As mentioned in previous columns, sea-surface temperature patterns usually have a strong influence on global weather patterns.
In El Niño years the Inland Northwest often sees more rain than snow in the winter months. By contrast, the cooler La Niña phase usually brings heavier-than-normal snowfalls.
La Niña and El Niño patterns are determined by the warming and cooling of sea-surface temperatures near the west coast of South America. As of late December, readings in that area are close to normal levels, indicating that we are now in a La Nada. There are now only pockets of cooler and warmer waters along the equator. But, looking at the entire globe, there are more warmer than cooler waters, especially near Australia and in the Gulf of Alaska.
Sea-surface temperatures in the Gulf of Alaska are much warmer than average and continue to climb. This recent warming may be influencing our drier-than-normal weather pattern across much of the western U.S. Low-pressure systems often form near these regions of warmer waters. This may be one reason why we’ve seen this extreme weather pattern across the country east of the Rockies as high-pressure ridges will be enhanced to the east of the strong low-pressure systems, like the one in the Gulf of Alaska. As the high builds, much colder air from the north comes down off the high, like a ball rolling off a table, sending temperatures to well below normal levels. It also appears that more frigid and extreme weather is expected across the central U.S. once again as high pressure will dominate most of the western U.S.
Many climate and atmospheric scientists believe that we’re going to be in a La Nada sea-surface temperature pattern through spring. Toward the middle of next year, however, a weak El Niño is expected to form based on the latest computer model forecasts.
If we stay in a La Nada, the Inland Northwest should start to see an increase in moisture, including snow, over the next few months. However, I’m starting to believe that we’re going to be a bit drier than normal into spring. California is already suffering from major drought and it doesn’t look like much relief is in sight.