Can someone please explain how a dry microburst forms?

Question

Can someone please explain how a dry microburst forms?

Answer 1

Basically, a thunderstorm develops in an airmass that is relatively dry, with little precipitation generated in the storm.  Now recall two physical laws:  Colder air is heavier than warmer air, and evaporation is a cooling process.  What basically happens is that a mass of air within the storm descends, and it descends into the relatively dry layer below the cloud base.  As it does that, the relatively meager amount of rain in that air gets evaporated as it descends through the dry lower level air.  This in turn cools the descending airmass, which makes it heavier and heavier with respect to the surrounding warm and dry air.  This causes the airmass to accelerate downward, eventually crashing to the surface and spreading out, with wind speeds equivalent to a weak tornado in some cases.    

Answer 2

Micro- bursts are one of the least known meteorological phenomenon simply because it is so sudden and it lasts only a very short time.

They appear as a kind of inverted tornado on the edge of a strong thunderstorm. The air then falls all the way to the ground and represent a great danger mostly to aviation.

Strong convection like thunderstorms are a mixture of ascending and descending air masses. The combination of the two creates shear winds that are not pleasant to aviation. If there is a possibility to see them develop, the met office diffuses a so called SIGMET (significant meteorology) with a SW (shear wind) probability).

Whenever I intend to fly my little aircraft and see such a warning, I stay on the ground. Micro-busts are never warned other than by other pilots who have flown in it prior to you. But they report it as shear wind.