Larry's Blog

What's an Atmospheric River?

No doubt youve heard of the Pineapple Express (PE). The PE is a West Coast term for a stream of warm, moist air, from near the Hawaii. PEs are attached to low-pressure areas migrating across the Pacific, aimed at the West Coast. Recent studies have show this type of pattern occurs in different forms all over the globe. The new term is called atmospheric river. The PE is considered a type of atmospheric river. Ive heard the term called the Rum Runner Express in the Atlantic - an AR from the Caribbean to Europe. There is always at least one AR somewhere on the globe. ARs are important corridors to export moisture from the tropics to the mid latitudes.

ARs are critical to the water resources and produce 30-50% of the West Coast water supply. Not all ARs are strong; many are weak and there is no flood threat. The strong ones can produce large floods and landslides. ARs are narrow (100 miles) and long (1000 miles). A single strong AR contains enough water to fill Lake Washington about four times! Remember that lake is over 200 ft deep in spots.

Although ARs create high snow levels, which is bad for skiers, you can almost bet that after the AR moves through, the snow level will drop and the snowpack improves with fresh snow, perfect for some great turns.

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