ICAO Doc 9817 - Manual of Low-Level Windshear ICAO
RECOGNITION OF WIND SHEAR
External MET clues

4.3.3 Recognition of external MET clues to the possible presence of low-level wind shear near an airport permits the pilot to make an early decision to avoid an encounter by going around or by delaying the approach or take-off until conditions improve. Even if the decision is made to continue, the recognition of external wind shear signs should alert the pilot to pay close attention to the progress of the landing or takeoff by reference to the flight deck instruments. External clues that may be directly visible to the pilot include the following:

a) strong, gusty surface winds, especially where the aerodrome is located near hills or where there are comparatively large buildings near the runway, indicating the possibility of local wind shear and turbulence;
b) lenticular cloud (smooth lens-shaped altocumulus) indicating the presence of standing waves, usually downwind from a mountain;
c) virga, i.e. precipitation falling from the base of a cloud but evaporating before reaching the ground (especially under convective cloud) because downdrafts may still exist and reach the ground even though the precipitation itself has evaporated;
d) roll cloud girding the base of a thunderstorm and advancing ahead of the rain belt, indicating the presence of a gust front;
e) areas of dust raised by wind, particularly when in the form of a ring below convective clouds, indicating the presence of a downburst;
f) wind socks responding to different winds;
g) smoke plumes sheared, with upper and lower sections moving in different directions; and
h) thunderstorms, which should always be assumed to have the capability of producing hazardous wind shear.

The implication of any of the foregoing for landing and take-off operations at an aerodrome would have to be assessed on a case-by-case basis, depending on the proximity of the phenomena to landing and take-off corridors, etc.