desertopsguy
Of course your ops manual/ops specs should define your dispatch weather criteria, which I assume in this case was ambiguos; also you don't mention if this is below your landing minima for the approach aid available at the destinations, but I'm assuming 200m is well below your minima- no CAT II/III I assume down there.
It is a difficult call; but in this TAF the 200 +DU is a temporary condtion 1216 (not a PROB) and your ETA is dab smack in the middle of that; 200 +DU is likely/forecast for periods of an up to an hour during the TEMPO period, but not more than 2 hours (ie. half the TEMPO period) the wind is also forecast to increase at your ETA which might reduce vis. in dust conditions. So far, you have no basis for thinking 6000m will actually develop as your call to the tower confirmed a much lower vis. of 1200m, and the 1200Z actual gave you 400m; at the moment the TEMPO is closer to the actual conditions rather than the forecast 6000m. However, the wind is backing to a more northly direction as forecast later on which might mean things are changing and even if you don't get your 6000m, you will likely get vis. above your landing minima; it seems the next actuals should show an improvment based on the tower report and landing aircraft and the 1200m.
The observing criteria of METAR reporting are such that the observer is reporting the min vis. even though the tower is calling it 1200m. Your alternate is solid which is good, so I'd discuss it with the crew and dispatch with 45-60 minutes extra fuel, update the crew on the next actual (or delay until you can get the 1300Z actual) and as you did, have a chat with the tower and keep the crew up to date with the condition. If the destination falls below your landing minima you can consider a hold or a divert en-route to your alternate. I would also specifiy a second alternate in the dispatch release.
Last edited by no sig; 2nd May 2008 at 09:36.