WMO table 011031: DEGREE OF TURBULENCE code meaning ---- ------- 0 NIL IN CLOUD 1 SLIGHT IN CLOUD 2 MODERATE IN CLOUD 3 SEVERE IN CLOUD 4 NIL IN CLEAR AIR 5 SLIGHT IN CLEAR AIR 6 MODERATE IN CLEAR AIR 7 SEVERE IN CLEAR AIR 8 NIL CLOUD/CLEAR AIR NOT SPECIFIED 9 SLIGHT CLOUD/CLEAR AIR NOT SPECIFIED 10 MODERATE CLOUD/CLEAR AIR NOT SPECIFIED 11 SEVERE CLOUD/CLEAR AIR NOT SPECIFIED 12 EXTREME IN CLEAR AIR 13 EXTREME IN CLOUD 14 EXTREME CLOUD/CLEAR AIR NOT SPECIFIED 15 MISSING VALUE