Co-variability of Tropical Cyclones in the North Atlantic and Eastern North Pacific

In the Western Hemisphere, tropical cyclones (TCs) can form and develop in both the tropical North Atlantic (NA) and eastern North Pacific (ENP) Oceans, which are separated by the narrow landmass of Central America. Here it is shown that TC activity in the NA varies out-of-phase with that in the ENP on both interannual and multidecadal timescales. That is, when TC activity in the NA increases (decreases), TC activity in the ENP decreases (increases). Our analyses show that both vertical wind shear and convective instability contribute to the out-of-phase relationship, whereas relative humidity and vorticity variations at the lower troposphere do not seem to cause the relationship. The paper also discusses its association with climate variability such as ENSO, the Atlantic multidecadal oscillation and the Atlantic warm pool. An implication is that seasonal hurricane outlook can be improved by considering the NA and ENP together.