Pacific Powder: Here Comes La Niña

Pacific Northwest (Shred White and Blue)-It’s time to start waxing up the big boards in the Pacific Northwest, as the prediction for a strong La Niña weather pattern is gaining strength across the U.S.

Compared to the El Niño pattern that rocked the Southwest Rocky Mountains with tons of wet snow last season (and actually resulted in some deep powder poaching in the off-limits hoodoos of Bryce Canyon National Park in Utah), La Niña tends to send the deepest days to places like Crystal Mountain and Baker in Washington State.

Consistent with nearly all of the forecast models, La Niña is expected to last at least into the Northern Hemisphere spring 2011. Just over half of the models, as well as the dynamical and statistical averages, predict La Niña to become a strong episode (defined by a 3-month average Niño-3.4 index of –1.5oC or colder) by the November-January season before beginning to weaken. Even though the rate of anomalous cooling temporarily abated during September, this model outcome is favored due to the historical tendency for La Niña to strengthen as winter approaches.

Likely La Niña impacts during October-December 2010 include suppressed convection over the central tropical Pacific Ocean, and enhanced convection over Indonesia. The transition into the Northern Hemisphere fall means that La Niña will begin to exert an increasing influence on the weather and climate of the United States. Expected U.S. impacts include an enhanced chance of above-average precipitation in the Pacific Northwest, and below-average precipitation across the southern tier of the country.

For the surf set, La Niña can contribute to increased Atlantic hurricane activity by decreasing the vertical wind shear over the Caribbean Sea and tropical Atlantic Ocean. Conversely, La Niña is associated with suppressed hurricane activity across the central and eastern tropical North Pacific.

According to the AFP media services, World Meteorological Organization climate services chief Rupa Kumar Kolli said a “moderate to strong” La Nina, which appeared in July, was now well established.
Kumar Kolli told journalists that forecasts showed “rather a strengthening of this La Nina episode for the next four to six months.”

Hang on Shred America, it’s going to be another wild ride!