I'm sure you're all bored of me by now although I'm still not convinced. Breaking that
very poorly written sentence down...
The prevailing weather conditions forecast in the initial part of the TAF...
Referring to the weather at the beginning of the TAF, in this instance, the 50m visibility, the Fog and the 010/7kts of wind.
...should be fully applied...
Applied to the whole period of the forecast, it can't mean anything else.
...with the exception of the mean wind and gusts (and crosswind)...
Meaning that rule does not refer to the wind conditions forecast at the beginning of the TAF - so in my example, just the low visibility and the Fog are the only relevant parts at the beginning of the TAF.
...which should be applied in accordance with the policy in the column “BECMG AT” and “FM….” in the table on the next page. ...
Meaning that ONLY the wind conditions should be applied with the policy of +/- 1hr given later on in the tables left column.
... This may, however, be overruled temporarily by a “TEMPO” or “PROB” if applicable, according to the table on the next page.
Meaning TEMPO or a PROB overrules the 'full application' of 'initial part of the forecast'. If that is the case, any condition regarded as an Improvement given in a TEMPO or a PROB 'Should be disregarded' anyway in accordance with the second from right column. So if it were to say TEMPO 10-12 CAVOK, it's not relevant.
Again, I know this is entirely academic and you'd take fuel accordingly. I am just trying to understand what the table says. I know how to interpret a TAF and I am not being disingenuous as to your responses. This table is not there to advise you on how much extra fuel you should take, your experience is there to tell you that, it's to legally define when an aerodrome is considered suitable and above planning minima - therefore one which you can declare on your flight plan before it gets sent off to Brussels.
In my interpretation, I think what they're getting at is that if there is currently a 'persistant condition' such as FOG, DUST or rain, they are covering themselves in case it lingers for a longer period. Wind on the other hand is slightly more predictable and can be forecast with a little more precision - so that confusing statement is allowing you to disregard it. They are just warning you that the airfield might not be therefore suitable for planning purposes so a second alternate might be required.