Rise of the Superstorms

Rise of the Superstorms

PBS Airdate: June 27, 2018

NARRATOR: Unprecedented devastation,…

JEFF MASTERS (Weather Underground): By Friday morning, they started using the word "catastrophic."

NARRATOR: …three monster hurricanes in a single month: Harvey, Irma, Maria.

RICK SCOTT (Governor, State of Florida): If you're told to evacuate, get out quickly.

NARRATOR: They strike violently, scouring the land,…

FORREST MASTERS (University of Florida): We saw winds in excess of a hundred-and-ninety miles per hour.

VALERIE BROWN (Rockport, Texas): The eye was right here, on top of us.

NARRATOR: …leaving devastation and thousands stranded in their wake.

SYLVESTER TURNER (Mayor, City of Houston): Today the focus is on rescue.

NARRATOR: Houston, the nation's fourth largest city, is under water.

HAL NEEDHAM (Marine Weather & Climate): You know that people are facing really catastrophic situations. They may be fighting for their lives.

NARRATOR: Islands like Puerto Rico and nations of the Caribbean are ravaged.

GASTON BROWNE (Prime Minister, Antigua and Barbuda): The entire country has been decimated. I have never seen anything like this before.

NARRATOR: The Florida Keys are in shambles. What explains one of the most disastrous hurricane seasons on record? Why did the strength of these storms take so many by surprise? Could a warming planet be driving the weather to new extremes? Are storms of this intensity the new normal? And how will we cope?

MARSHALL SHEPHERD (University of Georgia): Many organizations talk about climate refugees; 2017 Atlantic hurricane season may have ushered in that era.

NARRATOR: For the survivors, life may never be the same.

ANN O'BANNION (Hurricane Harvey Survivor): This is unreal.

MICHAEL GARCIA (San Juan, Puerto Rico): Here was the living room, right here.

NELIA MARTINEZ MELÉNDEZ (Yabucoa, Puerto Rico): I couldn't believe what was happening to us. We lost everything, everything.

NARRATOR: Rise of the Superstorms, right now, on NOVA.

A Houston neighborhood devastated…

STATE TROOPER #1: State troopers. Anybody here?

NARRATOR: …the terrible aftermath of Hurricane Harvey.

STATE TROOPER #1: State troopers. Anybody here?

NARRATOR: Now, rescue workers search for trapped residents.

STATE TROOPER #2: We're going to go here and knock on the door.

STATE TROOPER #1: State troopers.

NARRATOR: In 2017, three monster hurricanes strike the U.S. in rapid succession: Harvey,…

JEFF MASTERS: Houston, under water, the nation's fourth largest city;…

NARRATOR: …Irma…

JEFF MASTERS: …much of Florida, in extreme rains, storm surge flooding;…

NARRATOR: …and Maria.

JEFF MASTERS: …in Puerto Rico, their second heaviest rainfall on record.

NARRATOR: They bring life-threatening destruction to millions in their path.

STATE TROOPER: I've got 18 people I'm trying to get out.

NARRATOR: It's an unprecedented onslaught that breaks records with powerful winds and especially water.

JEFF MASTERS: Water is going to be part of our future, both on the rivers, at the oceans. We need to be using the best science we have to prepare ourselves for our Waterworld future.

NARRATOR: While we scramble to rebuild, following one of the most harrowing hurricane seasons on record, scientists, policymakers and citizens are asking, "Is this our future? And if so, how can we get ready with the next season already upon us?

It's August 2017, midway through the Atlantic hurricane season. So far, it's been fairly quiet, but that's about to end. There's a weather disturbance developing in the Atlantic, and it's moving steadily westward.

TONY MCNALLY (European Centre for Medium-Range Weather Forecasts): A storm starts off in a reasonably simple way. You need some warm surface temperatures, and that will give the air near the surface an initial trigger to start rising.

NARRATOR: On August 17th, the system grows in strength, becoming a tropical storm. It's given a name, which will not soon be forgotten: Harvey. Harvey loses strength and a few days later, crosses the Yucatán Peninsula into the Gulf of Mexico.

NEWSCASTER #1: There's the storm. It is very disorganized.

NARRATOR: But meteorologists at the National Weather Service predict that as the storm moves into the warm Gulf waters,…

NEWSCASTER #2: Remember, tropical systems just feed off of that warmer water.

NARRATOR: …Harvey will strengthen and hit Texas within a few days.

NEWSCASTER #3: If you are just waking up and tuning in, we're now just dealing with a tropical storm; we'll probably be dealing with a hurricane.

NARRATOR: A hurricane, but only a relatively weak one, Category 1. However, it is expected to bring at least 10 inches of rain and some flooding. On the Gulf Coast of Texas, residents prepare for a bad, but not catastrophic storm.

WOMAN BUYING GROCERIES: Water, canned goods, some fruit, lots of pouches for my little boy to eat, so, just trying to be prepared.

NARRATOR: But then Harvey takes a dramatic turn.

