What Is the El Niño Southern Oscillation and How Does It Impact Us? | WNYT.com

What Is the El Niño Southern Oscillation and How Does It Impact Us?

Christina Talamo
Updated: October 15, 2020 01:48 PM
Created: October 15, 2020 10:56 AM

Carrier Management | Carrier Management |
When talking about weather and climate forecasting, you will often hear scientists mention El Niño and La Niña, but what exactly are they, and why are they so important when forecasting the weather and climate for the upcoming season?

The El Niño Southern Oscillation, or ENSO, is a recurring climate pattern that involves changing the global atmospheric and oceanic circulation, and thus has impacts on temperature and precipitation across the globe. ENSO is important because by predicting the ENSO phase for the upcoming season, we can also predict how its impacts will affect the global climate; specifically how temperatures and precipitation could change in certain areas. This climate phenomenon can occur in three different phases, including the El Niño phase, the La Niña phase, and the neutral phase. These phases can influence the weather patterns and ocean conditions across the globe for extended periods of time. 

The three phases of ENSO. | Australian Bureau of Meteorology The three phases of ENSO. | Australian Bureau of Meteorology
The El Niño phase involves a large scale climate interaction between the ocean and the atmosphere, leading to a period of above average sea surface temperatures across the central and eastern tropical Pacific Ocean. This also causes increased rainfall over the tropical Pacific Ocean, reduced rainfall over Indonesia and the western Pacific, and for the low-level easterly trade winds near the equator to weaken, possibly enough to change direction and flow west to east. An El Niño scenario typically allows for above average temperatures over western and central Canada, with a warmer winter in the western and northern United States. It can also lead to wetter conditions along the Gulf coast and near Florida, with drier conditions in the Pacific Northwest and the Ohio Valley. 
NWS/NCEP Climate Prediction Center | NWS/NCEP Climate Prediction Center |
The La Niña phase is the opposing phase to El Niño, leading to a period of below average sea surface temperatures in the central and eastern tropical Pacific Ocean. This phase also causes decreased rainfall over the tropical Pacific, increased rainfall in Indonesia and the western Pacific, and for the low level easterly winds near the surface to become stronger. A La Niña scenario tends to lead to opposite conditions and impacts as opposed to El Niño, with below average temperatures in the western United States and Canada, drier conditions along the Gulf coast, and wetter conditions in the Ohio Valley. During a La Niña year, it is also typical that temperatures in the winter are cooler and a bit wetter than average in the Northwest, and warmer and drier than average in the Southeast.
NWS/NCEP Climate Prediction Center | NWS/NCEP Climate Prediction Center |
The neutral phase of ENSO involves sea surface temperatures in the tropical Pacific Ocean that are closer to average, with the trade winds blowing easterly across the surface near the equator. Currently as we head into the 2020/2021 winter season, La Niña conditions continue to develop in the tropical Pacific, and NOAA's Cliamte Prediction Center expects a stronger La Niña phase with a 75% chance of the pattern lasting throughout the winter. This could generally lead to increased precipitation and cooler weather across the northern portions of the United States, with warmer and drier weather across the southern United States. As we head further into the next few months, we will have a better idea of how these and other climate patterns could impact the upcoming winter season.


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