El Niño’s little brother in the Atlantic may not be so little when it comes to its impact on hurricanes

Atlantic Niño, characterized by warm sea surface temperature (SST) anomalies in the eastern equatorial Atlantic, is the Atlantic counterpart of the Pacific El Niño. Due to its smaller size in zonal extent, it is often referred to as El Niño’s little brother. It was previously thought to have a limited regional influence on rainfall variability in West Africa, but a new study published in Nature Communcations showed that Atlantic Niño increases Cape Verde hurricanes. What is the Cape Verde hurricane? According to Wikipedia, “a Cape Verde hurricane or Cabo Verde hurricane is an Atlantic hurricane that originates at low-latitude in the deep tropics from a tropical wave that has passed over or near the Cape Verde islands after exiting the coast of West Africa. Cape Verde hurricanes are often the largest and most intense storms of the season due to having plenty of warm open ocean over which to develop before encountering land or other factors prompting weakening. A good portion of Cape Verde storms are large, and some, such as hurricanes Allen, Ivan, Dean, and Irma have set various records. Most of the longest-lived tropical cyclones in the Atlantic basin are Cape Verde hurricanes“. So, how does Atlantic Niño affect Cape Verde hurricanes? Kim et al. (2023) stressed that El Nino-Southern Oscillation (ENSO) and the Atlantic Meridional Mode (AMM), two climate modes of variability known to modulate Atlantic hurricane activity, develop predominantly in winter or spring and are weaker during the Atlantic hurricane season (June–November), whereas the leading mode of tropical Atlantic climate variability during the Atlantic hurricane season is Atlantic Niño/Niña. This study used observations to show that Atlantic Niño strengthens the Atlantic inter-tropical convergence zone rainband. This, in turn, enhances African easterly wave activity and low-level cyclonic rotation across the deep tropical eastern North Atlantic. Such conditions increase the likelihood of powerful hurricanes developing in the deep tropics near the Cape Verde islands, elevating the risk of major hurricanes impacting the Caribbean islands and the U.S.

Image Credit: https://www.aoml.noaa.gov/hrd/tcfaq/CVtrak.jpg

Kim, D., Lee, SK., Lopez, H. Foltz, GR., Wen, C., West, R. & Dunion, J. (2023). Increase in Cape Verde hurricanes during Atlantic Niño. Nature Communications 14, 3704. https://doi.org/10.1038/s41467-023-39467-5