Climate Matters•September 10, 2024
Hurricane Rapid Intensification
KEY CONCEPTS
Warming oceans are fueling stronger tropical cyclones — the most costly weather disasters in the U.S.
Warmer sea surface temperatures may contribute to an increased fraction of tropical cyclones that undergo rapid intensification.
Rapidly intensifying hurricanes can be challenging to forecast, contributing to their high costs.
From 1980 to 2023, 177 landfalling Atlantic tropical cyclones rapidly intensified.
Most (70%) of the 63 total billion-dollar tropical cyclones in the U.S. since 1980 rapidly intensified.
Record-warm oceans, higher hurricane activity
Since April 2023, global sea surface temperatures have been continuously hotter than any period on record — and by a wide margin.
June 2024 marked 15 consecutive months of record-breaking global sea surface temperatures. Record ocean heat has contributed to NOAA’s outlook for a highly active 2024 Atlantic hurricane season, which extends through November 30.
Warm oceans fuel stronger hurricanes. Climate Central’s new Climate Shift Index: Ocean measures the influence of climate change on global sea surface temperatures every day.
Analysis using Climate Shift Index: Ocean found that human-caused climate change made the warm ocean waters that fueled Hurricane Beryl up to 400 times more likely.
To mark the historical peak of Atlantic hurricane season activity (September 10), we review the high costs of hurricane rapid intensification and its connection to climate change.
Warmer oceans fuel stronger, more costly hurricanes
Sea surface temperatures influence the weather we experience on land. Warm water is a necessary ingredient for tropical cyclones.
About 80% of major hurricanes (Category 3-5) undergo rapid intensification — defined as an increase in the maximum sustained winds of a tropical cyclone of at least 30 kt (about 35 mph) in a 24-hour period.
From 1980 to 2023, 177 landfalling Atlantic tropical cyclones rapidly intensified above the 30 kt threshold.
Nearly one-quarter of these 177 storms (39 or 22%) experienced extreme rapid intensification: an increase in maximum sustained winds of at least 50 kt (about 58 mph) in a 24-hour period.
Recent research suggests that warmer sea surface temperatures may contribute to an increased fraction of tropical cyclones that undergo rapid intensification.
Forecasting rapid intensification can be challenging, which contributes to the high human and economic toll of such storms.
Stronger storms, higher costs
Tropical cyclones, which include hurricanes and tropical storms, are the most costly weather and climate disasters in the U.S. by far.
Billion-dollar tropical cyclones account for over $1.4 trillion in damages since 1980 — more than half of the cost of all billion-dollar disasters since then. Over the same period, billion-dollar tropical cyclones have caused an estimated 6,934 deaths in the U.S.
Total billion-dollar tropical cyclone costs are highest in Louisiana, Texas, and Florida — but extend to 29 states throughout the South, Southeast, Northeast, and Ohio Valley, as well as to Hawaii, Puerto Rico, and the U.S. Virgin Islands.
Of the 63 tropical cyclones that have caused at least $1 billion in damage in the U.S. from 1980 to July 2024 (Hurricane Beryl), 44 (70%) underwent rapid intensification.
The five most costly hurricanes since 1980 — which caused a combined estimated $680 billion (inflation-adjusted) in damages — all had maximum rapid intensification rates between 40-70 kt in 24 hours:
Hurricane | Year | Total cost (billions of USD, CPI-adjusted) | Maximum 24-hour intensification rate (kt) |
|---|---|---|---|
Katrina | 2005 | $200.0 | 50 |
Harvey | 2017 | $158.8 | 40 |
Ian | 2022 | $118.5 | 40 |
Maria | 2017 | $114.3 | 70 |
Sandy | 2012 | $88.5 | 40 |
Rapidly intensifying hurricanes in a warming climate
Observations show an increase in tropical cyclone intensification rates in the Atlantic basin from 1982-2009. On a global scale, extreme rapid intensification events (50+ kt in 24 hours) have increased significantly from 1990 to 2021, and may be linked with warming sea surface temperatures.
In the North Atlantic, the number of storms that quickly intensified from Category 1 (or weaker) into a major hurricane has more than doubled in 2001-2020 compared to 1971-1990.
Emerging research suggests that rapid intensification could increase with continued warming from carbon pollution.
