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Hurricanes and severe thunderstorms are destructive, powerful

August 28, 2018

Did you know that winds generated by severe thunderstorms can rival the force of Category 1 hurricanes?

hurricane resilience

By Jim Breitkreitz, Vice President of Property Services, Risk Engineering, Zurich North America

For businesses situated far from the ocean coasts or the Gulf of Mexico, experiencing a powerful hurricane or tropical storm is not a concern. However, winds generated by severe weather events  such as powerful spring and summer thunderstorms can deliver the strength and destructive force of a hurricane inland, even without the formation of a tornado. Making preparations for severe thunderstorms should be a priority for your business so that people and the facility stay safe.

From a meteorological standpoint, hurricanes and severe thunderstorms share similar origins, as both draw strength from warm, unstable air masses. Powerful convection thunderstorms towering miles into the sky are fed by currents of warm, moist air rising from the land in the heat of summer. Hurricanes are spawned by a similar mechanism, with warm ocean waters providing the same source of energy and the Earth’s rotation providing the impetus for a tropical storm’s characteristic spin.

While a typical hurricane season may spawn about 12 named storms with perhaps six achieving hurricane strength, more than 100,000 thunderstorms develop in the U.S. each year with up to 10,000 reaching severe status. The Saffir-Simpson scale, which measures hurricane strength, pegs Category 1 hurricanes at having sustained winds of at least 74 miles per hour. However, the most intense thunderstorms can generate winds greater than 83 miles per hour on the Beaufort scale, a long-standing tool for measuring gale strength. It’s notable that the worst thunderstorms can be as threatening and as powerful as weaker hurricanes.


Commercial buildings can be particularly vulnerable to the ravages of severe thunderstorms, which can roll through an area with far less advance notice than the several days of warnings that usually precede a hurricane. Businesses need to be aware of vulnerabilities in their facilities to help ensure resilience against the worst impacts of severe weather occurrences. Make the difference between riding out a summer downpour and experiencing a preventable disaster by being aware of the following vulnerabilities:


  • Roof systems: Winds generated by a severe thunderstorm can exert powerful aerodynamic pressure on roof systems that cover a substantial square footage for commercial and retail structures. Periodic roof inspections are crucial to determine a roof’s ability to withstand spring and summer thunderstorms, as well as winter snow loads.
  • Roof-mounted equipment: Air conditioning units, telecommunications equipment and other components of roof-mounted equipment that are not properly secured can become missiles in a severe thunderstorm’s powerful winds. Secure these items or remove them from a rooftop before a storm.
  • Roof drains: Both hurricanes and severe thunderstorms produce powerful downpours that can result in ponding loads on flat roofs. Make sure all roof drains open and are free of obstructions, such as dirt or tree branches.
  • Building openings: High winds entering through dock doors or other large openings can increase aerodynamic pressure on a roof deck by 40 percent, with predictable effects on a deficient roof system.
  • Edge metal: Edge metal flashing used where walls meet rooflines can unzip under high winds, allowing the potential for damaging gales and wind-driven water into a structure.

Whether a business is located in Miami, Florida, or Miami, Indiana, hurricane-force winds associated with severe thunderstorms demand pre-event planning and preparation to help reduce loss potential, strengthen resilience and keep people safe.

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