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Tip Sheet: Explaining Hurricane Behavior, Impacts, and Possible Links to Global Warming

May 25, 2006 - Updated August 31, 2006

BOULDER—Although the 2006 Atlantic hurricane season has started slowly compared to last year’s record pace, with no major hurricanes reported by 31 August, the total of five named storms is on par with the long-term average. 

Meanwhile, the northeast Pacific has been somewhat busier than average, with 11 named storms and 7 hurricanes (5 of them major) through August.  And Supertyphoon Ioke—the central Pacific’s strongest storm in 12 years—devastated tiny Wake Island on August 31 with sustained winds topping 160 mph.

Scientists at the National Center for Atmospheric Research (NCAR) and its parent organization, the University Corporation for Atmospheric Research (UCAR), closely study hurricanes, typhoons, and other tropical cyclones (the term varies depending on geography, but refers to the same type of storm). The scientists use advanced computer models and draw on a wide range of observations to study the early development of cyclones, track the intense storms, and even predict major impacts before landfall.

Experts are available to explain

• whether global climate change is augmenting hurricane strength and what the future may hold;
• what may cause a hurricane to spin up initially, gain or lose intensity, or veer on a new course;
• how even weak tropical storms and hurricanes can lead to devastating floods;
• how scientists can help utilities and local governments to anticipate and prepare for hurricane impacts.

UCAR also offers background information on the Web about hurricanes and other cyclones (see the Background section of this tip sheet, below).

Experts at NCAR

Formation, intensity, and motion

Christopher Davis
NCAR Scientist, Mesoscale and Microscale Meteorology Division and Research Applications Laboratory
303-497-8990

Davis studies the systems that lead to hurricanes, thunderstorms, and other heavy rainfall events. He uses observations and sophisticated computer models to analyze the evolution of these systems. Recently Davis has focused on the role of weak nontropical disturbances in fostering the development of some tropical storms and hurricanes.

Wen-Chau Lee
NCAR Scientist, Earth Observing Laboratory
303-497-8814

Lee is a specialist in hurricane winds and intensity. He is the chief scientist for NCAR's ELDORA, an airborne Doppler radar, which captures detailed images of precipitation and winds from hurricanes and severe thunderstorms. Lee has developed a mathematical technique to extract more information out of radar depictions of hurricane eyewalls and other intense, fast-changing weather systems.

Climate change, global warming

Greg Holland
NCAR Scientist, Mesoscale and Microscale Meteorology Division
303-497-8949

Holland is director of NCAR’s Mesoscale and Microscale Meteorology Division, which studies weather on the local and regional scale. His background is in tropical meteorology and severe weather, and his specialties include hurricane structure and behavior. Holland coauthored a paper in Science last year showing that the frequency of Category 4 and 5 cyclones has nearly doubled since 1970. He also is an expert on the torrential rains and other effects produced as tropical cyclones move inland.

Kevin Trenberth
NCAR Scientist, Climate and Global Dynamics Division
303-497-1318

Trenberth’s research emphasizes the analysis of observational data. He has been on the forefront of scientists examining the question of whether climate change, including global warming, is affecting the intensity of hurricanes and other tropical cyclones. He also is an expert on El Niño and the water cycle.

Flooding

Matthew Kelsch
UCAR Hydrometeorologist, Cooperative Program for Operational Meteorology, Education and Training
303-497-8309

Kelsch specializes in weather events involving water, such as floods, droughts, rain, hail, and snow. He has studied some of the biggest U.S. flood events connected to hurricanes and tropical storms.

Societal Impacts

Brian Bush
NCAR Visiting Scientist, Research Applications Laboratory, Computational & Information Systems Laboratory
303-497-2829

Bush is an expert on computer simulations of energy and transportation infrastructure. Based at Los Alamos National Laboratory, he is spending two years at NCAR working to incorporate better weather data into the hurricane damage models developed at Los Alamos for the federal government. During last year’s major hurricane threats, Bush worked closely with colleagues at NCAR and Los Alamos to convert forecasts of wind, rain, and storm surge into experimental damage probabilities for utility generation stations, substations, and power lines.

Ilan Kelman
NCAR Visiting Scientist, Center for Capacity Building
303-497-8122

Kelman's research focuses on hurricanes and other disasters, their effects on people and infrastructure, and the vulnerabilities of communities. He is also interested in disaster deaths, analyzing the individuals who are most likely to die in disasters and why.

In Depth

The role of global warming

Recent studies using computer models and observations going back to the 1970s suggest that, because of warmer sea-surface temperatures and moister air, more energy goes into the showers and thunderstorms that feed hurricanes, pushing more of them into the extreme category. Follow these links for research news on the relationship between hurricanes and global warming:

• NCAR news release: Global Warming Surpassed Natural Cycles in Fueling 2005 Hurricane Season (June 22, 2006)
• Georgia Tech news release: Research Re-examines Strong Hurricane Studies (March 16, 2006)
• NOAA news feature: Area Where Hurricanes Develop Is Warmer, Say NOAA Scientists (May 1, 2006)
• NCAR news release: Hurricanes Are Getting Stronger, Study Says (September 15, 2005)
  

Modeling hurricanes

Most computer models designed to study global climate cannot depict the small-scale air motions at the heart of a hurricane. Weather prediction models can do this, but they don’t extend far enough in time or space to show how future climate change will affect hurricanes. A project at NCAR is linking global models with regional models in order to better understand how cyclones and other tropical disturbances vary over time. Meanwhile, NCAR is refining the Advanced Research WRF, its version of the multiagency Weather Research and Forecasting model. The ARW was among the most accurate models in projecting the track and intensity of 2005’s major Atlantic hurricanes. Follow these links to view last year’s ARW forecasts and to learn more:

• UCAR Quarterly: A giant step down the road to multiscale modeling (Fall 2005)
• NCAR news release: Rita and Beyond: Research Model Advances Hurricane Intensity Prediction (September 21, 2005)
• WRF-ARW 4-kilometer hurricane forecasts
  

Observing hurricanes

In August 2005, NCAR researchers and colleagues from the French space agency began launching specialized balloons, called driftsondes, carrying miniaturized weather instruments to detect hurricanes as they emerge over the far-eastern Atlantic. This critical region is out of range of U.S. hunter-hurricane aircraft. The driftsondes are probing weak weather systems, called easterly waves, that serve as seedlings for hurricanes. Dozens of these waves move across Africa into the Atlantic between about 10 and 20 degrees north. The project relies on new technology to provide early warning of potentially dangerous storms.

• NCAR news release: High-Flying Balloons Begin Tracking Emerging Hurricanes (August 31, 2006)

Related sites on the World Wide Web 

Current Conditions from NOAA's National Hurricane Center

The National Center for Atmospheric Research and UCAR Office of Programs are operated by UCAR under the sponsorship of the National Science Foundation and other agencies. Opinions, findings, conclusions, or recommendations expressed in this publication do not necessarily reflect the views of any of UCAR's sponsors.