Everybody meet that phenomenon if a big storm comes (for example a cold front after a long heater period), before the arriving there is a short silence time, when there isn't nothing (no wind, no bird sing, no annoying bugs), and after that suddenly the storm comes.
What causes this phenomenon (silence), and from where do the animals and bugs know that comes a storm?
As from this website
As the warm, moist air is pulled into a storm system, it leaves a low-pressure vacuum in its wake. The air travels up through the storm cloud and helps to fuel it. The updrafts in the storm, however, quickly carry the air upward, and when it reaches the top of the cloud mass, this warm moist air gets spit out at the top. This air is sent rolling out over the big, anvil-shaped head of the thunderclouds or the roiling arms of hurricanes. From there, the air descends -- drawn back toward lower altitudes by the very vacuum its departure created in the first place.
This warm, dry air is relatively stable, and once it blankets a region, it stabilizes that air in turn. This causes the calm before a storm.
A very good interactive animation is given in the site from which I qouted.
