But as the cyclone — a rarity in the Middle East — headed from Oman to the southeastern Iranian coast, it continued to lose steam, dropping off to tropical storm strength early Thursday, according to the U.S. military's Joint Typhoon Warning Center.
The center predicted Gonu would make landfall on the southeastern Iranian coast late Thursday. But it was likely to spare Iran's offshore oil installations that lie more than 120 miles to the west, the center and oil officials said.
At least 12 people were killed from the storm in Oman, including members of police rescue squads, and others were reported missing, said Oman Royal Police spokesman Abdullah al-Harthi. He did not provide further details.
Across the Gulf of Oman, Iranian state television reported that a resident of the port city of Bandar Abbas was killed in a car accident Wednesday due to low visibility from the storm.
Two provincial government workers bringing emergency supplies to a flooded area also were killed when a river overflowed and flipped their truck in Jask, a town 155 miles southeast of Bandar Abbas, state TV's Web site said.
Authorities also closed all operations at the port of Sohar and evacuated 11,000 workers, port spokesman Dirk Jan De Vink said.
To the north, the port of Fujairah in the United Arab Emirates reopened Thursday after it suspended all refueling and ship-to-ship supply operations at the world's third-largest shipping fuel center.
A few ships sailed through the nearby Strait of Hormuz despite 4- to 6-foot swells and strong winds, Suresh Nair of the Gulf Agency Co. shipping firm said Wednesday. About one-fifth of the world's oil passes through the narrow waterway at the entrance to the Persian Gulf.
"About 17-21 million barrels a day of oil are coming out of the Persian Gulf. Even if only some of the tankers are delayed, that could reduce the supply of oil and increase prices," said Manouchehr Takin, an analyst at the Center for Global Energy Studies in London.
But Tim Evans, an analyst at Citigroup Global Markets, said the storm shouldn't have a major impact on prices because while it may delay oil shipments, they eventually will get to their destinations.
On Thursday, the storm sustained winds of 41 mph, less than half its strength of 95 mph just 24 hours earlier, the Joint Typhoon Warning Center said. It was centered about 98 miles north of Muscat and was projected to weaken over the next several hours to as it moves through the Gulf of Oman toward Iran.
Even with the weaker wind speeds, Gonu — which means a bag made of palm leaves in the language of the Maldives — is believed to be the strongest cyclone here since record-keeping started in 1945.
In the capital, Muscat, highways and yards were flooded, and downed trees and power lines were scattered in the high waters. Residents washed cars in the flooded streets, while others snapped pictures.
"The capital Muscat became a lake," the police spokesman al-Harthi told Oman TV.
In coastal city of Sohar west of Muscat, violent waves continued to crash the shore as several residents returned to their homes Thursday after being evacuated.
"We all went to the school last night, and I came back to look at the house. Twice the water came into my house, and maybe the tide will come in again," said fisherman Salem Hassan al-Mukblai, 40, as he and his two sons tried to tie a downed fruit tree to a fence surrounding their house.
Shareefa bint Khalfan, Omani minister of social development, said more than 20,000 people were evacuated Wednesday and housed in government-provided dwellings stocked with medicine and supplies. Oman's eastern provinces have been cut off, with heavy rains making the roads unusable and communication lines severed.
In Iran, authorities evacuated hundreds of people living in the port city of Chabahr on the coast of the Gulf of Oman, believed to be next in the cyclone's path.
But the heavy storm, which caused trees to fall and windows to smash, eased Thursday morning, subsiding into light rain and wind.
"Thanks to God, people are back in the bazaars and streets of the city," said Abbas Jafari, a 47-year-old taxi driver. "Yesterday was terrible. I had never seen such a storm in my life."
Iran's state broadcasting company said on its Web site that some small villages in Sistan and Baluchistan province, on the Gulf of Oman, were still encircled by floods and authorities used helicopters to drop emergency supplies to them.
The storm affected power and telephone lines elsewhere in the province, but caused no major damage, provincial governor Habibollah Dehmardeh told the official IRNA news agency.
As a precaution, the Bandar Abbas oil refinery, which supplies the local petroleum market, closed jetties that receive oil from tankers, the Web site of Iran's Oil Ministry reported. The refinery was working as usual Thursday, the report said.