Weather radar may help during a rain storm, but don’t rely on it particularly when a storm has just passed and the runway is still draining.
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TP 14002E Wet Runway Friction: Literature and Information Review.
Page 10 table 2.1 Hydroplaning - correlates tyre tread / water depth with rainfall rates.
WXR colours indicate approximate rates – yellow up to 0.5 in/hr, red greater than 0.5 in/hr.
Thus with little tyre tread on a smooth runway you are at risk in yellow rainfall, elsewhere red rainfall.
Page 11, Figs 2.1, 2.2. suggest that water depth should not approach the 3 mm contaminated category, but I do not believe that this data takes into account puddles or only requiring 25% of the surface to be covered.
However Fig 2.7 on Page 15 does indicate the potential for flooding (0.1”) with yellow / red rainfall rates (0.5 in/hr). Note the text re factors and drainage.
Note page 34 re storms “The greatest decrease (friction) will probably occur at the start of the rainstorm if contaminants are present, as they are likely to produce a greasy surface.
Fig 3.11/12 Page 38 indicates that low friction levels can be experienced in ‘damp’ conditions on smooth concrete runways.
Note the summary on page 49 and the discussion on grooves, contaminants, and tyre pressure thereafter.
Hydroplaning aspects - page 59.
Summary Page 83.
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Colour standards for weather radar.