Ocean’s fluctuation has a local effect

For most of 2007, global weather patterns have been influenced, at least in part, by La Niña.

This phenomenon of lower-than-normal sea-surface temperatures in the south-central Pacific Ocean quickly sprang to life after the demise of El Niño early this year. El Niño is the higher-than- normal sea-surface temperature pattern along the west coast of South America.

With La Niña in control, moisture totals across the Inland Northwest have been below normal levels for 2007. It has been dry enough to declare much of North Idaho as a drought region. However, during the fall and winter months, this event often brings above-normal amounts of precipitation to much of the Northwest.

Much of last winter’s weather patterns were greatly influenced by El Niño. About 70 percent of the time, heavy rains will create mudslides in Southern California. Last winter, however, the southern portions of California had little moisture as the “Pineapple Connection” from Hawaii brought the usual heavier rains and mountain snows about 600 miles north into the Pacific Northwest and southwestern Canada.

The milder air from the tropical regions of the Pacific Ocean turned most of the snow to rain in the lower elevations of the Inland Northwest, especially in the Spokane area. However, it was cold enough that the higher elevations picked up plenty of snow to delight skiers and snowboarders during the 2006-07 season.

The back-and-forth events between El Niño and La Niña are another example of wide weather extremes – the worst in about 1,000 years. No one is certain as to why ocean waters warm up and cool down. I believe that short- and long-term climatological cycles and underwater volcanic activity may play a big part in the formation of each new alternating El Niño and La Niña. Prior to the late 1990s, we would experience an El Niño approximately every seven years.

Based on the current information, La Niña is expected to be a factor for influencing global weather patterns through at least this fall season. It did weaken in July but appeared to have strengthened a bit in late August and early September.

The rest of September still looks drier and warmer than normal in our region. But, we should start to see some increase in moisture toward the end of the month. I also believe that we’ve seen the last of the 90-degree days for this season, but we should see a few more in the 80s.

It’s also possible we could see chilly or frosty weather toward the end of September. Once this predicted cold spell ends, temperatures should quickly rebound giving the Inland Northwest much warmer conditions around the first week in October.

The storm door in our region should open by no later than mid-October if La Niña is still a factor in the south-central Pacific Ocean.

November should also see above normal amounts of precipitation across the area. However, conditions shouldn’t be quite as wet as last year. For 2007, much of the region should see approximately 20 percent to 30 percent higher than normal moisture totals. Up to half of our November 2007 precipitation may fall during the middle of the month.

I’ve been asked by a number of people on how our winter season is shaping up. If La Niña holds on, we should see a healthy snow pack in the mountains and a little more of the white stuff in the lower elevations when compared to last winter.