QF severe turbulence encounter last year.
AO-2009-029
Hit a CB top at night. There was no mention in the report of gain control use by the crew. Useful hint from radar manuals is to use manual gain control at max setting at high altitudes. This produces more radar power (3000 percent is the figure quoted) and CB tops of ice crystals can often be detected as a slight echo. However if gain control is in auto mode the tops may not show up at high altitudes. Once the very small echo of the ice crystals in the CB are seen on the radar screen (usually at 40-60 miles depending on tilt), the actual extent of the CB is readily seen by lowering the tilt with gain in auto. Good way to prove the theory is to practice this technique in the clear on isolated CB's. In one Pacific airline I flew with on 737's this technique worked well and saved us grief at night or IMC.