Mar 2024

Convective Storms

Estimated reading time: 10 minutes

Convective storms, including thunderstorms, tornadoes, and hailstorms, are a common weather phenomenon in America, affecting various regions throughout the country. These storms pose significant risks to life and property, causing damage through high winds, hail, heavy rainfall, and occasionally tornadoes. This article aims to provide a comprehensive overview of convective storms in America, including their characteristics, impacts, associated risks, and strategies for preparedness.

Global insured losses from severe thunderstorms hit a new all-time high of US$60 billion in 2023, with overall natural catastrophe claims surpassing $100 billion, according to the Swiss Re Institute. Convective storm insured losses could influence the outcomes for insurance in 2024. “The cumulative effect of frequent, low-loss events, along with increasing property values and repair costs, has a big impact on an insurer’s profitability over a longer period. The high frequency of severe thunderstorms in 2023 has been an earnings’ test for the primary insurance industry,” commented Jérôme Jean Haegeli, Swiss Re’s group chief economist.

The US $60 billion in insured losses in 2023 is a major increase from the US$29 billion in insured losses in 2022 as per the PropertyCasualty360 report based on Aon’s Impact Forecasting.

Throughout 2023, regions across the globe witnessed a marked uptick in convective storm activity. Factors such as shifting climate patterns, warmer ocean temperatures, and increased atmospheric moisture content have contributed to the conducive environment for convective storm development. As a result, many areas experienced a surge in thunderstorm occurrence, leading to an elevated risk of severe weather events, including tornado outbreaks and destructive hailstorms.

The escalating frequency and severity of convective storms in 2023 have prompted property insurance providers to reassess their risk models and underwriting practices. Insurers are incorporating updated data on convective storm patterns and trends to better assess risk and set premiums. Additionally, insurance companies are emphasizing the importance of mitigation measures for policyholders to minimize the risk of convective storm damage and reduce insurance claims.

Impact on Property Insurance:

The heightened frequency and severity of convective storms in 2023 have had a pronounced impact on property insurance. Insurers have faced a surge in claims related to convective storm damage, including:

  1. Structural Damage: High winds, hail, and tornadoes have caused extensive damage to residential and commercial properties, resulting in substantial insurance claims for repairs and rebuilding.
  2. Roofing and Exterior Damage: Hailstorms in particular have caused significant damage to roofs, siding, windows, and other exterior elements of buildings, leading to widespread insurance claims for property owners.
  3. Business Interruption: Severe weather events, such as tornado outbreaks, have disrupted business operations, resulting in financial losses and insurance claims for business interruption coverage.
  4. Auto Damage: Hailstorms and wind-driven debris have caused damage to vehicles, resulting in insurance claims for auto repairs or replacements.
  5. Increased Premiums: The surge in convective storm-related claims has prompted property insurance providers to adjust premiums to reflect the elevated risk of property damage, leading to higher insurance costs for policyholders.

NOAA’s National Severe Storms Laboratory (NSSL) and National Weather Service (NWS) are among the key agencies responsible for studying convective storms in the United States. Their research focuses on understanding the dynamics of severe weather phenomena such as thunderstorms, tornadoes, and hailstorms, as well as improving forecasting techniques and warning systems to enhance public safety.

NOAA regularly conducts research and publishes studies related to various aspects of convective storms, including their formation, behavior, and impacts. Some areas of research that NOAA may explore regarding convective storms include:

  1. Storm Prediction and Forecasting: NOAA researchers work to improve the understanding and prediction of convective storms, including the development of advanced forecasting models and techniques to anticipate the timing, intensity, and location of severe weather events.
  2. Storm Dynamics and Structure: NOAA conducts studies to investigate the internal structure and dynamics of convective storms, including the processes that lead to their formation, organization, and evolution. This research helps improve understanding of storm behavior and contributes to the development of more accurate storm-scale models.
  3. Impact Assessment: NOAA assesses the societal and economic impacts of convective storms, including property damage, casualties, and disruptions to critical infrastructure. Understanding the impacts of severe weather events helps inform emergency management and disaster response efforts.
  4. Climate Change and Convective Storms: NOAA scientists study the potential influence of climate change on convective storm patterns, frequency, and intensity. This research helps assess how climate variability and long-term trends may affect the frequency and severity of convective storms in the future.

