ENSO and North Atlantic Hurricanes

Intense Atlantic Hurricanes

Though only 20% of tropical cyclones that make landfall in the United States are major or intense Atlantic hurricanes (category 3, 4 or 5 hurricanes), these account for more than 70% of the damage (Landsea, 1993). The interannual variability of major Atlantic hurricanes is large, more than twice than that of weak tropical storms (Landsea 1993).

The number of intense Atlantic hurricanes per hurricane season seems to be influenced by ENSO too. Figure 5 shows the number of intense Atlantic hurricanes in each of ENSO category. In an El Niño year there are usually fewer intense Atlantic hurricanes than in a La Niña year. Only in two El Niño years (out of 12 years) there were more intense Atlantic hurricanes than the historical average (2.4), while in La Niña years this happened in 8 years (out of 12 years). In El Niño years there is a reduction in the probability of a U.S. landfalling hurricanes, it is also less likely for major hurricanes to make landfall in the U.S. in an El Niño year (Bove et al., 1998).

Figure 5: Number of Atlantic Intense Hurricanes August to October in different ENSO events, 1950-2001.