MEXICO BEACH, Fla. — Gage Wilson and David Segal, technicians for the U.S. Geological Survey, were roaming the obliterated city of Mexico Beach when they spotted the missing sensor.
It was a barometer that USGS employees had deployed in advance of Hurricane Michael, a pressure gauge housed inside a two-inch-diameter aluminum tube. The employees had noted the specific spot where it was to measure the storm: "Barometer located on second light post from Highway 98 in pier parking lot."
But there was no more light post after Michael destroyed just about everything here with a massive storm surge and intense winds when it made landfall Oct. 10.
The USGS desperately needed that sensor to make an accurate estimate of the storm surge that barreled through Mexico Beach. Eleven days after Michael hit, demolishing most buildings in this seaside town, Wilson and Segal found the shiny cylinder, propped up vertically in front of the splintered ruins of a house as if hoping someone would find it.
Using data from that instrument and another sensor that had been nailed to a pier piling, the USGS on Oct. 25 concluded the storm surge at Mexico Beach had reached 15.55 feet, half a foot higher than the previous estimate. If you add the waves on top of the surge, the water level here reached 20.6 feet, or close to the height of a two-story building.
That's what people in the hurricane business call "The Big One." The term has nothing to do with physical scale - Michael was average-sized. But it was unusually violent, among the four most-intense hurricanes to hit the mainland United States since records began in 1851.
"It might be the severest hurricane to hit the U.S. for as long as I'm still alive," said storm chaser Josh Morgerman, 48, who has penetrated the core of 45 hurricanes and typhoons and survived the eye of Michael in a disintegrating Holiday Inn Express in Callaway, Florida, an eastern suburb of Panama City.
Mike Brennan, chief of the hurricane specialist unit at the National Hurricane Center, said Hurricane Michael was violent in two really different ways.
"You had the violence of the winds, the Category 4 winds in the eyewall there, but then you had the violent storm surge that was obviously powerful enough to wipe buildings off their foundation," Brennan said.
The unlucky people of Mexico Beach suffered both the maximum winds and the maximum storm surge - the rise in ocean water above normally dry land as the storm plows ashore. In this violent zone, propped against the storm's calm eye, the forward speed of the hurricane adds to the speed of its counterclockwise circulation. The overlap maximizes the surge.
In a storm as intense as Michael, the eyewall's winds are equivalent to an EF3 tornado, strong enough to destroy solidly constructed homes and lift cars off the ground. The extreme wind damage in Panama City, on the left side of the eyewall, raises the possibility that Michael generated hurricane "mini-swirls," which are like tiny tornadoes, roughly the diameter of a couple of houses, and can create momentary wind speeds in excess of 200 mph.
Government scientists are still trying to take the measure of the historic storm. Although Michael was officially a Category 4 hurricane, with 155 mph sustained winds when it made landfall, that could potentially be revised upward, to Category 5 - 157 mph and higher - in the ongoing National Hurricane Center analysis.
No one in the Florida Panhandle would be surprised by such an upgrade. To the untrained eye, the damage along this coastline looks like it came from a Category 13, what some observers likened to the effect of a nuclear bomb.
Every hurricane has a different footprint. Florence, for example, hit the Carolinas in September as a broad, soggy Category 1 hurricane moving at a glacial pace and triggering record flooding. Michael dropped modest levels of rain but was a speed demon.
Michael hit the coast moving 14 mph toward the north-northeast and accelerated to 17 mph. The eye remained well-defined, with an eyewall functioning like a lawn mower blade long after Michael made landfall.
That led to one of Michael's most stunning features: It stayed a hurricane far inland. It was still a Category 3 hurricane in southwest Georgia, the strongest storm to hit that state since 1898. Not until Michael was about 30 miles from Macon, in the center of the state, did the sustained winds drop to the point where Michael was officially just a tropical storm.
Scientists say climate change might be supercharging such storms, which in recent years have often intensified with unusual speed. Michael was a prime example, making landfall as a monster just three days after it was considered Tropical Depression 14 down near the Yucatan.
