The carcass of a North Atlantic humpback whale was discovered on the shore of Norton Point beach by a passerby Friday. The carcass was carried east by a passing storm this weekend and remained in the surf on Monday midday.

The 30-foot whale was first spotted by Hailey Yetman at noon Friday on a stretch of beach near Atlantic Drive. Ms. Yetman noticed the animal while driving and reported it to the Coast Guard. Officials first classified the whale as a small adult, but Sam Hart, regional director of the Trustees, later said he believed the whale to be a juvenile, based on its small size.

Chris Kennedy, who said he was told about the sighting by the Edgartown police chief, went to see the whale later and posted a picture on Facebook taken by Ms. Yetman.

Mr. Kennedy said by his observation the whale was in good condition with no immediate signs of gashes or decomposition. The cause of death is undetermined, but Mr. Kennedy said NOAA, which has jurisdiction over marine mammal strandings, had been notified. He speculated that the animal died possibly from a vessel strike or entanglement in fishing gear.

“Unless it had a disease, it’s probably a manmade cause of death,” said Mr. Kennedy, who recently retired from his longtime post as regional director of the Trustees of Reservations. “This whale did not die of old age from what I can see.” Based on the whale’s condition, the animal likely died within the last week or so, he also said.

North Atlantic humpbacks, though not endangered, are currently on the protected species list, with humpback population declining in the past 50 years, Mr. Kennedy said. The last time a humpback washed ashore on Trustees property was 12 years ago, he also said.

Norton Point is owned by the county but managed by the Trustees.

In 2016, NOAA declared an unusual mortality event for humpback whales after elevated mortalities began to occur along the Atlantic coast, from Maine through Florida. Massachusetts has seen 26 strandings — including three on the Vineyard — since 2016, the second most of any state, behind New York.

“It’s really unfortunate but it does happen and it’s not that unusual,” Mr. Kennedy said. “More and more whales have died because of entanglement as well as you know ship strikes.” He said the national and state marine fishery services are working to alter regulations for fishing gear to minimize the number of whale deaths by entanglement.

In a message to the Gazette Saturday afternoon, Mr. Hart said the whale had moved a few miles down the beach in the storm. By midday, the whale was being carried eastward along the shoreline, Mr. Hart said. With stormy conditions and high winds Saturday, Mr. Hart spectulated that the animal would be swept back into the ocean naturally by the end of the tide cycle.

By Sunday morning, however, the whale became caught in the breakwaters and had ceased to move, Mr. Hart said, citing reports from Trustees rangers Sunday. The whale was last sighted Sunday, tumbling in the surf about a mile and three-quarters east of the Norton Point gatehouse. Reached by phone Monday, Mr. Hart confirmed that the whale had not moved since the weekend.

“It’s in the same place in the middle of the wash, not high or dry,” said Mr. Hart.

Normally, after discovering a whale carcass, state and federal government organizations conduct necropsies to determine the whale’s cause of death, but Saturday’s fierce northeast storm hindered the process, Mr. Hart said.

Representatives from NOAA have not yet investigated the whale, but Mr. Hart said he hopes the agency will conduct a full necropsy in the coming days. The Massachussetts environmental police have also been notified of the incident, he said.

The Trustees currently have no plans to extricate the whale from the beach, as the mammal poses no harm to the beach or its visitors, Mr. Hart said Monday. “Sometimes we’ll tie the whale to a line and drag it out to sea, but it’s not really necessary during the winter months,” he said.

Norton Point has been periodically closed to over-sand vehicles throughout the fall, due to trail detrioration and erosion, and sees minimal foot traffic during the winter season.

The organization expects the mammal will decompose naturally on the shore in the coming weeks.