EL NIÑO / FIELD GUIDE
How Does El Niño Form?
When equatorial Pacific trade winds weaken, warm water can spread toward the central and eastern Pacific. Changes in sea temperature then influence rainfall and circulation, creating an ocean–atmosphere feedback.
01 · Normally, warm water gathers in the west
Trade winds normally blow from east to west, pushing warm surface water toward the western Pacific. In the east, cooler water rises from below, helping maintain a temperature contrast across the ocean.
02 · Trade winds weaken
Weaker trade winds change the distribution of water and the strength of upwelling. The central and eastern Pacific can become warmer than average, and tropical rainfall shifts with it.
03 · The ocean and atmosphere interact
Warmer surface water influences convection and winds, which in turn affect the ocean. This feedback supports an event’s growth, while delayed ocean processes also help bring it to an end.
References
This article explains established climate science using official sources. Consult the references for background, and always check the publication date of any forecast.
NOAA Climate.gov: background referenceNOAA CPC: ENSO Diagnostic Discussion