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Lesson 1: Introducing the Enhanced Fujita Scale Dan McCarthy ( NWS SPC) and Jim LaDue (NWS WDTB)

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Presentation on theme: "Lesson 1: Introducing the Enhanced Fujita Scale Dan McCarthy ( NWS SPC) and Jim LaDue (NWS WDTB)"— Presentation transcript:

1 Lesson 1: Introducing the Enhanced Fujita Scale Dan McCarthy ( NWS SPC) and Jim LaDue (NWS WDTB)

2 Goal and Scope of Training The Goal of this Training is to effectively integrate the EF-Scale into the post storm damage assessment.The Goal of this Training is to effectively integrate the EF-Scale into the post storm damage assessment. Two lessons, each followed by a quizTwo lessons, each followed by a quiz –Comparison of the EF and F-Scale –Using the EF-Scale to estimate tornado strength

3 MotivationMotivation EF-Scale to be used by the NWS starting 01 Feb, 2007EF-Scale to be used by the NWS starting 01 Feb, 2007 More complex than F-ScaleMore complex than F-Scale

4 Lesson 1: Learning Objectives 1.Understand why the EF-Scale was created 2.Identify the methodology in creating the EF-Scale. 3.Understand the structure of the EF-Scale 4.Identify differences between the EF- and F-Scale 5.Understand the strengths of the EF-Scale 6.Understand the limitations of the EF-Scale

5 Performance Objective Apply the strengths and limitations of the EF-Scale when rating damage produced by a tornadoApply the strengths and limitations of the EF-Scale when rating damage produced by a tornado

6 Why the EF-Scale was created Need more damage indicatorsNeed more damage indicators recalibrate winds associated with F-scale ratingsrecalibrate winds associated with F-scale ratings better correlate wind and ratingbetter correlate wind and rating account for construction variabilityaccount for construction variability Flexibility, Extensibility, ExpandabilityFlexibility, Extensibility, Expandability Evidence indicates a well constructed house can be blown away by winds much less than 260 mph (. Evidence indicates a well constructed house can be blown away by winds much less than 260 mph ( Phan and Simiu,2003). Objectives: 1, Why the EF-Scale? The framed house is one of only a few F-scale damage indicators.

7 EF-Scale history: Steering Committee Organize a Steering Committee (2001) Jim McDonald - TTU Joe Schaefer - SPC Brian Smith, NWS OAX Michael Riley - NIST Objectives: 2, Methodology Kishor Mehta -TTU Don Burgess – NSSL

8 The Steering Committee Organizes a Forum Led by Wind Science and Engineering Center, Texas Tech University, 7-8 March 2001Led by Wind Science and Engineering Center, Texas Tech University, 7-8 March 2001 ObjectivesObjectives –Representative group of users –ID key issues –Make recommendations –Develop a strategy Objectives: 2, Methodology

9 The forum identifies EF-Scale development strategies Identify additional Damage Indicators (DI)sIdentify additional Damage Indicators (DI)s Correlate damage to wind speedCorrelate damage to wind speed –Degrees of Damage (DOD) for each DI Preserve the historical databasePreserve the historical database Seek input from usersSeek input from users Maximize usabilityMaximize usability Objectives: 2, Methodology

10 EF-Scale Damage Indicators (DIs) 28 DIs were identified by the Steering Committee28 DIs were identified by the Steering Committee DIs and DODs can be added or modifiedDIs and DODs can be added or modified Each DI has several Degrees of Damage (DOD)Each DI has several Degrees of Damage (DOD) Objectives: 2, methodology; 3, EF-Scale structure Framed house Single wide mobile home Small Retail Building

11 28 Damage Indicators Objectives: 3, EF-Scale structure Residences Commercial/retail structures Schools Professional buildings Metal buildings/canopies Towers/poles Vegetation

12 DODDamage DescriptionEXPLBUB 1Threshold of visible damage ??? 2Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 3Broken glass in doors and windows 4Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport 5Entire house shifts off foundation 6Large sections of roof structure removed; most walls remain standing 7exterior walls collapsed 8Most walls collapsed except small interior rooms. 9All walls collapsed 10Destruction of engineered and/or well constructed residence; slab swept clean Degrees of Damage DOD for a Framed House, FR12 or DOD2 Objectives: 2, methodology; 3, EF-Scale structure

