The term El Niño refers to the abnormal warming of the sea surface in the Pacific Ocean. It occurs along the equator from South America to the International Dateline.
For more detailed information about El Niño, visit this site
How much does the Pacific Ocean temperature have to warm to be considered the start of an El Niño season?
NOAA's Climate Prediction Center (CPC), which is part of the National Weather Service, declares the onset of an El Niņo episode when the 3-month average sea-surface temperature departure exceeds 0.5°C in the east-central equatorial Pacific [between 5°N-5°S and 170°W-120°W].
When does El Niño occur and how long does it last?
The El Niño usually lasts from 9 to 12 months, but can last up to 2 years. It usually starts to develop between March and June and reaches it's maximum strength from December to April. Then it will slowly weaken over the next couple of months.
El Niño's usually occur every 3 to 5 years, but it can occur as early as 2 years later or as late as 7 years later.
The term La Niña refers to the cooling of the sea surface in the Pacific Ocean. It occurs in the same location as El Niño.
For more detailed information about La Niña, visit this site
When does La Niña occur and how long does it last?
The La Niña usually lasts from 1 to 3 years. It usually starts to develop between March and June and reaches it's maximum strength from December to April. Then it will slowly weaken over the next several months to year.
La Niña's usually occur every 3 to 5 years, but it can occur as early as 2 years later or as late as 7 years later.
What is ENSO (El Niño / Southern Oscillation)?
The term ENSO refers to the consistent year-to-year variations in sea- surface temperatures, convective rainfall, surface air pressure, and atmospheric circulation that occur across the equatorial Pacific Ocean. El Niño and La Niña are the opposite extremes in the ENSO cycle.
For more detailed information about the ENSO cycle, visit the International Research Institute for Climate Prediction or the CPC's ENSO Cycle page.
For more information on El Niño, La Niña, and ENSO, visit the NOAA's Climate Prediction Center's FAQ