Convective storms are a significant weather hazard capable of causing widespread damage, injuries, and fatalities. Understanding the characteristics, impacts, risks, and vulnerabilities associated with convective storms is essential for effective preparedness and resilience-building efforts. By implementing proactive measures and strategies for preparedness, communities can better mitigate the impacts of convective storms and safeguard lives and property.

Characteristics of Convective Storms:

Convective storms are characterized by intense upward atmospheric motion within convective cloud systems. Key characteristics include:

  1. Updrafts and Downdrafts: Convective storms are fueled by strong updrafts, which lift warm and moist air rapidly into the atmosphere. As this air rises, it cools and condenses, forming clouds and releasing heat energy. Simultaneously, downdrafts, or downward-moving air currents, occur within the storm system, bringing cooler air back down to the Earth’s surface.
  2. Cumulonimbus Clouds: Convective storms are associated with towering cumulonimbus clouds, which can reach high altitudes and have distinctive anvil-shaped tops. These clouds are formed through the rapid upward movement of air within the storm system.
  3. Severe Weather: Convective storms can produce various forms of severe weather, including heavy rainfall, intense lightning, strong winds, hail, and tornadoes. The severity of these conditions depends on factors such as the strength of the storm and atmospheric instability.
  4. Duration and Movement: Convective storms can vary in duration, ranging from short-lived pulse storms to longer-lasting multicellular or supercell storms. They can also move across the landscape, driven by prevailing winds and atmospheric conditions.

Impacts of Convective Storms:

Convective storms can have significant impacts on communities, infrastructure, and the economy, including:

  • Property Damage: High winds, hail, and tornadoes can cause damage to buildings, roofs, windows, and vehicles, resulting in costly repairs and insurance claims.
  • Injuries and Fatalities: Severe weather associated with convective storms can lead to injuries and fatalities, particularly during tornado outbreaks and severe thunderstorms.
  • Disruption to Infrastructure: Convective storms can disrupt critical infrastructure, including power lines, transportation networks, and communication systems, leading to service outages and economic losses.

Risks and Vulnerabilities:

Several factors contribute to the risks and vulnerabilities associated with convective storms in America, including:

  • Regional Variability: Convective storm activity varies by region, with certain areas, such as Tornado Alley in the central United States, experiencing higher frequencies of tornadoes and severe thunderstorms.
  • Urbanization and Population Growth: Urban areas are particularly vulnerable to convective storm impacts due to dense population centers, increased infrastructure, and limited green spaces, which can exacerbate flooding and other hazards.
  • Climate Change: There is growing evidence that climate change may influence convective storm patterns, potentially leading to changes in storm frequency, intensity, and distribution.

Are convective storms worse than “hurricane season?”

Comparing convective storms to hurricane seasons involves considering different types of weather phenomena and their respective impacts. While both convective storms and hurricane seasons can cause significant damage and pose risks to life and property, they differ in several key aspects:

  1. Nature of Events:
    • Convective storms, such as thunderstorms, tornadoes, and hailstorms, are typically localized, short-lived weather events that can occur throughout the year in various regions. They are characterized by intense updrafts and downdrafts within a convective cloud system.
    • Hurricane seasons refer to the period when tropical cyclones, including hurricanes and tropical storms, are most likely to occur in specific regions, such as the Atlantic Basin or the Eastern Pacific Basin. These storms develop over warm ocean waters and are characterized by a well-defined circulation pattern and sustained wind speeds of at least 74 miles per hour (119 kilometers per hour) for hurricanes.
  2. Frequency and Duration:
    • Convective storms can occur frequently and unpredictably, with individual thunderstorms lasting from a few minutes to several hours. They can develop rapidly and affect relatively small areas.
    • Hurricane seasons typically occur during specific months of the year, such as from June to November in the Atlantic Basin. While individual hurricanes may last for several days to weeks, the entire hurricane season spans several months.
  3. Scale and Impact:
    • Convective storms can produce localized but intense impacts, including damaging winds, hail, flash floods, and tornadoes. They can cause significant property damage, injuries, and occasionally fatalities, particularly during severe weather outbreaks.
    • Hurricanes are large-scale weather systems that can affect extensive coastal and inland areas, causing widespread damage from storm surge, high winds, heavy rainfall, and inland flooding. Major hurricanes, in particular, can result in catastrophic impacts, including extensive property damage, loss of life, and long-term disruption to communities.
  4. Preparedness and Response:
    • Preparedness for convective storms involves staying informed about weather forecasts and warnings, seeking shelter during severe weather events, and taking steps to protect life and property, such as securing outdoor items and reinforcing structures.
    • Preparedness for hurricane seasons involves comprehensive planning and readiness efforts by governments, emergency management agencies, communities, and individuals. This includes evacuation planning, strengthening infrastructure, building resilient communities, and having emergency supplies and evacuation kits.

