Which condition could prompt a pilot to issue a PIREP for turbulence?

Issuing a PIREP (Pilot Report) for turbulence is important for ensuring the safety of flight operations. The correct answer involves reporting significant turbulence during flight. This action provides valuable information to other pilots and air traffic control about the conditions being experienced in the airspace.

Significant turbulence can greatly affect the safety and comfort of flights, and timely reports can help warn others to expect similar conditions. When pilots encounter turbulence that is strong enough to be classified as significant, it is crucial for them to communicate this to enhance situational awareness and facilitate better decision-making for upcoming flights in that area.

The other choices focus on visibility and wind speeds, which may be relevant for certain operational aspects but do not directly correlate with the pilot's experience of turbulence. Visibility over 5 miles and surface winds less than 10 knots do not indicate the presence of turbulence and therefore do not warrant a PIREP for that condition. Wind speeds below 10 knots may also suggest calm conditions that are less likely to be associated with significant turbulence. In contrast, the experience of turbulence is distinctly evident during flight, which is why that specific condition prompts a PIREP.