Learn how property-specific extreme wind risk is determined.
A property's Wind Factor™ is an indicator of its risk to extreme wind exposure over the next thirty years. The model assigns each property a Wind Factor, ranging from 1 (minimal risk) to 10 (extreme risk). For every location, the likely exposure to extreme wind is calculated for today and 30 years into the future, and takes into account the local conditions such as the roughness of the landscape surrounding a property. A property’s Wind Factor is based on a 30 year aggregate estimate, which means that a property with a higher Wind Factor has a higher likelihood to experience higher winds more frequently today /or in the future than a property with a lower Wind Factor score.
The impact of the changing environment
The expected change in extreme wind likelihood and intensity is influenced by the changing environment. A changing environment means higher air temperatures and higher humidities, which in turn impact weather patterns and hurricanes’ place within them. As the average global atmospheric temperature continues to increase at a faster rate than at any point in the planet’s geological record, it warms ocean waters that fuel hurricanes’ growth and produces changes in large scale weather patterns which impact hurricanes’ tracks. Learn more about the environmental factors increasing hurricane wind risk. Learn more.
The inclusion of environmental changes that impact future wind risk are an essential part of the First Street Foundation Wind Model. The model uses the IPCC CMIP6 SSP245 scenario to forecast how environmental conditions will change 30 years into the future, how those conditions will influence hurricane intensities and tracks, and uses those future hurricane characteristics to create a property-specific wind speed probability model. This allows the First Street Foundation Wind Model to predict likely wind speeds and associated damages 30 years from now, and builds upon previously-published science to create new applications that pass the same rigorous standard of scientific peer review.
Local variations in wind speeds are often driven by the land surface elevation and roughness of the surrounding area that impacts how winds may be slowed as they flow across and interact with the earth’s surface. This includes estimates of the surface roughness of the topography surrounding a building, which can vary from smooth (adjacent to a large body of water) to rough (near mountains and hills). Due to these local variations some properties may have higher or lower scores than other nearby properties.
The calculation of property-specific Wind Factor Scores
A property's Wind Factor is an indicator of its aggregate thirty-year risk of being exposed to extreme winds from hurricanes, tornadoes, or severe storms, ranging from 1–10. Properties with higher Wind Factors have a higher probability of exposure to severe winds.
The First Street Foundation Wind Model is used to determine the likelihood of a severe wind event occurring within any given year and the projected wind speed of that event. A property’s Wind Factor is determined by its likelihood of experiencing 3-second wind gusts over 50 mph (tropical storm speed) and the potential intensity of that wind event. Because risks accumulate over time, it specifically looks at the likelihood of at least tropical storm wind speeds (50 mph wind gusts) reaching the property at least once within the next 30 years. Wind Factors increase as likelihood of exposure and/or probable wind speeds increase.
Properties with less than 1% chance over the next 30 years of having tropical storm or hurricane-force winds reach the property are considered to have minimal risk, or a Wind Factor of 1. While it is still possible for properties with a Wind Factor of 1 to experience severe winds, they are below the ability of the model to resolve that rare event. The specific wind speed and likelihood of severe winds expected to reach a property are used to determine the boundaries for each level of risk. These boundaries produce a set of rules that can be used to understand why scores might differ across properties:
- Properties with no risk from tropical storm or hurricane winds but have wind risk from tornadoes or severe thunderstorm winds will have a Wind Factor of 2.
- Properties with at least an 1% chance of tropical storm winds reaching the property at least once over the next 30 years will have a Wind Factor of 2 or higher
- Properties with at least a 26% chance of tropical storm winds reaching the property at least once over the next 30 years will have a Wind Factor of 5 or higher
- Properties with at least a 80% chance of tropical storm or hurricane-force winds reaching the property at least once over the next 30 years will have a Wind Factor of 7 or higher
- Properties with at least a 99% chance of tropical storm or hurricane-force winds reaching the property at least once over the next 30 years will have a Wind Factor of 9 or higher
For example, a property that has a 6% chance of tropical storm or hurricane-force winds reaching the property at least once over the next 30 years could have a Wind Factor of 3. In contrast, a property that has a 27% chance of this occurring could have a Wind Factor of 5.
Ensuring scientific accuracy
The First Street Foundation Wind Model brought together top climate scientists, modelers, engineers, technologists, and analysts. Results of the model have been computed for the US, and compared against historical hurricane wind damage data, and historical hurricane records. Using Open Science protocols, all methods used by the First Street Foundation Wind Model have been submitted to scientific peer-review journals and are also available to read on the First Street Foundation website.
The methodology behind the model used by Wind Factor
Data sources used to determine Wind Factors