FOX NEWSCASTER: Well, it has changed, and it is bigger.

NARRATOR: In just a matter of hours, Harvey rapidly increases in strength. Now, with the storm just 300 miles offshore, forecasters quickly change gears.

CHAD MYERS (CNN METEOROLOGIST): A few hours ago, this was going to be a Category 1; now we're looking at a Category 3.

NARRATOR: They predict Harvey will be a dangerous "major hurricane," with winds up to a hundred-and-twenty-five miles an hour.

FOX NEWSCASTER: We haven't seen anything like that along this coast for at least 47 years, this part of Texas.

CHAD MYERS: …a major hurricane with big flooding, surge, wind and a lot of damage.

NARRATOR: As Texas officials prepare to face this rapidly evolving monster, wind engineer Forrest Masters recognizes a good opportunity to gather data.

FORREST MASTERS: We've been there for every major event that's happened, all the major storms you can think of, from Katrina to Sandy. We've been in about 30 storms, conducting experiments.

NARRATOR: He immediately travels from Florida to Texas to meet the storm.

Along with a team of engineers, he sets up a 5,000-pound wind tower to measure the speed and direction of wind close to the ground, one of the least understood components of violent storms.

FORREST MASTERS: We can haul these anywhere we need to and set them up in the span of 30 minutes. They have different levels of anemometry, which are precision wind instruments. They take measurements 10 times per second.

NARRATOR: Masters thinks that having better windspeed data at ground level, taken during the most powerful storms, can help in the design of more resilient buildings.

Harvey perfectly fits the bill. As it nears land, it reaches Category 4 out of 5 on the standard hurricane wind scale.

FORREST MASTERS: Once we get at three or above, we're in the major hurricane territory, and that's when things get very serious, because we see the likelihood of windborne debris happening. And ultimately, when we work our way up to a Category 5, were testing the limits of the infrastructure.

NARRATOR: On the morning of August 25th, Harvey is moving towards Corpus Christi, on the coast. Local officials issue mandatory evacuations, ordering several thousand coastal residents to move inland.

CBS NEWSCASTER: Many people in Corpus Christi are getting out, taking the city up on an offer to leave town for free. Hundreds of people boarded school buses, headed for an evacuation center in San Antonio.

NARRATOR: About 200 miles farther up the coast is Houston. Even though the storm is still to the south, it's so big, it will definitely have an impact on the city. But there's no evacuation order, in part because of a painful experience during a previous major hurricane. In 2005, when Hurricane Rita was bearing down on Houston, officials ordered an evacuation several days in advance of landfall. Millions took to the highways. In the massive traffic jams, cars ran out of gas, stranding thousands in 100-degree heat.

In the end, more people died while attempting to flee than while hunkering down. That memory is still fresh, so officials don't order a mass evacuation. Millions of Houston residents prepare to shelter in place.

ED EMMETT (County Judge, Harris County): At this time, there will be no mass evacuations called. We'll have a lot of water, but its not the kind of water that we would ask people to evacuate from.

NARRATOR: While residents anxiously await landfall of what is now expected to be a Category 4 hurricane, the winds suddenly intensify even further, reaching sustained winds of a hundred-and-thirty miles an hour.

JEFF MASTERS: Our biggest concern with hurricane forecasting is rapid intensification right as the storm is making landfall. Hurricane Harvey was an extremely dangerous storm in that regard, because in the last 30 hours it increased by 50 mile per hour in its winds.

CHAD MYERS: People along the shore need to leave. You need to be gone. It's not a Cat. 1 anymore, this is a Category 4, 130-, 135-mile-per-hour storm

NARRATOR: Just before 10 p.m., about four miles east of Rockport, Texas, Hurricane Harvey makes landfall.

MAN IN ROCKPORT, TEXAS: Oh, man, that vehicle is going to be gone.

VALERIE BROWN: We prayed a lot, talked a lot. We kept ourselves busy. We played cards. We could see things flying everywhere. Fences were coming down, things were flying all over the place.

NARRATOR: As predicted, when it comes ashore, Harvey's sustained windspeeds hold at a hundred-and-thirty miles an hour, making it the first Category 4 storm to strike the U.S. in 13 years. The eye passes directly over Rockport, Texas, about a hundred-and-fifty miles from Houston.

VALERIE BROWN: We came outside, we looked up, and it was a clear sky, nothing but stars. That was the eye. Not even two seconds after we shut the door it started all over again. The eye was on top of Rockport then. It was right here. The eye was right here.

NARRATOR: Lining the eye is the hurricane's eyewall, where the winds are strongest. Anyone in the eye's path gets hit twice by the supercharged eyewall winds, first as the storm approaches and then again as it departs.

In 20 years of hurricane research, Forrest Masters has seldom seen such a powerful storm.

FORREST MASTERS: We measured some of the highest winds we've ever recorded. We saw winds in excess of 190 miles per hour.