Tropical cyclones and climate change
The effects of climate change on hurricanes are complex, but research shows that rising temperatures are causing hurricanes to become more intense. Higher tropical cyclone rainfall rates are expected with continued warming. And rising sea levels further enhance the risk of flooding from tropical cyclones, sometimes increasing hurricane damages by billions of dollars.
Ocean warming due to human-caused climate change is fueling an increased proportion of intense tropical cyclones.
Since 1979, human-caused warming has increased the global likelihood of a tropical cyclone developing into a major hurricane (Category 3 or higher) by about 8% per decade.
The latest IPCC reports predict that the proportion of very intense (Category 4 and 5) tropical cyclones is projected to increase globally with continued warming.
In addition to this projected increase in intense tropical cyclones, the Atlantic hurricane season is expected to be about a month longer by the end of the century.
Rising losses from tropical cyclones
The rising risks from tropical cyclones reflect a combination of three factors:
physical hazards that result from tropical cyclones (e.g., storm surge),
exposure of people and property to these hazards where and when they occur, and
vulnerability of populations in the storm track (e.g., capacity to respond and recover).
While the frequency of landfalling hurricanes in the continental U.S. hasn’t changed from 1900-2017, the resulting economic losses have increased significantly over the same period. Population growth and regional wealth along the U.S. Gulf and East Coasts (increased exposure) contribute to the increased damage.
Tropical cyclones can generate multiple devastating hazards including storm surge, heavy rainfall, flooding, winds of 100 mph or more, and tornadoes.
Over the recent 2013–2022 decade, rainfall flooding accounted for 57% of all U.S. deaths from tropical cyclones, according to a 2023 report from the National Hurricane Center.
The risks multiply when hurricane-induced power outages overlap with other extreme events such as heat waves.
LOCAL STORY ANGLES
Official storm forecasts, safety guidance, and risk screening
NOAA’s National Hurricane Center monitors current conditions and provides 2-day and 7-day outlooks for the Atlantic, Eastern Pacific, and Central Pacific. NOAA’s National Hurricane Preparedness site includes safety tips, resources to determine local hurricane risk and evacuation zones, and guidance on insurance checkups. The Ready.gov hurricanes site provides guidance in 13 languages. NOAA’s National Storm Surge Risk Maps can be used to assess risk in hurricane-prone coastal areas. FEMA’s National Risk Index maps provide hurricane risk levels for counties and census tracts in the contiguous U.S.
Five ways to use the Climate Shift Index: Ocean
Use the tool. The online map tool allows you to explore data showing which parts of the world are experiencing high Ocean CSI levels — every day.
Share custom maps. Use yellow buttons in the tool’s left panel to share a direct link to a custom map or download the current map view as a PNG file.
Download maps in KML format. The tool’s left panel also includes a link to download daily Ocean CSI maps in KML format for use in TV broadcasts.
Read the FAQs. Review common questions and answers on the science behind the Ocean CSI and expert guidance and caveats on using the tool in climate reporting.
Go deeper: read the peer-reviewed paper. Published by Climate Central scientists in May 2024, this openly accessible peer-reviewed paper presents the science behind the Ocean CSI system.
More resources on climate change and tropical cyclones
NOAA regularly updates a comprehensive summary of the science on Global Warming and Hurricanes, and offers a hurricane season Media Resource Guide. Climate Central’s Extreme Weather Toolkit: Tropical Cyclones provides reporting resources and multimedia graphics in English and Spanish.
METHODOLOGY
Special thanks to Dr. Phil Klotzbach of the Colorado State Tropical Meteorological Project for assistance. A rapid intensification period (RI) is defined by the National Hurricane Center as an increase in the maximum sustained wind speed of at least 30 knots (approx 35 mph) in 24 hours. Hurricane data were collected from the HURDAT2 dataset and intensity of storms was analyzed at synoptic times (00, 06, 12, 18 GMT). Only storms that had reached tropical storm status were considered for the rapid intensification analysis and subtropical systems were excluded. Because of limitations in detection (before satellite and aircraft reconnaissance), HURDAT2 data before 1980 were excluded in this analysis.
As of September 5, 2024 there have been 63 total tropical cyclones that have caused at least $1 billion in damage in the U.S. since 1980 (including Hurricane Beryl in July 2024). Note that rapid intensification data are not available for two of these 63 events: Hurricane Iniki (1992, Hawaii) and Typhoon Mawar (2023, Guam). All billion-dollar tropical cyclone cost estimates are CPI-adjusted (NOAA/NCEI data accessed August 8, 2024).