Refer to figures.
LOW-LEVEL WINDSHEAR

Low-level wind shear are sudden changes in wind speed and/or wind direction up to altitudes of 1600 ft (500 m) above-ground and is a hazardous meteorological phenomenon in aviation. It may radically change the aerodynamic circumstances of the flight, particularly the critical phases of flight - during the final approach path and landing, take-off and initial climb-out flight paths - and consequently, it may threaten human lives and the health of passengers, people at the airport and its surrounding areas.

There can be several causes of low-level wind shear:

• The passage of the front in which the isobars change direction;
• A marked temperature inversion;
• Sea breeze;
• Topography and large buildings;
• Surface friction; and
• Cumulonimbus clouds, and their associated weather of heavy rain and hail, which can give rise to the phenomenon known as Microburst.

General information on Windshear

WIND SHEAR is a sudden, drastic shift in wind speed and/or direction that occurs over a short distance at any altitude in a vertical or horizontal plane. It can subject your airplane to sudden updrafts and downdrafts (vertical windshear), or extreme horizontal wind components, causing loss of lift or violent changes in vertical speed or altitudes.

• Vertical wind shear is defined as change of horizontal wind direction and/or speed with height, as would be determined by means of two or more anemometers mounted at different heights on a single mast.
• Horizontal wind shear is defined as change of horizontal wind direction and/or speed with horizontal distance, as would be determined by two or more anemometers mounted at the same height along a runway.