Longtime computer disk drive leader Seagate Technology PLC will have a new chief executive later this year after it badly missed quarterly earnings forecasts announced today.

Surprised investors hammered the company’s shares, which are down about 16 percent in midday trading, to $33.50 a share. Early this morning, Seagate reported a fiscal fourth-quarter profit of 38 cents a share or 65 cents before certain onetime items. Analysts had expected a much higher profit of 99 cents a share. Revenue of $2.41 billion, down 9 percent, also fell below analysts’ forecast of $2.55 billion.

Right after reporting the shortfall, the company also announced that longtime CEO Steve Luczo (pictured) is vacating the post come October, though he will stay on as executive chairman. He will be replaced in the top spot by current Chief Operating Officer Dave Mosley, who joined the board as of today.

Although the management change was unexpected by many, the company cast it as in the works for some time. “Steve and the Board have been actively working towards this transition for the last two years and we are confident that Dave Mosley is the right leader for the Company’s future success,” Mike Cannon, Seagate’s lead independent director and chairman of the Nominating and Corporate Governance Committee, said in a statement.

Luczo also sought in a prepared statement to cast Seagate as hitting a temporary slowdown. “Although the near–term dynamics of technology shifts present demand variations for the storage industry from time to time, we continue to see growing storage demand in the long-run driven by the proliferation of data growth from new technologies, emerging industries, and growing businesses,” he said.

But a near-term turnaround looks unlikely. “With ongoing execution struggles and a CEO succession plan announced, there could be more negative earnings revisions down the road,” Barclays analyst Mark Moskowitz wrote in a note to clients today. “Seagate is grappling with channel inventory issues and a high-cap technology platform that is trailing [Western Digital Corp.], resulting in market share loss and gross margin degradation.” He has an “underweight” or sell rating on Seagate’s shares.

In somewhat more candid comments on the conference call, according to a transcription from FactSet, Luczo described the disk drive business as extremely volatile. “As I said to someone the other day, that running a disc drive company is a little bit like driving in stop and go traffic,” he said. “Sometimes you’re going 15 miles an hour and sometimes you’re going 85 miles an hour. But you usually get to your destination on time and no one is hurt, but it’s stressful as s— for the driver and oftentimes for the passengers too.”

The company also said it’s cutting 600 workers worldwide as part of a restructuring plan. Although that’s expected to start saving money in the current quarter, amounting to about $90 million a year, Seagate is taking a pretax charge of $50 million for severance and related costs, mostly in the first quarter.

Western Digital, currently the largest maker of disk drives, will report its quarterly results Thursday afternoon. The Seagate news didn’t much affect Western Digital, whose shares were down less than 1 percent before the close. But shares of memory-chip maker Micron Technology was down nearly 5 percent.

Seagate shares had risen 4 percent since the start of the year, well behind the Standard & Poor’s 500 index, which is up 10 percent. The shares had risen 26 percent in the last year.

Photo: Seagate