Here's what you need to know about El Nino/La Nina in Texas

AUSTIN, Texas - There is a lot that goes into forecasting the weather and everything gets more complicated when you start to involve climate and semi-climatic events. Of those semi-climatic events, El Nino and La Nina are the most famous and most influential to Texas’ weather.

So what is it? According to Paul Yura, the Warning Coordination Meteorologist at the National Weather Service in New Braunfels, it’s "this big interaction. It’s the air currents, along with the ocean temperatures, which then change the rain patterns, which all of that then changes the jet stream configuration." So it’s complicated to say the least.

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In all, El Nino and La Nina are semi-climatic oscillations with two to five-year cycles of atmospheric and oceanic warming in the tropical pacific ocean. The cycles are typified by wind direction along and just north and south of the equator. The wind patterns affect sea surface temperatures by turning on and off deep ocean upwelling along the west coast of South America. The wind patterns and sea surface temperature in turn change the jet stream patterns in the northern hemisphere.

During an El Nino year, the trade winds are weak. This allows warm water to pool up along the west coast of South America. The warmer water along South America helps power a stronger subtropical jet stream which pumps moisture into the southern United States, Texas included.

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The effects of El Nino

NASA scientist George Huffman has more on how El Nino is affecting the weather.

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Yura says that during an El Nino year "the southern [sub-tropical] jet stream tracks across the southern United States. So when we’re in an El Nino time we tend to have pretty wet and cloudy winter times."

Conversely in La Nina years, the opposite happens. "That jet stream goes way to the north and leaves us with a lot of really pretty weather."

The end of 2020 saw a moderately strong La Nina develop. That is borne out in the very dry second half of the year which saw drought conditions develop across much of central Texas. The development of La Nina also helped with the record-breaking hurricane season 2020 brought to the Atlantic ocean and it’s all related to the placement of the jet stream.

Weather Facts: La Nina

Fall has been very warm and dry and it's a typical pattern when La Nina makes a comeback. Zack Shields has more on this weather even and how it will impact our winter.

"When we’re in a La Nina, and the jet stream goes away to the north, that jet stream allows for that tropical activity to exist." This is because high winds at upper levels of the atmosphere tear apart hurricanes. La Nina conditions, pushing the jet stream well north of the Gulf of Mexico and sub-tropical Atlantic keep the high-velocity winds well away from the tropics, allowing for busy hurricane seasons.

So what does that mean for this winter? Well, Yura says it should keep the sunshine out for much of the winter. He also says that it doesn’t really increase our chances for snow.

"It just doesn’t happen very often at all," says Yura, "It’s kind of hard to look at the data when there’s only like five instances ever!"