Disptching on TAF and Tempo

[desertopsguy]

Question,

Would you dispatch a flight to it's destination with the following wx forecast?
The destination is not important but the dept time was 12:00z
We don\t dispatch on these but I've included the latest 2 metars for trend purposes.

011200Z 04011KT 0400 +DU SKC 37/06 Q1006 NOSIG
011100Z 06013KT 0400 +BLDU SKC 37/05 Q1007 NOSIG
010800Z 011212 03008KT 6000 NSC
TEMPO 1216 0200 +DU
BECMG 1416 36018KTThe vis in the metar is bad but the tower was quoting 1200m.This was intermittent so they did not quote it in the metar although aircraft were arriving without issue.

The alternate, 30mins away, was fine.

STD 12:00z
ETA 14:00z

Would you release this flight based on the main body of the TAF of 6000m or on the tempo quoting 200+DU

This caused a pain in my a55 today cos so many people got involved to give their opinion. Mine was to release it based on the 6000m, not the 200+DU.

I'd like some feedback please, if you have a daft comment then keep it n your pocket...

D.O.G

[no sig]

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.

[acmi48]

damman.. ..

[pratham]

damn damn... wow.. just amazing breakdown without any question ... i believe thats wat experience speaks .... man... this was really informative... both the question and answer ....
thanks

[Lauderdale]

EU-Ops 1 AOM

=======================================================



An operator shall only select the destination aerodrome when appropriate weather reports or forecasts or any combination thereof indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival, the weather conditions will be at or above the applicable landing minimum as follows:
- RVR/VIS

- ceiling at or above MDH for non-precision or circling approaches
or two destination alternate aerodromes are selected if the weather conditions are below the applicable planning minimums.

An operator shall only select an aerodrome as a take-off alternate aerodrome when appropriate weather reports or forecasts or any combination thereof indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival, the weather conditions will be at or above the applicable landing minimum. The ceiling must be taken into account when only non-precision or circling approaches are available. Any limitation related to one-engine-inoperative operations must be taken into account.

An operator shall only select the destination aerodrome when appropriate weather reports or forecasts or any combination thereof indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival, the weather conditions will be at or above the applicable landing minimum as follows:
- RVR/VIS

- ceiling at or above MDH for non-precision or circling approaches
or two destination alternate aerodromes are selected if the weather conditions are below the applicable planning minimums.An operator shall only select an aerodrome as:
- destination alternate aerodrome,

- isolated aerodrome

- enroute alternate aerodrome (ERA)

- 3% ERA (an ERA selected for the purpose of reducing contingency fuel to 3%)
when appropriate weather reports or forecasts or any combination thereof indicate that, during a period commencing one hour before and ending one hour after the estimated time of arrival, the weather conditions will be at or above the planning minimums as in Table 17 below.


Type of approach
Planning Minimums
CAT II and III
CAT I (1)
CAT I
Non-precision (1)(2)
Non-precision
Non-precision (1)(2)
Circling
Circling
Notes:
(1) RVR.
(2) The ceiling must be at or above the MDH.

[DougADX]

In the US FAR 121 world - if I had that forecast, I would plan my dispatch based on the 200 DU and dispatch accordingly. The METARs are very telling that the TEMPO (the old CHC in the US) are what is occuring.

[desertopsguy]

Thanks for the responses...

NoSig, a goldmine of info...as always, thank you...

D.O.G