HN39,
Check the RuFAB results...(Runway friction charecturistics measurement and aircraft braking)
RuFAB
(ever used the SNOWTAM report???)
and
Runway surface condition assessment..
"4.41 Rainfall brings moisture to the runway, which will have an effect on aircraft performance. Flight test data shows that even small amounts of water may have a significant effect on aircraft performance, e.g. damp runways effectively reduce aircraft braking action below that of a clean and dry runway."
(based on ESDU data accounts that for variations in water depth from damp to flooded, runway surface texture within the defined texture levels, tire characteristics and experimental methods.)