Passengers onboard the Norwegian Escape found themselves dodging flying furniture and shards of glass while holding on for dear life as the vessel encountered high winds Sunday night.
The 326-metre ship had departed Cape Liberty Cruise Port across the Hudson from New York City about 3pm, bound for Port Canaveral, Florida, and eventually the Bahamas three days later. The weather wasn't superb, but not overly vicious - severe storms in the Deep South and heavy snow in New England, with the Escape set to sail through a more tranquil shield of rain in between. Maximum winds of 48 to 64km/h and occasional downpours looked to be in the offing.
Nothing could have prepared passengers for what was to come.
Shortly before midnight, the ship suddenly lurched portside. An onboard video shows passengers - who moments earlier had been celebrating the first night of their cruise - forced to duck and cover, in the crosshairs of tables, chairs and cutlery that become projectiles. The ship was northeast of the Delmarva Peninsula when it happened.
"Several injuries were reported," Norwegian wrote on Twitter. "Those guests and crew received immediate medical attention or are being treated by the ship's medical staff."
Norwegian said the ship wasn't damaged and remains "fully operational," with no impact to sailing or the itinerary.
The culprit for the commotion? What Norwegian described as a "sudden, extreme gust of wind, estimated at 100 knots." That's 185km/h - above the threshold for a Category 3 hurricane.
"It strikes me as a freak thing," said Jonathan O'Brien, a meteorologist at the National Weather Service office in Mount Holly, New Jersey. "We've seen the video and it happened not too far off our coastline. But it wasn't a hugely powerful system."
There was nothing to suggest a wind gust close to this magnitude would be possible. There were no reports of damaging wind anywhere in the Northeast.
"I was working Sunday and left shortly before the event happened," O'Brien said. "We were focused on heavy rain moving up the coast. It was a run-of-the-mill low pressure system. We didn't have any wind alerts up."
A nearby weather balloon sounding shows why winds weren't expected to be an issue: An inversion. The profile shows temperatures increasing dramatically with height just above the surface. That meant air near the ground and farther aloft were unlikely to mix, and strong winds wouldn't make it to the surface.
Meteorologists were left scratching their heads, but there are a few possibilities.
A barometer trace from a buoy off Cape May, New Jersey, shows the center of low pressure had been passing overhead at that point. Doppler radar reveals a number of heavy downpours - and a few thunderstorms - in the storm system's "comma head" region nearby at the time.
Despite air temperatures under 5 degrees, a powerful thunderstorm developed on the leading edge of a wind-shift line. Some of the precipitation on the northern end of the squall was falling as snow. The storm quickly became a "bow echo," a backward C-shaped storm where strong winds cause the line of storms to bow out in the middle. Even still, it's unlikely that winds more than 90-115km/h would have accompanied that storm. And they would have lasted about 10 minutes. This gust of wind was one-and-done.
There is a chance that it could have been a shallow waterspout. Radar shows a bit of rotation along the wind-shift line. Since the thunderstorm cell is so far away from the radar dome, we can't see closer to the ground. There might have been a funnel hanging down below that the beam overshot.
Most waterspouts have winds of 80 to 100km/h. If it was attached to the thunderstorm above - which was moving northeast at 96km/h - that could account for a brief, sporadic gust to 185km/h. There would be no way to see it coming, and no buildup. It sounds like it would match the description.
O'Brien notes "there was plenty of wind shear" that could help to spin something up, but low temperatures would make it a long shot. The fact that a thunderstorm was able to form, however, shows the atmosphere was unstable and lends support to this theory.
The Escape wasn't the only one to clock an extreme wind gust Sunday night. A rogue gust to 145km/h was measured by a weather station south of Fisherman's Island near Virginia Beach.
That one looks to be a mystery, too. The next closest wind report was more than 400 kilometres away.
This is the second stormy incident for Norwegian Cruise Lines in 15 months. Cruise Laws News reports it faces litigation for sailing into the January 2018 "bomb cyclone."