El Niño could bring more rain this winter

The latest sea-surface temperature analysis continues to have an expanding area of warmer ocean waters in the south-central Pacific Ocean. The region of warmer sea-surface temperatures have now expanded westward from the west coast of South America to Indonesia.

Much of the equatorial region, in terms of ocean temperatures, is above normal. Many scientists say that we’re now in a weak El Niño, the warmer than normal sea-surface temperature event. This phenomenon is also showing signs that it may become stronger over the next few months which would likely influence this winter’s weather. Our last two winters combined had the most snow on record in the Inland Northwest. Other parts of the northern U.S. also had record snows last year.

At Spokane International Airport, more than 190 inches of snow was measured when combining the winters of 2007-2008 and 2008-2009. Since early 2008, sunspot levels (storms on the sun) have been low and we had a La Niña, the cooler than normal sea-surface temperature event in the south-central Pacific Ocean. The combination of low solar activity and La Niña likely played a role during our record snowfall.

By this fall and winter, the upper-level sub-tropical jet stream should become stronger bringing much-needed rains to California. The polar jet stream, the river of air that directs most of the storms from the Pacific Ocean into our region, often becomes weaker during El Niño events. With the milder sea-surface temperature pattern, Pacific storms typically head into California about 70 percent of the time, leaving our region a bit drier and milder than normal.

I expect this winter to feature much less snow than the last two seasons. In this pattern of extremes, it’s possible that snowfall totals for 2009-2010 will be below average levels with more moisture falling as rain due to the milder conditions. This also increases the chances for freezing rain and even an ice storm. Depending on how the new El Niño develops, the jury is still out as far as our upcoming winter is concerned.

In the near-term, the hottest weather of the summer should arrive by late July into early August. Temperatures at that time may approach the century mark in the Spokane area with readings above 100-degrees in the Columbia Basin.

Cooler and wetter weather should arrive shortly after Labor Day. Some frosts and freezes may occur in the normally chilly zones of our region by the second week of September, well ahead of schedule and way ahead of last year.