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by Tim Marshall P.E.
Meteorologist
In the Eye of the Storm: Perspective From an Engineer, Meteorologist and Storm Chaser
Presented at 2017 Tornado Summit Oklahoma City, OK February 14, 2017
1957 Began to position chase vehicles
April 21, 1967Oak Lawn, IL Tornado
1967 -Oak Lawn, IL news
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Oak Lawn Tornado Damage Destroyed mobile home park
April 21, 1967Oak Lawn Tornado Track
Rated F4
Traveled 16.2 miles @ 60 mph33 deaths
>1000 homes damaged
http://www.weather.gov/media/lot/events/1967_Apr_Tornadoes/OakLawn_Tornado_survey.pdf
April 21, 1967 barograph trace from Albright Middle School
Drops in pressure with Belvidere
and Oak Lawn tornadoes.
Marvin Zeaman
1969 - Won top award for tornado exhibit at science fair.
Tornado
1970 – Lubbock, TX Tornado
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1970 – Lubbock, TX Tornado 1970- Dr. Fujita surveyed the
tornado damage
http://www.lubbocktornado1970.com/pdf/LubbockTornadoes_TetsuyaFujita.pdf
1971- Fujita Scale
https://swco-ir.tdl.org/swco-ir/handle/10605/261888
Institute for Disaster Research was formed at TTU
Kiesling, Peterson, Mehta, Minor, McDonald
DR. TED FUJITA
and the SuperOutbreakApril 3-4, 1974
I attended his lecture at the
Univ. of Chicago 11-12-74319 fatalities, 5,484 injuries
1974- F5 Xenia, OH Tornado
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1974- F5 Xenia, OH Tornado
Worst damage occurred on Marshall Street !
1974 – N.I.U. Meteorology
Prof. Jack R. Villmow
1976 – First Tornado Damage Survey 1976 – Lemont, IL Tornado
I walked the
damagepath
1978 – TTU Graduate School Saw a tornado first day in TX
Edmonson, TX – May 27, 1978
1978 – TTU Graduate School
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April 10, 1979 - Dr. Peterson and I prepare to chase storms
April 10, 1979 – Wichita Falls Tornado
Mobile home park adjacent to Hwy 287
June 3, 1980Grand Island, NE Tornadoes
Did aerial and ground surveys
June 3, 1980Grand Island, NE Tornadoes
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June 3, 1980Grand Island, NE Tornadoes
June 3, 1980Grand Island, NE Tornadoes
http://www.depts.ttu.edu/nwi/Pubs/Rep
ortsJournals/ReportsJournals/D6-3-80-
Tor-GrandIsland.pdf
June 3, 1980 Grand Island, NE survey
House failure modes Paths of roof planks
June 3, 1980 Grand Island, NE Tornadoes
Aug. 1980 – TTU CE student
August 10, 1980- Hurricane AllenMy first hurricane chase
Day before
hurricane
Day of
hurricane
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I witnessed the power of hurricane-force winds
1980- I witnessed the power of storm surge
http://www.depts.ttu.edu/nwi/Pubs/ReportsJournals/ReportsJournals/D8-10-80-Hurr-Allen.pdf
April 12, 1981 Warren, OK
https://stormtrack.org/wordpress/wp-content/uploads/the-
mesocyclone-evolution-of-the-warren-oklahoma-tornadoes.pdf
May 22, 1981 – Binger, OK
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May 22, 1981 – Binger, OK May 22, 1981 – Binger, OK
http://www.depts.ttu.edu/nwi/Pubs/ReportsJournals/ReportsJournals/D5-22-81Tor-Binger.pdf
1982 – Storm Chase Manual
� Listed procedures on how to chase storms and film them at close range.
� NRC contract to study debris generated by tornadoes
https://stormtrack.org/wordpress/wp-content/uploads/storm-chase-manual-1998-edition.pdf
Classic Supercell
May 9, 1982 Dawn, TX May 16, 1982 Silverton, TX
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May 19, 1982 Pampa, TX #2 May 19, 1982 Pampa, TX #4
May 19, 1982 Pampa, TX #6
https://stormtrack.org/wordpress/wp-content/uploads/storm-scale-of-the-pampa-storm.pdf
May 19, 1982 Tornado Tracks
1983 – Haag Engineering Co. Ice Ball Launcher
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Making Ice BallsHAIL SIZE
(IN)DAMAGE THRESHOLD
1 Lightweight comp shingles
1-1/4 Heavy weight comp, wood shingles
1-1/2 Medium wood shakes
1-3/4 Concrete tiles, modified bitumen
2 Smooth built-up roofing, EPDM
2-1/2Ballasted built-up roofing, EPDM, metal panels
https://ams.confex.com/ams/pdfpapers/45858.pdf
FM 4473 – Ice impact test Wood and Comp Pictorials
http://haageducation.com/books-tools/
1986
STORMTRACK MAGAZINE
Lasted 25 years
Now online at:
http://www.
stormtrack.org
1986 - First “portable” computer
Getting SAO’s with my PCjr – 64K no hard drive, 8 pin dot
matrix printer and 300 baud modem.
