El Nino Increases Likelihood of Unseasonable Weather Such as Tornadoes in Winter Months

El Nino Increases Likelihood of Unseasonable Weather Such as Tornadoes in Winter Months

Perhaps you remember the 2010 Vancouver Olympics in which they had to truck in natural snow from a park close to the Canadian Rockies. The snow machines could not meet the demand of replacing melting snow on lower mountain slopes. The 2009-2010 El Niño began in the summer of 2009 and its effects reached a peak just in time for the February Olympics. While that was an inconvenience, during the 1997-1998 El Niño event, 35 counties in California were declared federal disaster areas, and the state suffered 17 storm-related deaths and $550 million in damages. Like many other people, you may be wondering if El Niño is caused by climate change and how it impacts weather patterns.

What is El Niño?

Evidence suggests that El Niño has been happening for thousands of years, so climate change is not the culprit. Scientists, however, believe climate change may play a role, given that the most impactful events have taken place in the last 30 years. During an El Niño event, the Pacific Ocean warms up near equatorial South America and disrupts large-scale atmospheric circulation. Under normal conditions, Pacific trade winds blow over the region, typically moving from east to west, pushing the water at the ocean’s surface toward South Asia and Australia. The cessation of these trade winds triggers an El Niño event, but scientists have not been able to pinpoint the exact underlying mechanism that causes this phenomenon.

Under normal conditions, evaporation of the warmest water causes the air to fill with moisture, contributing to monsoon seasons in Asia and Australia. During an El Niño event, weather patterns reverse and Australia and South Asia experience drought instead of rain, while the Pacific Coast of South America experiences a heavy rainy season. The paths of jet streams are altered, with one jet stream driving storms to California, which may cause heavy rain from November through March in California, Texas, and other Gulf states. Even Hollywood is not immune—the highly anticipated Oscar ceremony has been impacted in recent years, with the glamorous red carpet drenched with soaking rains.

What to Expect?

According to the National Oceanic and Atmospheric Administration, the current El Niño may possibly be the biggest one in history. Warm air continues to push across the northern United States and Canada, which is why the Midwest enjoyed 60+ degree temperatures and the East Coast experienced 70+ degree temperatures in December 2015. While California and the Gulf states are most impacted, past El Niño events have caused severe thunderstorms and tornadoes in late winter in several regions.

Given the history of past El Niño events, the winter of 2015-2016 is predicted to be wetter and cooler in the Southern region of the United States—from California to the Carolinas, and drier and warmer in Northern states—including the Ohio Valley, Great Lakes, and Northern Rockies. So don’t be too surprised if you find yourself wearing rain boots and a slicker on a winter day normally reserved for snow boots and a parka!


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