The problem is overwhelmingly complicated by the fact that each individual aircraft will respond differently to the same meteorological conditions. Meteorologists forecast the meteorological factors, but the aerodynamic factors are as variable as the number of aircraft flying at the moment the forecast verifies. Likewise, pilots can not be expected to interpret forecasts of cloud liquid water, cloud droplet size, and air temperature. Upward vertical motion is necessary to create cloud liquid water and large cloud droplets.
Upward motions occur in many weather features.
Large-scale motions of a few centimeters per second cause much of the weather pilots experience and are well forecasted by today s operational numerical models. However, some upward motions are also caused by atmospheric instabilities which meteorologists call convection. Convective upward velocities may be as high as 50 meters per second in thunderstorms, rapidly creating cloud liquid water and large cloud droplets within the cloud. Lesser convective upward velocities are just as effective in creating cloud liquid water and large droplets although it takes more time. For example, stratocumulus cloud tops contain a substantial amount of cloud liquid water.