EL PASO, Texas (KTSM) – You may have heard, “Pineapple Express” or Atmospheric River” lately, as torrential rain comes down in California.
In fact, according to the National Weather Service in San Francisco, the Bay Area just saw its wettest 10 day period since 1871.
Downtown San Francisco received 10.33″ between Dec 26 – Jan 4 (yesterday). The all time 10 day record was 14.37″ in Jan 1862.
But what is an Atmospheric River?
Atmospheric River explained
The typical set up starts in the Tropics, where wind flows over the ocean and pushes moisture towards land.
These winds can create narrow bands of extremely high moisture, called “Atmospheric Rivers”.
The strength of these rivers depend on the wind speed and location.
Within these narrow bands, rainfall intensifies and as the Atmospheric River moves on land, lift along the mountains aids in heavier rain and, in some cases, snow.
You may have also heard the term “Pineapple Express”. This is a well-known atmospheric river that brings water from Hawaii over to the mainland U.S.
Atmospheric rivers can be incredibly destructive.
A 1998 study by MIT discovered this weather phenomenon can have the same moisture flux as the Amazon River, which can carry about 176,000 tons of water per second.
The United States Geological Survey says some atmospheric rivers can be as destructive as hurricanes.
In the Sierra Nevada, atmospheric rivers are nearly 3 times more likely to result in destructive “rain-on-snow” events, which is when rain falls on snowpack and freezes, than other types of winter storms, according to a study by NASA.
Atmospheric Rivers can also cause very strong winds.
The NWS in San Francisco tweeted Thursday, saying the peak winds from Wednesday’s storm system produced 101 mph peak winds in Pablo Point in the Marin County mountains.
What is next?
Weather models indicate another wave of heavy rainfall is expected this weekend, which means flooding will continue to be an issue.
The National Oceanic Atmospheric Administration is predicting an additional 5-10 inches of rain the next 7 days.