Assessment of NOAA National Weather Service Methods to Warn for Extreme Heat Events

Recent climate studies have predicted a future with longer, more intense, and more frequent heat events. Evolving challenges presented by this paradigm necessitate an assessment of current efforts to warn for extreme heat events. NOAA's National Weather Service (NWS) Weather Forecast Offices (WFOs) issue Excessive Heat Watch, Excessive Heat Warning, and Heat Advisory products as conditions warrant. In the fall of 2013 the NWS conducted an internal assessment with its WFOs to 1) document variations in the usage of heat-based watch, warning, and advisory hazard messages (products) across the country; 2) learn about the degree to which locally developed criteria are applied to forecaster decision-making processes in issuing these products; and 3) gather ideas for enhancing communication of expected excessive heat events in general. Survey responses indicate that WFOs selectively use one or a combination of products, and that various methodologies are used to develop criteria for issuing heat products. Given that forecasters use meteorological and nonmeteorological factors when deciding to issue heat products, forecaster judgment is a crucial element of the warning process. Results also revealed partner confusion due to inconsistent heat product issuance criteria. Suggestions were made for eliminating or revising existing products and policies, or creating new products, policies, or issuance criteria. Results of the survey led the NWS to investigate approaches for achieving higher levels of consistency in heat product issuance criteria, and to engage health partners to examine how heat product issuance criteria could incorporate the known health impacts of heat exposure.