NARRATOR: In a matter of hours, Rockport is left in pieces.

ALTA GARCES (Realtor, Rockport, Texas): We underestimated the power and the force behind this hurricane. It just went right through and just devoured everything. It's just devastating.

NARRATOR: Much of Rockport is flattened by Harvey's powerful winds. But having spent much of its energy over land, the storm quickly weakens, from a Category 4 hurricane into a tropical storm, maintaining winds of about 45 miles an hour.

But windspeed is not the only measure of a storm's destructive power.

HAL NEEDHAM: This category number really just relates to the maximum sustained windspeeds, but for the category system it tells us nothing about flood potential, as far as storm surge and heavy rain. The heavy rains were just beginning.

NARRATOR: Even though windspeeds are now much less hazardous, residents are far from safe. Harvey drifts east and stalls. Conflicting winds in the upper atmosphere pin it in place.

CHAD MYERS: We have a high pressure to the east and a high pressure to the west and there's nothing in the middle to move it away.

NARRATOR: Warm ocean water keeps the storm alive. The heat evaporates moisture into clouds, only to be dumped, in record amounts, as rain.

TONY MCNALLY: This storm was essentially just pumping water vapor, turning it into liquid, and dropping it on Texas.

NARRATOR: At the same time, the sustained winds blowing on shore push ocean water inland, potentially creating a six- to twelve-foot storm surge. With the addition of heavy rains, widespread flooding is inevitable.

MARSHALL SHEPHERD: Many of our best computer models showed that Hurricane Harvey was indeed going to be a one-two punch. This thing was going to linger for days as a tropical storm and produce rainfall amounts that would lead to significant and life-changing flooding.

CHAD MYERS: Any hurricane that puts down 10 inches of rain in one spot is going to make flooding; the forecast here is 30 to 50.

NARRATOR: Thirty to 50 inches of rain, a deluge that goes on and on. Rainfall totals surpass existing records. The National Weather Service introduces a new shade of purple on their rainfall maps to indicate the more than 30 inches of record-breaking rain Harvey drops on the region. As the rain falls, storm surge compounds the problem.

HAL NEEDHAM: It lowered the efficiency of the rainfall runoff. So, where was this 30, 40 inches of rain going to drain?

NARRATOR: Harvey's total inundation of rainfall plus wind-driven storm surge on top of the tides, creates a slow-motion catastrophe. Already, the rivers, reservoirs and bayous of Houston's Harris County, the third most populous in the country, are at record levels. And waters continue to rise for several more days.

HAL NEEDHAM: There's almost a level of despair there. You know that people are facing really catastrophic situations, and if they didn't get out, they may be fighting for their lives.

CHAD MYERS: This could be one of the worst flooding events in American history.

SYLVESTER TURNER: The City of Houston, we're going to do everything we can to assist people: get them off the roof, get them out of the attic, get them out of the home. So, today the focus is on rescue.

WOMAN BEING RESCUED: I'm sorry.

RESCUER #1: No, no. Don't be sorry.

NARRATOR: As part of the federal response, the U.S. Border Patrol Search, Trauma and Rescue team finds people swept away in floodwaters; their homes and cars no longer safe.

RESCUER #1: Here, we're going to put the lifevest on you.

WOMAN BEING RESCUED: Okay.

RESCUER #1: All right, try to climb in this. I'll push you up. Alright? One, two, three.

NARRATOR: The water's moving so rapidly, it takes about 10 people to haul in the victim, fighting the current.

RESCUER #2: Are you hurt? You injured?

WOMAN BEING RESCUED: No.

RESCUER #3: Let me take your lifejacket.

ERIN KINNEY (Houston Advanced Research Center): For most of this area, 25 inches of rain is a massive flood event. To have 50—and there's even been a report of 60—inches of rain is just beyond our comprehension. It's beyond anything that we could've really dealt with. Then it becomes an issue of what's the best way to triage a disaster.

NARRATOR: Now, the National Guard and other government agencies conduct 13,000 rescues, over thousands of square miles. The sheer volume of rainwater fallen is enough to fill the Houston Astrodome 85,000 times. And the flood is slow to retreat, the result of Houston's extensive, and some think unchecked, development.

Ecologist Erin Kinney has found that over 500 square miles of Houston's Harris County is covered by impervious surfaces that don't absorb water.

ERIN KINNEY: As Houston and the surrounding area expanded, it has done so often at the expense of natural lands. And it has resulted in the loss of acres and acres of freshwater wetlands. Things like asphalt and concrete are not meant to have water percolate through them.

TODD KING (Houston, Texas): Yeah, I grew up around here. There's a tennis court that's eight feet under water.

ERIN KINNEY: Our parking lots, our driveways, the strip malls, our highways, those are all impervious surfaces.

Natural vegetation is so much more efficient at not only allowing that water to absorb, but also filtering it as it goes. It filters out the microscopic viruses and the bacteria. That filtering capacity is really what I think is the unseen power of a wetland.

