What improvement in weather was reported at Lubbock (KLBB) between specific times?

The answer indicating that vertical visibility improved by 2,000 feet is correct because it directly addresses a specific weather change that can impact flight operations and ground visibility. In aviation, vertical visibility refers to the vertical distance that can be seen in a given direction, particularly useful in assessing cloud cover and fog conditions. An improvement in vertical visibility by 2,000 feet suggests that the conditions have become more favorable for flight operations, as pilots and dispatchers need clear visibility both horizontally and vertically to ensure safety during takeoff and landing.

When vertical visibility increases, it typically means that the weather conditions are improving, allowing for safer flight maneuvers. Clear vertical visibility helps in identifying obstacles and ensuring sufficient airspace for operations.

While shifting winds and frontal passages can affect weather conditions, they do not provide a clear improvement metric like vertical visibility does. Similarly, while temperature and dewpoint spread information is crucial for understanding potential weather changes, it doesn't explicitly indicate visibility improvements. Increased winds can signify changing weather systems but do not inherently indicate positive improvements in weather for flight operations. Therefore, the option related to vertical visibility stands out as the most relevant in the context of assessing weather improvements at the airport.