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-Scale Enhanced Fujita Scale Feb F Scale Wind Speed EF-Scale F045-78EF F EF F EF F EF F EF F EF Wind speeds in mph, 3-second gust Objectives: 3, EF-Scale structure; 4, EF vs F-Scale

DOD to Wind Speed to EF-Scale EF-Scale Categories Wind Speed Ranges EF EF EF EF EF EF5>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 constructed house can be blown away by winds much less than 260 mph (. Evidence indicates a well constructed house can be blown away by winds much less than 260 mph ( Phan and Simiu,2003). The framed house is one of only a few F-scale damage indicators.

Tornadoes Tornado outbreaks Families, super outbreak

Super tornado outbreak April 3-4, deaths

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

May Oklahoma City 66 tornadoes 46 fatalities, 800 injured 1.5 billion damage An F-5 tornado tornado-outbreak-highlights-importance-of-warnings/ tornado-outbreak-highlights-importance-of-warnings/

Fig , p. 396

Tornadoes Tornado Occurrence US experiences most tornadoes Tornado Alley (warm, humid surface; cold dry air aloft) Highest occurrence spring (may June), lowest winter Highest 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, deaths Super tornado outbreak April 3-4, deaths

Radar Doppler Radar Phased array radars

Tornadoes Tornado winds Measurement based upon damage after storm or Doppler radar For 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 shear Cold air aloft and warm moist air near surface (unstable conditions) Initiation of convection Capping inversion

Tornadoes Seeking shelter Basement or small, interior room on ground floor Indoor vs. outdoor pressure The Fujita Scale Based upon the damage created by a storm F0 weakest, F5 strongest Enhanced 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