August 11, 2011 in Washington Voices

Departure of La Niña likely means less snow

 

Sea-surface temperatures in the south-central Pacific Ocean are changing. For many months, we were under the influence of La Niña, the cooler than normal ocean event along the equatorial regions. La Niña played, at least in part, a role in our snowy winter and wetter and cooler-than-average spring.

Since June, ocean temperatures have reversed and have been warming. Japanese and Australian scientists recently stated that La Niña had weakened considerably and is now gone.

Ocean waters have actually climbed to above-normal levels near the west coast of South America. This is the main region where an El Niño, the warmer than normal sea-surface temperature event, will usually form. During El Niño years, our region often sees much less snow than normal, as was the case during the winter of 2009-10.

It looks like we have a La Nada (as I like to call it), or in between the La Niña and El Niño sea-surface temperature event. Based on the current data, La Nada should be with us through at least early fall. But, in this cycle of wide weather extremes, a new El Niño could form rapidly.

It does appear that the huge high pressure that has dominated the southern Great Plains for weeks, is showing signs of moving over the western portions of the country. This new pattern would likely bring a drier and milder than average late summer and fall across the Inland Northwest.

Also, the latest computer models are forecasting the neutral La Nada event to persist at least into early winter this year and early 2012. This would likely give our region the best chance for snow. Much less snow is expected during the second half of the season, especially if we were to see a new warmer El Niño enter the weather scenario.

With slightly warmer than normal temperatures in the Atlantic and Caribbean waters, this year’s tropical storm and hurricane season is still expected to be more active than average. Tropical storm and hurricanes should start increasing over the next several weeks.

In terms of our local weather, not much moisture is expected the next few weeks. Some of the hottest weather of the season may be felt toward the end of this month. It’s rare that August does not see a drop of rain, but that could happen if the high pressure system intensifies.

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