How Do El Niño and La Niña Affect Typhoons? Understanding the Seasonal Pattern
What Is ENSO?
ENSO (El Niño–Southern Oscillation) is the periodic warming and cooling of sea-surface temperatures in the central and eastern equatorial Pacific: abnormally warm waters indicate El Niño, while abnormally cool waters indicate La Niña. It generally occurs in a cycle every 2–7 years. It is the most important climate background influencing the overall character of a typhoon season.
Typhoon Characteristics in El Niño Years
- Formation farther east and south: As warm water shifts eastward, more typhoons are "born" over the open ocean east of Guam
- Longer journey at sea → greater intensity: A longer journey over the ocean allows more energy to be absorbed, resulting in a noticeably higher proportion of super typhoons
- Fewer landfalls in China overall: After forming farther east, typhoons are more likely to turn toward Japan and South Korea
- Higher probability of the Fujiwara effect (interaction between two typhoons): Simultaneous existence of multiple typhoons over the open ocean is more common
Typhoon Characteristics in La Niña Years
- Formation farther west: A higher proportion of locally formed typhoons appear over the South China Sea and waters east of the Philippines
- Shorter development period and warning window: Because they form close to shore, only two or three days may elapse between formation and landfall
- A higher proportion of landfalls in China: A stronger, farther-westward subtropical high often steers typhoons westward toward southern China
- Autumn typhoons combined with cold air carry a greater risk, potentially resulting in more severe rainstorm-related disasters
Some Classic Seasonal Patterns
| Year | Background | Typhoon Season Characteristics |
|---|---|---|
| 1997 | Super El Niño | Ten super typhoons formed throughout the year, with formation locations notably farther east |
| 2018 | El Niño developing | Remote-ocean super typhoons such as MANGKHUT occurred frequently |
| 2020 | La Niña | An unusual "typhoon-free" period occurred over the western Pacific in July, while numerous typhoons clustered and made landfalls in China in August |
| 2021 | La Niña | Typhoons such as IN-FA moved westward and made landfalls in eastern China, bringing extreme rainfall |
How Can ENSO Help with Typhoon Season Preparedness?
ENSO provides only a probabilistic background, not a definitive forecast: El Niño years can still feature severe typhoons making landfall in China, while La Niña years can also produce dominant super typhoons over the open ocean. The appropriate approach is to pay close attention during El Niño years to the potential turning paths of super typhoons over the open ocean, particularly their impact on shipping and island travel. During La Niña years, preparedness should focus on the risks of rapid formation near the coast and successive landfalls by multiple typhoons.