Warm ocean water boosting storm severity: consideration of new category 6.

Illustration by Natalie Renier, © Woods Hole Oceanographic Institution

Warmer Ocean Waters Impacting More Than The Environment

This year’s Atlantic hurricane season got off to an early start in May, but even though there was a brief reprieve from tropical storms — thanks to a plume of Saharan dust earlier this month – we are once again seeing an increase in storm activity. In the past week, we have observed Hurricanes Douglas and Hanna, and Tropical Storm Gonzalo. And this week brings Tropical Storm Isaias, the earliest “I” storm on record, beating out Irene that formed August 7, 2005.

There are several contributing factors to the high tropical storm activity this year, including a mild winter, reduced wind shear and La Niña conditions, but the above-average sea surface temperatures are the constant factor that has impacted record-breaking storm activity over recent years. This trend is expected to increase faster than even some recent predictions.  A new analysis found that the oceans are heating up 40 percent faster on average than estimated five years ago, breaking record temperature for several straight years.

There is well-documented evidence of how warmer sea temperatures affect sea life and the ocean environment, but the warmer ocean water also significantly affects industries. The accuracy of weather forecasting can impact efficiency and safety, especially in these challenging times.

Warmer waters create stronger hurricanes, which then act as giant heat engines, taking the energy from warm ocean waters and transferring that energy into the atmosphere. The warmer the sea surface temperature, the greater the tropical storm heat potential will be in a region. For coastal cities and businesses in the U.S., more storms making landfall means a higher risk for potential damage to ports, infrastructure, buildings, and livelihoods, as well as risk to health and safety. Flooding much farther inland is also a threat to businesses and agricultural supply chains.

Warmer sea surface temperatures also increase wave heights and wind speeds over ocean waters. A study published in Nature shows that over the last 30 years, observations note increases in average wave height and wind speeds, particularly in the Southern Ocean.  Depending on the precise level of wind speed, this could lead to more opportunities for offshore power generation. Conversely, for land-based wind farms, warmer waters may mean weakened winds across the Northern hemisphere due to warmer Arctic waters creating a weaker polar vortexbetween the North Pole and equator. One study predicts that this may lead to as much as a 10 percent drop in wind across much of the Northern hemisphere by 2050, with a 14 to 18 percent drop by the end of the century. Accurate weather information helps to refine expected energy yield projections. Even small miscalculations can have long term effects on profitability, energy load and accessibility.

Warmer  air and sea surface temperatures also means that the Northwest Passage could become an economically viable shipping route. Once considered impassable due to ice blocks throughout most of the year, the route is increasingly accessible and could cut considerable time at sea. The Arctic voyage opens up one of several routes that ships can take to traverse the Atlantic to Pacific Oceans. Weather forecasts created for seakeeping can help optimize routes and safety by factoring in marine conditions such as currents, wave height, ship build and cargo. These weather optimized routes can increase efficiency and reduce fuel usage by as much as 5 percent per voyage depending on the type of vessel, season and ocean.

As ocean temperatures rise, it continues to create secondary effects that impact the environment and the industries in ways that we are still discovering. All of this brings new challenges for forecasting and emphasizes the need for advanced weather models tailored for specific industry needs. As the meteorological community continues to research and model weather data based on evolving climate conditions, we can continue to help keep employees and operations safe, while helping industries prepared to respond and adapt to new weather trends and intensifying extreme weather.

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Jim Foerster is one of just 239 Certified Consulting Meteorologists (CCM) in the world. CCMs are experts in the application of weather information to a host of practical challenges. He serves as Chief Meteorologist for DTN, the largest business-to-business weather organization in the world where he and his team provide actionable weather forecasts and consulting services in the Aviation, Transportation, Marine, Energy, Agriculture and Safety markets.

Is this the beginning of the Category 6 hurricane?

Category 5 is what we use to identify the strongest hurricanes on the planet, with sustained winds of 157 miles per hour or more. But some Atlantic hurricanes are arguably strong enough to merit a Category 6 designation thanks to climate change.

An aerial view of Lafitte, La., after Hurricane Ida, one of the strongest storms in the state’s history, made landfall in September.JOHNNY MILANO/NYT

Imagine a world where Category 6 hurricanes threaten the East Coast, with sustained winds of 200 mph and storm surges in the 30-foot range. The devastation would be almost unimaginable — all the glass blown out of high-rise buildings, homes wiped off their foundations, and neighborhoods well inland completely underwater from the storm surge.

