El Nino: Subtle weather shift with global impact

In 1983, abnormal weather patterns in the tropical Pacific caused 1,500 deaths and $8 billion in damages worldwide. These weather patterns, termed El Nino (“little boy” in Spanish), cause exceptionally warm and long-lived ocean currents in the tropical Pacific. This set off a series of events that led to dry areas receiving more rain than usual and wet areas receiving rare droughts. The impact is global - in 1983, El Nino caused heavy flood damage in California. In other parts of the world, droughts caused famine and illness. El Nino historically rears its ugly head every 2-7 years. During the past few months, scientists have witnessed water temperatures off the South American coast increasing by an alarming 5 degrees, setting up conditions for another El Nino. It appears El Nino will strike again this year, but what effect will it have?

Global effects

To understand how El Nino can affect the Earth’s climate globally, the National Oceanic and Atmospheric Administration suggests picturing a river flowing around boulders. As the river flows around the boulders, it creates distinct waves that extend downstream, with crests and troughs showing up in fixed positions.

The El Nino effectively shifts these boulders, which causes the waves to travel differently. In terms of weather, this has many effects, such as causing the jet stream to split. (The jet stream is a global “breeze” that runs across the United States from the west to the east. During the winter, the jet stream shifts down, drawing colder air down from Canada.)

When the jet stream splits in two, it tends to cause fewer hurricanes in the Southeast, unusually wet weather in California and drier winters in the Northwest. While California receives more rain than usual, areas such as Australia, Brazil, India, Indonesia and Africa often witness droughts. These droughts can lead to famine and disease.

The “domino effect” El Nino sets off has some unexpected consequences. The 1983 El Nino produced many ecological effects in the Pacific Ocean, severely damaging the coral population. In the eastern Pacific, elevated sea surface temperatures and a large increase in rainfall resulted in the death and migration of fish and sea bird populations. Many guano producing sea birds desert their nests, migrate, or die. In 1983, it is estimated that up to 85% of the sea bird population in Peru was killed.

The causes and effects of El Nino are only now beginning to be understood. Scientists will be studying this year’s El Nino closely in an effort to learn more about its global impact.

Effects on the Mid-Atlantic region

What does El Nino mean for the Mid-Atlantic area? (And, specifically, what types of snow conditions can we expect?)

Each El Nino is different than the last, so it’s difficult to forecast, with any accuracy, exactly what effect an El Nino will have. However, historically, El Nino has caused the D.C. area to experience wetter winters. El Nino may also cause an elevation in average temperatures, although this increase is more evident in areas such as Ohio, western Pennsylvania, and particularly in states such as North and South Dakota, Montana, and Wisconsin. Nevada and Texas generally witness cooler temperatures than normal.

El Nino may cause a significant increase in precipitation in the D.C. area this winter. It tends to increase precipitation in the southern part of the United States, extending from California to Florida and up along the east coast.

Assuming temperatures stay low this winter, an increase in precipitation might result in a healthy ski season. However, if the temperature is too warm, you might want to keep your water skis out.