The new hurricane scale doesn’t take storm surge into account but includes damage estimates
The National Weather Service and NOAA have adopted a revised Saffir-Simpson Hurricane Wind Scale for the current hurricane season. The updated scale retains the familiar wind-speed ranges but refocuses the categories on expected wind-caused damage rather than tying each category to storm surge, rainfall-induced flooding, or tornado potential.
The revision recognizes that storm surge and coastal flooding are influenced by multiple, highly localized factors—not just wind speed. In practical terms, the new wording for each of the five categories emphasizes the type and extent of structural and property damage likely from the respective wind speeds, with illustrative examples to help the public and emergency managers better understand potential impacts.
“It’s been in the works for the past couple years,” says Dr. Michael Brennan, a senior hurricane specialist. He explains that storm surge depends on local coastline characteristics: the strength and size of the storm, the extent of the wind field, the storm’s forward motion, barometric pressure, and the depth and shape of coastal waters. Because of that complexity, surge values tied to a single category can be misleading.
The original Saffir-Simpson scale was developed in 1971 by consulting engineer Herbert Saffir and Robert Simpson, then-director of the National Hurricane Center. That early version attempted to associate central pressure and surge and flooding effects with each category. At the time, central pressure provided a useful proxy for intensity because direct wind measurements—especially from aircraft reconnaissance—were less available than they are today.
Brennan notes that advances in observation and modeling, and input from both the wind-engineering and meteorological communities, prompted NOAA to revise the scale. The wind speed thresholds for Categories 1 through 5 remain unchanged, but the descriptive language now focuses on the likely damage from those winds in the United States. The intent is clearer messaging: people can better prepare when they understand the expected type and severity of wind impacts.
NOAA points to historical examples to show why the change was necessary. Hurricane Ike (2008) made landfall on the upper Texas coast as a Category 2 storm by wind speed, yet produced peak storm surges far exceeding what the original scale associated with that category. By contrast, Hurricane Charley (2004) made landfall in Florida as a Category 4 storm but produced a much smaller surge than the original category guidance would suggest. Such discrepancies demonstrate that surge and wind-driven damage do not always align neatly with a single categorical number.
Alongside the revised scale, the National Hurricane Center is also extending lead times for watches and warnings. Officials will issue watches and warnings for tropical storms and hurricanes along threatened coastal areas earlier—up to 48 hours before the expected onset of tropical-storm-force winds—so communities have more time to prepare and evacuate if necessary. “A hurricane watch will be issued up to 48 hours before the onset of tropical storm force winds,” Brennan says, stressing the need for additional time to move people, manage traffic, and secure vulnerable property.
The revision aims to improve public comprehension of storm threats by separating wind-impact guidance from surge and flooding guidance, which are better handled through targeted local forecasts and surge products. Emergency managers and residents are encouraged to use the full suite of National Weather Service and local products—storm surge forecasts, rainfall predictions, evacuation guidance, and the updated wind-damage descriptions—to build a complete picture of risk for any approaching storm.
A measure of strength
Category 1
(sustained winds 74–95 mph)
Very dangerous winds likely to cause some damage to homes, trees, and power lines.
Category 2
(sustained winds 96–110 mph)
Extremely dangerous winds capable of causing extensive damage to residences, roofs, and outbuildings, and widespread power outages.
Category 3
(sustained winds 111–130 mph)
Devastating wind damage expected, with many structures suffering major roof and siding loss and a high risk of prolonged outages.
Category 4
(sustained winds 131–155 mph)
Catastrophic wind damage likely, including severe structural failure of well-built homes, extensive debris hazards, and long-term disruption to services.
Category 5
(sustained winds 156+ mph)
Catastrophic and widespread destruction expected; most framed homes will be destroyed, and affected areas may be uninhabitable for an extended period.
This article originally appeared in the May 2010 issue.