Chapter 14. Oldest Known Photograph of a Tornado (1884)

Chapter 14

Oldest Known Photograph of a Tornado (1884)

Tornadoes

Rapidly rotating column of air that flows around a small area of intense low pressure with a circulation that reaches the ground.

Tornadoes

Table 14-2, p. 400

Tornadoes

When

F-Scale Converted to EF-ScaleF-Scale Converted to EF-ScaleEnhanced Fujita Scale Feb 1 2007Enhanced Fujita Scale Feb 1 2007

F ScaleF Scale Wind SpeedWind Speed EF-ScaleEF-Scale Wind SpeedWind Speed

F0F0 45-7845-78 EF0EF0 65-8565-85

F1F1 79-11779-117 EF1EF1 86-10986-109

F2F2 118-161118-161 EF2EF2 110-137110-137

F3F3 162-209162-209 EF3EF3 138-167138-167

F4F4 210-261210-261 EF4EF4 168-199168-199

F5F5 262-317262-317 EF5EF5 200-234200-234

Wind speeds in mph, 3-second gust

Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

DOD to Wind Speed to EF-ScaleDOD to Wind Speed to EF-Scale

EF-Scale CategoriesEF-Scale Categories Wind Speed RangesWind Speed Ranges

EF0EF0 65-8565-85

EF1EF1 86-11086-110

EF2EF2 111-135111-135

EF3EF3 136-165136-165

EF4EF4 166-200166-200

EF5EF5 >200>200

Objectives: 3, EF-Scale structure

Wind speeds in mph, 3-second gust

Why the EF-Scale was created Need more damage

indicators recalibrate winds

associated with F-scale ratings

better correlate wind and rating

account for construction variability

Flexibility, Extensibility, Expandability

Evidence indicates a well Evidence indicates a well constructed house can be blown constructed house can be blown away by winds much less than away by winds much less than 260 mph 260 mph ((Phan and Simiu,2003)..

The framed house is one of only The framed house is one of only a few F-scale damage a few F-scale damage indicators.indicators.

Tornadoes

Tornado outbreaksFamilies, super outbreak

Super tornado outbreak April 3-4, 1974 315 deathshttp://www.april31974.com/

Palm Sunday April 11 196547 Tornadoes in 12 hours span 271 deaths, 3400 people injured 1.1 billion damage (2003 $$$$)

May 3-4 1999 Oklahoma City

66 tornadoes 46 fatalities, 800 injured 1.5 billion damage An F-5 tornado

http://www.norman.noaa.gov/2000/05/first-anniversary-of-may-3-1999-tornado-outbreak-highlights-importance-of-warnings/

Fig. 14-37, p. 396

Tornadoes

Tornado OccurrenceUS experiences most tornadoesTornado Alley (warm, humid surface; cold

dry air aloft)Highest occurrence spring (may June),

lowest winterHighest Death Toll , April

Where else do tornadoes form?

Two of the highest concentrations of tornadoes outside the U.S. are Argentina and Bangladesh. Both have similar topography with Brazil (Argentina) or from the Indian Ocean (Bangladesh). mountains helping catch low-level moisture from over Brazil (Argentina) or from the Indian Ocean (Bangladesh).

Palm Sunday Tornado April 11 , 1965 271 deathshttp://www.crh.noaa.gov/dtx/palmsunday/

Super tornado outbreak April 3-4, 1974 315 deathshttp://www.april31974.com/

http://www.tornadoproject.com/toptens/toptens.htm

Radar

Doppler Radar

http://www.oar.noaa.gov/spotlite/2008/spot_radar.html

Phased array radars

Tornadoes

Tornado windsMeasurement based upon damage after

storm or Doppler radarFor southwest approaching storms, winds

strongest in the northeast of the storm, 220 kts maximum

Multi-vortex tornados

Tornadic Formation

Basic requirements are: an intense thunderstorm Vertical wind shear Cold air aloft and warm moist air near

surface (unstable conditions) Initiation of convection Capping inversion

Vertical wind shearCold air aloft and warm moist air near surface (unstable conditions)Initiation of convectionCapping inversion

Tornadoes

Seeking shelterBasement or small, interior room on ground

floorIndoor vs. outdoor pressure

The Fujita ScaleBased upon the damage created by a stormF0 weakest, F5 strongestEnhanced Fujita Scale

Severe Weather and Doppler Radar Doppler radar measures the speed of

precipitation toward and away radar unit Two Doppler radars can provide a 3D

view TVS, Doppler lidar NEXRAD

Waterspouts

Rotating column of air that is connected to a cumuliform cloud over a large body of water

Tornadic waterspout