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Synthesis of Knowledge of Extreme Fire Behavior: Volume I for Fire Managers

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United States Department of Agriculture Synthesis of Knowledge of Forest Service Pacific Northwest Extreme Fire Behavior: Research Station General Technical Volume I for Fire Managers Report PNW-GTR-854 November 2011 Paul A. Werth, Brian E. Potter, Craig B. Clements, Mark A. Finney, Scott L. Goodrick, Martin E. Alexander, Miguel G. Cruz, Jason A. Forthofer, and Sara S. McAllister A SUMMARY OF KNOWLEDGE FROM THE The Forest Service of the U.S. Department of Agriculture is dedicated to the principle of multiple use management of the Nation’s forest resources for sustained yields of wood, water, forage, wildlife, and recreation. Through forestry research, cooperation with the States and private forest owners, and management of the national forests and national grasslands, it strives—as directed by Congress—to provide increasingly greater service to a growing Nation. The U.S. Department of Agriculture (USDA) prohibits discrimination in all its programs and activities on the basis of race, color, national origin, age, disability, and where applicable, sex, marital status, familial status, parental status, religion, sexual orientation, genetic information, political beliefs, reprisal, or because all or part of an individual’s income is derived from any public assistance program. (Not all prohibited bases apply to all programs.) Persons with disabilities who require alternative means for communication of program information (Braille, large print, audiotape, etc.) should contact USDA’s TARGET Center at (202) 720-2600 (voice and TDD). To file a complaint of discrimination, write USDA, Director, Office of Civil Rights, Room 1400 Independence Avenue, SW, Washington, DC 20250-9410 or call (800) 795-3272 (voice) or (202) 720-6382 (TDD). USDA is an equal opportunity provider and employer. Authors Paul A. Werth is a fire weather meteorologist (retired), Northwest Interagency Coordination Center, 150 SW Harrison Street, Suite 400, Portland, OR 97201. Brian E. Potter is a research meteorologist, U.S. Department of Agriculture, Forest Service, Pacific Wildland Fire Sciences Laboratory, 400 N 34th St., Suite 201, Seattle, WA 98103. Craig B. Clements is an assistant professor of meteorology, San Jose State University, San José, CA 95192. Mark A. Finney is a research forester, Jason A. Forthofer is a mechanical engineer, and Sara S. McAllister is a research mechanical engineer, U.S. Department of Agriculture, Forest Service, Missoula Fire Sciences Laboratory, 5775 Highway 10 West, Missoula, MT 59808. Scott L. Goodrick is a research meteorologist, U.S. Department of Agriculture, Forest Service, Southern Research Station, 320 Green Street, Athens, GA 30602. Martin E. Alexander is an adjunct professor of wildland fire science and management, Department of Renewable Resources and Alberta School of Forest Science and Management, University of Alberta, Edmonton, AB T6G 2H1, Canada. Miguel G. Cruz is a senior research scientist, Bush Fire Dynamics and Applications, CSIRO Ecosystems Sciences–Climate Adaptation Flagship, GPO Box 284, Canberra, ACT 2601, Australia. Cover Photos Cover photos by Rick Trembath, USDA Forest Service (retired). Synthesis of Knowledge of Extreme Fire Behavior: Volume I for Fire Managers Paul A. Werth, Brian E. Potter, Craig B. Clements, Mark A. Finney, Scott L. Goodrick, Martin E. Alexander, Miguel G. Cruz, Jason A. Forthofer, and Sara S. McAllister U.S. Department of Agriculture, Forest Service Pacific Northwest Research Station Portland, Oregon General Technical Report, PNW-GTR-854 November 2011 Published in cooperation with: U.S. Department of Agriculture, Forest Service Southern Research Station GENERAL TECHNICAL REPORT PNW-GTR-841 This page was intentionally left blank. ii Abstract Werth, Paul A.; Potter, Brian E.; Clements, Craig B.; Finney, Mark A.; Goodrick, Scott L.; Alexander, Martin E.; Cruz, Miguel G.; Forthofer, Jason A.; McAllister, Sara S. 2011. Synthesis of knowledge of extreme fire behavior: volume I for fire managers. Gen. Tech. Rep. PNW-GTR-854. