Tornadoes - Severe Convective Storms and Tornadoes: Observations and Dynamics - page 309

Figure 6.4. Tornadoes surrounded by precipitation and partially obscured, when viewed
looking to the south or southwest. (Top) May 14, 1986, near Snyder, OK; (bottom) June
13, 2010, in the eastern Oklahoma Panhandle (photographs by the author).

gusts, by aerodynamic effects produced as the airflow interacts with structures
(e.g., lift may develop and rip roofs from buildings), from the impact of flying
debris, and from structures tipping over and even being rolled over repeatedly.
Engineers have been investigating the nature of tornado wind damage under con-
trolled conditions in the laboratory, particularly at Texas Tech University in
Lubbock. The results of such studies are beyond the scope of this text.
Damage debris may be lofted directly by upward wind currents or by
aerodynamic effects. Debris may be detected by polarimetric Doppler radar as a
region of relatively low co-polar cross-correlation coecient

HV ( Figure 6.6 )
because debris tends to tumble so that the longest axis of radar cross sections of
the debris tend not to be favored along any direction. To be detected by radar at
long range, the debris must obviously be lofted high enough so that it is above the
radar horizon. While ground teams often survey damage from tornadoes, swaths
of damage are often best seen from aircraft or helicopters or from satellites
( Figure 6.7 ).