I am truly amazed that there seems be be such difficulty with this concept. An Alternate is required whenever the conditions fall below ALT MIN, that is why it is called ALT MINIMA.
Icarus53
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.
If the PIC has done all that s/he can be reasonably expected to do, in order to obtain the most up-to-date operational information, then they would not be breaking the law if an unforeseen operational requirement was put in place. Sometimes, despite all the best planning, 'stuff happens'. However, it would be indefensible if you failed to do all that you could be reasonably expected to do in order to get info, and just 'blundered on'.
AIP 2.1.1
Pilots are responsible for requesting information necessary to make operational decisions.
AIP. 2.4.1
The in-flight information services are structured to support the
responsibility of pilots to obtain information in-flight on which to
base operational decisions relating to the continuation or diversion
of a flight.
Dragun:
If alternates were required to be replanned in flight, wouldn't they also have made it a requirement to obtain updated forecasts in flight at X minute intervals to enable you to do this? To reiterate, you are only legally required to obtain a forecast prior to flight, and as alternate planning depends on having obtained a forecast...
See AIP above. As the PIC you are required to obtain information in-flight that can be used to assist in operational decisions. I cannot access the reference to reproduce it verbatim, but you ARE required to have a forecast, that covers your ETA plus 60 mins (TTF or TAF). If your ETA falls within this, then you don't need to obtain an update. If your ETA is not covered by this, then you are required to obtain updated wx that is valid for your arrival.
You can depart from an airfield without a valid forecast, provided you obtain a valid forecast within 30 min (again can't find the reference). If this Wx requires an INTER/TEMPO/ALT then you must adhere to those requirements.
This indicates that you do have to get airborne reports.
It seems pretty simple - if the wx (obtained preflight or inflight) requires additional fuel, then you either have to get it (in-flight: change route/speed/height etc) or divert to an airfield that you have the required reserves to make.