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Goodbye La Nina hello uncertainty

As La Niña weakens and El Niño threatens, forecasters admit the weather forecast for summer remains a mystery. La Niña has entered “neutral status”, meaning it no longer is considered a significant event that drives weather patterns for North America. There is still a chance lasting effects of a strong La Niña, called the La Niña footprint, may be with us at least through spring.

It wasn’t so many years ago that weather forecasters were feeling confident about technology advancements that armed them with better ways of accurately predicting the weather. But in the words of one National Weather Service meteorologist, “the more we discover about the weather the more we realize how little we know.”

A case in point is the forecast for developing weather in the 2012 crop year.

According to the Australia Bureau of Meteorology, effective this week (Mar. 25), the weather event known as La Niña has entered “neutral status”, meaning it no longer is considered a significant event that drives weather patterns for North America.

Why is this significant? The best answer would be because La Niña is being credited with causing the worst drought in Southwest U.S. history, the drought of 2011, and was a major contributor to the extreme and searing heat that complicated the lack of moisture in the region, resulting in the largest loss to agriculture ever recorded, over $7.2 billion in losses in Texas alone according to the latest numbers.

So if La Niña is no longer steering dry, hot weather patterns across the Southwest, and considering that rain (in some cases significant rain) has fallen since early January across much of the region, then the forecast models going forward into late spring and summer should be calling for more of the same—namely rain, and the end of the drought as we have come to know it.

Not So Fast

Barry Goldsmith is a warning coordination meteorologist at the National Weather Service’s Brownsville, Texas, station (among other titles) and a student of complex pattern forecasting. Part of his job requires him to work with local and state disaster emergency personnel in preparing for major weather developments such as hurricanes and wildfires. His passion, and often the subject of classes he stages for professionals and novices alike, is determining why weather develops the way it develops and how to better understand modeling as a method of accurate forecasting.

“There was a time when people would look out the window and see clouds developing and predict that it was going to rain. But we know now that there are multiple reasons why weather happens the way weather happens. It’s a science, and we’re learning more about it all the time,” Goldsmith says.

Goldsmith says predicting the end of a dry season based upon just one contributing event is like choosing the white horse to win the race every time. He says there is a multitude of things that can happen that can influence when and where rain will fall or how hot the summer will be or how cold the winter will get and how long it will last. While La Niña and El Niño events are two major contributors to weather feast or famine, there are other things to consider.

“The Southern Oscillation Index (SOI) gives us an indication of the development and intensity of El Niño or La Niña events in the Pacific Ocean, and variations in the temperature of the surface of the tropical eastern Pacific Ocean. The temperature of these waters greatly affects weather development in North America. But also of concern is an event known as the North Atlantic and Arctic Oscillations, another major event that radically changes SOI behavior, especially in the Americas,” Goldsmith says.

In layman’s terms, La Niña and El Niño events can be negatively or positively influenced by both Arctic and North American oscillation and the result can bring drought when rain is expected and floods when drier conditions are expected to prevail.

“And these aren’t the only things that affect global weather. We’re just now beginning to understand the dynamics of wave action, for example, and the role these and other factors play as they react with other significant global weather events,” he adds.

And the Forecast Calls For What?

What's happening now as April approaches is a volatile weather pattern across North America. While La Niña may have entered the “neutral zone” and is losing influence over weather developments in North America, there is still a chance lasting effects of a strong La Niña, called the La Niña footprint, may be with us at least through spring. Then we may or may not see an El Niño, or ENSO, event, and that may or may not bring more normal rainfall to large areas of North America.

“For all we know and in spite of all the computer models—which are exceptional forecast tools—we may not be able to forecast long range weather patterns until we know more about the many contributing factors, the wind and wave patterns that may or may not develop. There are just too many variables,” Goldsmith adds.

Goldsmith says the difficult-to-understand weather pattern currently setting up over North America reminds us how little we know when it comes to being able to ‘predict’ long range weather.

“We’re always learning new things, a trend that will continue on the wings of technological advancements. But just when you think you have it all figured out, something new occurs and you’re back to square one all over again,” he adds.

“When it comes to weather, we expect the worse and hope for the best. When all is said and done, it’s the best we can do at the end of the day.”

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