The mild temperatures and persistent rain on the West Coast this week are being caused by yet another El Nino, the abnormal warming of ocean waters along the equator.
The funny thing is El Nino usually gets blamed for drought in the Pacific Northwest.
But this year is different. Weather stations throughout the Northwest are reporting precipitation higher than normal. California is under a deluge.
Forecasters aren’t surprised. The change shows how complex and sometimes fickle the weather can be.
John Livingston, meteorologist in charge of the National Weather Service bureau in Spokane, put it this way: “El Nino has different manifestations in different years.”
There is no indication the Inland Northwest is going to see the heavy snow and deep cold that prevail in a normal winter.
This year, the upper-level winds that carry storms around the globe are converging off California and sending waves of precipitation onshore.
The storms have been particularly fierce because cold air from the north is clashing with moist air from the subtropics.
This clash unleashes a lot of rain and snow, particularly when the storms form to the southwest and then rise over mountain ranges such as the Cascades, Sierras and Rockies.
Beginning last fall, flooding has occurred sporadically from Western Washington into California. East of the Cascades, precipitation has been above normal.
The National Weather Service reports accumulations of rain and snow at 150 percent of normal in central Washington from October through December.
This is good news for farmers who were short of irrigation water last year.
Spokane got 6.6 inches of precipitation in the same period, which is 119 percent of normal.
The snowpack in Idaho is at 105 percent of normal, with some river basins showing accumulations up to 150 percent of normal.
Ski areas opened in November and have been running on plenty of snow since.
And the extra water should help efforts to flush young salmon to the sea next spring.
This is in stark contrast to the drought that has been hurting the Inland Northwest in recent years.
As of the end of November, extreme drought was reported in the agricultural regions of central Washington and forests of northeastern Oregon, according to the Climate Analysis Center.
Moderate drought was reported elsewhere, including the forests of northeast Washington.
This apparently was the result of dry weather associated with four earlier El Nino episodes starting in the winter of 1986-87, according to the climate center.
Typically, El Nino allows low pressure in the North Pacific to move farther south as trade winds die down in the tropics. El Nino refers to the warming of ocean waters along the equator, and the weakening of trade winds.
In a dry year, the presence of this low-pressure area north of the tropics allows a ridge of high pressure to form along the North American coastline.
The ridge blocks storms, diverting them into British Columbia or southeast Alaska.
In a wet year, the low pressure area moves closer to the North American coastline. The ridge in turn sets up farther to the east over the Rocky Mountains and Alberta.
This pattern allows storms spawned by the low pressure area to come ashore in California, Oregon and Washington.
“Every El Nino has its own little nuances,” said geography professor Robert Quinn of Eastern Washington University. Quinn is an expert on El Nino.
El Nino means “the boy” in Spanish, or the baby Jesus when it is capitalized. El Nino is known to bring unusual rains to coastal South America during the Christmas season. Hence the name, which comes from the folk culture there.
Quinn said El Nino typically brings temperatures that are warmer than normal to the Inland Northwest.
For example, December was 2.5 degrees above average in Spokane. January is keeping with the pattern. On Tuesday, the high was 16 degrees above normal.
During the El Nino episode of 1983, the average January temperature was 10.1 degrees above normal.
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