Frontal Turbulence

AVIATION WEATHER

CHAPTER FIVE

Avoid the rotor, lenticular, and the cap clouds since they contain intense turbulence and

strong updrafts and downdrafts.

Approach the mountain range at a 45 angle, so a quick turn can be made away from the

ridge if a severe downdraft is encountered.

Avoid the leeward side of mountain ranges, where strong downdrafts may exist, until

certain turbulence is not a factor.

Do not place too much confidence in pressure altimeter readings near mountain peaks.

They may indicate altitudes more than 2500 feet higher than the true altitude.

Slow to the turbulence penetration airspeed recommend in your aircraft NATOPS or

Dash-One Technical Order.

Frontal Turbulence

Frontal turbulence is caused by lifting of warm air, a frontal surface leading to instability, or the

abrupt wind shift between the warm and cold air masses. The vertical currents in the warm air

are the strongest when the warm air is moist and unstable. The most severe cases of frontal

turbulence are generally associated with fast-moving cold fronts. In these cases, mixing between

the two air masses, as well as the differences in windspeed and or direction (wind shear), add to

the intensity of the turbulence.

Figure 5-6 Frontal Turbulence

Ignoring the turbulence resulting from any thunderstorm along the front, Figure 5-6 illustrates

the wind shift contributing to the formation of turbulence across a typical cold front. The wind

speeds are normally greater in the cold air mass.

Wind Shear Turbulence

Large-scale wind shear turbulence results from a relatively steep gradient in wind velocity or

direction producing eddy currents that result in turbulence. Wind shear is defined as a sudden

Weather Hazards of Turbulence, Icing, Ceilings, Visibility, and Ash Clouds

5-9