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May 1, 1988 - Carson Eads Chase Van 1996- “TWISTER” movie
with star Bill Paxton At OKC premiere
with Don Burgess and Jim Bellville with Oprah Winfrey
Involved in the development of the new EF-scale
� Upgrades the original Fujita Scale using 28 damage indicators.
� Adopted by the NWS in 2007.
http://www.depts.ttu.edu/nwi/Pubs/FScale/EFScale.pdf
1978-2016 chase statistics
� ~ 800 chase days (2.1 years)
� ~ 400 days of severe storms (50%)
� ~ 300 tornadoes
� ~ 100 tornado days
� ~ 500,000 miles (625 mi/chase)
� ~ 10,000 hours chasing (416 day hours)
Does not include hurricane chases or air miles.
1978-2016 Tornado Days and Surveys
Birmingham UK Tornado Survey
My Tornado Library
� Over 30,000 slide images of Over 30,000 slide images of Over 30,000 slide images of Over 30,000 slide images of tornadoes, chasing, and damage.tornadoes, chasing, and damage.tornadoes, chasing, and damage.tornadoes, chasing, and damage.
� Thousands of hours of video and Thousands of hours of video and Thousands of hours of video and Thousands of hours of video and tape recordings of chases in tape recordings of chases in tape recordings of chases in tape recordings of chases in formats from Super8, VHS, SVHS, formats from Super8, VHS, SVHS, formats from Super8, VHS, SVHS, formats from Super8, VHS, SVHS, HiHiHiHi----8, MiniDV, and SD.8, MiniDV, and SD.8, MiniDV, and SD.8, MiniDV, and SD.
� Thousands of papers, books, and Thousands of papers, books, and Thousands of papers, books, and Thousands of papers, books, and newspaper articles on tornadoes.newspaper articles on tornadoes.newspaper articles on tornadoes.newspaper articles on tornadoes.
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Books, videos
and files
– oh my!
Chase logs and hand drawn maps are
kept in notebooks
Slides are labeled and sleeved
Tornado Room “Ring of Honor”
THE 2016TWIRL PROJECT
http://www.cswr.org
Tornadic Winds: In-situ and Radar measurements at Low levels (TWIRL)
5 pods in
SCOUT 3
Team: Brandon Molyneaux, Jacob DeFlitch, and Katie Griffith
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The instrumented pod cost 6K each
2016 TWIRL PROJECT
Dr. Josh Wurman Dr. Karen Kosiba3 SCOUTS
3 DOWS
Dr. Josh Wurman inside DOW-72016 TWIRL PROJECT
2016 TWIRL PROJECT
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SULPHUR, OKCHASE
MAY 9, 2016
4:05pI-35
WYNNEWOOD
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
SM
4:05pI-35
WYNNEWOOD
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
4:07 PM Multi-vortex
tornado SW
4:07PM – POD L deployed4:11pI-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
1m
WYNNEWOOD
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4:11pI-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
1m
WYNNEWOOD
4:15 PM Pod M deployed
4:18pI-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
4:18pI-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
4:17 PM POD N deployed4:19 PM Tornado crossed Meridian Rd.
The tornado went south of all 3 pods
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4:25 PM Tornado lifts and destroys house4:44 PM – Multi-vortex
tornado forms south
4:50p
I-35
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
SULPHUR
4:50p
I-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
4:52 PM – Wedge just south 4:55 PM – Wedge just south
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Quickly deployed pod in front of wedge tornado
Thanks to Scott Peake
SCOUT 3
Reality duplicates HollywoodV O R T E X 2 S P E C I A L E D I T I O N
V
4:57p
I-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
4:57p
I-35
SULPHUR
HWY
177
DAVIS Rt. 7
SCOUT 3
WYNNEWOOD
5:00 PM Tornado
approaching us. Pod hit.
1 m/s = 2.237 mph
89 mph
Courtesy of CSWR
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1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
1 km
78mph
Courtesy of CSWR
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1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
1 km
Courtesy of CSWR
FIRST POD HIT FOR
CSWR
TORNADO TRACKS by
NWS
KATIE
TORNADO
9 MILES
LONG
21 MINUTES
RATED EF-4
SULPHUR
TORNADO
17 MILES
LONG
43 MINUTES
RATED EF-3
I-
3
5
OKC AreaDamage Surveys
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1999, 2003 and 2013 PATHS
1 SQ. MILE
May 3, 1999 – Moore, OK
Still images from video by Tim Marshall
117
Variation of damage: F0 to F5
118
F-scales overlaid on aerial photo
CRITICAL
CONNECTIONS
Problems with foundation attachment
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Typical connection of wall to slab
F indicates likely failure areas
Types of connections to slab
Straight-nailed studs pulled away from bottom plate (May 1999)
Studs pulled out from strapped bottom plate (May 1999)
Bottom plate had been secured with shot pins (May 1999)
Scrape in slab where cut nail moved (May 1999)
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Cut nails were all that was left of this house (May 1999)
I returned to Moore in August 1999 and examined 40 homes under construction…
� Five homes were bolted to their foundations (12.5%).
