I don't know what's so difficult to understand about this.
Doesn't matter whether your'e driving to the airport, flight planning, airborne etc. - if a TTF indicates weather conditions forecast below the alternate minima, THE AIRPORT REQUIRES AN ALTERNATE.
The courses of action available in the airborne case are:
1. Nominate a suitable alternate (If FOB on board allows)
2. Divert to an en-route airport to pick up extra fuel. (Insufficient FOB)
3. If the departure or any en-route airport can not be reached with required fuel reserves, declare a PAN and continue.
If a Hazard ALert is broadcast, then it needs to be broken down into 2 elements:
1. Weather conditions above the alternate minima. Is it safe to continue (Pilot judgement)
2. Weather conditions below the alternate minima. (Pilot Judgement + comments above)