NARRATOR: But the flooding isn't just a problem in Houston. The storm leaves a massive footprint. A hundred miles northeast, Lumberton, Texas receives a record-setting 48 inches of rain. It's one of the worst hit, but it's not alone. And because the number of flooded areas is so large, the federal relief effort is stretched thin. Residents here are mostly managing on their own, conducting search and rescue.

Jerry Haire, "Snuffy" to his friends, lives near the Pine Island Bayou, which flooded over its banks, even damaging homes built on stilts to stand above the water. Gary Arnold lives a few hundred miles away, but rushed to Lumberton to help his friend rescue neighbors and ferry them to safety.

GARY ARNOLD (Linden, Texas): We were taking people back and forth from one side to the other to go get their medicines at the store. We were taking M.R.E.s back and forth to people. Some of them didn't have no place to go. Some of them's older people, didn't have no family. And some of them just didn't want to leave their home, because they were scared that they would get throwed in with a bunch of people somewhere, and just be, you know, whatever, robbed, raped, killed. I mean, you don't ever know. It's just a bad deal.

JERRY "SNUFFY" HAIRE (Lumberton, Texas): This is these people's backyards.

GARY ARNOLD: Be careful stepping in that water, for real.

LIESL CLARK (Producer): What could happen to me?

GARY ARNOLD: You could get MRSA, you could get typhoid, you could get…what's that other stuff? What else they say is in that water, Snuffy? E. coli.

And there's no telling what other chemicals are in here, because, I mean, fertilizer plants blew up upstream. All this water's coming from that direction. So, just think about that.

SNUFFY HAIRE: That's a sad deal.

NARRATOR: The sheer power of inundating water upends houses, trees and even cars.

GARY ARNOLD: Somebody was probably driving down that road, and the waterforce forced it over here to where it's at.

NARRATOR: Experts begin calling Harvey a "500-year storm," meaning it has a one in 500 probability of happening in a given year. Yet, in the past three years, the Houston area has experienced three 500-year storms.

All together, it takes about five days for the storm to blow itself out, and the clean up will take much, much longer.

ERIN KINNEY: Because it's not just water that gets carried, it's viruses and bacteria that are floating around in people's homes, and the rescue workers are walking around in that. We're going to be dealing with the aftermath of those floodwaters for years.

NARRATOR: But this hellish hurricane season is far from over.

Six days after Harvey hit, while much of Southeast Texas remains under water, a new hurricane out in the Atlantic, Irma, forms and intensifies rapidly.

JEFF MASTERS: It went from a Category 3 hurricane, with 120-mile-per-hour winds, to a Category 5, with 175-mile-per-hour winds in just 30 hours.

NARRATOR: Irma continues moving westward. It's heading across unusually warm waters, fuel for hurricanes, giving it the potential to develop into a monstrous storm.

The island of Barbuda is first to feel the force of Irma. Winds up to a hundred-and-eighty-five miles an hour grind across the 62-square-mile island, leaving 90 percent of properties damaged. All communication with the outside world is cut off. The prime minister declares the island "uninhabitable."

GASTON BROWNE: We just did a fly-over, and I have to tell you, my heart sunk. This has been one of the worst days of my life. The entire country has been decimated. I have never seen anything like this before.

NARRATOR: The powerful onslaught continues. Irma hits St. Martin and then the British Virgin Islands. Both suffer extensive damage. For these islands it's one of the worst hurricanes in modern history.

CHAD MYERS: This storm is so unusual, because it stayed strong for so very long.

NARRATOR: Irma maintains top winds of a hundred-and-eighty miles an hour for 18 hours. And now it may be headed for Florida.

All the computers modelling this storm agree it will take a northward turn, pushed by high altitude wind currents, but they disagree about exactly when and where it will change direction.

CHAD MYERS: One model has it going up the east coast, grazing Daytona; the other has it going into the Gulf of Mexico; and then, the next run, they switch. Where is this thing really going to go? We can't evacuate the entire state of Florida.

NARRATOR: Because of the Florida peninsula's narrow geography, every coastal city, whether on the Atlantic side or the Gulf side, faces potential flooding from a storm this massive.

FRANK MARKS (Director, National Oceanic and Atmospheric Administration, Hurricane Research Division): Florida's not a wide state, and the east coast and west coast aren't that far apart, in terms of our understanding and our ability to predict.

CHAD MYERS: If this does hit Florida, because the arms of this storm are so big, it's going to hit both sides. So, whether it goes on the east side of the state or the left side of state or right up the middle, the entire state of Florida is going to see damage.

NARRATOR: Miami is already prone to flooding. If Irma strikes the city directly, the storm surge there could be devastating, but Miami isn't the only major population center at risk. Cities on the west coast, like Tampa, also have very little defense against a possible eight-foot storm surge, which could take out billions of dollars of coastal development and put thousands of lives at risk.

