Wow...i can't believe there are people out there who call themselves professional pilots, yet would not carry an alternate (or holding, or divert) if they were in flight and the TAF changed to below alternate minima. (Its basic, there is no argument!) Yes...all of a sudden you need extra fuel as the TAF changed while you were inflight...that has never meant you continue...that has always meant you divert or slow to create fuel. 'Who cares', you need to seriously read up on your reg's, and yes i am someone who knows a hell of a lot about the regs.
And to 'pilots' who would not divert if their destination went below alternate minima with a tempo and they didn't have tempo fuel. Preflight or inflght it doesnt matter...if your dest goes tempo after takeoff you have to have tempo fuel...if you don't you have to divert. I am very worried that there are so called professional pilots who think its only a preflight requirement! DID YOU PASS YOUR ATPL'S THE FIRST TIME OR THE TENTH TIME....OR NOT QUITE YET????
That is a real worry. One wonders how they are getting through airline checking and training...or perhaps CASA needs to oversee certain airlines more?
Of course, an observation is an observation. A TAF or TTF METAR is what matters, not an observation. An observation is open to interpretation, subject to the TAF. There is no legal requirement for an observation, as there is no trend (it just adds to one's situational awareness)...only for a TAF/TTF METAR.