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c. It is important to remember that both up and down drafts develop. Turbulence is
more severe when updrafts and downdrafts are close together. Even if the air is very dry with
no clouds, convective turbulence may be present.

5. Mechanical Turbulence
a. An object placed in any moving air current disturbs the flow by causing the wind to
change its direction of flow to go around the object. Mechanical turbulence is caused by wind
flowing over or around an obstruction. The area before the obstacle is called the windward
side; the area after is the leeward side

b. Air currents separate to flow around an obstacle and rejoin after they pass the
obstacle. When they rejoin, eddy currents develop in the flow that has passed the obstacle.
These eddy currents create mechangcal turbulence. If the obstacle had not been there, and
no other factor influenced the flow, the wind would flow smoothly and undisturbed.
Mechanical turbulence is caused by obstructions in the path of the wind, and is not caused by
meteorological processes in the air mass itself. Some objects which tend to produce this type
of turbulence are mountains, hills, buildings, and moving aircraft.