Texas Tech University's Wind Engineering Research Center, which has been conducting research in tornado safety and damage for more than twenty-five years, dispatched a team of three people to both sites. The on-site damage documentation efforts were designed to answer the following questions: (1) Why or what circumstances caused such a large number of fatalities? (2) What was the type and extent of damage considering the quality of construction? (3) What wind speed intensity would be necessary to cause this type of damage? and (4) If In-Residence Shelters, the design specifications of which were developed by Texas Tech, were in the path of these tornadoes, would they have provided protection for residential occupants? The answers to these questions in the Jarrell, Texas tornado have been assembled; the answers for Central Florida tornadoes are under consideration.
The Jarrell, Texas tornado was a 1500 ft wide, very slow moving (5-10mph) tornado which impacted each single-family residential structure with high winds for more than two minutes. Residences in rural Jarrell were not built according to good quality construction practices. The combination of the long duration of high winds and the low quality of construction allowed roof, exterior walls and interior walls to be swept from the foundation. The clean appearance of foundations after the tornado would lead to a classification of the tornado as an F5 category though wind speeds of 150-180 mph are capable of inflicting this type of damage. The loss of exterior and interior walls removed any protection to people even if they hid in interior rooms. It is conjectured that people themselves became missiles in the persistently high winds. The In-Residence Shelter which is designed for a 260 mph wind speed would have survived and would have provided protection to residential occupants in this tornado.
The documented data from Central Florida tornadoes are under review. Preliminary observations are: (1) most of the fatalities occurred to occupants of manufactured (mobile) homes and recreational vehicles, (2) manufactured homes and recreational vehicles are vulnerable to toppling, rolling and disintegration; (3) most of the reinforced concrete block masonry walls remained standing, (4) hurricane straps provided a good connection between roof trusses and walls, (5) garage doors and garage walls are vulnerable to wind pressure failure and (6) wind speeds of 150-170 mph could have caused the type of damage observed.
The presentation will discuss current technology in occupant protection in tornadoes and project into the future for what is needed to save lives in severe storms.