What does "VIS 3/4 V 1 1/2" signify in weather reports?

The notation "VIS 3/4 V 1 1/2" in weather reports indicates that visibility is varying between two specific values, in this case, 3/4 mile and 1.5 miles. This means that the meteorological observer has noted fluctuations in visibility, which can be influenced by factors like weather conditions such as fog, rain, or dust.

The "V" in this context serves as a separator, indicating a range rather than a single, constant measurement of visibility. When interpreted correctly, it shows that at times, visibility may be as low as 3/4 mile and at other times may increase up to 1.5 miles.

Other interpretations would not appropriately reflect the nature of the visibility report, as the first option suggests a fixed visibility of 3/4 mile, which is inaccurate in this case. The second option infers a direction of change that is not indicated in the report; the notation does not imply that visibility is decreasing from one measurement to another. Finally, the last option misunderstands the units used in the context – visibility is reported in statute miles, not nautical miles.

Thus, understanding how "VIS" and the accompanying values function clarifies that this specific report denotes