Meteorologists use the term "atmospheric river" to describe a long, narrow plume piping deep moisture from the tropics into the mid-latitudes. One type of atmospheric river (hereafter, AR) you may have heard of is the "Pineapple Express", a pronounced plume tapping moisture from the Hawaiian Islands to the U.S. West Coast.
Amazingly, according to NOAA's Earth System Research Laboratory (ESRL), a strong AR can transport as water vapor up to 15 times the average flow of liquid water at the mouth of the Mississippi River!
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Suffice to say, if an AR stalls over a particular area, significant flooding can be the result. In fact, a study by Ralph et al. (2006) found ARs responsible for every flood of northern Calfornia's Russian River in a 7-year period.
That said, they're also important for western water supply considerations. According to NOAA/ESRL, 30-50% of the average annual precipitation in the West Coast states typically occurs in just a few AR events. With that in mind, one such AR is poised to soak parts of the West Coast this week. Let's get to the forecast details
Comment: Update - video footage of the enormous sinkhole in Ohio: