A calm hurricane season has a subtle unnerving quality. Communities in Florida, Louisiana, and Georgia that have spent decades rebuilding after Katrina, Irma, and Ian typically react with something akin to relief when meteorologists declare that El Niño is controlling Atlantic storm activity. However, that feeling of security is based on a partial image. Because El Niño tends to return what it takes away from the Atlantic—sometimes violently—somewhere else.
For those who haven’t kept up with its rhythms, El Niño is a rise in sea surface temperatures in the eastern and central equatorial Pacific. Its fingerprints appear in weather systems from Peru to Indonesia to the American Midwest, and it occurs sporadically, about every three to five years. The mechanism is surprisingly simple: the vertical wind shear over the Atlantic basin is strengthened by warmer water in the Pacific, which modifies atmospheric circulation patterns. In essence, wind shear destroys the organized structure that hurricanes require to develop, making it their enemy. The Atlantic tends to calm down during an El Niño year, giving the Southeast United States a much-needed respite.
However, this is where the narrative becomes more intricate and, to be honest, more unsettling. El Niño is inhibiting the formation of hurricanes in the Atlantic, but in the eastern Pacific, it is having the opposite effect. Reduced upwelling, warmer sea surface temperatures, and an atmosphere ready for convection are all created by the same warm water pool that interferes with Atlantic circulation. As a result, the coastlines of Mexico, Guatemala, El Salvador, Honduras, Nicaragua, and Costa Rica are at risk from an eastern Pacific hurricane season that can be much hotter than usual. Even the most unprepared areas of Florida lack the infrastructure necessary to withstand the force of a major hurricane.
It’s worth taking a moment to consider that geography. Oaxaca and Guerrero, two small fishing communities on the Pacific coast, lack the emergency management systems, evacuation networks, and post-disaster reconstruction budgets found in US states. During a strong El Niño year, a Category 4 storm that makes landfall close to Acapulco can have disastrous effects that aren’t always adequately reported in global news cycles. In the Pacific, the number of storms increases. Often, the headlines don’t.
Additionally, the influence extends beyond the border with Mexico. Hawaii is in a unique position during El Niño years because, despite occasional fluctuations in basin-wide activity, the Central Pacific can actually witness increased hurricane formation and intensity. On the Hawaiian islands, direct landfalls are still comparatively uncommon, but the risks include intense rainfall, harsh surf, and the kind of disruption to infrastructure related to tourism and agriculture that can take years to fully recover from. Although tropical systems rarely directly affect the West Coast of the continental United States, bands of tropical moisture from dissipated Pacific storms can bring flooding rains to California and Oregon, states already dealing with complex relationships with wildfire and drought.
Some climate observers believe that the trade-off that El Niño produces is often framed too narrowly, as good news for American East Coasters, with little consideration given to what that “good news” actually costs throughout the Pacific. Another layer of complexity is the current warm phase of the Atlantic Multidecadal Oscillation; despite El Niño dampening activity, the underlying conditions for storm development in some basins are still elevated. These systems interact in ways that defy easy forecasting.
It’s difficult to avoid feeling that the public discourse surrounding El Niño is overly focused on local self-interest when you see all of this happening year after year. El Niño’s impact on hurricane season is almost always addressed from an Atlantic-centric standpoint. Coastal American communities have a lot riding on the outcome, so perhaps that makes sense. However, the Pacific coastlines that bear the brunt of that slower Atlantic season are deserving of much greater attention than they usually get. As it happens, nobody is getting a discount from nature. The bill is simply being moved.
