Auckland IFR: No Alternate Despite TEMPO Below Minima
You are the chief pilot of a Part 135 operator reviewing a filed IFR flight from Wellington (NZWN) to Auckland (NZAA), ETD 2200 UTC, ETA 2305 UTC. The latest NZAA TAF is: NZAA 021500Z 0218/0224 24015KT 9999 SCT025 BKN040 FM222000 25025G40KT 5000 SHRA BKN012 TEMPO 2220/2306 2000 +SHRA BKN006. The pilot has nominated no alternate, arguing that Auckland has multiple approaches and that the bad weather is only TEMPO. The operator's exposition requires an alternate when the destination forecast at ETA is below 800 ft ceiling or 4 km visibility, or when TEMPO/PROB conditions below those values are forecast. The flight has 45 minutes holding fuel and no extra fuel for a distant alternate. The pilot holds a current instrument proficiency check.
1. Does the filed plan comply with the operator's alternate requirement? Show the TAF reasoning.
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No. At ETA 2305 UTC the FM222000 group is in force: wind 25025G40KT, visibility 5000 m, SHRA, BKN012. The base forecast gives ceiling 1200 ft and visibility 5 km, which is above the operator's 800 ft/4 km alternate threshold. However, the TEMPO group 2220/2306 includes ETA and forecasts 2000 m visibility, +SHRA and BKN006. BKN006 is a 600 ft ceiling, below 800 ft, and 2000 m is below 4 km. The exposition explicitly requires an alternate when TEMPO conditions below those values are forecast. The pilot cannot dismiss the TEMPO group because Auckland has multiple approaches; the requirement is forecast-based, not approach-count-based. The filed no-alternate plan is therefore non-compliant.
2. What is the regulatory significance of the TEMPO group and of an AIRMET for the destination?
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The TEMPO group is part of the aerodrome forecast and has regulatory significance for flight planning because the operator's exposition says to consider TEMPO/PROB conditions below minima. It is not a guarantee that the weather will occur, but it is a credible forecast fluctuation that may coincide with ETA. An AIRMET is an advisory warning of conditions such as moderate turbulence, icing or mountain obscuration; it does not amend the TAF and does not create alternate minima. It can support hazard awareness, but it is not a substitute for an aerodrome forecast when selecting an alternate. If a SIGMET were issued for the destination, that would be a more serious operational warning, but it still would not replace the TAF-based alternate calculation.
3. What should you require before the flight departs?
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Before departure I would require the pilot to nominate an alternate with a current TAF that meets the operator's alternate minima for the estimated time of arrival, and to carry fuel to that alternate plus the required reserve. The pilot must use the latest TAF, including any amendment; an amended TAF that removes the TEMPO below minima could restore the no-alternate plan. If no suitable alternate can be nominated within fuel range, the options are to delay until the TAF improves, change destination, or cancel the flight. I would also require a check of SIGMET/AIRMET for the route, but those products do not replace the TAF-based alternate calculation. The decision and the forecast used should be recorded.