Natural Hazards Project Update

Next-Generation Severe Weather Forecasting and Communication

A new concept called Forecasting a Continuum of Environmental Threats (FACETs) aims to enhance weather forecasting with high-resolution probabilistic hazard information.

By Lans P. Rothfusz, Christopher Karstens, and Douglas Hilderband

Despite advances in the hazardous weather predictive skills of forecasters from the National Oceanic and Atmospheric Administration’s (NOAA) National Weather Service (NWS) [Simmons and Sutter, 2011], the underlying methodologies used to generate severe weather watches (i.e., announcements that the potential for severe weather exists) and warnings (i.e., announcements that severe weather conditions are occurring or imminent) have changed little since they were first issued in 1965. The resulting text-based, deterministic (i.e., a single, most accurate value) messages lack the detail and flexibility to match the technology, science, diversity, lifestyles, and vulnerability of society today.

In conjunction with NOAA’s Weather-Ready Nation goals, the National Severe Storms Laboratory (NSSL) and NWS are jointly addressing these limitations with a proposed new concept called Forecasting a Continuum of Environmental Threats (­FACETs). FACETs proposes to enhance NWS deterministic products (Figures 1a and 1c) with ­high-​­resolution forecasts of probabilistic hazard information (PHI) [Stumpf et al., 2008] conveyed on ­fine-​­resolution (≤2 kilometers) grids (Figures 1b and 1d).


FACETs is designed to address all environmental threats (including regional phenomena, airborne toxins, hazmat events, etc.) extending along the continua of time (days to seconds) and space (global to local). However, for brevity, this brief report will describe FACETs in the context of thunderstorm phenomena. More information is available from Rothfusz et al. [2014].

The Facets of FACETs

To address the proposed ­watch/​­warning paradigm change methodically and holistically, FACETs is composed of seven inter­related “facets.”

Facet 1: Method and Manner. This initial facet describes the basic nature of NWS hazardous weather messages, which are presently deterministic, text-based, and ­product-​­centric. FACETs would shift to providing a continuously updated stream of ­high-​­resolution PHI forecasts. PHI, in this context, is defined as the probability of a given weather phenomenon within a specified spatial and temporal range. For example, PHI might describe the probability of a ­5-centimeter hailstone occurring within 1 kilometer of a location in the next 30 minutes. Shifting to this new starting point will affect the entire downstream forecast process, so ­FACETs attempts to address the process holistically.

Facet 2: Observations and Guidance. This facet comprises the tools and data used to make forecast decisions (radar, satellites, meteorological observations, numerical weather prediction, statistical guidance, ­forecaster-​­to-​­forecaster interaction, etc.). An important FACETs goal is to capitalize on future (and current) probabilistic storm-scale (resolution ≤2 kilometers) output generated by ­multi-​­member numerical weather prediction ensembles such as ­Warn-​­on-​­Forecast [Stensrud et al., 2009] and others. In such ensembles, the frequency of threshold exceedances determines the probabilities used in PHI. Using the PHI tool (see Facet 4 below), a forecaster would augment this guidance on the basis of observational data.

Facet 3: The Forecaster. In the FACETs paradigm, the forecaster remains a vital component of the process by adjusting PHI grids on the basis of expertise and observational interpretation. FACETs will keep the forecaster “over the grids,” adding value to the guidance through their knowledge and skills. To move from deterministic to probabilistic practices, however, a culture change is needed within the NWS, supported by training, policy, leadership, and end user support.

Facet 4: Threat Grid Tools. NSSL is developing a prototype PHI tool for generating ­hazard-​­specific probabilities that tracks storms using geospatial “objects” with self-describing attributes and trends. An object is defined here as an area encompassing the current and predicted spatial extent of a given hazard. The attributes describe the current and future character of the hazard, including motion, motion uncertainty, and probability of occurrence. As the objects update, their associated properties provide mineable, ­decision-​­supporting, location-specific forecast information such as time of arrival, time of departure, event duration, and probability of occurrence. In addition, legacy NWS ­watches/​­warnings would be derived from the exceedance of predefined probability thresholds. Future research will determine how such information will be derived.