When faced with a superstorm like Irma, small changes to the hurricane's path can result in dramatically different outcomes. To hone the prediction, more measurements of temperature, pressure, humidity and windspeed are needed.

These come from satellites, buoys, ships and ground-based weather stations, and also from rugged aircraft that fly directly into the storm, like this P-3 Hurricane Hunter, penetrating Hurricane Irma's eyewall, with scientists on board.

JEFF MASTERS: That's the most intense part of the hurricane. That's where the strongest winds are and the greatest turbulence. It gets immediately dark, because you're surrounded by clouds. The rain starts to stream off the windows.

They've got a lot of instruments on the fuselage of the aircraft, so as they fly through the storm, they're taking measurements of the pressure, winds, temperature and humidity.

Also, they have instruments called "dropsondes," and they're little packages that fall down through the storm on parachutes and radio back as they fall. And a hurricane hunter aircraft will typically drop maybe 20 of those, sending back data for about a 15-minute period till they splash in the ocean.

We fly what's called a "figure 4," where you fly to the periphery, and then you chop through at right angles to the last pass you did, because you want to sample all four quadrants of the hurricane to find out, you know, what are the winds in all four areas?

NARRATOR: Measurements collected in the storm reach supercomputer centers in the U.S. and the U.K. There, the data flows into numerical models that generate forecasts for Irma.

The European Centre for Medium-Range Weather Forecasts, in England, uses some of the fastest computers on Earth to output what are regarded as the most accurate models of a hurricane's path.

TONY MCNALLY: So, this is Ventus, one of our two supercomputers. And inside this machine we process approximately 100-million observations every hour, so this machine has to be incredibly powerful, equivalent to 100,000 desktop computers.

NARRATOR: These massive number-crunching computers predict the future weather for any point on the globe. Right now they're figuring out where Irma is headed.

SARAH-JANE LOCK (European Centre for Medium-Range Weather Forecasts): We have a set of grid points around the globe, 500-million. And at each of those grid points, we solve the equations that tell us what the winds are doing at those points, what the temperature is doing, what the humidity is doing.

NARRATOR: As Irma approaches Florida, the solutions to all those equations result in a forecast of Irma's track, which is updated every six hours.

The National Hurricane Center, in Miami, analyzes the output of the computer models to issue its official storm warnings. They have Irma hitting somewhere in Florida in just three days, but the models have not yet nailed down where it will make landfall, a crucial determinant of damage.

Now, just 250 miles from the Florida Keys, Irma hits Cuba, the first Category 5 hurricane to make landfall there since 1924.

It's a disaster for the island and its residents, but as it crosses land, it loses strength, which is good news for Florida.

CHAD MYERS: The land interaction that Irma had with Cuba took about 25 miles per hour off the storm.

JEFF MASTERS: Cuba did a huge favor for Florida, because if Irma had not hit Cuba, passed maybe just 20 miles to the north of where it did, I'm convinced that it would have been a Category 5 hitting Florida and would have caused just unbelievable catastrophic damage there.

NARRATOR: As Cuba takes the brunt of the storm, Irma leaves $13-billion in damage and 10 dead in its wake.

A hundred miles to the north, Florida is now under a State of Emergency, with mandatory evacuations for the Keys and Miami.

The last catastrophic hurricane to hit Miami was Andrew, a Category 5 storm, 25 years earlier. The extreme damage was concentrated between the Keys and Miami, leaving dozens of people dead and more than a hundred-and-sixty-thousand homeless. That's why residents are so anxious to know where Irma will make landfall.

All the models are considered, to make a forecast of Irma's track, but there is uncertainty that is represented in a cone. The cone covers the area where Irma will most probably go, and it gets wider the further out in time. So, two days out, with a hurricane 400 miles wide and the width of the Florida peninsula less than that, it shows everyone could be in danger.

As a consequence, those in the most vulnerable areas, some 6- to 7,000,000 people, have been urged to evacuate.

ROBERT PORTER (Homestead, Florida): You look at the roads, it's an evacuation all the way up. The storm's going all the way up. No matter where you are, you're going to get hit, unless you're out past, like, Tennessee or something. I've got a five-gallon can sitting in the trunk, I've got some gas still in the car, but not enough to try and outrun a Category 4 or 5 storm. Forget it.

RICK SCOTT (Newsclip): Do not sit and wait for this storm to come. It is extremely dangerous and deadly and will cause devastation. Do not ignore evacuation orders. Remember, we can rebuild your home, but we cannot rebuild your life.

MELISSA MANGINO (Pasco County Schools): We're full, but we don't turn anyone away. We're serving three meals a day. Right now, we're wrapping up with breakfast. We have around 500 people here, and so far so good.

Our biggest concerns would be food supplies, and also, later in the evening, when we are hunkering down, people who might need medical support or any type of 911 situations.

CHAD MYERS: If you're near the water, if you're in the Keys, you need to leave now.

NARRATOR: One thing all the models agree on: the Florida Keys are right in the path of destruction.

