Lesson 1 Introducing the Enhanced Fujita Scale Dan

Lesson 1: Introducing the Enhanced Fujita Scale Dan Mc. Carthy ( NWS SPC) and Jim La. Due (NWS WDTB)

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

Motivation • EF-Scale to be used by the NWS starting 01 Feb, 2007 • More complex than F-Scale

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

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

Why the EF-Scale was created • Need more damage indicators • recalibrate winds associated with F-scale ratings • better correlate wind and rating • account for construction variability • Flexibility, Extensibility, Expandability The framed house is one of only a few F-scale damage indicators. 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?

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

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

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

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

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

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

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

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

How the winds were derived for each DOD • Possible Candidates – Structural analysis to determine resistance and theoretical failure modes – Simulation of tornado winds to produce structural damage – Expert Elicitation • Chosen method? – Expert Elicitation 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 Objectives: 2, EF-Scale methodology

Derive Wind Speeds by Expert Elicitation 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 Mc. Donald analyze results and present to experts for review Iterate again Experts revise their wind speeds Objectives: 2, EF-Scale methodology Present final estimates to forum for review

Degrees of Damage Note some consecutive DODs have larger overlap than others DOD Damage Description EXP LB UB 1 Threshold of visible damage 63 53 80 2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 79 63 97 3 Broken glass in doors and windows 96 79 114 4 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 97 81 116 5 Entire house shifts off foundation 121 103 141 6 Large sections of roof structure removed; most walls remain standing 122 104 142 7 exterior walls collapsed 132 113 153 8 Most walls collapsed except small interior rooms. 152 127 178 9 All walls collapsed 170 142 198 10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220 Example DODs for a Framed House DI (FR 12 or DI 2) Objectives: 3, EF-Scale structure

Degrees of Damage Note some consecutive DODs have larger overlap than others Damage Description EXP LB UB 1 Threshold of visible damage 63 53 80 2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 79 63 97 3 Broken glass in doors and windows 96 79 114 4 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 97 81 116 5 Entire house shifts off foundation 121 103 141 6 Large sections of roof structure removed; most walls remain standing 122 104 142 7 exterior walls collapsed 132 113 153 8 Most walls collapsed except small interior rooms. 152 127 178 9 All walls collapsed 170 142 198 10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220 Wind Speed (mph) DOD Example DODs for a Framed House DI (FR 12 or DI 2) Objectives: 2, methodology; 3, EF-Scale structure

Relating the F-scale with the EF-Scale • Need of historical continuity • 2 nd set of experts assigned F-scale ratings to the same damage descriptions • Median F-scale wind speeds compared to that of expected EFScale wind speeds Bill Bunting – NWSFO – Fort Worth, Texas Y = 0. 6246 x + 36. 393 Brian Peters – NWSFO – Calera, Alabama R 2 = 0. 9118 John Ogren – NWSFO – Indianapolis, Indiana Dennis Hull – NWSFO – Pendleton, Oregon F 5 to Tom Matheson. EF 5 NWSFO – Wilmington, North – threshold wind speed Carolina Brian Smith – NWSFO – Valley, Nebraska The F-Scale wind speed was converted from the fastest ¼ mi to a 3 sec gust. Objectives: 2, methodology; 4, EF vs F-Scale

F-Scale Converted to EF-Scale F Scale Wind Speed EF-Scale Wind Speed F 0 45 -78 EF 0 65 -85 F 1 79 -117 EF 1 86 -109 F 2 118 -161 EF 2 110 -137 F 3 162 -209 EF 3 138 -167 F 4 210 -261 EF 4 168 -199 F 5 262 -317 EF 5 200 -234 Wind speeds in mph, 3 -second gust Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

DOD to Wind Speed to EF-Scale Categories Wind Speed Ranges EF 0 65 -85 EF 1 EF 2 86 -110 111 -135 EF 3 136 -165 EF 4 166 -200 EF 5 >200 Wind speeds in mph, 3 -second gust Objectives: 3, EF-Scale structure

Comparing Beaufort, F, and Mach Scales These scales have wind speed defined first, impacts/damage were assigned to wind speeds. Beaufort: V = 1. 870 B 3/2 F – scale: V = 14. 1(F+2)3/2 Mach scale: V = (742 +1. 3)M M 1. 0 F 12 M 0. 8 mph mph M 0. 7 M 0. 6 F 5 F 4 B 1 B 3 B 5 B 7 B 9 F 3 B 11 F 0 B 17 F 2 F 1 0 1 2 3 4 5 6 7 8 9 10 11 12 Beaufort Scale Fujita Scale 0. 6 1. 0 Mach Scale Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

Comparing F and EF-Scales The EF-Scale is a damage scale: speeds were estimated from the damage M 1. 0 F 12 M 0. 8 M 0. 7 M 0. 6 EF-Scale 0 1 2 3 4 5 EF 5 B 1 B 3 B 5 B 7 B 9 EF 1 B 11 EF 0 EF 4 EF 3 F 4 EF 2 F 5 B 17 F 3 F 2 F 1 0 1 2 3 4 5 6 7 8 9 10 11 12 Beaufort Scale Fujita Scale 0. 6 1. 0 Mach Scale Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

DOD to Wind Speed to EF-Scale question DOD Damage Description – Framed House EXP LB UB 1 Threshold of visible damage 63 53 80 2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 79 63 97 3 Broken glass in doors and windows 96 79 114 4 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 97 81 116 5 Entire house shifts off foundation 121 103 141 6 Large sections of roof structure removed; most walls remain standing 122 104 142 7 exterior walls collapsed 132 113 153 8 Most walls collapsed except small interior rooms. 152 127 178 9 All walls collapsed 170 142 198 10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220 Quiz: What DOD best corresponds with this damage? Objectives: 3, EF-Scale structure

DOD to Wind Speed to EF-Scale review DOD Damage Description – Framed House EXP LB UB 1 Threshold of visible damage 63 53 80 2 Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding 79 63 97 3 Broken glass in doors and windows 96 79 114 4 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 97 81 116 5 Entire house shifts off foundation 121 103 141 6 Large sections of roof structure removed; most walls remain standing 122 104 142 7 exterior walls collapsed 132 113 153 8 Most walls collapsed except small interior rooms. 152 127 178 9 All walls collapsed 170 142 198 10 Destruction of engineered and/or well constructed residence; slab swept clean 200 162 220 Expected wind 97 mph Objectives: 3, EF-Scale structure

EF-Scale answer EF-Scale Categories Wind Speed Ranges EF 0 65 -85 EF 1 EF 2 86 -110 111 -135 EF 3 136 -165 EF 4 166 -200 EF 5 >200 Wind Speed in mph, 3 -Second gust Objectives: 3, EF-Scale structure

Strengths of EF-Scale • EF-Scale • F 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 – 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

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

Summary: Lesson 1 • EF-Scale created to provide more DIs, more realistic wind speeds • EF-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 winds significantly lower than F-scale for EF (F 3) and higher • EF-Scale is complicated requiring a longer time for familiarization Objectives: 1 -6

References and suggested reading Mc. Donald, 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, 1997. 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/CR 6372, UCRL-ID 122160, Vol. I, Lawrence Livermore National Laboratory, Livermore, CA, 131 pp. Suggested reading: A Recommendation for the Enhanced Fujita Scale: http: //www. spc. noaa. gov/efscale/

In Lesson 2 • Lesson 2 provides you a chance to use the EFScale on some damage tracks

Contacts • If you have any questions about this lesson, contact – Jim La. Due, James. G. La. Due@noaa. gov – Dan Mc. Carthy, Daniel. Mc. Carthy@noaa. gov