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 144 p. The National Wildfire Coordinating Group definition of extreme fire behavior (EFB) indicates a level of fire behavior characteristics that ordinarily precludes methods of direct control action. One or more of the following is usually involved: high rate of spread, prolific crown- ing/spotting, presence of fire whirls, and strong convection column. Predictability is difficult because such fires often exercise some degree of influence on their environment and behave erratically, sometimes dangerously. Alternate terms include “blow up” and “fire storm.” Fire managers examining fires over the last 100 years have come to understand many of the factors necessary for EFB development. This work produced guidelines included in current firefighter training, which presents the current methods of predicting EFB by using the crown fire model, which is based on the environmental influences of weather, fuels, and topography. Current training does not include the full extent of scientific understanding. Material in current training programs is also not the most recent scientific knowledge. National Fire Plan funds have sponsored newer research related to wind profiles’ influence on fire behavior, plume growth, crown fires, fire dynamics in live fuels, and conditions associated with vortex development. Of significant concern is that characteristic features of EFB depend on condi- tions undetectable on the ground, relying fundamentally on invisible properties such as wind shear or atmospheric stability. Obviously no one completely understands all the factors contributing to EFB because of gaps in our knowledge. These gaps, as well as the limitations as to when various models or indices apply should be noted to avoid application where they are not appropriate or war- ranted. This synthesis will serve as a summary of existing extreme fire behavior knowledge for use by fire managers, firefighters, and fire researchers. The objective of this project is to synthesize existing EFB knowledge in a way that connects the weather, fuel, and topographic factors that contribute to development of EFB. This synthesis will focus on the state of the science, but will also consider how that science is currently presented to the fire management community, including incident commanders, fire behavior analysts, incident meteorologists, National Weather Service office forecasters, and firefighters. It will seek to clearly delineate the known, the unknown, and areas of research with the greatest potential impact on firefighter protection. Keywords: Extreme fire behavior, fuels, fire behavior. Preface In 2008, the National Wildfire Coordinating Group (NWCG) Fire Behavior Committee (FBC) asked the Joint Fire Science Program (JFSP) to fund a synthesis and review of the scientific literature pertaining to extreme fire behavior (EFB). In September 2008, the JFSP announced a call for proposals that included a request for “an examination of the state of the science underlying predictions of extreme fire behavior, and an assessment of the appro- priate uses and limits of this information.” This document is the result of that request. In performing the review, it became progressively clearer that the concept of extreme fire behavior (EFB) is vaguely defined and means something different to everyone. The authors examined the official NWCG definition and solicited input from the management community to develop a definition that was both operationally useful and scientifically tractable. This definition and the initial stages of the review eventually led to the recogni- tion that some relevant topics had not been included in the original outline. Other topics from the original outline were expanded to include sections of their own. The authors communicated these changes to both the JFSP and the FBC as they arose. In those conversations, it became apparent that these two groups had different needs. The JFSP needed something for fire managers and others without the technical background of a fire behavior analyst. The FBC needed a document for fire behavior analysts that would allow them to better understand the use and limitations of the tools they now have and may have in the near future. To meet these two needs, this review has two parts. Volume 1 summarizes the state of the science for fire managers and firefighters with pertinent references to scientific papers. It is intended to be of use to anyone who works at or near the fireline. Volume 2 covers the same topics (with one exception) in more detail and includes information necessary for fire behavior analysts to understand what is scientifically known, what science lies behind the tools they have, and what the limitations are on scientific knowledge and tools. It includes more references to scientific literature. The one difference in topical content between the volumes is that volume 2 includes a chapter on fuel dynamics and volume 1 does not. As the study progressed, the scope of this topic led to the need to include more experts, and the short time available precluded that section from publication in volume 1. iv Summary A working definition of extreme fire behavior (EFB) was necessary for development of this synthesis. Because the subjective nature of four of the five properties of the EFB definition established by the National Wildfire Coordination Group makes the definition intractable for scientific purposes, the lead authors asked the fire behavior community
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