wrote:

...I've got problems with this
http://en.wikipedia.org/wiki/Microburst

This text seems to suggest that you can take an unenclosed 'parcel'
of air, and move it through the surounding air....

Chris,

It is true. Microbursts are real, and they can be deadly.

Do you feel the air from a fan "impact" your hand? Can you see the
effect of its impact on a curtain? I believe you will agree that the
answer is, Yes. Obviously then, there can be parcels of air that
move in a different way then the larger air mass. The surface effect
of the microburst may be seen on the surface of a lake, or a field
of grain, or even on a forest.

Several airline accidents, including Delta 191 in Dallas
http://www.airdisaster.com/special/special-dl191.shtml
have been caused by microbursts.

The NWS (US National Weather Service) says:
"Microburst - A small, concentrated downburst affecting an area
less than 4 kilometers (about 2.5 miles) across. Most microbursts
are rather short-lived (5 minutes or so), but on rare occasions
they have been known to last up to 6 times that long."

Google "microburst" and you'll find much useful information.


Jack