Irma makes landfall at 9:10 a.m., on September 10th, at Cudjoe Key, Florida, with a hundred-and-thirty-mile-an-hour winds. Storm surge engulfs entire neighborhoods; thousands of homes are wrecked. There is no way these islands, just a few feet above sea level, can be protected.

After hitting the Keys, Irma heads towards the mainland, making landfall at Marco Island and Naples, which are lashed by the eyewall's most intense winds, ripping into infrastructure like a giant on a rampage.

JOSH MORGERMAN (Storm Chaser): The wind just tore that sign down. And that wreckage is going to become airborne missiles when the core of the hurricane arrives.

NARRATOR: Landfall here spares Miami and eastern Florida much of the worst, but Irma is still a dangerous storm as it tears into the Everglades and continues up the west coast.

Those directly in the storm's path take the most severe wind damage, as expected. But it's the location of the greatest flood damage that is surprising. For example, Irma leaves Tampa unexpectedly dry, but drowns parts of Jacksonville under five feet of water. It's a tough problem. Storm surges brought by hurricanes are notoriously difficult to predict.

Much depends on the exact strength and direction of winds blowing on shore, as well as how they interact with the landscape, and even the rhythm of local tides. Sudden changes in any of the variables can quickly render a prediction useless.

Irma is a case study in how tricky it can be to issue a timely forecast for a densely settled coastal area where lives and property are at stake.

Though Irma's impact is not as severe as some anticipated, the hurricane exacts a heavy price: some 40 people die in the Caribbean and at least 80 in Florida, most in the hardest hit area, the Keys.

JED SCANLON (Big Pine Key Fishing Lodge): Total devastation. All we've got left is a pile of rubble. Howling winds, sideways rain, tornadoes dropping down, everything going haywire, water about 8-, 10-foot deep.

RESCUER: May I dump some water down the back of your neck?

KEITH SIGAFOOSE (Florida Keys): Nobody knows, in my family, if I'm alive or dead. And there's quite a few people that passed away in the storm.

Oh, my god.

Thank god we have this. If we didn't have this and those M.R.E.s, we wouldn't eat, because there's no grocery stores open. There's nothing that's going to be open in the near future. They're devastated, too. And thank god the army came in.

NARRATOR: It could have been worse, had there not been a timely evacuation order for the Keys and other vulnerable areas. But on the mainland, why was it so difficult to precisely predict landfall?

TONY MCNALLY: The nature of the problem is that it is a fundamentally chaotic system, our atmosphere, so that we will always maybe be one step behind our last mistake. But as long as we learn from that mistake, it's okay.

NARRATOR: Improving both track and intensity predictions is of utmost importance, if we are to face more seasons like 2017, already one of the most destructive on record, and now, with the arrival of a storm named Maria, not yet over.

Like Harvey and Irma before it, Maria rapidly intensifies.

JEFF MASTERS: It went from a tropical depression to a Category 5 hurricane in just 54 hours.

NARRATOR: Maria is now one of most rapidly intensifying hurricanes on record. Rapid intensification of the three major storms to hit the U.S. in 2017 has taken forecasters by surprise, primarily because it is so difficult to take measurements deep inside a hurricane, just above the surface of the ocean, where atmospheric conditions have a powerful influence on a storm's ferocity.

FRANK MARKS: What is critical for determining the energy transfer from the ocean to the atmosphere, which is what drives the hurricane, is not only the sea surface temperature but the atmospheric temperature right above it.

NARRATOR: In a powerful hurricane, that's a dangerous no-go zone for a ship or plane, but not for a drone.

FRANK MARKS: The NOAA Hurricane Research Division is testing an unmanned aerial system that we can deploy from the plane. This is called the "Coyote." It can sustain flight for about an hour, and the idea is to do as much sampling at low altitude, where we will not fly the manned aircraft, to get humidity measurements that are driving the energy exchange.

NARRATOR: Deployed at a high altitude by a hurricane hunter aircraft, a Coyote can fly in the powerful winds above the sea surface and radio back continuous measurements.

All models agree: Maria, now a Category 5, is on a collision course with the island nation of Dominica. As it passes over, it leaves in its wake one of the worst natural disasters ever to hit the island. But Maria's not finished.

CHAD MYERS: So, what we have now is a Category 4, or maybe even 5, heading right toward Puerto Rico.

NARRATOR: Two days later, the storm barrels into Puerto Rico. It's the second strongest hurricane to hit the island in recorded history.

The worst Atlantic seasons on record have only seen one Category 4 or 5 hurricane hit U.S. territory. Incredibly, this is now the third monster storm to make landfall in 2017. Maria hits on the southeast corner of the island, where storm chaser, Josh Morgerman, has come to film.

JOSH MORGERMAN: Okay, my neighbors' windows broke.

NARRATOR: He's holed up in a hotel there, where locals have also sought shelter.

JOSH MORGERMAN: Can you guys open the door?

