TEMPO in WX forecast?

[Checkboard]

To illustrate the differences, imagine an airfield with a single north/south (00/18) runway, a CAT 1 ILS with a 200' minma, and an NDB with a 600' minima.

In Australia the chart would also show an "Alternate minima" of about 1100' (about 500' above the second lowest minima)

TAF 010/15 BKN 4500 15/3 1013

In Europe, you would require a single alternate (because of the single runway).

In Australia, you could plan with just destination fuel (cloud base above the Alternate minima, no CBs)

TAF 010/15 BKN 1500 15/3 1013 TEMPO SCTCB1200 TSRA

In Europe you would still require a single alternate (not because of the TEMPO, but still because of the single runway)

In Australia, you would now require either 60 minutes holding, or an alternate (thunderstorms count, even above the alternate minima).

TAF 010/15 BKN 1500 15/3 1013 TEMPO BKN 0100
(i.e. TEMPO below the landing minima)

In Europe you may disregard this tempo, and still only carry a single alternate - of course this carries the risk that the weather is actually present on arrival, requiring a divert. Any holding is at the pilot's experience/discretion.

In Australia, 60 mins or an alternate, as above.

TAF 010/15 BKN 0100 15/3 1013
(i.e. weather continuously forecast below the minima)

In Europe you may plan to this destination, but require TWO alternates. (This means the option of two alternates on arrival - i.e. carry fuel for the second closest, rather than the closest, as opposed to flying to the alternate, then flying to the second alternate.)

In Australia, planning to this destination at all is probably not permitted under CAR 257.

In summary: the whole "disregard the TEMPOs" bit in Europe is about how many alternates you need plan to carry. In Australia most operations DON'T plan an alternate at all - so TEMPOs need to be accounted for to ensure that alternates or sufficient holding fuel IS carried when needed.

In Europe the alternate need only have a cloud base higher than the second most limiting approach (i.e. CAT 1 minima, if you are CAT 3 approved.) In Australia, the alternate needs weather above the alternate minima - a mich higher value (about 500 feet above the second approach, and without CAT 3 in Australia the second highest is invariably a non-precision approach).

In Erope destination only fuel is only permitted if the weather is VFR, and two independant runways with two independant approaches are available. In practice this is never used, and an alternate is carried on every flight - even CAVOK days. In Australia, destination fuel is the norm, and alternate fuel is only carried on the odd occaision when weather turns up.