"Florence was certainly a bigger storm, in terms of the broader windfield, but Michael was a more powerful hurricane, because of its much lower central pressure," Brennan said.
At ground level, there is a strange pattern of destruction that stretches 70 miles along the storm-ravaged coast, approximately 70 miles of damage from Panama City to Carrabelle, along U.S. Highway 98. The road runs along the coast of the Florida Panhandle, sometimes through piney woods, sometimes hard against the water and built directly on top of what used to be the dune line.
The two-lane slash of pavement - initially impassable, but now open except for the stretch through Mexico Beach - is like a diagnostic tool for understanding the hurricane.
A few feet of elevation marked the difference between destruction and survival, something that is evident all along Highway 98 - some stretches of waterfront battered by storm surge sit adjacent to slightly higher ground that seems almost not to have been touched.
Coastal development in the Southeast United States often has challenged the forces of nature. There are homes built low, close to the water, completely unprotected. Many natural sand dunes, anchored by the deep roots of grasses and shrubs, have been destroyed in the creation of a sunny paradise. Mexico Beach had minimal sand dunes and no barrier island. It faced the open Gulf of Mexico. It was defenseless when The Big One arrived.
That wasn't the case for Cape San Blas, a peninsula that emerges from the Panhandle toward the west and takes a sharp right turn into a state park. That state park is now an island, because Michael's storm surge blasted a breach in an especially narrow portion of the peninsula. Scientists hadn't seen that breach coming, said Kara Doran, the USGS coastal change hazards storm team leader.
But most of the homes along the cape survived. Many of them are new, built after Hurricane Andrew chewed up South Florida in 1992 and spurred stricter building codes.
"I'm a third-generation Floridian," said Anne Hanson, whose house on the cape suffered no damage. "I told the builder, build me a Category 5 house."
Other factors might have attenuated the storm surge here. The cape is aligned north-south and was sideswiped by the hurricane rather than being hit flush. And the dunes, heavily vegetated, are a vestige of the way the whole coast used to look.
"This still has the Old Florida natural dune system, and I think that really helped us out," said Victor Rowland, 48, manager of the Rish Recreational Park, where cottages were spared the storm surge.
The powerful right side of the storm hit one of the least-populated areas in the Southeast United States - what state tourism officials call the Forgotten Coast. You can drive for miles and see nothing but pines, bent and snapped. In the early 1930s, Alfred I. duPont began purchasing huge amounts of cheap land in north Florida, and after his death in 1935, his descendants amassed more than 1 million acres, the pines harvested for a paper mill in Port St. Joe.
The mill employed thousands of workers from 1938 to the mid-1990s, and because nobody wanted beachfront condos with views of belching smokestacks, nearby beaches remained relatively undeveloped.
In neighboring Apalachicola, the local seafood industry was so productive and had so much clout that by the 1960s and 1970s Franklin County began imposing severe development restrictions: no buildings higher than three stories anywhere, no golf courses on barrier islands. For decades, Apalachicola Bay supplied 90 percent of Florida's oysters.
The paper mill is gone. Apalachicola's oyster fishery had largely collapsed even before the hurricane. The working-class base has shrunk, replaced by wealthier people from Atlanta and the entire East Coast who crave beach views. Michael's aftermath could further the trend toward a wealthier population that can afford newly constructed second homes built to Category 5 standards.
Tyler Matney, 38, who grew up in the Pacific Northwest, has been a local for only a year and a half. His home just a block from the bayfront in Port St. Joe was crushed. "This was not in the brochure 18 months ago when we moved here," Matney said.
The brochures might need to be updated. Brennan, the National Hurricane Center meteorologist, said Michael should remind coastal residents that "you can always be hit by a Category 4 or 5 hurricane."
Kevin Grimsley, a hydrologist with the USGS, was stunned by the destruction when he went into Mexico Beach two days after landfall. He was looking for those barometers, doing shoe-leather reconnaissance essential to hurricane science. All around him were the remains of houses that had been scraped from their foundations, a community that had gambled and lost.
"This could have been a lot of places in Florida or the Gulf Coast or along the Atlantic Seaboard," Grimsley said.