Skip Navigation Links 
NOAA logo - Click to go to the NOAA home page National Weather Service   NWS logo - Click to go to the NWS home page
Climate Prediction Center

HOME > El Niño/La Niña > The ENSO Cycle > EL Niño Conditions
December to February Conditions

El Niño episodes feature large-scale changes in the atmospheric winds across the tropical Pacific, including reduced easterly (east- to- west) winds across the eastern Pacific in the lower atmosphere, and reduced westerly (west-to-east) winds over the eastern tropical Pacific in the upper atmosphere near the tropopause. These conditions reflect a reduced strength of the equatorial Walker Circulation, which in strong El Niño episodes can be completely absent.

During the developing phase of the El Niño, the subsurface ocean structure is characterized by an abnormally deep layer of warm water and an increased depth of the thermocline across the eastern tropical Pacific. Thus, the slope of the thermocline is reduced across the basin. In very strong El Niño episodes, the thermocline can actually become flat across the entire tropical Pacific for periods of several months. Accompanying these conditions, the sea level height is higher than normal over the eastern Pacific, resulting in a decreased slope of the ocean surface height across the basin.  There is also considerable evolution in the subsurface temperature and thermocline structure during both El Niño and La Niña episodes.

Go To Previous Page Go To Next Page
Back to the ENSO-Related Rainfall Patterns over the Tropical Pacific Forward to El Ni$ntilde;o-Related Global Temperature and Rainfall Patterns
Back to Table of Contents

NOAA/ National Weather Service
NOAA Center for Weather and Climate Prediction
Climate Prediction Center
5830 University Research Court
College Park, Maryland 20740
Page Author: Climate Prediction Center Internet Team
Page last modified: December 19, 2005
Information Quality
Privacy Policy
Freedom of Information Act (FOIA)
About Us
Career Opportunities