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United States Department of Agriculture Synthesis of Knowledge of Extreme Fire Behavior: Volume 2 for Fire Behavior Specialists, Researchers, and Meteorologists Paul A. Werth, Brian E. Potter, Martin E. Alexander, Miguel G. Cruz, Craig B. Clements, Mark A. Finney, Jason M. Forthofer, Scott L. Goodrick, Chad Hoffman, W. Matt Jolly, Sara S. McAllister, Roger D. Ottmar, and Russel A. Parsons Forest Pacific Northwest General Technical Report March Service Research Station PNW-GTR-891 2016 Pacific Northwest Research Station Web site http://www.fs.fed.us/pnw Telephone (503) 808-2592 Publication requests (503) 808-2138 FAX (503) 808-2130 E-mail [email protected] Mailing address Publications Distribution Pacific Northwest Research Station P.O. Box 3890 Portland, OR 97208-3890 A SUMMARY OF KNOWLEDGE FROM THE Authors Paul A. Werth is a fire weather meteorologist (retired), Northwest Interagency Coordina- tion 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. Martin E. Alexan- der is an adjunct professor of wildland management, Department of Renewable Resources and Alberta School of Forest Science and Management, University of Alberta, Edmonton, AB T6G 2H1, Canada. Craig B. Clements is an assistant professor of meteorology, San Jose State University, San Jose, CA 95192. 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. Mark A. Finney is a research for- ester, Jason M. Forthofer is a mechanical engineer, W. Matt Jolly is an ecologist, Sara S. McAllister is a research mechanical engineer, and Russel A. Parsons is a research ecolo- gist, 5775 US West Highway 10, Missoula, MT 59808. Scott L. Goodrick is a research me- teorologist, U.S. Department of Agriculture, Forest Service, Southern Research Station, 320 Green Street, Athens, GA 30602. Chad Hoffman is an instructor, Wildland Fire Program, College of Natural Resources, University of Idaho, Moscow, ID 83844. Roger D. Ottmar is a research forester, U.S. Department of Agriculture, Forest Service, Pacific Wildland Fire Sciences Laboratory, 400 N 34th St., Suite 201, Seattle, WA 98103. (Werth and Potter were lead co-authors on this project. Other authors are listed alphabetically per location.) Funding for the printing of this volume was provided by the Joint Fire Science Program Project 09-5-03-1. The use of trade or firm names in this publication is for reader information and does not imply endorcement by the U.S. Department of Agriculture of any product or service. Abstract Werth, Paul A.; Potter, Brian E.; Alexander, Martin E.; Clements, Craig B.; Cruz, Miguel G.; Finney, Mark A.; Forthofer, Jason M.; Goodrick, Scott L.; Hoffman, Chad; Jolly, W. Matt; McAllister, Sara S.; Ottmar, Roger D.; Parsons, Russell A. 2016. Synthesis of knowledge of extreme fire behavior: volume 2 for fire behavior specialists, researchers, and meteorologists. Gen. Tech. Rep. PNW-GTR-891. Portland, OR: U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. 258 p. The National Wildfire Coordinating Group’s definition of extreme fire behavior 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 dif- ficult as such fires often influence their environment to some degree 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 neces- sary for extreme fire behavior development. This effort produced guidelines included in current firefighter training, which presents the current methods of predicting extreme fire behavior 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 nor does it include the most recent scientific knowledge. National Fire Plan funds and the Joint Fire Science Program 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 extreme fire behavior depend on conditions undetectable on the ground, namely invisible properties such as wind shear or atmospheric stability. No one completely understands all the factors contributing to extreme fire behavior 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 appropri- ate or warranted. This synthesis summarizes existing extreme fire behavior knowledge. It consists of two volumes. Volume 1 is for fire managers, firefighters, and others in the fire community who are not experts or specialists in fire behavior but need to understand the basics of extreme fire behavior. Volume 2 is more technical and is intended for fire behav- iorists and fire researchers. The objective of this project is to synthesize existing extreme fire behavior knowledge in a way that connects the weather, fuel, and topographic factors that contribute to develop- ment of extreme fire behavior. This synthesis focuses on the state of the science but also considers 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. The synthesis seeks to delineate the known, the unknown, and areas of research with the greatest potential impact on firefighter protection. Keywords: Extreme fire behavior, fuels, fire behavior. ii Preface In 2008, the National Wildfire Coordinating Group (NWCG) Fire Behavior Com- mittee (FBC) asked the Joint Fire Science Program (JFSP) to fund a synthesis and review of the scientific literature pertaining to extreme fire behavior. 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 behav- ior, and an assessment of the appropriate 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 is vaguely defined and means something different to every- one. 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 recognition that some relevant topics had not been included in the original outline. Other topics from the original outline 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 fire line. 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. 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. Summary A working definition of extreme fire behavior was necessary to develop this syn- thesis. Because the subjective nature of the National Wildfire Coordination Group’s definition of extreme fire behavior makes it intractable for scientific purposes, the iii lead authors asked the fire behavior community for input on possible definitions of extreme fire behavior and examples of phenomena they considered extreme fire behavior. The only coherent theme was that extreme fire behavior is not steady state. After discussing responses, the authors agreed on the following working definition of extreme fire behavior: “Fire spread other than steady surface spread, especially when it involves rapid increases.” This definition does not emphasize any one element of the behavior triangle. The state of the science at present can be summed up as follows: • Fire is three dimensional and is not steady state. • The tools available to us today are two dimensional and are predomi- nantly steady state. • Additional research into extreme fire behavior may one day result in development of three-dimensional tools. Complexity It is imperative that fire managers understand that much extreme fire behavior happens where it cannot be seen. Multiple factors come into play, and not all factors need be present for extreme fire behavior to occur, nor must one factor be present in every case. Extreme fire behavior can occur on any scale, great or small, in any fuel type, and at any time of the day or night. At no time or under any circumstance should fire managers assume that extreme fire behavior will not occur.
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