The biggest cargo ship to ever enter San Francisco Bay is here.

MSC Anna originated in Shanghai and was off the coast of Half Moon Bay at 10 a.m. Thursday morning. It will berth at the Port of Oakland this afternoon.

At 1,312 feet long, it outmeasures the 1,070-foot-tall Salesforce Tower, S.F.'s tallest skyscraper.

The monster vessel is also longer than America's largest aircraft carrier and among the most gargantuan ships in the world. There are about a dozen oil tanks that are bigger. It's about a meter shorter than the biggest container ship. It's bigger than CMA CGM Benjamin Franklin, which came to Oakland in 2016.

The ship can hold 19,200 20-foot containers; the big ships that typically dock in Oakland are 1,200-feet long and hold 14,000 containers.

Port of Oakland spokesperson Mike Zampa said the ship is part of weekly service that runs between China and California and the Mediterranean Shipping Company, which owns MSC Anna, has used a larger ship for this run to pick up a backlog of empty containers in Long Beach. Typically, the larger ships are used for longer hauls between Asia and Europe for efficiency.

MSC Anna is delivering consumer products to Oakland. "It’s carrying the things container ships always bring to the U.S.," Zampa said. "Most everything you’re wearing, clothes and shoes, consumer electronics furniture, ceiling fans, components for factory assembly lines, toys."

Zampa said Oakland is preparing for more regular visits from the bigger ships.

"Oakland is ready," he said. "We can handle it. We’re raising our cranes. We’re buying new cranes so we can reach the tops of the ships."

“We’ve spent years, and millions of dollars keeping ahead of the pace of trade and the size of ships,” added the Port of Oakland Executive Director Danny Wan. “We’re ready for the MSC Anna and we’ll welcome her back any time.”

To prepare for the arrival of MSC Anna, San Francisco's bar pilots who guide the ship into the bay underwent special training at the Cal Maritime Academy in Vallejo.

"That extra 100 feet and the greater width is a challenge," Zampa said. "They work on computer simulations to prepare."

While the Port of Oakland remains an essential service during the COVID-19 emergency and the shelter-in-place order, cargo volume is down 11% and Zampa said it's a sign of "the drag on the economy." The Port of Los Angeles is seeing a more drastic decline at 30%.

"There’s less demand," Zampa said. "It’s reflected in the shipping lines."

Amy Graff is a digital editor with SFGATE. Email her: agraff@sfgate.com.