Facet 5: Usable Output. This facet addresses the format, content, technology, and media by which PHI is communicated. Given the grid-based nature of PHI and its rapid update cycling, ­data-​­mining techniques and display technologies are envisioned by which a wide variety of decision makers can be assisted in specific and timely ways (GPS-based NOAA weather radios, impact probabilities derived from geographic information system databases, smartphone apps with ­user-​­specifiable alerts, etc.). FACETs lays the groundwork for significant (and as yet unknown) public and private sector innovations in hazard communication.

Facet 6: Effective Response. Facet 6 relates to PHI recipients’ responses (or nonresponses), including all factors leading up to and after that (non)­response (e.g., education, preparedness, situational awareness, understanding, response, and recovery). Social and behavioral scientists will contribute to FACETs development to ensure effective interpretation and response by PHI recipients (sophisticated or otherwise).

Facet 7: Verification. The final facet pertains to the quantitative and qualitative measures used to validate the effectiveness of the hazard forecasting program and the appropriateness of response. As opposed to deterministic forecasts verified by a single occurrence of a forecast phenomenon (the current system), PHI places forecasts and observations on the same geospatial grid, allowing for new metrics such as Brier scores (with reliability and resolution statistics), false alarm ­duration/​­area, ­site-​­specific lead/end time, and others. Verification of human response to PHI is another component of this facet and represents an entirely new approach for NWS. Such measures and data collection techniques would need to be devised through collaboration with social and behavioral scientists and key stakeholders.

Opening the door to new verification methodologies will prompt new questions (­use/​­presentation of results, ​­national/​­regional/local comparisons, sample size considerations, etc.). A key goal of FACETs, however, is to identify (and use) the measures necessary to make forecasts as effective as possible.

Encouraging Dialogue on a New Paradigm

The FACETs paradigm described above affords a continuous stream of localized, relevant, actionable information for ­life-​­protective decisions. The FACETs team encourages dialogue and questions that can help guide the work necessary to make this comprehensive, ­next-​­generation paradigm a success.

A “master plan” for FACETs research, development, and implementation will be completed in 2014 and will guide all activities related to changing the ­watch/​­warning paradigm of the United States. First operational iterations of FACETs concepts are anticipated in 2019.


Funding for this work was provided by NOAA’s Office of Oceanic and Atmospheric Research’s Special ­Early-​Stage Experimental or Development Project.


Rothfusz, L. P., P. T. Schlatter, E. Jacks, and T. M. Smith (2014), A future warning concept: Forecasting a Continuum of Environmental Threats (­FACETs), paper presented at Second Symposium on Building a ­Weather-​­Ready Nation: Enhancing Our Nation’s Readiness, Responsiveness, and Resilience to High Impact Weather Events, Am. Meteorol. Soc., Atlanta, Ga., 2–6 Feb. [Available at ams​.­confex​.com/​ams/​­94Annual/​­webprogram/​­Paper232407​.html.]

Simmons, K. M., and D. Sutter (2011), Economic and Societal Impacts of Tornadoes, 282 pp., Am. Meteorol. Soc., Boston, Mass.

Stensrud, D. J., et al. (2009), ­Convective-​­scale ­Warn-​­on-​­Forecast system: A vision for 2020, Bull. Am. Meteorol. Soc., 90, 1487–1499.

Stumpf, G. J., T. M. Smith, K. Manross, and D. L. Andra (2008), The Experimental Warning Program 2008 Spring Experiment at the NOAA Hazardous Weather Testbed, paper presented at 24th Conference on Severe Local Storms, Am. Meteorol. Soc., Savannah, Ga., 27–31 Oct.


—Lans P. Rothfusz, National Severe Storms Laboratory, Office of Oceanic and Atmospheric Research (OAR), National Oceanic and Atmospheric Administration (NOAA), Norman, Okla.; ­email: [email protected]; Christopher Karstens, Cooperative Institute for Mesoscale Meteorological Studies, The University of Oklahoma, Norman, and National Severe Storms Laboratory, OAR, NOAA, Norman, Okla.; and Douglas Hilderband, National Weather Service, NOAA, Silver Spring, Md.

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