Hey, I am just curious as to what these Trubulence Codes i heard today!? here in HNL it's pretty rainy and Cloudy today, and Listening to my scanner i hear ATC Center Control tell aircraft leaving HNL-ASIA areas like Narita And Kansai, that starting from Flight level 24,000ft-30,000Ft that there was Code 1-4 level of Turbulence at those Flight Levels, So Can someone explain the terminology of these codes and what they mean, I heard him say Light to Moderate to Severe turbulence, is that waht those codes mean?? Was pretty Intresting to hear, as planes were cruzing at Flight level 22,000Ft for a while to stay out of the stuff, and some went straight to 34,000Ft-37,000Ft! Just curious about this! thank's for the info! MIKE-:)

Essentially, light is significant turbulence. Moderate is enough to cause occasional periods of uncontrollability (bank, yaw or pitching significantly). Severe has more frequent periods of uncontrollability. Anything beyond light turbulence requires slowing to the green arc on the ASI to avoid potential damage to the airframe. I have also heard of "extreme" turbulence which essentially means you'll have no control over the aircraft.Further, turbulence is sometimes reported with a frequency i.e. "occasional", "continuous" or "chop".Clear-air turbulence is the kind you'll usually find in the upper atmosphere and can be associated with jet-stream or mountain-wave activitiy. This is the dangerous kind.. it usually comes without warning and is in the severe to extreme category.I have not heard of codes 1-4 - this may be light, moderate, severe and extreme.-Damian Clark