), and a Pacific sea surface temperature zonal gradient index. We examined the association of their August–October values with central Pacific convection, tropical cyclone‐related variables in the Atlantic (e.g., vertical wind shear and potential intensity), and Atlantic tropical cyclone activity. We also assessed the skill of seasonal forecasts of the ENSO indices and the skill of index‐based forecasts of Atlantic tropical cyclone activity. We found that the modern ENSO indices outperform the traditional Niño‐3.4 index in nearly all aspects, with the relative Niño‐3.4 index showing statistically significant advantages in many cases.