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Tuesday, November 17, 2009
El Nino Outlook: Wet Winter for N.M.
By John Fleck
Journal Staff Writer
Joe Galewsky pointed at a computer image of last weekend's storm. It rolled in from the northwest, dumping snow in Colorado and clipping the northern half of New Mexico before charging out onto the Great Plains.
But this was last Thursday. The storm hadn't happened yet.
It was not magic, just a weather forecast. Galewsky, a University of New Mexico professor who works on weather and climate models, is not a wizard, just a really smart guy. But our day-to-day familiarity with weather forecasts makes it easy to forget just how remarkable computer images like that are.
Without thinking twice, I acted on the information to rearrange my weekend plans, shifting my usual Sunday morning bike ride to Saturday to avoid the worst of the storm.
I do this sort of planning most weekends, using the forecasts to help me decide when and where to ride. I know from experience that the information is less than a perfect prediction. Some days I end up wet, or freezing, or riding into an ugly headwind I didn't expect.
But like last weekend, it almost always works. The forecast models developed by a host of researchers like Galewsky, refined over decades as computers get faster and scientists' knowledge improves, get it right most of the time. Add in the knowledge of the meteorologists at the local National Weather Service office, skilled in interpreting how the model results will play out across New Mexico's unique topography, and I've got a fabulous set of decision-support tools with which to maximize my weekend bike riding fun.
Using them is a matter of playing the odds, taking advantage of the best information available to make a decision in the face of uncertainty.
People are used to making decisions based on weather forecasts, comfortable with the associated uncertainty, Galewsky said during an interview in his University of New Mexico office.
But I didn't sit down with him for help planning my weekend.
What I wanted to know was how my confidence translates to longer time scales. For example, can we expect a wet winter this year in New Mexico?
Out in the Pacific, El Niño is gaining strength, a seasonal warming of the ocean along the equator every few years that influences weather across North America and around the globe.
Much like the weather forecasters who warned me last Thursday that a storm was coming, climate models by last May were forecasting an imminent El Niño. The forecast wasn't perfect. Increasing sea surface temperatures sneaked up on the modellers, and El Niño stalled for a while in September before cranking up again.
I first enjoyed El Niño's special charms in 1983.
I had just graduated from college and was on one of those road trips peculiar to that stage of life. While visiting friends in Chico, in California's central valley, the rains started, and they just didn't stop. More than 11 inches of rain fell in Chico in March 1983. The roads were sufficiently impassable, and I was sufficiently unemployed, that we just stayed and watched in awe.
The El Niño in the winter of 1982-83 was one of the strongest of the last half century. Wave after wave of storms across the West dumped so much rain and snow that runoff filling Lake Powell almost took out Glen Canyon Dam.
New Mexico's middle Rio Grande Valley got 2.7 inches of precipitation from January through March 1983, the heart of the El Niño rainy period. That's the second wettest it's been here for those months in the last half century. The wettest? It was 2005, also an El Niño year.
That is the story the forecast models are telling us for the winter of 2009-10. Fresh model runs released by federal forecasters Monday say December is hard to call one way or the other, but that odds favor wetter weather from January through the spring across the southwest, from California through the Four Corners states.
So, does this mean a wet winter and spring are a sure bet in New Mexico?
Galewsky, who understands the models and their limitations from the inside, would say no. At all time scales, whether we're talking about a short-term weather forecast or a seasonal forecast, the models have their limitations, "fundamental uncertainties," in Galewsky's words.
But as long as you keep the uncertainties in mind, and recognize that it is in their very nature that they will sometimes be wrong, the computer models have something useful to say.
UpFront is a daily front-page opinion column. John Fleck can be reached at 823-3916 or jfleck@abqjournal.com.
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