Chapter Nineteen – Tornadoes Reading: SHW 19*, MMM Chapter 10 through Pt. 1: Tornado Overview and Taxonomy Figures/Images from Severe and Hazardous Weather © 2008, 2012 Kendall Hunt Publishing Company Figures/Images from Mesoscale Meteorology in Midlatitudes © 2010 John Wiley and Sons

Tornado Trivia (not!) Average # of people killed annually _____ Size range __________ m, ________ miles Wind Speed Range ________mph/knots Widest path _______ _____ % U.S. exclusive rights Lifespan: most short, some can last ____ min. and have a damage swath of ____ long.

Enhanced Fujita scale for tornado intensity Based on damage – rating is assessed after the tornado (different from hurricanes, when the category is assigned while the storm is happening) Originally developed Fujita in the 1970s Updated in 2007 to the “Enhanced Fujita” scale

Table 19.1 Comparison of EF scale to old Fujita scale Fujita Scale 3-second gust speed (mph) Operational Enhanced Fujita Scale 3 Second Gust Speed (mph) F045-78EF F EF F EF F EF F EF F EF5> 200

Table 19.2 For the structures listed below, damage assessors use detailed tables that describe the degree of damage, together with example photographs from damaged structures to establish the likely wind speed and EF scale rating for a tornado No.Damage Indicator 1Small Barns or Farm Outbuildings 2One or Two Family Residences 3Manufactured Home – Single Wide 4Manufactured Home – Double Wide 5Apartments, Condos, Townhouses 6Motel 7Masonry Apartment or Motel 8Small Retail Building 9Small Professional Building 10Strip Mall 11Large Shopping Mall 12Large Isolated Retail Building 13Automobile Showroom 14Automobile Service Building 15Elementary School 16Junior or Senior High School 17Low-Rise Building (1-4 stories) 18Mid-Rise Building (5-20 stories) No.Damage Indicator 19High-Rise Building (> 20 stories) 20Institutional Building 21Metal Building System 22Service Station Canopy 23Warehouse Building 24Electrical Transmission Lines 25Free Standing Towers 26Free Standing Light Poles, Luminary Poles, Flag Poles 27Trees (Hardwood) 28Trees (Softwood) Table 19.2 Damage Indicators for establishing EF-Scale ratings

Table 19.3 Degree of Damage Damage DescriptionEXPECTED WIND SPEED LOWE ST WIND SPEED HIGHEST WIND SPEED 1Threshold of visible damage Loss of roof covering material (<20%), gutters and/or awning; loss of vinyl or metal siding Broken glass in doors and windows Uplift of roof deck and loss of significant roof covering material (> 20%); collapse of chimney, garage doors collapse inward, failure of porch or carport Entire house shifts off foundation Large sections of roof structure removed; most walls remain standing Exterior walls collapsed Most walls collapsed, except small interior rooms All walls collapsed Destruction of engineered and/or well constructed residence, slab swept clean Estimating the EF scale rating from damage to a one or two family residence (Indicator 2 in Table 19.2)

If you want all the details, check out this page from the SPC about the EF scale:

Figure 19.13

NSSL Animation: Tornado probability climatology

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Figure 19.15

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Figure 19.9 As tornado decays (complete RFD wrap), new updraft may produce new tornado

Figure Tornado Family

Figure 19 C Tri-State Tornado of ’25 Was this a tornado family, or a single tornado? Most fatalities ever (695)

Tornadoes with Hurricanes Relatively Weak, but add insult to injury Found mostly in Right Front Quadrant (only NE quadrant if it is moving North!) Hurricane Dolly (2008) BCS’s best tornado chance?

Figure 19 E

Figure 19.21

Figure 19 I

Figure 19 J TVS

Figure 19 K