Figure 3-9. Wind Shift Across a Cold Front

CHAPTER THREE

AVIATION WEATHER

maintain your original ground track (Figure 3-9). This wind shift often creates a hazardous wind

shear when departing or approaching an airfield. For example, winds at 220 at 10 knots ahead

of the front can rapidly change to 330 at 20 knots gusting to 30 knots immediately after the

front.

WINDSHIFT X

WINDSHIFT REQUIRES

ALTERATION TO

WINDSHIFT REQUIRES

THE RIGHT

ALTERATION TO THE RIGHT

WINDSHIFT

Figure 3-9 Wind Shift Across a Cold Front

307.

FACTORS INFLUENCING FRONTAL WEATHER

The weather along fronts is not always severe. Flying conditions can vary from insignificant

weather to extremely hazardous situations. The hazardous situations can include thunderstorms,

turbulence, icing, low ceilings, and poor visibility. The severity of the clouds and precipitation

occurring along a front are dependent on the following factors:

The amount of moisture available (shown by the dew point),

The degree of stability of the lifted air,

The slope of the front,

The speed of the frontal movement, and

The contrast in the amounts of temperature and moisture between the two air masses.

The amount of moisture available, as indicated by the dew point, greatly determines the amount

of weather associated with a front. Often little or no significant weather is associated with a

front or a portion of a front because of a lack of moisture, despite the presence of all other

factors.

The degree of stability of the air lifted determines whether cloudiness will be predominantly

stratiform or cumuliform. With stratiform clouds, there is usually steady precipitation and little

3-10 Mechanics of Frontal Systems