Cat 3b would have allowed a safe approach and landing in the event described at ADL. Compared to what transpired it would have been a much better outcome. There would in fact be no emergency Nev. A report to CASA maybe. Under the EU OPS policy that dictates an alternate for most flights, an alternate is not required when the weather is better than 1000/2.5k and the dest has separate runways for sectors less than six hours. The same crew could have been caught out with the weather change but they would have had a legal approach to fly. I think we need 3b for all our major commercial ports.