The Effectiveness of the Hurricane Threats and Impacts Product Suite in Support of Community Decision-Making during the 2018 Hurricane Season

During high impact hurricane situations, it is essential for local forecast offices to assess the associated threats and message the potential impacts. To be effective, the information must be targeted, actionable, and timely. The intent is not to provide a perfect forecast of each respective hazard, but to change the outcome of the event by recommending to threatened populations the extent to which local preparations should be made knowing that the forecast isn’t perfect. This is best accomplished by leveraging objective-based probability guidance to account for forecast error and offering a responsible safety margin to community decision-makers and the public at large. Emergency managers understand the vulnerability of their jurisdictions and the measure of risk that can be reasonably tolerated during hurricanes. Yet the use of exceedance-based probabilities is not always intuitive, especially in stressful situations. For this reason, the National Weather Service has fostered the development of the Hurricane Threats and Impacts (HTI) product suite. Forecasters use HTI tools to assess the potential magnitude and likelihood of occurrence of a tropical hazard to yield graphics which depict increasing threat as stratified by colorized levels. For each threat level (and for each hazard (wind, surge, rain, tornadoes)), a descriptive statement of the potential impacts is provided. The statements have been optimized and are unique to the region of interest. It represents an effort to emphasize the hurricane footprint relative to the hazards to properly message potential impacts irrespective of a hurricane category in the Saffir-Simpson scale. This presentation will reacquaint the audience with the origins and background of the HTI initiative, and outline its development over recent years. It will then consider its effectiveness during the 2017 and 2018 hurricane seasons relative to community decision-making in preparation for Hurricane Irma as it approached Florida, Hurricane Florence in the Carolinas, Hurricane Michael in the Florida Panhandle, and Hurricane Lane in Hawaii. In context, examples will be shared that highlight the strengths and limitations of the HTI hazard information for wind, storm surge, and flooding rain. Development of the HTI website will also be discussed.