NARRATOR: Their windows have been blown out,…

JOSH MORGERMAN: Can you open it?

NARRATOR: …creating a suction effect, so they can't get out of their room.

JOSH MORGERMAN: Here, I'm pushing. One, two, three, okay, okay. Come on, come on, just get in there. Go in there. Go in there, it's safer. Go in there. Okay, here's some pillows.

HAL NEEDHAM: The windspeeds were really catastrophic as it made landfall. The track of the storm was really a worst-case scenario for Puerto Rico.

JOSH MORGERMAN: The wind seems to have changed directions, and it's now just blasting these windows, and we're all in the bathroom. As I've always said, the bathroom is the best place to be during really bad winds.

NARRATOR: Maria wreaks widespread destruction across Puerto Rico. Whole neighborhoods are devastated, and the entire island loses power. Mountain rivers flood the highlands, hundreds of landslides cover roads, engulfing buildings, while winds gusting up to a hundred-and-fifty-five miles an hour leave homes gutted.

MICHAEL GARCIA: This here was my room, "was." This one, right here, was my grandmother's room. The kitchen, right here, and, here was the living room, right here. "Was."

NARRATOR: Although the official death toll is 64, some later estimates for those who died during the storm and its aftermath exceed 4,000.

In the months following the storm, getting the basic necessities of life is an uphill battle.

LESLIE (Dorado, Puerto Rico): We don't have any electricity, we don't have any water. We don't have any signal; we cannot communicate.

NARRATOR: There are only a few spots, along highways, where people can find cell signals.

ARTURO MORALES (Dorado, Puerto Rico): We have a crisis, you know, in P.R. Basically, we got hit hard. People are dying: no water, no electricity, and, it's just pure chaos, basically.

SUSAN RIVERA (Dorado, Puerto Rico): It is so sad to see this island. And there's no more food, either. We can't get food in here. And my dog died from the hot…, from the storm. She got so nervous, and it was so hot, she died. So, we've been through a lot.

NARRATOR: Days are spent in line for the essentials, just to survive.

JOHANNES (San Juan, Puerto Rico): We wait for water, food, first aid, any kind of help that they can give us.

NARRATOR: Three-point-three-million Americans endure what many see as a lackluster government response to the crisis.

ALEJANDRO GARCÍA PADILLA (Former Governor, Puerto Rico): I think that the message is clear. Puerto Rico is devastated by the hurricane, and we are in need of help. FEMA is here, but we will need more. These supplies beside me just will last a couple of days.

NARRATOR: Three devastating hurricanes hitting the U.S. in a single season, is it a fluke, bad luck, or is there a reason this is happening, a reason that can be traced to the fact that our climate is warming?

We now know 16 of the 17 warmest years on record occurred since 2001. A century and a half of burning fossil fuels on an industrial scale has released billions of tons of long-buried carbon into the atmosphere.

In the form of carbon dioxide, it traps heat, warming the oceans. This not only provides more fuel for powerful storms, it raises sea level, as glaciers melt and warm water expands. During storms, even a small rise in sea level can have an impact, causing powerful storm surges and increased flooding.

One way to gauge the speed of sea level rise due to climate change is to track the history of changing sea levels, going back millennia, before we began burning fossil fuels.

Andrea Dutton collects samples from ancient coral reefs, like this one, exposed just above the shoreline. Since the corals she studies need sunlight, they can only grow where the water is shallow, making them a measuring stick for sea level.

By analyzing the cores, Andrea can compare how fast sea level rose in the past, with current rates.

ANDREA DUTTON (University of Florida): Today, the global average sea level is rising at about three millimeters a year. So, that's about the thickness of about two pennies stacked together, which doesn't sound very impressive, right? But when you look at the rate of sea level rise we see today, it far exceeds anything we've seen in the past several thousand years, at least. And so, sea level was going along and then it started rising very rapidly, during the industrial period.

Sea level has responded to this increase in temperature and is now rising very quickly.

NARRATOR: Andrea has also found evidence of hot spots along the Florida coast, where sea level is rising at an even greater rate.

ANDREA DUTTON: We started pulling the tide gauge records, and we realized that there was a very rapid acceleration of sea level, by almost five inches. And so, when we talk about three millimeters of sea level rise—that's the global average that we see right now—that's about one foot per century. And all of a sudden we get five inches in five years. I mean, that's a huge amount.

NARRATOR: That kind of increase in areas that are already vulnerable to flooding and storm surge will serve to magnify the impact of hurricanes.

HAL NEEDHAM: When we have a prolonged onshore wind, we already have heightened sea levels along the coast. So, this compound flooding from storm surge and heavy rain is just going to get worse because of sea level rise.

NARRATOR: In fact, in May 2018, a new study concluded that above-average ocean temperatures increased rainfall during Hurricane Harvey by 15 to 38 percent. These authors warn that future Atlantic hurricanes are likely to be bigger, more intense and longer lasting than in the past.

