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THE NEW TORNADO RATING SYSTEM the Enhanced Fujita Scale Table 1

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THE NEW TORNADO RATING SYSTEM the Enhanced Fujita Scale Table 1 THE NEW TORNADO RATING SYSTEM The Enhanced Fujita Scale Table 1. Structure damage indicator he Enhanced Fujita Scale (EF) to rate tornadoes went into How Strong Was That Tornado? Enhanced F Scale Damage Indicators effect on February 1, 2007. The original Fujita Scale (F) These pictures are from an actual tornado that hit a was developed in 1971 by Dr. T. Theodore Fujita. Over double-wide mobile home in South Carolina. Number (Details Damage Indicator Abbreviation T Linked) the years, National Weather Service personnel recognized that 1. The observer would determine the type of structure 1 Small barns, farm outbuildings SBO improvements to the scale were necessary due to some limitations. damaged based on Table 1. Table 1 only shows a The primary limitations were the lack of damage indicators, no partial list of the 28 structure types. This tornado 2 One- or two-family residences FR12 account of construction quality and variability, and no definitive hit a double-wide mobile home. 3 Single-wide mobile home MHSW correlation between damage and wind speed. This sometimes (MHSW) 2. The observer would determine the degree of resulted in inconsistent ratings of tornadoes and in some cases an 4 Double-wide mobile home MHDW damage based on Table 2. In this example 1 overestimate of tornado wind speeds. 5 Apt, condo, townhouse (3 ACT complete destruction occurred to the mobile home, The Enhanced Fujita Scale is a more precise way to assess the stories or less) which has winds estimated between 110 mph and damage from a tornado. It classifies tornado damage (EF0-EF5) Transmission line tower TLT 148 mph. The observer used his or her judgement 24 as calibrated by those from the meteorological and engineering FST and estimated winds near the upper bound of 148 25 Free-standing tower communities. The proposal was led by the Texas Tech University FSP mph. 26 Free standing pole (light, flag, Wind Science and Engineering Research Center. The Enhanced luminary) 3. The observer now takes the 148 mph and rates the TH Fujita Scale is a set of wind estimates, not measurements, based 27 Tree - hardwood on damage. It uses a three-second gust estimated at the point of tornado using the Enhanced Fujita Scale shown in TS 28 Tree - softwood damage. The damage is based on a judgment of up to 12 levels of Table 3. According to the Operational EF Scale, 3 damage or Degrees of Damage (DOD) to 28 Damage Indicators second gust, 148 mph is an EF3 Tornado! (DI). Examples of Damage Indicators are buildings, structures, and trees. By observing the Degree of Damage to each Indicator, the Table 2. person conducting the survey can assign an estimate of wind speed. The estimated wind speed then determines the EF-Scale category DOD* Degree of Damage Scale appropriate for the observed damage. —Leonard Vaughan, National Weather Service Meteorologist of wind (mph) wind of bound Upper of wind (mph) wind of Table 3. bound Lower (mph) Expected wind wind Expected description Damage Damage Enhanced F Scale for Tornado Damage DOD* 61 51 76 1 Threshold of visible damage 74 61 92 Fujita scale Derived EF scale Operational EF 2 Loss of shingles or partial uplift of scale one-piece metal roof covering 87 72 103 F Fastest 3 EF 3 EF 3 Unit slides off block piers but remains Number 1/4-mile 3 Second Number Second Number upright 73 112 (mph) Second 89 Gust Gust Gust Vaughan Leonard (mph) 4 Complete uplift of roof; most walls (mph) (mph) remain standing 114 0 98 84 40-72 45-78 0 65-85 0 65-85 5 Unit rolls on its side or upside down; 1 73-112 79-117 123 1 86-109 1 86-110 Important: The 3 second gust is not the same remains essentially intact 105 87 2 113-157 118- Destruction of roof and walls leaving 2 110- 2 111- wind as in standard surface observations. Standard 6 161 floor and undercarriage in place 137 135 measurements are taken by weather stations in 109 96 128 3 158-207 162- 3 138- 3 136- open exposures, using a directly measured “one 7 Unit rolls or vaults; roof and walls 209 separate from floor and undercarriage 136 2 167 165 minute mile” speed. 118 101 4 208-260 210- Undercarriage separates from unit; 4 168- 4 166- 3 8 261 199 rolls, tumbles and is badly bent 200 127 110 148 5 261-318 262- 5 200- 5 Over 9 Complete destruction of unit; debris 317 234 200 blown away.
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