To be considered above average, a hurricane season must have an Accumulated Cyclone Energy (a summation of the duration and intensity of all named storms in a year) higher than the median value from 1981-2010. The season must also meet two of the three following: at least 13 named storms, seven hurricanes, or three major hurricanes. Nestor was the 14th named storm of the year, and while the Atlantic has only seen five hurricanes this season, three of them have been considered major hurricanes. NOAA’s estimation is that about 45% of years will be above average, but 2019 is the fourth year in a row to meet these requirements, and the seventh to do so since 2010.
While this season is comparable with recent years, it has been unusual in other ways. Most notably, Hurricane Dorian was nearly stationary as it wreaked havoc on the Bahamas, resulting in at least 61 deaths so far. Hurricane Lorenzo also set the record for the easternmost category 5 storm.
An early end to El Niño weather patterns caused conditions to be more favorable to hurricanes than predicted this year. Though late-season storms are less common, there is still over a month left, and an average year does see one more hurricane formation after October 21st, which would bring this year up to the thirty-year average of six hurricanes per season.
Natural disasters are enormously costly. The U.S. incurred an estimated $306 billion in physical damage from extreme weather events like hurricanes and floods in 2017 alone.
CGRER member Eric Tate, a professor in the University of Iowa geography department, quantifies disaster impacts in a bigger way.
“Looking at these impacts just by dollars affected may not really get at the true impact of how people are affected, how their livelihoods are affected,” he said.
Tate studies the social effects of disasters, with an emphasis on floods. Looking beyond physical damage, he determines how population characteristics like age, disability, education and poverty create social vulnerability to harm.
Listen to Tate explain social vulnerability in his own words.
Disaster impacts are typically distributed unevenly; certain groups suffer disproportionately due to social, political, economic and institutional inequalities. These processes may debilitate some households while neighbors go unaffected during the same storm.
Using mainly government disaster relief data, Tate has measured and mapped the social reality of disasters like 2012’s Hurricane Sandy. He’s currently examining 2015 flooding in South Carolina. His research aims to inform planning and policy by lending insight into how various population characteristics contribute to vulnerability.
“What is needed in this field is a bunch of studies looking at different disasters at different scales of analysis, looking at different variables, looking at different outcomes,” he said. “When you put them all together, now you start to get some generalizable understanding.”
Officials can use such analyses to help vulnerable populations before, during and after disasters with adjusted mitigation and primary response plans. The social dimension of sustainability is often underemphasized, but is crucial for implementing effective change.
“If we want to have sustainable futures but the gains aren’t equitably shared, then is that sustainable?” Tate asked.
Tate on the need for research into the spillover effects of disasters.
He sees several ways policymakers on all levels can more deeply embed equity into decision making. They can model vulnerability among their constituents themselves or look to academic research that does so. They can seek to be inclusive and involve a diverse cross section of the population early on in the decision making process.
Tate pointed to the National Environmental Policy Act as well, which requires the government to complete environmental impact assessments prior to undergoing all federally funded executive projects. He thinks a similar statute could mandate assessments of the far-reaching social consequences of such projects.
He also advised considering climate change in proactive disaster planning, as atmospheric carbon seems to amplify climatological weather events. In Iowa, flooding has already become pronouncedly more intense and will continue to get worse in coming decades.
“Regardless of your belief in climate change or not, we’re seeing changes in hydrological extremes,” Tate said.
Tate on how to help protect yourself and your community from flooding.
Intensified flooding will increase pressure on the already vulnerability and likely push some previously unaffected households beyond their coping capacities.
Tate calls for updated statistical analysis to better inform everyone from city planners to homeowners about risk and vulnerability in different areas. The 100-year floodplain of today may become the 50-year floodplain in 15 years, but flood maps are based on historical frequencies and do not reflect projections for the future.
“Trying to understand future risk based on past occurrences is likely to lead you to faulty conclusions,” he said. “We should be thinking maybe a little less probabilistically and a little more possibilistically.”
***This post is part of “CGRER Looks Forward,” a new blog series running every other Friday. We aim to introduce readers to some of our members working across a wide breadth of disciplines, to share what the planet’s future looks like from their perspective and the implications of environmental research in their fields. ***
North and South Carolina have both issued evacuation warnings in anticipation of a very destructive weekend. The eye of Hurricane Florence is made landfall this afternoon, though her rain bands touched land late Thursday.
As of Thursday morning, Florence’s strongest sustained winds of 105 mph put her in Category 2 classification for wind. As of Friday afternoon, she has downgraded to Category 1. Forecasters say her storm surge, the swell of water pushed onshore by hurricane winds, will be a Category 4. The National Hurricane Center predicts floods over 9 feet above ground in some areas.
States as far inland as Indiana may receive the tail end of the hurricane, which will most likely have weakened to a less windy but still wet tropical storm or depression by then.
Experts debate whether climate change will increase the frequency and severity of tropical storms and hurricanes in coming years, and whether it already has. It is difficult to separate natural variability from human-induced effects when examining any specific storm, but many of the conditions needed to spawn hurricanes are certainly undergoing change.
To many experts, it seems to many that rising sea levels exacerbate storm surge, that rising sea surface temperatures could add more fuel to storms, and that a warmer, wetter atmosphere increases rainfall. Just look to 2017’s especially devastating season for evidence that these storms are getting nastier.
Other experts say that climate change will increase wind shear, friction between upper and lower level winds moving in different directions, which could actually stop more hurricanes from forming. Only time will tell which factors
As climate change is variable over the Earth’s surface, models show both increase and decrease of all those different factors in different locations. While climate change will almost certainly impact hurricanes, only time will tell the nature of that impact.
This week’s On The Radio segment discusses the unprecedented severity of hurricane activity in the Atlantic ocean this September.
Transcript: September 2017 was a record-setting month for hurricane activity in the Atlantic Ocean.
This is the Iowa Environmental Focus.
It is common for September to be the most active month for hurricanes because low pressure systems often move across the Atlantic and meet the tropical waters of the Caribbean during that month, but September 2017 was a cut above the rest.
The beginning of September brought Hurricane Harvey, a category four storm which caused unprecedented damage to, Houston, the U.S.’s fourth largest city. Five additional hurricanes left paths of destruction across the Caribbean and Florida during September, with Irma and Maria both reaching category five status.
Last month, the overall intensity and duration of storms, known as “accumulated cyclone energy,” was 175 units, significantly higher than September 2014’s record of 155 units. While climate change has not been found to cause hurricanes, there is evidence to say that rising sea temperatures make them stronger.
For more information, visit Iowa-environmental-focus-dot-org. From the UI Center for Global and Regional Environmental Research, I’m Betsy Stone.