ENSO and North Atlantic Hurricanes

Atlantic Tropical Cyclone Activity

Another measure of the tropical cyclone activity is the accumulated hurricane energy, defined as the sum of the squares of the maximum windspeed for all events that reached hurricane strength during their existence. This measure takes into account the duration of the tropical cyclone activity, the intensity and frequency simultaneously.

Figure 4 shows the accumulated hurricane activity in types on ENSO events (El Niño, La Niña and Neutral years) for the period 1950-2001. From the 12 El Niño years only 3 years had an accumulated hurricane energy larger than the mean. In La Niña years this happened in 8 out of 12 years, a significant difference. From the 28 Neutral years only 3 had hurricane accumulated energy out of the boundaries of the historical mean plus/minus one standard deviation. This helps emphasize that though in a El Niño (La Niña) year there is a larger probability of having a less (more) active season, this is not always true.

Figure 4: Atlantic accumulated hurricane energy August to October in different ENSO events, 1950-2001.