More showers on horizon before dry spell

The first day of fall is just over a week away and weather patterns are changing across the Inland Northwest.

Some much-needed rain fell in Coeur d’Alene and surrounding areas late Friday and Saturday. Even parts of drought-ravaged Northern California saw some measurable rainfall last Friday, but amounts were generally light. It’s been so dry in the Golden State that any moisture at all is better than nothing.

Here in the Inland Northwest, more showers are expected by late this week and again next week. However, it also looks like the big ridge of high pressure may rebuild into the region in late September and early October.

Eventually, the high-pressure system should push back to the southwest and open the storm door later in October or November. Based on current weather patterns and our climatological history, the chances are looking good for much above-normal moisture late in the year.

We’re still keeping a close eye on the sea-surface temperature patterns in the waters of the south-central Pacific Ocean. As I’ve mentioned for several months, we’re currently in a La Nada pattern, the in-between warmer El Nino and cooler La Nina.

However, ocean waters along the Equatorial regions are cooling and many forecasters believe that a new La Nina will form by late in the year.

During La Nina years, our region will typically see more snow than normal. However, due to milder temperatures, much of the moisture that has fallen in Coeur d’Alene and other locations in the lower elevations came as rain over the last several years.

The last snowfall season, which was a La Nina year, had only 53.9 inches compared to the normal of 69.8 inches in Coeur d’Alene. For this season, if the air stays cold enough, then our snowfall totals should be a little higher. We’ll have our annual snowfall forecast next month.

Speaking of sea-surface temperatures, the waters along the Equator may be cooling down, but they are getting much warmer in the Pacific Ocean north of Hawaii and in the Bering Sea west of Alaska. Readings in those areas are at least 5 degrees above normal, which could influence the air masses to the warmer side that move over the Pacific Northwest.

In the Arctic regions, sea-surface temperatures are warming up once again, especially in the Eastern Hemisphere north of Russia.

Although ocean waters are getting warmer, according to the National Snow and Ice Data Center, the sea ice melt in the Arctic was relatively slow last month when compared to other years in the past decade. In fact, they are predicting that September’s ice cover will likely be among the highest since 2007.

However, the overall ice melt in the Arctic has been declining at about 13 percent per decade when compared to the 1981 to 2010 average.

One thing that may be contributing to ice melt in the Arctic is the underwater hydrothermal vents. They are fissures that act as geysers, or hot springs on the ocean floor. Hydrothermal vents can heat the surrounding water up to 750 degrees.

Nearly 200 vents have been officially discovered since the late 1970s, but scientists say there may be six times as many undiscovered vents, including in the Arctic regions.

Many scientists also attribute the decline of ice in the Arctic is due to climate change, including the warming of the oceans. Some also believe that the warmer Arctic regions may show a correlation with a weakening of the polar vortex, an area of very cold air that circles the North Pole. When the polar vortex weakens, the colder air will move southward, which brings frigid conditions down into the U.S., especially east of the Rockies as well as Europe and Asia.

The warmer ocean waters in the Arctic could also be impacting the polar jet stream, the river of air that often directs Pacific storms into the western U.S.

One theory points to the possibility that we’re seeing longer periods with a high-pressure system over the western U.S. resulting in the current megadrought as the upper-level jet stream winds are becoming weaker.

In the Southern Hemisphere, scientists say Antarctica is one of the fastest-warming areas on the planet. Since the 1980s, Antarctica’s Thwaites glacier, also known as the “Doomsday Glacier,” has lost about 600 billion tons of ice.

However, the melting may not be entirely due to warmer air or ocean temperatures. According to a study published last month in Communications Earth and Environment, researchers have found that that heat from the Earth may be having an impact on the melting. The crust under West Antarctica is about 10 to 15 miles thick, which is much thinner compared to East Antarctica — around 25 miles thick.

Since temperatures below the Earth’s crust are very hot, the thinner crust may be absorbing some of that heat, which may affect the overlying glaciers over long periods of time.

By the way, the thickness of the Earth’s continental crust in the Northern Hemisphere is about 25 miles.

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Contact Randy Mann at randy@longrangeweather.com