Effective Conveyance of Hurricane Threats and Potential Impacts

“When hurricane watches or warnings are issued for an area, to what extent should emergency action plans be implemented to proportionally meet the current situation?”

In order to minimize the loss of life and reduce property damage during hurricane and tropical storm emergencies, this question must be thoughtfully and recurringly addressed. Under-preparation needlessly places a threatened population at greater risk, while excessive over-preparation exhausts vital resources. Having up-to-date threat assessments for each hurricane hazard combined with corresponding statements of potential impacts can effectively convey information useful for emergency planning and decision making processes. This is especially true when such information is presented graphically. The purpose of the National Weather Service's Tropical Cyclone Threat/Impacts Graphics (TCIG) initiative is to facilitate the proportionate implementation of prepared action plans by emergency managers, businesses, and families whenever hurricanes or tropical storms threaten. In part, this is accomplished by coastal Weather Forecast Offices (WFOs) who provide threat maps of associated hazards. The individual hazards include wind, storm surge, flooding rain (from over-abundant rainfall and runoff), and tornadoes. For each tropical cyclone hazard, a threat assessment scheme is programmed within a gridded forecast tool. The tools employ a combination of deterministic and probabilistic forecast guidance to derive a practical, least regret threat depiction for the product user. This assessment perspective is sometimes referred to as the reasonable, worst case scenario and is needed by decision makers to safely account for inherent forecast error within emergency action plans. Through the use of colorized maps that contour levels of threat, the plausibility of whether or not specified hazard thresholds will be exceeded is readily ascertained. The maps may be viewed according to each WFO's area of responsibility for local users or mosaiced together for state, regional, and national users. To help with information relevance, descriptive statements of potential impacts are also provided. They describe the damage that would be realized if the assessed worst case were to actually occur. Generalized statements are offered by default and are useful for course interpretation. More detailed descriptions, unique to each WFO's area or responsibility, are also made available. Collectively, the suite of threat assessment maps accompanied by potential impact statements is a powerful decision-making guide.

The NWS has been experimenting with TCIG concepts for several years among coastal WFOs from Brownsville, TX to Caribou, ME. Messaging designs are being finalized based on recent studies and focus group surveys conducted by social scientists with the NWS is moving toward official implementation in 2015. This presentation will describe a short history behind this effort, development of the concept, provide examples of its applications, and provide an update on the progress and status.