As twisted said, the 1 in 60 rule works fine. To determine the cloud ht, the wx beam is raised by turning the tilt knob until the cloud just disappears from the screen. Let's say our beam has a width of 5°:
- if the cloud disappears as tilt setting reads, for example, "4½° UP" (which means a beam centreline 4½° above the horizontal), then the beam's LOWER line (& hence the cloud top) is 2° above your current alt.
- should U B, for example, 45nm away, using the 1 in 60 rule U get a cloud top of 9,000' above your current alt.... so plenty of time to climb & pass above it. Don't forget the recommended 2,000' margin if your cloud is a CB !!
MF