Microbursts

Remarkably valuable material is available these days on wikipedia.

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

Sailplaners will have a good understanding of natural air flow.
This text seems to suggest that you can take an unenclosed 'parcel'
of air, and move it through the surounding air, like you can throw
a solid object through the air.

I can't find good explanations of why the text is 'wrong'.

Microburst

From Wikipedia, the free encyclopedia

[5]A photograph of the surface curl soon after an intense microburst
impacted the surface

A falling potatoe may 'impact' the floor, but air can't impact the floor
any more than a 'swirl' [being a separate volume of the liquid] inside
your coffee cup can impact the surface.

A microburst is a very localized column of sinking air, producing
damaging divergent and [7]straight-line winds at the surface that are
similar to but distinguishable from [8]tornadoes which generally have
convergent damage.

The 'localisation' is the problem.
To move a small volume with respect to its surroundings, you have to
apply energy to this 'localisated package' and not to its surroundings.
I guess lightning/thunder does that ?
Perhaps a laser could too.

The term was defined by severe weather expert [9]Tetsuya Theodore
Fujita as affecting an area 4 km (2.5 mi) in diameter or less,
distinguishing them as a type of [10]downbursts and apart from common
[11]wind shear which can encompass greater areas. Dr. Fujita also
coined the term macroburst for downbursts larger than 4 km (2.5 mi).

A distinction can be made between a wet microburst which consists of
precipitaiton and a dry microburst which consists of [12]virga. They
generally are formed by precipitation-cooled air rushing to the
surface, but they perhaps also could be powered from the high speed
windsofthe [13]jet stream deflected to the surface in a
[14]thunderstorm (see [15]downburst).

Microbursts are recognized as capable of generating wind speeds higher
than 75 m/s (168 mph; 270 km/h).

Danger to aircraft

See also: [17]downbursts

The scale and suddenness of a microburst makes it a great danger to
aircraft, particularly those at low altitude which are taking off and
landing.The following are some fatal crashes that have been
attributed to microbursts in the vicinity of airports:
* [18]Delta Air Lines Flight 191
* [19]Eastern Air Lines Flight 66
* [20]Pan Am Flight 759
* [21]USAir Flight 1016

A microburst often causes aircraft to crash when they are attempting
to land. The microburst is an extremely powerful gust of air that,
once hitting the ground, spreads in all directions. As the aircraft is
coming in to land, the pilots try to slow the plane to an appropriate
speed. When the microburst hits, the pilots will see a large spike in
their airspeed, caused by the force of the headwind created by the
microburst. A pilot inexperienced in microbusts would try to decrease
the speed. The plane would then travel through the microburst, and fly
into the tailwind, causing a sudden decrease in the amount of air
flowing across the wings. The sudden loss of air moving across the
wings causes the aircraft to literally drop out of the air. The best
way to deal with a microburst in an aircraft would be to increase
speed as soon as the spike in airspeed is noticed. This will allow the
aircraft to remain in the air when traveling through the tailwind
portion of the microburst.

OTOH I've heard the big-jet's 'exhaust' and downwash also
'stays together like a solid' and doesn't disperse.

How much of this is true ?

If you've got a conical bucket of white-water, with a mechanism
to close off the lower 25% of the cone, can you project a black-ball
of water down through the white-water, and capture it by closing
of the lower clone section ?

Or will the black-ball of water just be dispersed ?

If an aircraft/bomber had it's front blown-off so that the
pilots had no shielding in front of them, would they necessarily have
near flying speed winds 'impacting' them, if the airflow had no
'reason' to flow in, 'cos it's got no low resistance path to flow out ?

== Chris Glur.