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 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 atmospheric river can transport as water vapor up to 15 times the average flow of liquid water at the mouth of the Mississippi River!
Suffice to say, if an atmospheric river stalls over a particular area, significant flooding can be the result. In fact, a study by Ralph et al. (2006) found atmospheric rivers 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 atmospheric river events.
With that in mind, one such atmospheric river is now soaking parts of the West Coast and will continue to do so through the weekend. Let's get to the forecast details
Flood Threat Through the Weekend
The graphic at the top of this article depicts the upper-air pattern that will stay in place through the weekend. Namely, a deep dip, or trough, in the jet stream is currently in place over the eastern Pacific Ocean.
This will continue to send a parade of frontal systems and upper-level disturbancesinto the West Coast.
The first storm arrived on Wednesday and brought rainfall from California to the Pacific Northwest. The combination of wind and rain led to hefty delays at San Francisco International Airport.
The upper-level pattern has now tapped into the atmospheric river of moisture extending from just north and west of Hawaii to the West Coast. This will continue to send the ongoing latest round of very heavy rain and gusty winds into northern California through Friday afternoon. Expect a very wet commute with more possible airport delays in the Bay Area Friday morning.
Though rain showers will continue Friday night into Saturday, the intensity should let up some before the next round of very heavy rain and strong winds arrives in northern California and southwest Oregon for Saturday night into Sunday.
Amazingly, according to NOAA's Earth System Research Laboratory (ESRL), a strong atmospheric river can transport as water vapor up to 15 times the average flow of liquid water at the mouth of the Mississippi River!
Suffice to say, if an atmospheric river stalls over a particular area, significant flooding can be the result. In fact, a study by Ralph et al. (2006) found atmospheric rivers 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 atmospheric river events.
With that in mind, one such atmospheric river is now soaking parts of the West Coast and will continue to do so through the weekend. Let's get to the forecast details
Flood Threat Through the Weekend
The graphic at the top of this article depicts the upper-air pattern that will stay in place through the weekend. Namely, a deep dip, or trough, in the jet stream is currently in place over the eastern Pacific Ocean.
The first storm arrived on Wednesday and brought rainfall from California to the Pacific Northwest. The combination of wind and rain led to hefty delays at San Francisco International Airport.
The upper-level pattern has now tapped into the atmospheric river of moisture extending from just north and west of Hawaii to the West Coast. This will continue to send the ongoing latest round of very heavy rain and gusty winds into northern California through Friday afternoon. Expect a very wet commute with more possible airport delays in the Bay Area Friday morning.
Though rain showers will continue Friday night into Saturday, the intensity should let up some before the next round of very heavy rain and strong winds arrives in northern California and southwest Oregon for Saturday night into Sunday.
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