radnav
If you update the tower wind from the last report you are well on the way to coming a cropper and it is potentially a serious error of judgement. Contrary to all your instincts, if you put in a higher tower wind (resolved along the runway axis) you will lower the target approach speed. It is perfectly possible that ATC have given you a short term wind, which in theory is what you want. The problem is that the tower wind is basically there to enable you to fly at as low an approach speed as is safe. You are saying to the system that the tower wind is always there and therefore you do not need to worry to much about it and it is only gusts that should concern you. Remember, a gust in Airbus terms is the difference between the tower wind and the actual wind calculated by the IRS. If the tower wind is high because you put in the last value from ATC then you are telling the system that anything up to that value is not a gust. If that wind subsequently disappears quickly you will have an instantaneous loss of energy which the autothrust may not be able to react to quickly enough. A low tower wind is therefore a protection. As I have said before there is clearly a balance but great caution should be exercised in puting in the last wind from ATC as it can and does lead to low energy situations. Having said that, if your tower wind is 10 knots or less it does not matter what wind or direction you put in - it will never alter the target approach speed. Hence messing around with the tower wind in light and variable conditions is an unnecessary acitivity as nothing changes.