The Hurricane Risk Calculator: Translating Potential Wind Impacts for Coastal and Inland Residents

Coastal and inland residents in the U.S. often face a barrage of information when a hurricane landfall threatens. These include information and products from official sources such as the National Hurricane Center (NHC), graphical and text products from local National Weather Service Forecast Offices, information from local and state governments (including evacuation orders/recommendations), and other information from a wide variety of unofficial channels such as TV/radio/internet media, blogs and other web sites, and social media. Yet, residents still grapple with making effective decisions in the face of uncertainty, products they do not understand, and conflicting information. Worse yet, residents often get hung up on deterministic forecast scenarios which they view as either favorable or unfavorable to their particular situation, sometimes delaying action to see if a more favorable situation develops. Finally, residents struggle with understanding how various forecast scenarios will translate into impacts at their specific location. As a result, the decision-making process of residents is often haphazard and leads to less-than-optimal personal and collective outcomes.

The current work aims to develop a “hurricane risk calculator” which provides detailed and relevant information about potential hurricane wind impacts for a user’s specific location. In the initial version, slated to be ready by the 2018 hurricane season, a user will be able to enter in their street address (or geographical coordinates) into a web page and then view a dashboard-like interface with graphical and textual products that detail the expected magnitude and timing of potential wind impacts for the user's location. Initially, the tool will be driven using wind information from official sources, such as the NWS TCM Wind Tool (via the National Digital Forecast Database grids), the NHC Hurricane Wind Speed Probability product, and some other customized wind sources based on parametric modeling using the Geoscience Australia Tropical Cyclone Risk Model (TCRM). A key aspect of the dashboard will be to translate the projected wind impacts into terms easily understood by layman. One way this can be done is to explain what the projected wind impact means in terms of the potential damage to their residence. This translation process will reference American Society for Civil Engineers (ASCE 7-10) hurricane hazard simulation data (which is typically used to set local design wind speeds for coastal building codes) and then contextualize the wind risk in terms of the basic and ultimate wind speeds for the building category of the resident. The basic (or design) wind speed corresponds to the threshold at which damage may begin to occur to the structure. The ultimate wind speed corresponds to the threshold at which major structural failure starts to become likely. (Exact terminology and translation in the tool will be determined in consultation with experts from the structural engineering community). Additional future translation capabilities could include providing information about the potential likelihood and duration of power outages and the severity of tree damage.

An eventual goal is for the calculator to be driven by a fully probabilistic treatment of wind hazard potential that accounts for the trajectory and fetch of the wind over land, local site exposure, and topographical influences. Coupled with information about the resident’s structure class, age, and local building codes, the calculator may then be able to offer information about the expected range of damage to the resident’s structure as well as the probability that that structure may lose its life-protective ability. Importantly, this tool is not meant to supersede any evacuation orders made by local authorities. For residents outside of mandatory evacuation zones (e.g., in voluntary evacuation zones or residents who are well inland, but still facing considerable wind threat), this tool can better inform the key decision of whether to evacuate or shelter-in-place. It can also inform decisions such as if and when to put up protection (such as hurricane shutters, etc.).