Observed hazards to aircraft in deep summertime convective clouds from 4-7 km

These flights, usually flown during the summer months in the central and high plains in the United States, targeted regions of convective storms containing vigorous updrafts, downdrafts, and precipitation, including hail.

Observations indicate that three of the most hazardous components of flying in summertime deep convective clouds are aircraft icing, turbulence from strong vertical wind gradients, and hail. There is also a smaller, but still important, threat from lightning. Statistics of the observations show that at any given time there is approximately a 10% probability of encountering severe icing conditions, approximately a 0.1% probability of encountering extreme turbulence, and approximately a 0.2% probability of encountering hail with mean diameter 2.5 cm or greater within convective clouds in the 4-7 km mean sea level altitude range.