National Weather Service Certifies Meteotsunami on Northern Sanibel

by SC Staff Writer Barbara Linstrom

Thanks to a video that was posted to Facebook shortly after a rogue wave made a big splash as it washed ashore at Castaways Inn at Blind Pass, the National Weather Service was alerted to a rare event on Sanibel.

I just certified it yesterday as a coastal flood event that we call a meteotsunami,” said Dan Noah, a meteorologist with the National Weather Service on Jan. 4. “We monitor social media and were alerted by key words to a video posted on Facebook shortly after it happened.”

At 12:28 p.m. on Dec. 20, as a TV news crew was preparing to shoot an interview with the manager of Castaways as gusts of winds were being recorded up to 50 mph, a big wave came crashing ashore and sent people running toward Sanibel-Captiva Road.

The video, which has since gone viral and has been posted across the globe as far away as Australia and Italy, gave Noah insight into a weather event he had never witnessed in his 30 years with the weather service.

I’ve been here in Tampa for 16 years and it’s the first meteotsunami I’ve every documented,” said Noah. “It’s not a tsunami like in the Pacific, but a meterology-induced tsunami that we call a meteotsunami. It’s a rapid rise in water that just happens once. With a tsunami, the waves will occur every 60 to 90 minutes.”

While tsunami warning systems are in place in the Pacific with buoys which measure wave height, the closest buoy that the weather service has is in Naples, which measured a peak wave of over 5-feet at 1:30 p.m. the same day.

The coast was under a gale warning that day due to a strong cold front that was moving across Southwest Florida, with strong southerly winds ahead of the front that were expected to make a quick shift westerly into gale-force strength.

We monitor social media for key words that alert us to weather events,” explained Noah. “It’s amazing how many more waterspouts we’ve been able to document. It doesn’t mean there are more happening, it’s that we’re being alerted to more.”

The weather service encourages citizens to participate in helping them document and monitor weather events by using the hashtag #flwx on Twitter and through descriptive words on Facebook.

We can’t predict meteotsunamis. They probably happen all the time, but are just a few centimeters in size,” says Noah. “Ones as big as this are rarely documented.”

The biggest meteotsunami recorded in Florida occurred at Daytona Beach at midnight on July 3, 1992, when a 10-foot wave caused by a collapsing thunderstorm off South Carolina generated the disturbance, he said.

Because waters are so shallow off Sanibel, a meteotsunami couldn’t reach that height here, he added.

The wave that crashed ashore at the Castaways was thigh-high as it reached Sanibel-Captiva Road, flooding out three cottages, as captured in the video. Its height upon reaching shore is estimated to have been higher than the 5-foot wave measures by the buoy in Naples.

If the city of Sanibel hadn’t cleared out the three culverts under San-Cap Road last spring that were plugged up, the water could’ve just stayed put, but it flowed out,” said Tony Lapi, president of Sanibel Captiva Beach Resorts, which includes the historic Castaways resort. “The breakwall in front of Castaways that was built 50 years ago created a tremendous looking splash, but I wouldn’t have called it a tsunami – more like a rogue wave.”

Lapi, who has been on the islands for 42 years, recalls a time when much larger waves washed ashore in front of ‘Tween Waters Inn on Captiva, another resort he runs. Wave action was so intense during a storm in 1988 that it washed away a 1200-foot stretch of Captiva Road in front of the inn up to the curve at Jensen’s on the Gulf.

This was not that big of an event. We had minimal damage to the cottages. They were back up and running within three days,” he says, noting the exceptional sunny weather that followed and lasted through New Year’s Day. “We’ll have to replace some shrubbery that wasn’t salt tolerant, but that’s it.”

James Evans, natural resources director for the city of Sanibel, says his team’s assessment of the beach didn’t find any significant damage.

There was no major erosion. We saw accretion of sand in some areas from that cold front and some erosion in others, but nothing major,” he said. “With the incremental rise of sea levels, though, we need to be aware meteotsunamis as one of the threats we face as we continue to build up the dune with vegetation to protect our beaches.”

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