Lesson 2: Damage Surveys with the EF-Scale Steve Kuhl (NWS Quad Cities, IA/IL) Brian Smith (NWS Omaha, NE) Jim LaDue (NWS WDTD)

MotivationMotivation Rating a tornado event can be filled with subjectivity and this can lead to inconsistent ratingsRating a tornado event can be filled with subjectivity and this can lead to inconsistent ratings This lesson will help you mitigate avoidable subjectivity in rating damageThis lesson will help you mitigate avoidable subjectivity in rating damage

Lesson 2: Learning Objectives 1.Restate the methodology on using the EF- Scale to rate an individual Damage Indicator 2.Restate the methodology on using the EF- scale to rate a tornado 3.Indicate the construction practices that are most likely to be associated with exceeding and falling below the expected wind speed of a one- and two-family house. 4.Recall how to account for collateral damage in rating a DI

Performance Objectives 1.Evaluate the DOD of a DI. 2.Estimate the wind speed of, and apply a rating to, a DI using your evaluation of the DOD, exposure, potential collateral damage, and its construction quality. 3.Rate the DI using the EF scale. More to damage surveying than covered in this lesson.

From 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 Strategy A damage survey strategyA damage survey strategy Make handy the EF-Scale toolsMake handy the EF-Scale tools Two casesTwo cases –Several “you make the call” situations –Follow through at least one or both cases.

EF-Scale Tools A Recommendation for the Enhanced Fujita Scale The EFkit

EF kit 2008 Files Download from this site: from this site: Make sure you have EFkit folder unzippedMake sure you have EFkit folder unzipped In the EFkit folder, double click on EFkit.exeIn the EFkit folder, double click on EFkit.exe Software developed by Ed Mahoney, WDTD Image library compiled by Kishor Mehta, TTU Simulated images by Matt Murnan, WDTD

EF kit 2008 Main Display Scroll through DODs Scroll through DIs

EF 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 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 Indicators Objectives: 1, Damage Indicators residences Commercial/retail structures Schools Professional buildings Metal buildings/canopies Towers/poles vegetation

Rating a DI with the EF-Scale Match the description and/or pictures with the damage you seeMatch the description and/or pictures with the damage you see Expected wind = structure adhering to codeExpected wind = structure adhering to code Example: For FR12, what construction is normal (benchmark)?Example: For FR12, what construction is 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 Two-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 Path Failing Exceeding Photographs ©Tim Marshall

FR12: Benchmark Continuous Load Path Matching Load Path Photographs ©Tim Marshall

FR12: Benchmark Continuous Load Path Standard Photographs ©Tim Marshall ExceedingFailing 220 lbs 414 lbs (assuming no split wood) 1200 lbs

Accounting for construction quality in F 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 (stronger) than standard, lower (raise) wind speed toward the LB (UB) and then see if that lowers (raises) the EF rating.If structure is weaker (stronger) than standard, lower (raise) wind speed toward the LB (UB) and then see if that lowers (raises) the EF rating. EF 2 Lower the rating

Collateral damage increases DOD but not necessarily 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 with the EF-Scale Identify DIs first with broad surveyIdentify DIs first with broad survey Carefully rate DODs for chosen DIsCarefully rate DODs for chosen DIs Use the highest rated DIs to help rate the tornadoUse the highest rated DIs to help rate the tornado LIRB: DOD 6: Inward, outward collapse of exterior walls. Expected wind = 137 mph EF3 FR12: DOD7: Exterior walls collapsed. Expected wind = 132 mph, EF2 scale/lesson2/FinalNWSF- scaleAssessmentGuide.pdf scale/lesson2/FinalNWSF- scaleAssessmentGuide.pdf

Rating a tornado event Rate the tornado based on the highest EF-Scale rating for any DIRate the tornado based on the highest EF-Scale rating for any DI –…however… –…if you cannot then… Be careful about too much precision with wind speed estimatesBe careful about too much precision with wind speed estimates Confirm with another DI Photo used with permission by Tim Marshall Check surrounding non DIs for consistency Photo used with permission by Jim LaDue

Rating 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 Marshall Photo 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 maximum rating possible? A tornado can only be rated within the ranges of available DIsA tornado can only be rated within the ranges of available DIs EF#+, where + means you’ve maximized the rating of a DI before EF5 was reached.

Summary: Lesson 2 advanced damage surveys EF-Scale provides more capability to contour EF-Scale ratings than the F-scale See the benefits at

Summary: Lesson 2 advanced damage surveys EF-Scale provides more capability to contour EF-Scale ratings than the F-scale See the benefits at Damage points centerline contours

Summary: Lesson 2 EF-Scale strategy for rating a single DIEF-Scale strategy for rating a single DI –Start with identifying a DI –Then identify a DOD –Then adjust the wind depending on the structural integrity of the DI –Then 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 severe damage –For each DI, document the DODs –Detailed survey on the most damaged DIs –Rate the tornado by applying the highest EF-Scale rating found by a DI provided that. –two confirming DIs of similar rating –highest rated DI makes sense given surrounding non DI damage

Additional Information Storms Prediction Center EF-Scale Website: Prediction Center EF-Scale Website: Texas Tech Wind Science Engineering Center: Tech Wind Science Engineering Center: A Guide to F-Scale Damage Assessment scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdfA Guide to F-Scale Damage Assessment scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdf scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdf scale/lesson2/FinalNWSF-scaleAssessmentGuide.pdf

ContactsContacts If you have any questions about this lesson, contactIf you have any questions about this lesson, contact –Jim LaDue,