In some ways, we don’t have to imagine it — we are already living in a new era of superstorms. Category 5 is what we use to identify the strongest hurricanes on the planet, with sustained winds of 157 miles per hour or more. But some Atlantic hurricanes, such as Dorian in 2019, have had sustained winds in the 185 miles-per-hour range. That’s arguably strong enough to merit a Category 6 designation.

Thanks to human-caused climate change, we are hurtling toward a world where such Category 6 storms may become a familiarity. Estimates are that the maximum wind speeds of Atlantic hurricanes increase about 17 miles per hour per degree Celsius. That’s enough to shift storms a whole category given 1 degree Celsius (approximately 2 degrees Fahrenheit) of warming, which is what we’ve already seen over the past century.

The calls for adding this next category of storms are growing louder. And I’ve added my voice to them. My own scientific work adds to a growing body of research suggesting that climate change is exacerbating the coastal threat from these storms.

If the concept of a Category 6 storm isn’t scary enough, there may be an even worse future in store if we fail to act on the climate crisis. Picture an EF-5 tornado hundreds of miles wide scouring the landscape. That would be the same as a theoretical Category 7 hurricane packing 220-plus miles-per-hour sustained winds and a 40-foot storm surge that could swamp a coastal metropolis and leave a region uninhabitable for years. The human toll would be unbearable.

While this might sound like the stuff of a sci-fi film, it could one day become our reality — if we continue to elevate the concentration of carbon pollution in the atmosphere through the burning of fossil fuels and warm the planet another 1 degree Celsius.

We’re living in a new world where rapid intensification and major hurricanes are becoming more and more frequent. The parade of deadly and destructive hurricanes over the past two decades are etched in our memories: Ivan, Katrina, Rita, Wilma, Matthew, and Michael, among others. Each was a Category 5 storm, packing winds of 160 miles per hour or more with storm surges in excess of 15 feet. Such devastating storms were once extremely rare. Today, they are considerably more common. If we continue to warm the planet, they’ll get worse still.

Burning fossil fuels — such as coal, oil, and natural gas —not only warms the surface of the planet, but the ocean is getting warmer as well. The heat content of the upper ocean, which has reached record levels in recent years, is like a huge, fully-charged battery that supercharges hurricanes — stronger wind, higher storm surge. Take Ida for example: As it went over an unusually deep layer of warm water in the Gulf of Mexico, it was able to rapidly intensify from a Category 1 to a near-Category 5 hurricane in just a day, shortly before it made landfall in Louisiana. A degree or two warmer and it might well have fit the Category 6 definition.

But it isn’t just the wind and surf that threaten human life and livelihood. There’s the additional flooding rain. It’s not a coincidence that the two worst flooding events in US history were associated with two recent landfalling hurricanes — Harvey and Florence. Warmer oceans evaporate more moisture into the atmosphere, and stronger storms entrain more moisture into them. It’s a double whammy that gives us unprecedented flooding events.

That might sound a bit theoretical, but let me give you a real-world example: Ida. This historic storm drenched not only the Gulf Coast where it made landfall, but also well inland days later as it produced catastrophic flooding in the Northeast United States: 3.15 inches fell in Central Park in New York in just 60 minutes.

In Eastern Massachusetts, Ida brought a tornado to Cape Cod and more than 9 inches of rain in New Bedford. And if you’re looking for one more piece of bad news, a growing body of research, including my own, suggests that climate change is increasing the odds of monster storms drifting farther north and striking New England.

We must as a society decide if we want to continue down the path we’re on, where climate change loads the dice in favor of withering heat waves, explosive wildfires, devastating flooding, and major hurricanes. Or do we want to decide to make the changes necessary to mitigate climate change, namely by ending the use of fossil fuels and slowing down the runaway train of global warming? The choice is ours to make.

Michael E. Mann is distinguished professor of atmospheric science and director of the Earth System Science Center at Penn State University. He is author most recently of “The New Climate War: The Fight to Take Back our Planet.”

Warm summer temperatures often bring thunderstorms. Under the right conditions, some of those storms can grow into large tropical storms. Or even monstrous hurricanes. These massive storms stretch hundreds of miles across. Their powerful winds and heavy rains cause billions of dollars of damage each year. Tropical storms require warm ocean waters. Many travel across entire oceans, gaining strength as they go. The ocean plays a huge role in how strong they eventually become.

