Revelation is a trainer is advocating a factor of 0.5 in the evaluation of visibility in precipitation. This means in rain a 2km visibility can be interpreted as 1km. The dynamic term is also introduced by him. I search everywhere to no avail. I do discount the concept but the experience may be contrived from the simulation job.
Thereafter the correlation interpretation of the visibility to contingency planning and fuel uplift is up to the individual. With particular reference to single runway stations without the luxury of low visibility operations, which could possibly due to cost and funding.
Thanks again for sharing and the inputs.