Lesson 2: Damage Surveys with the Lesson 2: Damage Surveys with the EF-ScaleEF-Scale

Steve Kuhl (NWS Quad Cities, IA/IL)Steve Kuhl (NWS Quad Cities, IA/IL)Brian Smith (NWS Omaha, NE)Brian Smith (NWS Omaha, NE)

Jim LaDue (NWS WDTD)Jim LaDue (NWS WDTD)

MotivationMotivation

• Rating a tornado event can be filled with subjectivity Rating a tornado event can be filled with subjectivity and this can lead to inconsistent ratingsand this can lead to inconsistent ratings

• This lesson will help you mitigate avoidable This lesson will help you mitigate avoidable subjectivity in rating damagesubjectivity in rating damage

Lesson 2: Learning ObjectivesLesson 2: Learning Objectives

1.1. Restate the methodology on using the EF-Restate the methodology on using the EF-Scale to rate an individual Damage IndicatorScale to rate an individual Damage Indicator

2.2. Restate the methodology on using the EF-Restate the methodology on using the EF-scale to rate a tornadoscale to rate a tornado

3.3. Indicate the construction practices that are Indicate the construction practices that are most likely to be associated with exceeding most likely to be associated with exceeding and falling below the expected wind speed of and falling below the expected wind speed of a one- and two-family house.a one- and two-family house.

4.4. Recall how to account for collateral damage Recall how to account for collateral damage in rating a DIin rating a DI

Performance ObjectivesPerformance Objectives

1.1. Evaluate the DOD of a DI.Evaluate the DOD of a DI.2.2. Estimate the wind speed of, and apply a rating to, Estimate the wind speed of, and apply a rating to,

a DI using your evaluation of the DOD, exposure, a DI using your evaluation of the DOD, exposure, potential collateral damage, and its construction potential collateral damage, and its construction quality.quality.

3.3. Rate the DI using the EF scale.Rate the DI using the EF scale.

More to damage surveying than covered in this More to damage surveying than covered in this lesson.lesson.

From Lesson 1From Lesson 1

• EF-Scale has 28 Damage Indicators (DIs)EF-Scale has 28 Damage Indicators (DIs)• Each DI has 3-12 Degrees of Damage (DODs)Each DI has 3-12 Degrees of Damage (DODs)

Lesson 2 StrategyLesson 2 Strategy

• A damage survey strategyA damage survey strategy• Make handy the EF-Scale tools Make handy the EF-Scale tools • Two cases Two cases

– Several “you make the call” situationsSeveral “you make the call” situations– Follow through at least one or both cases. Follow through at least one or both cases.

EF-Scale ToolsEF-Scale Tools

http://www.spc.noaa.gov/efscale/ http://wdtd.noaa.gov/courses/ef-scale

A Recommendation for the Enhanced Fujita Scale The EFkit

EF kit 2008 FilesEF kit 2008 Files

• Download from this site: Download from this site: http://wdtd.noaa.gov/courses/ef-scale

• Make sure you have EFkit Make sure you have EFkit folder unzippedfolder unzipped

• In the EFkit folder, double In the EFkit folder, double click on EFkit.execlick on EFkit.exe

Software developed by Ed Mahoney, WDTDImage library compiled by Kishor Mehta, TTUSimulated images by Matt Murnan, WDTD

EF kit 2008 Main DisplayEF kit 2008 Main Display

Scroll through DODs

Scroll through DIs

EF kit 2008 version controlsEF kit 2008 version controls

Up 2 DODs

EF rating and estimated wind speed

Button appears with more than one example

Typical construction of DIs in the reportTypical construction of DIs in the report

Typical Construction•Steel undercarriage supported on concrete block piers•Metal straps and ground anchors (Frame and/or over the top strap anchors•Asphalt shingles or one-piece metal roof covering•Wood roof joists•Metal, vinyl or wood siding•Wood stud walls and partitions•Better construction in post 1974 models in coastal areas

28 Damage Indicators28 Damage Indicators

Objectives: 1, Damage Indicators

residences

Commercial/retail structures

SchoolsProfessional buildings

Metal buildings/canopies

Towers/poles

vegetation

Rating a DI with the EF-ScaleRating a DI with the EF-Scale

• Match the description Match the description and/or pictures with the and/or pictures with the damage you seedamage you see

• Expected wind = Expected wind = structure adhering to structure adhering to codecode

• Example: For FR12, Example: For FR12, what construction is what construction is normal (benchmark)?normal (benchmark)?

FR12, DOD 7: Exterior Walls Collapsed, 132 mph, EF3

FR12, DOD 6: Large Section of roof removed, most walls standing, 122 mph, EF2

Building Benchmark Integrity for One- and Building Benchmark Integrity for One- and Two-Family HousesTwo-Family Houses

• Continuous load path

• Normal exposure– normal window coverage– reinforce garage doors

• No collateral damage

• International Residential Code (IRC) 2003

FR12: Benchmark Continuous Load PathFR12: Benchmark Continuous Load Path

Failing Exceeding

Photographs ©Tim Marshall

FR12: Benchmark Continuous Load PathFR12: Benchmark Continuous Load PathMatching Load Path

Photographs ©Tim Marshall

FR12: Benchmark Continuous Load PathFR12: Benchmark Continuous Load PathStandard

Photographs ©Tim Marshall

ExceedingFailing

220 lbs 414 lbs(assuming no split wood)

1200 lbs

Accounting for construction quality in Accounting for construction quality in F vs EFF vs EF

• F-scale paradigm• If structure is weaker

(stronger) than standard, consider dropping (raising) F-scale

• EF-Scale paradigmEF-Scale paradigm• If structure is weaker If structure is weaker

(stronger) than standard, (stronger) than standard, lower (raise) wind speed lower (raise) wind speed toward the LB (UB) and toward the LB (UB) and then see if that lowers then see if that lowers (raises) the EF rating.(raises) the EF rating.

