Lesson 1: Introducing the
Enhanced Fujita Scale
Dan McCarthy ( NWS SPC)
and
Jim LaDue (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.
Know why the EF scale was created
Identify the methodology in creating the EF scale.
Understand the structure of the EF-scale
Know the differences between the EF and F scale
Understand the strengths of the EF-scale
You will know 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
Jim McDonald &
Kishor Mehta -TTU
Don Burgess – NSSL
Joe Shaefer - SPC
Objectives: 2, Methodology
The Steering Committee Organizes a Forum
• Led by Wind Science and
Engineering Center, Texas Tech
University, 7-8 March 2001
–
–
–
–
–
–
–
–
–
–
NOAA/NSSL
NOAA/NWS/SPC
NIST (Nat’l Institute of Standards)
NOAA/NWS
Office Naval Research
University of Oklahoma
The Weather Channel
NOAA/Forecast Systems Laboratory
The Tornado Project
Building Technology Research Lab
(Insurance)
–
–
–
–
–
–
–
–
–
–
–
Lawrence Livermore Research Lab
Institute for Building & Home Safety
U.S. Department of Energy
Haag Engineering
National Science Foundation
FEMA
Cooperative Institute for Mesoscale
Meteorological Studies
Clemson University
Kent State University, Department of
Geography
Applied Research Associates
UCLA
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
• Each DI has several Degrees of Damage (DOD)
• DIs and DODs can be added or modified
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
Each DOD has a Lower Bound (LB), an Upper Bound (UB) and an
Expected (EXP) wind speed estimate associated with it.
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, FR12 or DOD2
Objectives: 2, methodology; 3, EF scale structure
Reason behind an upper and lower bound
wind speed
UB: Design
exceeds codes for
typical US home,
better than average
load path.
One, Two Family House
WInd
Speed
(mph)
(mph)
Speed
Wind
250
EXP
200
LB
150
UB
EXP: Design
exhibits good load
path, at least
matches US
building codes
100
50
0
1
2
3
4
5
6
DOD
7
8
9
10
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 Experts:
• Chosen method?
– Expert Elicitation
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 McDonald
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 (FR12 or DI2)
How did these winds come about?
Objectives: 3, EF scale structure
Degrees of Damage
Note some consecutive DODs have larger overlap than others
DOD
Damage Description
One, Two Family House
Threshold of visible damage
2
250 material (<20%), gutters and/or awning; loss of vinyl or metal siding
Loss of roof covering
WInd
Speed
(mph)
(mph)
Speed
Wind
1
EXP
EXP
LB
UB
63
53
80
79
63
97
3
Broken glass200
in doors and windows
96
79
114
4
Uplift of roof deck and loss of significant
roof covering material (>20%); collapse of chimney;
UB
garage doors150
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
0 except small interior rooms.
Most walls collapsed
152
127
178
9
All walls collapsed
170
142
198
200
162
220
LB
100
50
1
2
3
4
5
6
7
8
DOD
10
Destruction of engineered and/or well constructed residence; slab swept clean
9
10
Example DODs for a Framed House DI (FR12 or DI2)
Objectives: 2, methodology; 3, EF scale structure
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
Y = –0.6246x
+ 36.393
Brian Peters
NWSFO
– Calera, Alabama
2
R = 0.9118
John Ogren – NWSFO – Indianapolis, Indiana
Dennis Hull – NWSFO – Pendleton, Oregon
Tom Matheson – NWSFO – Wilmington, North
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
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
DOD to Wind Speed to EF Scale
EF Scale Categories
Wind Speed Ranges
EF0
65-85
EF1
EF2
86-110
111-135
EF3
136-165
EF4
166-200
EF5
>200
Wind Speed 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 = 1.870B3/2
F – scale: V = 14.1(F+2)3/2
Mach scale: V = (742 +1.3)M
M1.0
F12
M0.8
mph
mph
mph
M0.7
M0.6
F5
F4
B1
B3
B5
B7
B9
F3
B11
F0
B17
F2
F1
0 1 2 3 4 5 6 7 8 9 10 11 12
Fujita Scale
0 1 2 3 4 5
6 7 8 9 10 11 12
Beaufort 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
M1.0
F12
M0.8
M0.7
M0.6
EF Scale
0 1 2
3 4 5
EF5
EF4 F5
B17
EF3 F4
EF2
B1
B3
B5
B7
B9
EF1
B11
EF0
F0
F3
F2
F1
0 1 2 3 4 5 6 7 8 9 10 11 12
Fujita Scale
0 1 2 3 4 5
6 7 8 9 10 11 12
Beaufort 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 is the expected wind speed that did 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
EF0
65-85
EF1
EF2
86-110
111-135
EF3
136-165
EF4
166-200
EF5
>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
• 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
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-ID122160, 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 LaDue, James.G.LaDue@noaa.gov
– Dan McCarthy, Daniel.McCarthy@noaa.gov