Aviation Weather Services, Advisory Circular 00-45F, Change 2 (March 2009) 19 APPENDIX J: Turbulence and Icing Intensity Depictions Table J-1. Turbulence Intensity Intensity Aircraft Reaction Symbol Light Loose objects in aircraft remain at rest.
Moderate Unsecured objects are dislodged. Occupants feel definite strains against seat belts and shoulder straps.
Severe Occupants thrown violently against seat belts. Momentary loss of aircraft control. Unsecured objects tossed about.
Extreme Aircraft is tossed violently about, impossible to control. May cause structural damage.
Table J-2. Icing Intensity Intensity Aircraft Reaction Symbol Trace Ice becomes perceptible. Rate of accumulation slightly greater than sublimation. Deicing/anti-icing equipment is not used unless encountered for an extended period of time (over 1 hour).
Light The rate of accumulation may create a problem if flight is prolonged in this environment (over 1 hour). Occasional use of deicing/antiicing equipment removes or prevents accumulation. It does not present a problem if this equipment is used.
Moderate The rate of accumulation is such that even short encounters become potentially hazardous, and use of deicing/anti-icing equipment or diversion is necessary.
Severe The rate of accumulation is such that deicing/anti-icing equipment fails to reduce or control the hazard. Immediate diversion is necessary.
AC 00-45F, CHG 2 Appendix J: Turbulence and Icing Depictions Page 19-1