I know that
BLU is military code and means "Ceiling at or above 2,500 feet; Visibility at or above 8,000 meters".
ETSH 241320Z 19007KT 9999 SCT048 SCT160 BKN200 08/03 Q1008 BLU+
ETSH 241220Z 20005KT 9999 FEW050 SCT160 BKN240 08/03 Q1009 BLU+
But what does
+ at the end signify?