Another factor that has extensive influence on the probability of hurricanes in the Atlantic is the El Niño-Southern Oscillation (ENSO).
El Niño results in a SST anomaly that exerts an influence on atmospheric pressure and wind patterns. El Niño is associated with higher atmospheric pressures whereas La Niña is associated with the lower atmospheric pressures in the Southern Oscillation. A period of SST warming or cooling created by ENSO is classified as an El Niño or La Niña "episode" if it occurs for longer than nine months.
The shifts in pressure and temperature associated with ENSO affect weather around the world. Some areas have milder weather while others are subjected to unusually heavy precipitation or drought. Keep in mind that ENSO, like climate change, only influences the probability that weather will be different from normal; it does not actually cause extreme weather events.
Although ENSO occurs in the Pacific Ocean, it has significant impacts on weather around the world. In the Atlantic, El Niño is generally associated with a decrease in hurricane activity and severity, whereas La Niña is linked to an increased risk of hurricanes.