Ice a density about one quarter of that of pure ice. Hard rime is comparatively dense. Ice pellets are a form of precipitation consisting of small, translucent balls of ice. This form of precipitation is also referred to as "sleet" by the United States National Weather Service. (In British English "sleet" refers to a mixture of rain and snow). Ice pellets are usually smaller than hailstones. They often bounce when they hit the ground, and generally do not freeze into a solid mass unless mixed with freezing rain. The METAR code for ice pellets is "PL". Ice pellets form when a
Cumulonimbus and aviation the shear between rising and sinking air. If the airspeed is too high at this point, the airplane will break apart. The crash of Flight AF 447 is indirectly related to this situation: the pilot, being short on fuel, opted for the shortest path while crossing the thunderstorm line associated with the intertropical convergence zone, and the pitot tubes iced over. What followed is known. On-board radars can be deceiving. Hail shafts generate weak radar echoes and are significantly more dangerous than cloudbursts. Close to the ground, heavy rain (or snow at altitude) tends to dampen turbulence (it is said