The influence of climate change can already be seen in many extreme weather events, including hurricanes. Earth’s strongest storms are changing, increasing their destructive potential. Researchers continue to study satellite data and model predictions to understand what changes we will see in a future warming world.
Recipe for a Hurricane
Hurricanes are a type of tropical cyclone – a rapidly rotating storm system with a low-pressure center, closed low-level atmospheric circulation, strong winds, and a spiral arrangement of thunderstorms. In order for a hurricane to form, four main ingredients are needed:
- Pre-existing weather disturbance
- Warm ocean waters
- High humidity
- Light winds high in the atmosphere
Hurricane formation begins when warm tropical water evaporates and rises. Cool air rushes in to fill the gap and the process repeats. Warm, moist air in the atmosphere condenses into huge storm clouds that spiral around a central column of wind. If there is enough warm water to continue fueling the process and no strong winds to break the system apart, a cyclone forms.
Seasons Greetings!
The Atlantic hurricane season runs from June 1 through November 30. In the northeastern Pacific, the season runs from May 15 to November 30. In the northwestern Pacific, typhoons are most common from late June through December. And the northern Indian Ocean sees cyclones from April to December.
What’s in a Name?
For centuries, tropical cyclones were named after places, objects, or people (usually saints). Today the World Meteorological Organization maintains six rotating alphabetic lists of Atlantic storm names, which alternate between male and female names.
If a storm is particularly damaging or deadly, the storm’s name is retired and replaced with a new name starting with the same letter.
Wild Winds
Tropical cyclones are categorized according to wind speed:
- Tropical Depression: less than 39 mph
- Tropical Storm: 39-73 mph
- Hurricane: greater than 74 mph
- Category 1: 74-95 mph
- Category 2: 96-110 mph
- Major Hurricane:
- Category 3: 111 to 129 mph
- Category 4: 130 to 156 mph
- Category 5: 157 or higher mph
Hurricane Hunters
Hurricane Hunting began as a dare during World War II, when an Air Force pilot flew into the eye of a Category 1 storm.
Today, Hurricane Hunters from both the Air Force and the National Oceanic and Atmospheric Administration routinely fly into tropical cyclones each season, gathering invaluable data used for forecasting and improving model predictions.
Hurricane Capital, U.S.A.
Florida is the most hurricane-prone state in the nation, with 120 storms striking the state between 1850 and 2018. Texas is a distant second with 64. With more than 8,000 miles of coastline, Florida is a big target.
- Category 4 at landfall, 145 mph winds
- Also known as the San Felipe Segundo Hurricane, this massive storm killed more than 2,500 people, mostly from flooding around Lake Okeechobee.
- Category 5 at landfall, 185 mph winds
- One of only four Category 5 hurricanes to make landfall in the U.S., this hurricane devastated the upper Keys, and remains the most intense hurricane to hit land in U.S. history.
- Category 3 at landfall, 120 mph winds
- Looping twice over Northwest Florida, this storm produced record amounts of precipitation, dumping about 38–45 inches of rain in Cedar Key and surrounding areas in 24 hours.
- Category 5 at landfall, 165 mph winds
- A record storm surge of about 17 feet was recorded at Biscayne Bay during this hurricane. Though no deaths were linked to the surge, Andrew’s winds caused massive destruction and loss of life.
Andrew’s damaging winds drove a wooden plank through a palm tree. Photo courtesy of NOAA.
Photo courtesy of NASA.
- Category 4 at landfall, 130 mph winds
- With a path going directly over Florida and a massive wind field, this storm left an estimated 6.7 million homes and businesses without power and caused more than $50 billion in damage.
Photo courtesy of NASA/NOAA GOES Project.
Irma caused record-setting power outages in Florida. Image courtesy of Energy Information Administration.
- Category 5 at landfall, 140 mph winds
- After rapidly intensifying in the Gulf, this devastating storm was the first Category 5 on record to strike the Florida Panhandle. It’s also the strongest hurricane on record to hit the U.S in October. Michael opened many eyes to the possibility that climate change was impacting the nature of hurricanes.
Michael caused catastrophic damage to Mexico Beach. Photo courtesy of NOAA.
Photo courtesy of NASA/NOAA GOES Project.
Weather vs. Climate
Weather describes the short-term changes and conditions of the atmosphere – a hot day or afternoon thunderstorm. Climate is the weather in a region over a long period of time. Weather can change in minutes, but climate change spans decades to thousands of years.
Today the Earth is warming much more quickly than in the past. As global climate changes, weather patterns change as well. Scientists are working to better understand the links between climate change and extreme weather events such as hurricanes.
“Weather is your mood and climate is your personality”
— J. Marshall Shepherd, past president of the American Meteorological Society
Changes linked to global climate change
Warm air holds more moisture than cool air. In a warming world, hurricanes produce more rainfall. Climate simulations indicate that we will likely see even greater increases in rainfall in future storms.
Hurricanes get their “fuel” from the ocean, so warmer oceans means more fuel to power the storms. There has been a noticeable increase in the number of major hurricanes, especially in the Atlantic.
Changes with uncertain link to climate change
Atlantic hurricanes are becoming more intense more quickly in recent decades, likely from natural causes. But scientists using advanced climate models indicate global warming might be a factor, and continue to search the data for answers.
Scientists have documented that hurricanes are moving more slowly, exposing areas to damaging storm impacts for longer. Some point to disrupted air patterns in a warmer atmosphere, but the reason for slower storms cannot yet be confidently linked to human activity.
No changes observed
While the number of tropical cyclones varies each year, the average remains fairly consistent, about 80 worldwide. Scientists don’t have a good understanding of what controls the number of cyclones, and it’s uncertain if these storms will become more or less frequent in the future.
Myths, Facts, and Maybes
Climate attribution studies examine the role climate change plays in extreme weather events. These studies use satellite data to calculate long-term trends and computer models to simulate hurricane responses to various climate scenarios. This allows climate scientists and meteorologists to study patterns that may reveal climate change’s influence on hurricanes.
“In the past, a typical climate scientist’s response to questions about climate change’s role in any given extreme weather event was ‘We cannot attribute any single event to climate change.’ The science has advanced to the point that this is no longer true as an unqualified blanket statement.”
— National Academies of Sciences, Engineering, and Medicine, 2016
World’s Largest Hurricane Simulator
Researchers at the SUSTAIN Laboratory at the University of Miami’s Rosenstiel School of Marine and Atmospheric Science use a massive hurricane simulation tank to conduct tests that are usually too difficult or dangerous to complete during a natural storm. These researchers hope that by studying heat and momentum transfer in the simulator they might better understand how hurricanes intensify.
Rising Seas
Often the most damaging consequence of a hurricane is not from wind, but flooding from precipitation and storm surge. When you add sea level rise – one of the most well-known effects of climate change – storm surge and flooding from hurricanes and tropical storms are more damaging and penetrate farther inland.