Weather Academy: What are La Nina and El Nino?

MONROE, La. (KNOE) - This week on the Weather Academy we’re going to be talking about climate patterns, and how warmer than average and cooler than average sea surface temperatures can impact our weather all around the globe.

First off, we’re going to be talking about El Nino. Our trade winds usually flow from East to West. This will push warm waters along the equator towards Asia. But in El Nino years, we usually see those trade winds weakening, which allows for those warm waters to shift back towards South America. This plays a big role in the type of weather that we see, especially during the wintertime, our Pacific jet stays further to the south, allowing for that warm, moist air to move across the southern United States. And it usually leads to a wet pattern or some more flooding in the South. It keeps the north and Northwestern areas warmer during the winter, as the polar jet stays closer up into Canada, the opposite can be said for Lavinia so our trade winds flow as usual, from east to west.

But in a La Nina year, these winds are typically a little bit stronger. So it keeps that warm ocean water towards Asia and allows for cold ocean water to pull closer to South America. This pushes our Pacific jet a little bit further to the north, allowing for those wet conditions to persist and the Pacific Northwest. This jet meets up with the polar jet allowing for those colder conditions to stay a little bit further north, and therefore the south experiences dry and warm conditions. This is something that we’ve been experiencing over the last two years and a reason why we have some of those extreme drought conditions back in the West. Now la Nino can also play a big role in our hurricane activity. It typically supports higher hurricane activity and stronger hurricane activity in the Atlantic basin. The reason for this is due to some weak vertical wind shear or the changing of a when different directions and speed as you go up in the atmosphere.

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