Although both convective storms and hurricane season pose risks and challenges, they differ in terms of their nature, frequency, scale, and impact. Both types of weather events require vigilance, preparedness, and effective response efforts to mitigate their respective impacts on affected communities.

Convective storm history in America:

In The United States, convective storms, particularly severe thunderstorms, tornadoes, and hailstorms, are relatively common and can occur in various regions throughout the country. Here are some notable convective storm events in recent history:

  1. Dixie Alley Outbreak (April 25-28, 2011): This outbreak affected several southern states, including Alabama, Mississippi, and Tennessee. It produced numerous tornadoes, including several violent EF4 and EF5 tornadoes, resulting in widespread destruction and loss of life. One of the most significant tornadoes was the EF5 tornado that struck the town of Hackleburg, Alabama, causing catastrophic damage.
  2. Super Outbreak (April 3-4, 1974): Often regarded as one of the most significant tornado outbreaks in U.S. history, the Super Outbreak produced over 140 tornadoes across 13 states, primarily in the Midwest and Southeast. It resulted in 315 fatalities and thousands of injuries, with several communities devastated by multiple tornadoes within a short period.
  3. Joplin Tornado (May 22, 2011): The EF5 tornado that struck Joplin, Missouri, was one of the deadliest tornadoes in U.S. history. It caused widespread destruction across the city, resulting in 161 fatalities and thousands of injuries. The tornado’s path was estimated to be nearly a mile wide at times, and it caused billions of dollars in property damage.
  4. Moore Tornadoes (May 3, 1999, and May 20, 2013): The city of Moore, Oklahoma, has been struck by multiple devastating tornadoes in recent decades. The May 3, 1999, tornado was one of the most powerful tornadoes ever recorded, rated as an EF5. It caused extensive damage and resulted in 36 fatalities. The May 20, 2013, tornado was also rated EF5 and caused widespread destruction, including the collapse of two elementary schools. It resulted in 24 fatalities.
  5. Hailstorms: Large hailstorms can also cause significant damage in certain regions of the United States. For example, the Colorado Front Range, including the Denver metropolitan area, is known for experiencing severe hailstorms that can damage vehicles, roofs, and other property. The costliest hailstorm in U.S. history occurred in the Denver area on July 11, 1990, causing over $1 billion in insured losses.

These are just a few examples of major convective storm events in America. Convective storms remain a significant weather hazard in the United States, and efforts to understand, forecast, and mitigate their impacts continue to be a priority for meteorologists, emergency managers, and communities across the country.

Strategies for Preparedness:

Preparedness is key to mitigating the impacts of convective storms and ensuring community resilience. Strategies for preparedness include:

  • Early Warning Systems: Utilize advanced weather forecasting technologies and early warning systems to provide timely alerts and notifications of approaching convective storms.
  • Emergency Planning: Develop and implement comprehensive emergency plans at the local, state, and national levels, including evacuation procedures, sheltering strategies, and communication protocols.
  • Building Resilient Infrastructure: Strengthen building codes and infrastructure standards to enhance resilience against convective storm hazards, including wind-resistant construction, improved drainage systems, and stormwater management measures.
  • Public Education and Outreach: Educate the public about convective storm risks and safety measures, including the importance of seeking shelter during severe weather events and preparing emergency kits.

For more information on convective storms, strategies for preparedness, or property assessments with natural catastrophe focus, contact Risk Logic Inc. –