If the minimum visibility in one direction is less than 50% of that in the other sectors and less than 5 km, it is included so '9000 4000NW' means 9km vis generally, minimum 4km in the NW sector. It is also included if it's less than 1500m and the 50% doesn't apply.
Last edited by DB6; 24th November 2008 at 07:40.