San Francisco weather: The difference between a bomb cyclone and an atmospheric river
OAKLAND, Calif. - Heavy rains are expected to pound the Bay Area early Wednesday, making the early morning commute a sure headache for many.
That's paving the way for the National Weather Service to educate meteorologist-wannabes about the differences between a bomb cyclone and an atmospheric river – because both are headed to the Bay Area.
And in a social media post, the NWS broke down the two terms with glossary terms and fancy charts.
The bottom line: A bomb cyclone is a low pressure system that experiences a fall in pressure of 24 millibars in 24 hours. They are often associated with atmospheric rivers and typically form in winter when cold and warm air masses collide. Other nicknames include "explosive cyclogenesis" or a "weather bomb."
An atmospheric river is a flowing column of condensed water vapor responsible for producing significant levels of rain and snow. Powerful atmospheric rivers can create extreme rainfall and floods, which can also trigger mudslides and cause "catastrophic damage to life and property," according to the National Oceanic Atmospheric Administration.
The North Bay braces for freezing temperatures, heavy rain
The North Bay is preparing for a one-two punch from Mother Nature. Freezing temperatures are expected at midnight, before heavy rain moves in late Tuesday.
Put more simply, National Weather Service meteorologist Daltton Behringer told KTVU that a bomb cyclone is how quickly a storm strengthens and an atmospheric river is a steady stream of moisture coming from the tropics.
You can have one without the other, but in this case, Behringer said, both are going to slam into the Bay Area, with the heaviest days of rain expected on Wednesday and Friday.
The flooding, wind and rain are first expected at about 6 a.m. Wednesday in the North Bay, and by the end of the weekend, cities like Santa Rosa could see a total rainfall of about 8 inches. By 7 a.m. or 8 a.m., the wet weather should make its way down to San Jose, which could see about 1 inch of rain by the end of the weekend.
Snow is expected in the Sierra – perhaps up to two feet in the higher elevations.
Meteorologists predict this atmospheric river will continue for several days, possibly into next week.