82 NC counties and 1 VA county are under alert, including Wake, Cumberland, Durham, Johnston, and Orange counties. Details
Published: 2007-07-13 10:55:43
Updated: 2007-07-13 10:55:43
Posted July 13, 2007
By Russel Ford Jr
MIKE MOSS SAYS: Russell, The color of a tornado depends on quite a variety of factors, and how they combine in various shades of importance will yield the final appearance. Some of these factors include the direction and elevation of the sun, the surrounding cloud cover in the vicinity of the tornado, the direction from which it is seen with respect to the sun and any precipitation of cloud cover in the foregraound or background, what kind of surface the tornado is passing over (i.e. a tornado crossing an expanse of mixed sand and red clay might take on a reddish hue, while a tornado crossing farmland with rich, dark topsoil may appear almost black, etc). A tornado that forms with plenty of humid air around it will likely form a thick cloud that may look dark, grey, or white depending upon whether it is lit from the front or from behind, and one that forms with a shallow layer of relatively dry air around it may be largely invisible, at least until the pressure drops enough to cause at least some condensation or until there is enough dust, dirt and debris in the air to give it some form and color.
As to the F0 versus EF0 tornado intensity scales. The F0 rating represents the classic Fujita damage scale and corresponded to an estimated wind speed range of 40-72 mph, while the newer "Enhanced Fujita" or "EF" scale estimates that wind speeds for a "0" rated tornado fall into the range of 65-85 mph.