13 Reason behind an upper and lower bound wind speed EXP: Design exhibits typical construction Wind Speed (mph) Objectives: 2, methodology; 3, EF-Scale structure

14 Reason behind an upper and lower bound wind speed (contd) EXP: Design exhibits typical construction UB: Design exceeds codes for typical US home, better than average load path. LB: Design fails to meet US building codes, poor maintenance and/or load path Wind Speed (mph) Objectives: 2, methodology; 3, EF-Scale structure

15 How the winds were derived for each DOD Possible CandidatesPossible Candidates –Structural analysis to determine resistance and theoretical failure modes – –Simulation of tornado winds to produce structural damage – –Expert Elicitation Chosen method? – –Expert Elicitation Objectives: 2, EF-Scale methodology Chosen Experts: Greg Forbes – Meteorologist, TWC Don Burgess – Meteorologist, NSSL Doug Smith – Engineer, TTU Tim Reinhold – Engineer, Clemson University Tom Smith – Architect, Consultant Tim Marshall – Meteorologist/Engineer, Haag Engineers

16 Derive Wind Speeds by Expert Elicitation Objectives: 2, EF-Scale methodology Describe the DIs and DODs and present to experts Train the experts in elicitation process Experts individually estimate wind speeds for each DOD Mehta and McDonald analyze results and present to experts for review Experts revise their wind speeds Iterate again Present final estimates to forum for review

17 Degrees of Damage DODDamage DescriptionEXPLBUB 1Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing exterior walls collapsed Most walls collapsed except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence; slab swept clean Objectives: 3, EF-Scale structure Example DODs for a Framed House DI (FR12 or DI2) Note some consecutive DODs have larger overlap than others DODDamage DescriptionEXPLBUB 1Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing exterior walls collapsed Most walls collapsed except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence; slab swept clean

18 Degrees of Damage DODDamage DescriptionEXPLBUB 1Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing exterior walls collapsed Most walls collapsed except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence; slab swept clean Example DODs for a Framed House DI (FR12 or DI2) Note some consecutive DODs have larger overlap than others Wind Speed (mph) Objectives: 2, methodology; 3, EF-Scale structure

19 Relating the F-scale with the EF-Scale Need of historical continuityNeed of historical continuity 2 nd set of experts assigned F-scale ratings to the same damage descriptions2 nd set of experts assigned F-scale ratings to the same damage descriptions Median F-scale wind speeds compared to that of expected EF-Scale wind speedsMedian F-scale wind speeds compared to that of expected EF-Scale wind speeds Objectives: 2, methodology; 4, EF vs F-Scale The F-Scale wind speed was converted from the fastest ¼ mi to a 3 sec gust. Bill Bunting – NWSFO – Fort Worth, Texas Brian Peters – NWSFO – Calera, Alabama John Ogren – NWSFO – Indianapolis, Indiana Dennis Hull – NWSFO – Pendleton, Oregon Tom Matheson – NWSFO – Wilmington, North Carolina Brian Smith – NWSFO – Valley, Nebraska Y = x R 2 = F5 to EF5 threshold wind speed

20 F-Scale Converted to EF-Scale F Scale Wind Speed EF-Scale F045-78EF F EF F EF F EF F EF F EF Wind speeds in mph, 3-second gust Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

21 DOD to Wind Speed to EF-Scale EF-Scale Categories Wind Speed Ranges EF EF EF EF EF EF5>200 Objectives: 3, EF-Scale structure Wind speeds in mph, 3-second gust

22 Comparing Beaufort, F, and Mach Scales Beaufort Scale Fujita Scale Mach Scale B1 B3 B5 B7 B9 B11 F0 F1 F2 F3 F4 F5 F12 M1.0 M0.6 M0.7 M0.8 B17 Beaufort: V = 1.870B 3/2 mph F – scale: V = 14.1(F+2) 3/2 mph Mach scale: V = ( )Mmph These scales have wind speed defined first, impacts/damage were assigned to wind speeds. Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

