What does the VV001 in a METAR report signify?

In a METAR report, the notation VV001 signifies a vertical visibility of 100 feet, indicating an indefinite ceiling at that height. This typically means that an observer cannot determine a more precise ceiling because of obscuration such as fog or other phenomena preventing clear visibility. A vertical visibility report is often issued when the weather conditions are such that the ground cannot be seen clearly.

The use of "VV" denotes vertical visibility, and the digits following it indicate the distance, generally measured in feet. Therefore, if the visibility is listed as "VV001," it is interpreted as an indefinite ceiling of 100 feet. Recognizing this notation is essential for assessing flight safety, particularly regarding takeoff and landing conditions, where understanding the ceiling height in relation to aircraft operations is critical.

Understanding the context of METAR reports is crucial for pilots and dispatchers, as these reports contain vital weather information that influences flight plans and safety measures.