WASHINGTON — In what could be the first major labor showdown of the Trump administration, the National Weather Service announced it will cancel its contract with the union representing about 3,800 of its meteorologists and other workers.

The federal agency said it’s a somewhat routine move to restart negotiations, but the union called it a bizarre surprise.

An outside expert, University of California labor law professor David Rosenfeld, called it “a shot across the bow of the union.”

Weather Service deputy director Mary Erickson said terminating the 16-year-old contract is the next step in the negotiating process. In 2015, the agency sent a notice to the union that it intended to do this.

She said it is not about cutting jobs.

“Our intent is to get a stronger, newer more modern agreement in place,” Erickson said.

Union president Daniel Sobien said the move blindsided his group, which has already enlisted a mediator.

“Honest to God, I don’t understand why they did this; it makes no sense,” Sobien said. “To my knowledge it’s never been done before. To my knowledge it violates our agreement.”

Sobien pointed to part of the agreement that says the contract can be terminated, but not if one side has enlisted a mediator. Sobien pointed to a document on the Federal Mediation and Conciliation Service website showing that the weather workers union asked for a mediator in February.