JEFF MASTERS: By the end of the century, three Category 4 storms hitting is going to be not that unusual. It's going to happen more often with warmer oceans and climate change.

SARAH-JANE LOCK: As the atmosphere warms and the ocean warms, there's more energy in the system, and that energy has to be released somehow. So, we expect, from our understanding of the global Earth system, that as we increase the temperatures of the system, we, we should expect to see stronger and probably more frequent storms.

NARRATOR: Today, Category 4 and 5 storms only make up about 10 percent of the hurricanes that hit the U.S., but they produce half the damage. Even one or two more of these powerful storms each year will be devastating to vulnerable communities.

JEFF MASTERS: We need to plan for a future where storms are going to be more intense, and sea level rise is going to be higher, and storm surge is going to wipe out a lot more of the coast when it hits.

MARSHALL SHEPHERD: One of the things that I hope comes from 2017 is forethought on how we plan, in terms of resiliency, in places like Puerto Rico or perhaps even the Keys. We know that we are going to see hurricanes again and perhaps even stronger ones, if the climate change literature is correct.

FERDINAND ALVAREZ-RIVERA (University of Puerto Rico at Arecibo): In 1998, we had George. Their houses were destroyed, and they're building the same thing in the same place. We don't learn. We need to prepare for the next hurricane season.

FORREST MASTERS: I look forward to the day when we can move from tactical to strategic, when we talk about hurricanes. And case in point would be evacuation versus shelter in place. Today, we are heavily reliant on people getting out of the way when storms come through. Are we going to be able to do that 50 years from now, a hundred years from now, when the coastal population has exploded?

NARRATOR: Four months after Maria pounded Puerto Rico, the storm's power still reverberates in the lives of the people.

IVAN BALLESTER ACOSTA (Punta Santiago, Puerto Rico): It's a little rough, because it's so limited. The only gas station we have right now is just ruined.

NELIA MARTINEZ MELÉNDEZ: The stores were closed. We had to drive far away to even get money to even go buy things for us to survive in our family. Everybody was getting sick, because we didn't have a way to find food or water.

NARRATOR: Families in the mountains still have no running water, and power is months away.

RAYMOND MOLINA (Guaynabo, Puerto Rico): Well, electricity, as you can see, we still don't have no electricity, 100 days after.

NELIA MARTINEZ MELÉNDEZ: And this is reality. I couldn't believe what was happening to us. We lost everything, everything.

NARRATOR: It will take eight months and two-and-a-half-billion dollars to restore power for most islanders, and even then, blackouts continue.

For the fishing industry, the loss of boats, traps and piers puts hundreds out of work. And many more jobs and homes are lost permanently, spurring hundreds of thousands to leave the island in what some have called a mass exodus.

MARSHALL SHEPHERD: Many organizations talk about environmental or climate refugees, and I think 2017 Atlantic hurricane season may have ushered in that era for the Caribbean.

NARRATOR: Maria, a single storm, causes some $90-billion in damage in Puerto Rico alone, the third costliest behind Katrina and Harvey, and in a territory whose gross national product barely clears $100-billion a year.

RAYMOND MOLINA: We're going to get back up. We're going to rebuild Puerto Rico again.

NELIA MARTINEZ MELÉNDEZ: The climb has been hard, but we're getting there. We are getting there.

NARRATOR: This is hurricane country. Indeed, the word "hurricane" comes from "huracán," the Caribbean god of evil. These islanders' considerable grit has been forged by the winds.

MICHAEL GARCIA: At first, it was really hard to take in, you know? I cried for a few hours. But you just have to accept it, because there's nothing I can do right now, so I've got to stay positive and work.

NARRATOR: In Houston as well, many are also struggling to stay positive with the help of neighbors and community.

ARIC BRIAN HARDING (Friendswood, Texas): A canoe shows up on our street, with these two guys: "We heard there were people here that needed to get out."

My wife is obviously crying at this point. And he just says, "Where are you going now?" She's like, "I have no idea."

And, I always joked about, like, you know, if there's ever an apocalypse, we're the first to die, because we have seven children, who are not helpful, and a dog. So, I'm like, "No one takes in the family of nine and a dog," and, and the Ramseys did. And they live, literally, like two blocks up, and they were on a high point, and they just said, "All right, come on." And it starts pouring down rain again, and they're taking these wet rowdy kids and their dog into their home.

NARRATOR: When Aric first returned to his Houston home after Harvey, he shot a video that went viral, bringing a message of hope to the millions who lost so much to this hurricane season.

ARIC BRIAN HARDING: My son who's 13 loves playing piano, plays every day. He was kind of worried about his piano, and so I was like, "Hey." I handed him my phone, I was like, "I'm going to just play real quick, and let him know that it works."

I'm going to have to tune this one.

WRITTEN, PRODUCED AND DIRECTED BY

Liesl Clark

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Chris Schmidt

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IMAGE: Image credit: (Hurricane Irma, Puerto Rico) © Alvin Baez/Reuters