The wreck of a private plane at Salt Lake Airport No. 2 this week apparently was caused by a weather phenomenon called a microburst, meteorologist Bill Alder said.
The isolated but violent wind storms can be deadly for aircraft, Alder said, because they produce "wind speeds of up to 80 miles per hour and can drop a plane 7,000 feet in a minute."Microbursts are produced by dying cumulonimbus cloud formations, "and the easiest way to spot them is to look for virga - rain falling from the cloud that evaporates before it can reach the ground - and a rough looking cloud base," said Alder, meteorologist in charge at the National Weather Service Salt Lake station.
"During this later stage, the thunderstorm can be in the state of total collapse, with light amounts of rainfall," he said. If the air beneath the cloud is very dry, "most of the rainfall normally evaporates, and evaporative cooling further cools the already cold air aloft.
"The colder and more dense air then races to the ground. This down rush of air resembles the water from a hose aimed downward, spreading out in all directions when it reaches the ground."
The winds usually die out after covering only a few miles and have a "lifetime of less than 15 minutes, but they can be extremely damaging," Alder said.
Several major aircraft disasters have been attributed to microbursts, he said, including the crash Aug. 2, 1985, of an L-1011 at Dallas-Fort Worth Airport that killed 131 people and the crash June 24, 1975, of a Boeing 727 at Kennedy International Airport that killed 112.
In the minor crash Wednesday at the suburban Salt Lake airport, Alder said, the strong winds "forced a small plane down and later flipped it over." There were no serious injuries in the accident.
The winds also are a danger to boaters, he said, because they can "quickly capsize a sailboat or swamp many small boats."