2021 Hurricane Season Preview

KEY CONCEPTS

• The Atlantic hurricane season officially begins next week, running from June through November. While experts with the World Meteorological Organization (WMO) and the National Hurricane Center are considering advancing the start date of hurricane season to May 15th, it’s not yet clear that climate change is causing tropical systems to occur earlier.

• So what do we know about how climate change influences hurricanes? We know that warming sea surface temperatures due to climate change add fuel to hurricanes, making for stronger hurricanes that can strengthen much more quickly (rapid intensification).

• Climate change can also lead to worse flooding with hurricanes. A warmer atmosphere holds more moisture, increasing the amount of rainfall during a tropical storm. Sea level rise also contributes to higher and more dangerous coastal storm surges.

The Atlantic Hurricane Season officially begins next week, running from June 1 through November 30. And while a repeat of 2020’s record season is not expected, it is projected to be busier than average. According to NOAA’s hurricane research group, these are the dates when the majority (97%) of tropical cyclone activity occurs in the Atlantic Ocean, Caribbean Sea, and Gulf of Mexico. However, experts at the World Meteorological Organization (WMO) and the National Hurricane Center are considering advancing the start date to May 15 for future seasons. While the 1950s had several preseason storms, this year marks the seventh consecutive year with a named tropical storm developing before June 1. 

While this recent trend is important and consistent with what we know about how warm water fuels tropical storms, it is difficult to confidently pull a trend from the data. A big challenge is that the tools which make hurricane forecasts better, like more consistent aircraft reconnaissance and geostationary satellites, also means that we now see storms that we might have missed in the past.

So what do we know about climate change and hurricanes? 

• No changes expected in the overall number of hurricanes. Even though there was a record-breaking number of hurricanes in the Atlantic basin last season, overall there is no solid evidence to suggest that the number of hurricanes is changing globally.

• Stronger hurricanes. Research shows that the proportion of strong hurricanes (Category 4 and 5 storms) has increased due to warming.

• Rapid intensification. Studies suggest that warmer sea surface temperatures may enable hurricanes to strengthen more quickly. The record-breaking 2020 hurricane season included 10 rapidly intensifying storms (meaning their maximum wind speed increased at least 35 mph within 24 hours). 

• More rainfall. A warmer atmosphere can hold more moisture, which can contribute to more costly flooding. Studies project a 10-15% average increase in rainfall rates of tropical cyclones in a 2°C warming scenario.

• Higher storm surge. Due to sea level rise, coastal storm surge accompanied by tropical cyclones is more dangerous and costly. 

For a more technical state of the science, see the recent NOAA blog, based on a Science Brief this spring from the NOAA Geophysical Fluid Dynamics Lab.

Climate Central is here to help you connect the dots between tropical systems and climate change this hurricane season. Check out these additional resources for more information:

Updated Graphics:

Warming Oceans

Strongest Storms by Region

Previous Releases:

Stronger Hurricanes

Hurricanes & Climate Change

Tropical Cyclone Records & Rainfall Extremes

2020 Hurricane Season

Rapid Response Workshop: Hurricane Season - Impacts

Rapidly Intensifying Hurricanes

POTENTIAL LOCAL STORY ANGLES

How is sea level rise contributing to storm surge in my area?
Before a storm, Climate Central’s Risk Finder tool allows you to explore the populations, properties, and infrastructure at risk. Following a storm’s damage, many communities and individuals are faced with questions about rebuilding and relocating. Our Coastal Risk Screening Tool allows users to view U.S. and global coastal locations threatened by sea level rise and coastal flooding now and in the future. You can also find region-specific resources for understanding coastal risks from the U.S. Climate Resilience Toolkit.

You don’t have to be on the coast to experience heavy precipitation from a tropical system. Want to know what typically floods near you?
FEMA collects information on flood insurance for each state and you can check out NOAA’s interactive billion-dollar weather and climate disasters website to find historic events near you. Using FEMA data, the National Resources Defense Council has created an online tool to find repeatedly flooded properties in each state and county, along with National Flood Insurance Program claims. Pew Charitable Trusts has compiled research on local flood mitigation efforts around the country, and the National Conference of State Legislatures collects resources on state level actions on flood issues.

LOCAL EXPERTS 

The SciLine service, 500 Women Scientists or the press offices of local universities may be able to connect you with local scientists who have expertise on carbon emissions in your area. In addition, the American Association of State Climatologists is a professional scientific organization composed of all 50 state climatologists. You can contact the International Association of Emergency Managers media office to find local emergency managers or experts in your area.

NATIONAL EXPERTS 

• Athena Masson, Ph.D. Meteorologist and hurricane specialist for Florida Storms and the Florida Public Radio Emergency Network (FPREN) at the University of Florida. amasson@ufl.edu

• Jhordanne Jones, Doctoral Candidate, Department of Atmospheric Science, Colorado State University Tropical Meteorology Project. jhordanne.jones@colostate.edu

• Jim Kossin, Ph.D. Climate Scientist, NOAA National Centers for Environmental Information (NCEI). Research focuses on tropical meteorology and impacts of climate change. kossin@ssec.wisc.edu

METHODOLOGY

Date of the first named storm based on the HURDAT2 dataset provided via Brian McNoldy at University of Miami. The occurrence of Hurricane Alex in January 2016 is categorized as a remnant of the 2015 season. Start date of 1971 chosen based on consistent geostationary satellite coverage.The map of global ocean temperature trends was built using data from NOAA’s Extended Reconstruction Sea Surface Temperature dataset. At each location, we fit the monthly trend (change in temperature per year) to data from 1901-2020. The map of temperature change  is this trend multiplied by 120 years. Globally strongest storm analysis based on Velden et al. 2017 with updated data through March 2021. Special thanks to Phil Klotzbach from Colorado State for the timeline on advances in detection technology.