So, what's our problem? Mostly, it's La Nina, that little trollop. She's been messin' with Texas for a long time. And the relationship between her cool Pacific sea-surface temperatures and dry times here is pretty well established.
For nearly 120 years, since we've kept any kind of reliable records, La Nina has visited us 20 times, 19 of those resulting in below normal precipitation, according to Dr. Robert Hoerling, a National Oceanic and Atmospheric Administration research meteorologist, who served as the lead author of the U.S. Climate Change Science Plan Synthesis and Assessment Report.
In fact, of all southwest states, Texas is pretty unique because a relatively long-term forecast of below-average rainfall can be made with some certitude where she's concerned. Now, just looking at La Nina won't tell us how deep the drought will be, but her presence tells us something's coming -- or not.
La Nina started developing during the late summer of 2010, hit us throughout the winter and lingered into this spring. As a result, westerly storms moving across the Tropical Pacific with the jet stream got deflected northward. But by late spring, we were declared La Nina-neutral. And still, no rain of any consequence fell throughout the summer.
What gives? Just plain bad luck, Hoerling says. "If you look at the official forecast before the season from NOAA, there wasn't any strong indication of it being dry or wet," he says. "The summer rains are hard to forecast. You're basically left at the whim of a meandering tropical storm."
Take Tropical Storm Lee. It could have been ours. Instead, it tracked to New Orleans, where there was at least some moisture, and broke their drought decisively. It only fanned fires here in Texas. Drought, it seems, begets more drought. Different mechanisms bring rain to Texas during the summer than in the fall or winter. Technically, we can't lay it all at the feet of The Little Girl.
Now La Nina has returned, portending more drought into next spring.
We're in the midst of a huge weather cycle called the Pacific Decadal Oscillation, which can last, as its name suggests, decades. Its cool phase is apparently ongoing. The bad news is that makes La Nina a likelihood. So, does that mean we're in for a 50s-type drought that drags on for almost a decade? "We don't have the ability to be able to forecast ocean temperatures, which were key in determining that 1950s prolonged drought," he said.
Besides, he added, much about that drought -- like this one -- was unpredictable. Exactly why it was so dry, even when La Nina was dormant, is largely unknowable, left to unhappy chance and the Butterfly Effect. Or, at least, that's what it looks like now.
The good news, Hoerling says, is that this isn't global warming. "This is not the new normal in terms of drought. Texas knows drought. Texas has been toughened on the anvil of droughts that have come and gone. This is not a climate change drought. What we do anticipate from climate change is a situation where temperatures progressively increase."
In other words, this hot damned summer is another story entirely.
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