� Six homes were strapped to their foundations (15%).
� 29 homes were nailed or pinned to their foundations (72.5%).
Building Code Requirements
� Wood bottom plates on exterior walls shall be bolted to the foundations a maximum of 6 feet apart.
� A nut with washer must be tightened on each bolt.
� There shall be a minimum of TWO bolts per plate section.
130
Anchor Bolt Placement
12.5% foundations had bolts ( Aug. 1999) Properly bolted wall plates (Aug. 1999)
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15% of foundations had straps (Aug. 1999) Oops. Strap outside wall insulation board (Aug. 1999)
Oops #2 – Straps outside of insulation board (Aug. 1999)
72.5% of walls were to be nailed or pinned to their foundations (Aug. 1999)
Shot pinned wall plate to slab (Aug. 1999)Use of cut nails on perimeter walls was a code violation (Aug. 1999)
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How deep does a cut nail extend into the slab?
About a half inch if it doesn’t spall the concrete!
Problems with wall attachment
Let-in brace helps stiffen wall (Aug. 1999) Oops. What you don’t see WILL hurt you.
(Aug. 1999)
Solid sheathing help stiffens wall corner in lieu of let-in brace. But what about the pink stuff? (August 1999)
Problems with the attachment of roof framing
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Typical rafter-top plate connection that performs poorly when it is uplifted
New house built after it was destroyed by tornado. Note nails through corner of top plate (Aug. 1999)
One house had clips between rafters and top plate (Aug. 1999)
148
Brick toppled suction side – ties not engaged
149
How ties are to be installed per FEMA
TTU publication resulted from the damage survey
http//www.depts.ttu.edu/nwi/Pubs/Reports/Journals/ReportsJournals/Tornadoes-of-OKC-may-3-1999.pdf
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Survey Results (1999)
� Many homes were poorly built and thus, provided more flying debris.
� Many homes failed at the wall/foundation or roof/wall connections.
� A number of homes built after the tornado contained building code violations.
� The next violent tornado will do just as much if not more damage. May 20, 2013
Houses south of Plaza Towers School
Houses swept clean south of Plaza Towers
Destroyed
home
2013
Cut nails on exterior walls Cut nails on exterior walls
Destroyed
home
2013
Cut nails on interior walls Shot pins on exterior walls
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Roof failures (2013) Roof failures (2013)
Roof failures (2013)
I returned to Moore in December 2013 and examined 20 homes under construction…
� All 20 homes were bolted to their foundations (100%) !
� No homes had been strapped to their foundations !
� 4 homes had shelters ! (3 above ground, 1 below ground) This was above-code.
� 3 homes had rafter clips ! This was above-code.
Inspection Comparison
AUGUST 1999
DECEMBER 2013
Bolted perimeter 12.5 % 100 %Strapped perimeter 15 % 0%Nailed or pinned
perimeter72.5% *
*Bolted plates frequently had added nails or pins.
A BIG IMPROVEMENT, right ?
DEC. 2013
Bolts with no nuts or washers throughout entire house
“A nut and washer shall be tightened on each anchor bolt.”
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DEC. 2013
Bolt under cut stud. No washer
Bolt outside of plate
Bolt outside of plate
Nail
“Studs shall have full bearing on nominal 2x.”
Of the 20 homes examined in December 2013…
� All homes had anchor bolts. However…
� 25 % of homes had nuts and washers properly tightened on centered bolts
� 75 % of homes had certain bolts with no nuts or washers or bolts were installed too close to the edges of the plates.
All 20 inspected homes had solid sheathing (Dec. 2013)
But wind uplift resistance is
poor
Rafters were toe nailed to top plates per code (Dec. 2013)
3 of 20 houses had rafters clipped to top plates (above-code) 2013
4 of 20 homes had shelters
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So what was learned after three major tornado
disasters in the OKC area:
� Homes have changed from a variety of perimeter connections to bolts (+).
� However, most homes (75%) had problems with the bolted plates (i.e. no nuts/washers, cut plates, cut studs, etc.) (-)
� All homes had solid exterior sheathing (+)
� 3 of 20 homes had rafter clips (+)
� 4 of 20 homes had shelters (+)
Many thanks to:
� National Science Foundation
� Center for Severe Weather Research
� National Weather Service
� Storm Prediction Center
� City of Moore, OK.
� Haag Engineering Co.
email: [email protected]
THE END