Ask the Meteorologist: What Do El Niño and La Niña Mean?
If you have ever watched weather reports on the news, you’ve likely heard the terms El Niño and La Niña. But, do you really know what they mean? Both conditions can play a big role in global weather patterns, so it’s important to understand what both El Niño and La Niña mean and their potential effects.
What Are Neutral Weather Conditions?
To understand El Niño and La Niña, you first need to understand neutral conditions — which exist when neither La Niña nor El Niño are present. Weather has a lot do with the trade winds and the sea surface temperature — which is basically the temperature on the surface of an ocean.
Trade winds are prevailing winds that circle the Earth near the equator. These winds blow east to west along the equator, allowing the upwelling of cold, nutrient-rich water off the northwest coast of South America. Upwelling occurs as deep ocean water rises up to replace the surface water that was blown away. Because of this, sea surface temperatures in neutral weather conditions are typically 14 degrees Fahrenheit cooler in these waters off South America than the waters in the Western Pacific.
According to the National Oceanic and Atmospheric Administration (NOAA), scientists use various methods, such as satellites and buoys, to monitor the temperature on the ocean’s surface. This helps them to track potential El Niño and La Niña conditions.
What Are El Niño Conditions?
El Niño conditions have been occurring for centuries, according to NOAA. Spanish fisherman noticed the conditions off the South American coast near Peru and Ecuardo in the 1600s. They named the event El Niño, which means “Little Boy” in Spanish, because it typically occurs near Christmas.
During El Niño weather conditions, the trade winds become weaker than they are in neutral conditions. Warm surface water near the equator moves east — reducing the upwelling of cold water off the coast of South America.
The weather impacts of El Niño can be felt globally. In North America, they are most noticeable during the winter. El Niño affects the track of the jet stream, which steers weather patterns and currents — separating warm air in the south from cold air to the north. During an El Niño winter, the jet stream intensifies and shifts south, potentially bringing heavy rain to the Southern United States and drier, warmer weather to the Northern U.S., Pacific U.S. and Canada, notes Climate.gov.
What Are La Niña Conditions?
During La Niña, which means “Little Girl” in Spanish, the trade winds increase and become stronger than normal — which is essentially the opposite of El Niño. Warm water near the equator is blown back into the western Pacific and upwelling cold water is brought to the surface off the western coast of South America.
Like El Niño, La Niña’s effects are also global. The jet stream shifts northward and may lead to drought in the Southern United States while bringing heavy rain and cooler temperatures to the Pacific Northwest. Environmental conditions that occur during La Niña can lead to more tropical weather systems as well, says Climate.gov.
Are El Niño and La Niña Related?
It wasn’t until the 1960s that scientists realized neutral, El Niño and La Niña conditions are connected, according to Climate.gov. They are now collectively called the El Niño Southern Oscillation (ENSO).
Just like the weather constantly changes, so do ENSO events. While El Niño and La Niña conditions are typically 9 to 12 months long, Climate.gov notes that they can last much longer.
Thanks to today’s weather and climate knowledge, as well as technology like the satellites and buoy sensors noted earlier, scientists can often predict ENSO conditions months before they fully develop. With the knowledge that changing weather conditions may be ahead, you can be better prepared for what El Niño and La Niña may bring your way.