Hurricanes Sally and Paulette, Tropical Depression Rene, and Tropical Storms Teddy and Vicky were all active on Sept. 14, 2020. NOAA
It was clear before the 2020 Atlantic hurricane season started that it was going to be busy. Six months later, we’re looking back at a trail of broken records, and the storms may still not be over even though the season officially ended on Nov. 30.
This season had the most named storms, with 30, taking the record from the calamitous 2005 season that brought Hurricane Katrina to New Orleans. It was only the second time the list of storm names was exhausted since naming began in the 1950s.
Ten storms underwent rapid intensification, a number not seen since 1995. Twelve made landfall in the U.S., also setting a new record. Six of those landfalling storms were hurricane strength, tying yet another record.
Brian McNoldy, CC BY-ND
As atmospheric scientists, we target our research at better understanding both what drives the formation of tropical cyclones and how climate change is affecting them on longer time scales. Here’s what research tells us about the 2020 season and what may be ahead.
Why did 2020 have so many storms?
An unfortunate combination of two key factors made this season ripe for tropical storms.
Ironically, cooling in the equatorial Pacific makes it easier for tropical storms to form and gain strength in the Atlantic. That’s because La Niña weakens the vertical wind shear over the tropical Atlantic. Vertical wind shear – a change in wind speeds with altitude – is highly disruptive to storm development.
As the La Niña pattern became established this season, it made the tropical Atlantic much more hospitable for storms to form and intensify.
The second critical factor was the extremely warm temperatures in the Atlantic, including the Gulf of Mexico and the Caribbean.
Hurricanes are powered by the transfer of heat from the ocean to the atmosphere. The sea surface temperature therefore dictates the maximum potential intensity a storm can attain under perfect conditions – it’s like a thermodynamic “speed limit” on hurricane intensity.
The sea surface temperature approached record levels in the Atlantic hurricane basin this season, including in September, the most active Atlantic storm month on record.
What does climate change have to do with it?
An important part of this season’s story is the Atlantic warming trend we’re witnessing, which is unprecedented going back at least several millennia.
The oceans store much of the excess heat trapped by greenhouse gases. With greenhouse gas concentrations still increasing due to human activities, such as the burning of fossil fuels, average sea surface temperatures are likely to continue rising over the coming decades.
Whether climate change caused the extremely high number of storms this season is unclear. There is no detectable trend in global hurricane frequency, and computer modeling studies have had conflicting results.
However, the warming climate is increasing the threat posed by hurricanes in other ways.
A growing proportion of high-intensity storms, Category 3, 4 and 5, is being observed around the world, including in the Atlantic. Since ocean temperature controls the potential intensity of tropical cyclones, climate change is likely behind this trend, which is expected to continue.
The U.S. is also seeing more storms with extreme rainfall. Think about Hurricane Harvey’s 50 inches of rain in the Houston area in 2017 and Florence’s 30-plus inches in North Carolina in 2018. The warming climate plays a key role here, too. With warmer temperatures, more water is able to evaporate into the atmosphere, resulting in greater moisture in the air.
Implications of the 2020 season
Ten storms this season underwent rapid intensification – a 35 mph increase in maximum winds within 24 hours. Rapidly intensifying storms are especially dangerous because 1) they are challenging to accurately predict, and 2) they provide minimal time for evacuations when they intensify just before making landfall.
NOAA; James H. Ruppert Jr.
Hurricanes Laura and Sally both rapidly intensified just before making landfall on the Gulf Coast this season. Eta rapidly intensified to a Category 4 just before hitting Nicaragua, and just two weeks later, Iota essentially repeated the act in the same location.
Forecasts for the tracks or paths of tropical cyclones have dramatically improved in recent decades, as much as five days in advance. However, forecasts of storm formation and intensification have improved very little by comparison.
The forecasts for hurricane rapid intensification are especially poor.
While the official forecasts issued by the National Hurricane Center are issued by human forecasters, they depend on the guidance of prediction models, which aren’t very accurate when it comes to rapid intensification.
The complexity of weather models makes this a daunting challenge. However, it becomes more tractable as researchers learn more about how hurricanes form and intensify and identify the root causes for errors in computer model predictions.
Our latest research explores how clouds create their own greenhouse effect, trapping heat that causes hurricanes to form and intensify more quickly. Improving how numerical models account for this cloud feedback may ultimately hold promise for more accurate forecasts. Innovative ways of collecting new measurements in developing storms, down to their smallest scales, will also be necessary for guiding these improvements.
Given the upward trend in high-intensity storms, the risks from these storms will only grow. The ability to accurately predict how and when they will form, intensify and threaten coastal populations is crucial.
This article has been updated with the season ending and NOAA video of 2020’s Atlantic storms.
About the Authors
James H. Ruppert Jr., Assistant Research Professor, Penn State and Allison Wing, Assistant Professor of Meteorology, Florida State University
Life After Carbon: The Next Global Transformation of Cities
by Peter Plastrik , John Cleveland
The future of our cities is not what it used to be. The modern-city model that took hold globally in the twentieth century has outlived its usefulness. It cannot solve the problems it helped to create—especially global warming. Fortunately, a new model for urban development is emerging in cities to aggressively tackle the realities of climate change. It transforms the way cities design and use physical space, generate economic wealth, consume and dispose of resources, exploit and sustain the natural ecosystems, and prepare for the future. Available On Amazon
by Elizabeth Kolbert
Over the last half-billion years, there have been Five mass extinctions, when the diversity of life on earth suddenly and dramatically contracted. Scientists around the world are currently monitoring the sixth extinction, predicted to be the most devastating extinction event since the asteroid impact that wiped out the dinosaurs. This time around, the cataclysm is us. In prose that is at once frank, entertaining, and deeply informed, New Yorker writer Elizabeth Kolbert tells us why and how human beings have altered life on the planet in a way no species has before. Interweaving research in half a dozen disciplines, descriptions of the fascinating species that have already been lost, and the history of extinction as a concept, Kolbert provides a moving and comprehensive account of the disappearances occurring before our very eyes. She shows that the sixth extinction is likely to be mankind's most lasting legacy, compelling us to rethink the fundamental question of what it means to be human. Available On Amazon
Climate Wars: The Fight for Survival as the World Overheats
by Gwynne Dyer
Waves of climate refugees. Dozens of failed states. All-out war. From one of the world’s great geopolitical analysts comes a terrifying glimpse of the strategic realities of the near future, when climate change drives the world’s powers towards the cut-throat politics of survival. Prescient and unflinching, Climate Wars will be one of the most important books of the coming years. Read it and find out what we’re heading for. Available On Amazon
From The Publisher:
Purchases on Amazon go to defray the cost of bringing you InnerSelf.comelf.com, MightyNatural.com, and ClimateImpactNews.com at no cost and without advertisers that track your browsing habits. Even if you click on a link but don't buy these selected products, anything else you buy in that same visit on Amazon pays us a small commission. There is no additional cost to you, so please contribute to the effort. You can also use this link to use to Amazon at any time so you can help support our efforts.