Total obscuration occurs when which fraction of the sky is obscured by surface-based obscuration?

Total obscuration is defined as the situation in which the entire sky, or 100% of the sky (8/8), is obscured by surface-based obscuration. This means that no portion of the sky is visible due to phenomena such as fog, mist, rain, or other conditions that block the observer's view of the sky. When determining obscuration levels, it is important to recognize that a measure of 8/8 indicates the complete obscuration of the sky, aligning with the definition of total obscuration.

In contrast, fractions such as 4/8, 6/8, or 2/8 indicate partial obscuration, where a portion of the sky remains visible. Understanding these fractions helps aviators and meteorologists assess weather conditions and make informed decisions regarding flight safety and operations.