When a thunderstorm forms, heat causes air to warm and expand. It rises up into the atmosphere. This creates low pressure at the earth’s surface, like a vacuum, that draws in air from surrounding areas. That air keeps feeding the vacuum, adding more water vapor to the growing clouds. Thunderstorms can form anywhere there’s humidity and enough heat to cause air to rise.

In the tropics, when storms move out over the ocean, they can begin to grow into something much bigger. The ocean surface is warm in the tropics—almost like bath water in certain places. When the sea surface is at least 80° Fahrenheit (27° Celsius), it can supercharge a thunderstorm. The storm sucks up that heat and water, which make the storm bigger. As it grows, air pressure at the center of the storm continues to drop, which causes the vacuum in the middle to grow stronger. More warm water is added to the storm, causing more clouds to build, more rainfall, and faster winds.

Earth’s spin on its axis deflects those winds, causing them to move in a circle. This creates the spinning tropical storm that we see on satellite images. Trade winds blow from east to west in the tropics, pushing the storm across the ocean toward land on the other side.

Depending on how the storm travels, it may continue to grow or weaken. Storms that stay over warm, tropical waters intensify. The winds around the calm, central eye of the storm get faster and faster. Winds in this eyewall are always the fastest in the storm and cause the most damage. The most powerful hurricane to hit the United States had winds estimated at 190 miles per hour.

Storms that pass over the Caribbean Sea and Gulf of Mexico often intensify very rapidly. Warm currents there create loops of warm water that fuel storms. When these storms make landfall, they damage buildings and flood areas near shore with a wave of water called a storm surge. Once over land, the storms lose contact with the warm waters and begin to weaken. As they travel across land, they can dump several feet of rain.

Sometimes storms move back out over warm waters and gain strength again. Often, they break apart over land or once they reach the cooler waters of the temperate oceans. But climate change is warming even those waters. Scientists estimate that hurricanes in the future will be stronger because the ocean will be warmer.

Hurricanes draw their energy from warm sea surface waters. As lower strata of the ocean warm up along with the rest of the planet, deeper waters once cool enough to weaken hurricanes at the surface, are now becoming warm enough to strengthen them. (Illustration by Natalie Renier, © Woods Hole Oceanographic Institution)
Hurricanes draw their energy from warm sea surface waters. As lower strata of the ocean warm up along with the rest of the planet, deeper waters once cool enough to weaken hurricanes at the surface, are now becoming warm enough to strengthen them. (Illustration by Natalie Renier, © Woods Hole Oceanographic Institution)




When wind moves from high pressure to low over a vast reservoir of heat and water, such as an ocean, the forces quickly escalate.

climate and ocean

Climate & Ocean

The ocean plays a central role in global climate and regional weather patterns, including droughts, rainstorms, and hurricanes.

Aumann, H.H. et al. Frequency of severe storms and global warming. Geophysical Research Letters. October 3, 2018. doi: 10.1029/2008GL034562.

Buis, A. How climate change may be impacting storms over Earth’s tropical oceans. NASA Global Climate Change Blog. https://climate.nasa.gov/blog/2956/how-climate-change-may-be-impacting-storms-over-earths-tropical-oceans/. March 10, 2020.

Geology.com. What was the largest hurricane to hit the United States? https://geology.com/hurricanes/largest-hurricane/. Accessed on January 29, 2021.

Lubofsky, E. ‘High-octane’ hurricane fuel swirls in the Gulf of Mexico. Oceanus. November 8, 2020. https://www.whoi.edu/oceanus/feature/high-octane-hurricane-fuel-swirls-in-the-gulf-of-mexico/

Morsink, K. Hurricanes, Typhoons, and Cyclones. Smithsonian. https://ocean.si.edu/planet-ocean/waves-storms-tsunamis/hurricanes-typhoons-and-cyclones. Accessed on January 28, 2021.

NASA. Warming seas may increase frequency of extreme storms. January 28, 2019. https://climate.nasa.gov/news/2837/warming-seas-may-increase-frequency-of-extreme-storms/

NOAA. How does the ocean affect hurricanes? https://oceanexplorer.noaa.gov/facts/hurricanes.htmlAccessed on January28, 2021.

University of Miami. Study targets warm water rings that fuel hurricane intensification in the Caribbean Sea. Phys.org. February 23, 2017. https://phys.org/news/2017-02-fuel-hurricane-intensification-caribbean-sea.html

WHOI. Hurricanes. https://www.whoi.edu/know-your-ocean/ocean-topics/hazards/hurricanes/ Accessed on January 28, 2021.

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