Lesson 1: Introducing the Enhanced Fujita Scale

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.
• Two lessons, each followed by a quiz
• Comparison of the EF and F-Scale
• Using the EF-Scale to estimate tornado strength

3
Motivation

• EF-Scale to be used by the NWS starting 01 Feb,
  2007
• More 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 tornado

6
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?
7
EF-Scale history Steering Committee
Organize a Steering Committee (2001)
Michael Riley - NIST
Brian Smith, NWS OAX
Joe Schaefer - SPC
Jim McDonald - TTU
Don Burgess NSSL
Kishor Mehta -TTU
Objectives 2, Methodology
8
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
9
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
10
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
11
28 Damage Indicators
Residences
Commercial/retail structures
Schools
Professional buildings
Metal buildings/canopies
Towers/poles
Vegetation
Objectives 3, EF-Scale structure
12
Degrees of Damage
DOD Damage Description EXP LB UB
1 Threshold of visible damage ? ? ?
2 Loss of roof covering material (lt20), 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 (gt20) 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, 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
Objectives 2, methodology 3, EF-Scale
structure
14
Reason behind an upper and lower bound wind speed
(contd)
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
15
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
16
Derive Wind Speeds by Expert Elicitation
Describe the DIs and DODs and present to experts
Experts individually estimate wind speeds for
each DOD
Train the experts in elicitation process
Mehta and McDonald analyze results and present to
experts for review
Iterate again
Present final estimates to forum for review
Experts revise their wind speeds
Objectives 2, EF-Scale methodology
17
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 (lt20), 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 (gt20) 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
DOD Damage Description EXP LB UB
1 Threshold of visible damage 63 53 80
2 Loss of roof covering material (lt20), 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 (gt20) 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 (FR12 or DI2)
Objectives 3, EF-Scale structure
18
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 (lt20), 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 (gt20) 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 (FR12 or DI2)
Objectives 2, methodology 3, EF-Scale
structure
19
Relating the F-scale with the EF-Scale

• Need of historical continuity
• 2nd 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 speeds

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
F5 to EF5 threshold wind speed
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
20
F-Scale Converted to EF-Scale
F Scale Wind Speed EF-Scale Wind Speed
F0 45-78 EF0 65-85
F1 79-117 EF1 86-109
F2 118-161 EF2 110-137
F3 162-209 EF3 138-167
F4 210-261 EF4 168-199
F5 262-317 EF5 200-234
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
EF0 65-85
EF1 86-110
EF2 111-135
EF3 136-165
EF4 166-200
EF5 gt200
Wind speeds in mph, 3-second gust
Objectives 3, EF-Scale structure
22
Comparing Beaufort, F, and Mach Scales
These scales have wind speed defined first,
impacts/damage were assigned to wind speeds.
M1.0
F12
M0.8
Beaufort V 1.870B3/2 mph F scale
V 14.1(F2)3/2 mph Mach scale V (742
1.3)M mph
M0.7
M0.6
F5
B17
F4
F3
B11
B9
F2
B7
F0
B5
F1
B3
B1
1
2
3
4
5
6
7
8
9
0
10
11
12
Fujita Scale
1
2
3
4
5
6
7
8
9
10
11
12
0
0.6
1.0
Mach Scale
Beaufort Scale
Objectives 3, EF-Scale structure 4, EF vs
F-Scale
23
Comparing F and EF-Scales
The EF-Scale is a damage scale speeds were
estimated from the damage
M1.0
F12
M0.8
M0.7
M0.6
EF-Scale
EF5
F5
EF4
B17
EF3
F4
EF2
EF1
F3
B11
EF0
B9
F2
B7
B5
F1
B3
B1
F0
1
2
3
4
5
6
7
8
9
0
10
11
12
Fujita Scale
1
2
3
4
0
5
6
7
8
9
10
11
12
0.6
1.0
Mach Scale
Beaufort Scale
Objectives 3, EF-Scale structure 4, EF vs
F-Scale
24
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 (lt20), 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 (gt20) 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
25
EF-Scale_L1_1
26
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 (lt20), 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 (gt20) 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
27
EF-Scale answer
EF-Scale Categories Wind Speed Ranges
EF0 65-85
EF1 86-110
EF2 111-135
EF3 136-165
EF4 166-200
EF5 gt200
Wind Speed in mph, 3-Second gust
Objectives 3, EF-Scale structure
28
Strengths of EF-Scale

• EF-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 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 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
30
EF-scale_L1-2
31
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 (F3) and higher
• EF-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, 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/CR6372,
  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/ef
scale/
33
In Lesson 2

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

34
Contacts

• If you have any questions about this lesson,
  contact
• Jim LaDue, James.G.LaDue_at_noaa.gov
• Dan McCarthy, Daniel.McCarthy_at_noaa.gov