Final answer:
A pilot can determine that a front has been penetrated by observing atmospheric discontinuities such as changes in air temperature, wind direction, and pressure along with cloud formations, visibility and precipitation.
Step-by-step explanation:
While in flight, a pilot can identify that a front has been penetrated by noting certain atmospheric discontinuities. Some clear indicators may include a sudden change in air temperature, wind direction, and air pressure. When crossing a front, a pilot might also notice variations in cloud formations, visibility, and precipitation. For instance, if a pilot passes from a warm air mass to a colder one typically associated with a cold front, they would experience a noticeable drop in temperature. This colder air mass is typically more stable and can lead to clearer skies.
On the other hand passing from a cold to warm air mass often associated with a warm front might present with increased cloudiness and potential precipitation. These changes are important because they can affect flight safety and performance, and being aware of these weather conditions is crucial for pilots.