On the afternoon of January 6, local time, when the US NOAA-20 satellite flew through the northeast Pacific Ocean, it recorded the fierce weather that was encountering here - a strong and thick cloud belt was like a waving wing, from the depths of the Pacific Ocean to the United States and Canada in western North America.
In this thick cloud layer, there is a large amount of warm and moist water vapor, which is the exuberant "atmospheric river" system in the eastern Pacific Ocean. On a larger satellite map, this steam-filled atmospheric river stretches from the hawaiian islands in the depths of the Pacific Ocean to the western coast of North America, and as the atmospheric river reaches many parts of the United States and Canada, it is triggering heavy rainstorms and heavy snow at high altitudes in many states.
According to the forecast of the American Meteorological Service (NWS), the strong atmospheric river system will bring strong precipitation to many states in the northwest of the United States, and the cumulative precipitation in many places from January 6 to January 9 can reach 150-200 mm (that is, 6-8 inches), and the three-day precipitation in some areas can reach more than 450 mm (18 inches), which means that the rain in some areas is fierce, and the possibility of flood disasters is not ruled out.
As a result, the NWS has also issued a series of early warnings about flooding to many parts of the western United States. Of course, this ferocious atmospheric river is actually part of a strong temperate cyclone in western North America, so many places in the northwest of the United States have also hung a series of warnings related to winter storms and high winds.
Atmospheric rivers are not a rare phenomenon on the west coast of North America, but in 2021, atmospheric rivers have already brought some catastrophic events - from October 22 to 25, 2021, a rare atmospheric river event hit the west coast of North America, in Washington, Oregon and California, where wild storms swept across coastal areas, dry California had heavy rainstorms - heavy rainstorms, localized heavy rainstorms, and the maximum precipitation in San Francisco reached about 200 mm, several times the average precipitation in October, breaking the local record.
The water vapor in the atmosphere, sometimes forming long and narrow concentrated water vapor belts, brings large amounts of water to the middle and high latitudes, and this water vapor belt is called "atmospheric rivers" and is part of the global water cycle. Commonly known as the "Pineapple Express" in western North America, it is able to bring atmospheric moisture around the Hawaiian Islands to the Pacific coastlines of Canada and the United States.
But since last fall, the power of atmospheric rivers has been particularly unusual, except for strong winds, flash floods and mudslides/landslides in the western United States in late October, and the surging atmospheric rivers around November 16 have brought extreme torrential rains near Vancouver in southwestErn Canada, with record-breaking rainfall in some areas, resulting in a rare flood near Vancouver once in a century.
Although precipitation from atmospheric rivers is an important part of the annual rainfall in western North America, it is indeed not normal for atmospheric rivers to cause extreme rainstorms frequently from 2021 to 2022. Some meteorologists pointed out that this may be related to the change in the distribution of sea temperature in the North Pacific, resulting in the westerly wind belt of the North Pacific being more prone to winter storms, strengthening the ability of atmospheric rivers to produce heavy rainfall, which may be a symbol of climate anomalies.