The Vanishing La Niña

October 13, 2016
Weather Dogs
The Weathervane

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Here is the good news. The La Niña is vanishing.

One of the major factors that shaped the autumn and winter of 201½012 was the La Niña in the Pacific. This pattern of wind and water in the Pacific helped to shape weather around the world.

Here in the US, it helped create the drought that eliminated so much of the snow in the Western mountains. It created a two-year drought in Texas and left large stretches of the South high and dry.

By the middle of March, 58% of the contiguous US was dry or in drought conditions.

La Niña   SOURCE: NOAA

The La Niña is a large pool of unusually cool water in the Central and Tropical Pacific. It cools the air above it, altering not only the air’s temperature but also its ability of hold moisture. The air pressure changes and that, in turn, alter wind patterns. When over a million square miles of tropical air changes pressure, it changes wind and weather patterns around the globe, particularly in the tropics and the Pacific Rim.

The impact of a La Niña can be magnified or reduced by other climate factors. In the Northern Hemisphere, the wintertime behavior of the Arctic Oscillation (AO) can overwhelm the impact of a wintertime tropical oscillation. Normally a La Niña creates cold weather in Canada and the northern states. This year a positive Arctic Oscillation trapped the cold polar air north, leaving temperatures in most of the US positively toasty.

The Arctic Oscillation kept the La Niña from creating a cold winter. SOURCE: The Weathervane

This winter’s La Niña was weaker than the winter of 2010/2011, when the US froze and 49 of 50 states were covered with snow. It peaked in January and started to fade in February. At this point, most scientists expect La Niña to be gone by mid-to-late spring.

The good news is that to all intents and purposes, the La Niña is over. It is so weak that we are beginning to see a return to more normal winter. Rain has begun to return to the West and Texas. Storms lashed western states in late March, bringing near-normal snowpack to northern portions of the Pacific Northwest and welcome moisture, if not relief to central and southern portions of the West. Even parched Texas saw some relief, although 90% of the state remains in dry or drought conditions.

With La Niña fading, rains are returning to much of the drought-stricken USA. SOURCE: Wikipedia

Looking to the future, the majority of scientists expect the Pacific to be neutral this summer. Think of it – normal water and more normal weather.

Wouldn’t that be a nice change?

About This Blog

Are you a weather watcher? Welcome to “Weather Whispers” by James Garriss and until recently, Evelyn Browning Garriss. With expertise and humor, this column covers everything weather—from weather forecasts to WHY extreme weather happens to ways that weather affects your life from farming to your grocery bill. Enjoy weather facts, folklore, and fun!

With heavy hearts, we share the news that historical climatologist and immensely entertaining Almanac contributor Evelyn Browning Garriss passed away in late June 2017. Evelyn shared her lifetime of weather knowledge with Almanac editors and readers, explaining weather phenomena in conversation and expounding on topics in articles for the print edition of The Old Farmer’s Almanac as well as in these articles. We were honored to know and work with her as her time allowed, which is to say when she was not giving lectures to, writing articles for, and consulting with scientists, academia, investors, and government agencies around the world. She will be greatly missed by the Almanac staff and readers.

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