23 Comparing F and EF-Scales Beaufort Scale Fujita Scale Mach Scale B1 B3 B5 B7 B9 B11 F0 F1 F2 F3 F4 F5 F12 M1.0 M0.6 M0.7 M0.8 B17 EF0 EF1 EF2 EF3 EF4 EF EF-Scale The EF-Scale is a damage scale: speeds were estimated from the damage Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

24 DOD to Wind Speed to EF-Scale question DODDamage Description – Framed HouseEXPLBUB 1 Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing exterior walls collapsed Most walls collapsed except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence; slab swept clean Objectives: 3, EF-Scale structure Quiz: What DOD best corresponds with this damage?

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26 DOD to Wind Speed to EF-Scale review DODDamage Description – Framed HouseEXPLBUB 1 Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (>20%); collapse of chimney; garage doors collapse inward or outward; failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing exterior walls collapsed Most walls collapsed except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence; slab swept clean Objectives: 3, EF-Scale structure Expected wind 97 mph

27 EF-Scale answer EF-Scale Categories Wind Speed Ranges EF EF EF EF EF EF5>200 Wind Speed in mph, 3-Second gust Objectives: 3, EF-Scale structure

28 Strengths of EF-Scale EF-ScaleEF-Scale –28 DIs –Accounts for differences of structural integrity within a DI –Wind speeds determined from damage –Continuity from the F-scale –Expandibility, Flexibility, Extensibility F ScaleF Scale –Only a Couple DIs –No accounting for differences of structural integrity within a DI –Wind speeds not derived from damage Objectives: 5, EF-Scale strengths

29 EF-Scale limitations Change in scale may introduce artifacts into the historical recordChange in scale may introduce artifacts into the historical record ComplicatedComplicated Wind speeds subject to change for each ratingWind speeds subject to change for each rating No function relating wind speed to ratingNo function relating wind speed to rating Debate continues about wind speed assignmentsDebate continues about wind speed assignments Objectives: 6, EF-Scale limitations

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31 Summary: Lesson 1 EF-Scale created to provide more DIs, more realistic wind speedsEF-Scale created to provide more DIs, more realistic wind speeds EF-Scale winds were estimated using expert elicitationEF-Scale winds were estimated using expert elicitation EF-Scale contains 28 DIs, each with several DODs ranging from first damage to destruction or if the estimated wind speeds correspond to an EF 5 rating.EF-Scale contains 28 DIs, each with several DODs ranging from first damage to destruction or if the estimated wind speeds correspond to an EF 5 rating. EF-Scale winds significantly lower than F-scale for EF (F3) and higherEF-Scale winds significantly lower than F-scale for EF (F3) and higher EF-Scale is complicated requiring a longer time for familiarizationEF-Scale is complicated requiring a longer time for familiarization Objectives: 1-6

32 References and suggested reading McDonald, J.R. and K.C. Mehta, 2001: Summary report of the Fujita Scale forum. Wind Science and Engineering, Texas Tech University, Lubbock, TX, 36 pp. Phan, L.T. and E. Simiu, 1998: The Fujita tornado intensity scale: a critique based on observations of the Jarrell tornado of May 27, NIST Tech. Note 1426, U.S. Department of Commerce, Gaithersburg, MD, 20 pp. SSHAC, 1997: Recommendations for probabilistic seismic hazard analysis: guidelines on uncertainty and use of experts, NUREG/CR6372, UCRL-ID , Vol. I, Lawrence Livermore National Laboratory, Livermore, CA, 131 pp. Suggested reading: A Recommendation for the Enhanced Fujita Scale:

33 In Lesson 2 Lesson 2 provides you a chance to use the EF- Scale on some damage tracksLesson 2 provides you a chance to use the EF- Scale on some damage tracks

34 ContactsContacts If you have any questions about this lesson, contactIf you have any questions about this lesson, contact –Jim LaDue, –Dan McCarthy,


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