Riddle me this When you receive an updated forecast that has either INTER or TEMPO, do you just ignore it because "you're already airborne" or do you do something about it - divert, 'make fuel', declare MIN FUEL. Of course you don't just blunder on... do you?
I don't think anyone on here has suggested that. The argument here seems to have been reduced to semantics. Some (myself included) suggest that
alternates can only be "provided for" in the planning stage. If we hold onto an absolute requirement to carry an alternate whenever the wx conditions require (regardless of how little fuel we are carrying when we are notified of the conditions), then we are stating that the PIC is capable of breaking the law without any possible way of foreseeing or avoiding the situation. Sometimes it's hard to "provide" an alternate unless AAR is an option for you.
I would hold to the view that once airborne, operational changes become matters of
diversion planning. To refer to it as "providing for an alternate" ignores the many other options available to a crew, including autoland, ditching (we all know it's been discussed!), using up their reserves etc. Not saying they're good options, but they don't involve "alternates". As others suggest, it comes down to command decision, airmanship, whatever you want to call it - not a matter of obeying a legal requirement.
Put it into another perspective and consider the myriad other scenarios that might make a destination unsuitable, but which are not covered by AIP alternate requirements. eg. Hydraulic failure in flight makes the destination runway too short for landing requirements. At no stage is the concept of an "alternate" as defined in the AIP applicable, but the crew are still going to have to make some decisions about where they're going to go. It may just be that their best option is to land anyway and hope they can pull it up in time!
As a side note - I suspect I remember the day clakajak's colleague received his "roasting". Un-forecast cloud in SY, BKN 01 earlier this month (below landing mins). You could almost hear everybody changing their mind over the radio!