EF 2Lower the rating

Collateral damage increases DOD but not Collateral damage increases DOD but not necessarily wind speednecessarily wind speed

Maximum DOD with anchored sill plate, bolts every 24”!.

But there’s a mobile home frame resting in the debris.

East of Dibble, OK 2011 May 24 Photo by Jim LaDue

Tornado

motion

A strategy for surveying tornado tracks A strategy for surveying tornado tracks with the EF-Scalewith the EF-Scale

• Identify DIs first with Identify DIs first with broad survey broad survey

• Carefully rate DODs for Carefully rate DODs for chosen DIs chosen DIs

• Use the highest rated Use the highest rated DIs to help rate the DIs to help rate the tornadotornado

LIRB: DOD 6: Inward, outward collapse of exterior walls. Expected wind = 137 mph EF3

FR12: DOD7: Exterior walls collapsed. Expected wind = 132 mph, EF2

http://wdtd.noaa.gov/courses/EF-scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdf

Rating a tornado eventRating a tornado event

• Rate the tornado based Rate the tornado based on the on the highesthighest EF-Scale EF-Scale rating for any DIrating for any DI

– ……however…however…

– ……if you cannot then…if you cannot then…

• Be careful about too Be careful about too much precision with much precision with wind speed estimateswind speed estimates

Confirm with another DIConfirm with another DIPhoto used with permission by Tim Marshall

Check surrounding Check surrounding non DIs for consistencynon DIs for consistency

Photo used with permission by Jim LaDue

Rating a tornado event – Confirming DIsRating a tornado event – Confirming DIs

FR12 DOD=10, EXP wind = 200 mph (EF5)

TH DOD=3, EXP wind = 87 mph (EF1)

No confirmation here. Do not use this FR12

Non DI (bush), not damaged

Photo used with permission by Tim MarshallPhoto used with permission by Jim LaDue

FR12 DOD=10, EXP wind = 200 mph (EF5)

Confirmation present – FR12 can be used

TH DOD=5, EXP wind = 131 mph (EF3+)

Severe damage to non DI (tractor)

Rating a tornado event – exceeding your Rating a tornado event – exceeding your maximum rating possible?maximum rating possible?

• A tornado can only be rated within the ranges of A tornado can only be rated within the ranges of available DIsavailable DIs

EF#+, where + means you’ve maximized the rating of a DI before EF5 was reached.

Summary: Lesson 2 advanced damage Summary: Lesson 2 advanced damage surveyssurveys

• EF-Scale provides more capability to contour EF-Scale ratings than the F-scale

• See the benefits at http://www.nctcog.org/weather/study/

Summary: Lesson 2 advanced damage Summary: Lesson 2 advanced damage surveyssurveys

• EF-Scale provides more capability to contour EF-Scale ratings than the F-scale

• See the benefits at http://www.nctcog.org/weather/study/

Damage points

centerline

contours

Summary: Lesson 2Summary: Lesson 2

• EF-Scale strategy for rating a single DIEF-Scale strategy for rating a single DI– Start with identifying a DIStart with identifying a DI– Then identify a DODThen identify a DOD– Then adjust the wind depending on the structural integrity of the DIThen adjust the wind depending on the structural integrity of the DI– Then document the resulting ratingThen document the resulting rating

• EF-Scale strategy for rating a tornadoEF-Scale strategy for rating a tornado– Do a broad survey documenting DIs, note several with the most Do a broad survey documenting DIs, note several with the most

severe damagesevere damage– For each DI, document the DODsFor each DI, document the DODs– Detailed survey on the most damaged DIsDetailed survey on the most damaged DIs– Rate the tornado by applying the highest EF-Scale rating found by a Rate the tornado by applying the highest EF-Scale rating found by a

DI provided that. DI provided that. – two confirming DIs of similar ratingtwo confirming DIs of similar rating– highest rated DI makes sense given surrounding non DI damagehighest rated DI makes sense given surrounding non DI damage

Additional Information Additional Information

• Storms Prediction Center EF-Scale Website: Storms Prediction Center EF-Scale Website: http://www.spc.noaa.gov/efscalehttp://www.spc.noaa.gov/efscale

• Texas Tech Wind Science Engineering Center: Texas Tech Wind Science Engineering Center: http://www.depts.ttu.edu/nwi/Pubs/FScale/EFScale.pdfhttp://www.depts.ttu.edu/nwi/Pubs/FScale/EFScale.pdf

• A Guide to F-Scale Damage Assessment A Guide to F-Scale Damage Assessment http://www.wdtd.noaa.gov/courses/EF-scale/lesson2/Finhttp://www.wdtd.noaa.gov/courses/EF-scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdfalNWSF-scaleAssessmentGuide.pdf

ContactsContacts

• If you have any questions about this lesson, contactIf you have any questions about this lesson, contact– Jim LaDue, James.G.LaDue@noaa.govJim LaDue, James.G.LaDue@noaa.gov