A different question on Microburst? I'm really confused.?

Question

I can't understand the part on Why the microburst is formed so quickly ...

On hot day shouldn't the hot air rises continuously throughout the day?! ... if so, once it's cool it will sink back to down which should also be a continuous process ...

Why does microburst form very quickly & only last a short period of time?? ... i kept thinking it should last thoughout the day as long as the sun is out & temperature is high ...

Answer 1

here site and some info for you.A microburst is a very localized column of sinking air, producing damaging divergent and straight-line winds at the surface that are similar to but distinguishable from tornadoes which generally have convergent damage. and thats what a micoburst does so it normal.

Location of Highest Probability within the United States Midwest/West Southeast

Precipitation Little or none Moderate or heavy

Cloud Bases As high as 500 mb Usually below 850 mb

Features below Cloud Base Virga Shafts of strong precipitation reaching the ground

Primary Catalyst Evaporative cooling Downward transport of higher momentum

Environment below Cloud Base Deep dry layer/low relative humidity/dry adiabatic lapse rate Shallow dry layer/high relative humidity/moist adiabatic lapse rate

Surface Outflow Pattern Omni-directional Gusts of the direction of the mid-level wind

Answer 2

I'll try and help you visualize.  The thing is that thunderstorms aren't one large region of constant smooth updraft.  Rather, it's more like watching a roiling boil in a pot of water.

A thunderstorm works to overturn the thermally unstable air and make the environment more stable, so the hot thermal updrafts you mention go hand-in-hand with the cold air microburst coming down.   Cold air on the bottom and warm air up top is more stable.

Now, as you know microburst forms in intense convection where rain cooled air rushes down from the cloud.  Of course the thunderstorm is very turbulent with areas of strong updrafts and areas of little updraft, and even regions dynamic downdraft.  When the cool air moves into a part of the cloud that doesn't have an intense updraft, it is suddenly able to come down to the ground.  This is why it happens rather quickly.   It's because the intense updrafts aren't constant through the whole cloud.  Just as when you watch water boil, you see bubbles in some spots (updrafts) but not others (neutral or dynamic downdraft).