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NWS: Bombogenesis Conditions Off Northern California Coast

SAN FRANCISCO (CBS SF) – Weather weary Bay Area residents had another word to add to their vocabulary Friday – Bombogenesis.

The National Weather Service and other forecasters took to social media hours before the latest winter storm slammed into the California coast, warning of the possibility of rare bombogensis conditions forming in the Pacific off the Bay Area.

The apocalyptic sounding bombogenesis is a mid-latitude cyclone that drops in surface barometric pressure by 24 or more millibars in a 24-hour period.

What it means is moments of intense downpours, but also really, really strong winds battering the Bay Area. The weather service issued a wind advisory for the entire Bay Area with gusts of 60 mph or more predicted.

Already strong downpours had caused flooding and ponding on local roadways, turning the morning commute into a slow and treacherous journey.

Winds will likely topple trees already weakened by weeks of rain disrupting power service, flights will be delayed at airports and ferry traffic on the San Francisco Bay will be impacted.

Rain had already begun to fall early Thursday but the surface low – the source of the potential bombogensis conditions — was deepening and parking itself off the San Mateo Coast.

Forecasters said downpours of 0.50 to 1 inch per hour were possible until 10 a.m.

That news was unwelcomed for water officials watching the rapidly rising waters of the Anderson Reservoir in Morgan Hill.

Water was gusting out of the spillway early Friday and the reservoir neared flood levels. The arriving storm also had officials at the Oroville Dam watching the situation with a heightened awareness.

Meanwhile, flooding continued at Lakeport in Clear Lake as the lower Sacramento River continued to run over its banks.
Work on removing a massive landslide blocking lanes of Highway 17 – the main artery between San Jose and Santa Cruz – was halted because of the rain and winds.