I am living in what can be called a high plains environment near Denver, Colorado. A day ago we had close encounter with a high wind knocking a 40 year old tree out at the root base. News media referred to this as a dry micro burst. So I wnet onto the wiki and looked:
https://en.wikipedia.org/wiki/MicroburstWhen rain falls below the cloud base or is mixed with dry air, it begins to evaporate and this evaporation process cools the air. The cool air descends and accelerates as it approaches the ground. When the cool air approaches the ground, it spreads out in all directions. High winds spread out in this type of pattern showing little or no curvature are known as straight-line winds.[5]
Dry microbursts produced by high based thunderstorms that generate little to no surface rainfall, occur in environments characterized by a thermodynamic profile exhibiting an inverted-V at thermal and moisture profile, as viewed on a Skew-T log-P thermodynamic diagram. Wakimoto (1985) developed a conceptual model (over the High Plains of the United States) of a dry microburst environment that comprised three important variables: mid-level moisture, a deep and dry adiabatic lapse rate in the sub-cloud layer, and low surface relative humidity.
A news report with video and a picture of the fallen tree:http://www.newslocker.com/en-us/regi...nto-home/view/
We get quite a few of these here because it can be 65% humidity up in the mountains near Georgetown and 10% or 15% out on the plains. I had always known of these things as simply downdrafts or wind shears (pilots in the family). I never did check out the science of this before though. I know that cold air drops the same as rocks though. That is why NCAR (Home | National Center for Atmospheric Research) is based at Boulder, Colorado. No matter where you live, there are risks from the weather or nature in one form or another. This is one of our local risks that I never really thought about.