30 hour TAFs coming

[IO540]

Met Office: Changes to Civilian TAF issue/validity times (http://www.metoffice.gov.uk/aviation/news/changes/civilian.html)

for a few airports only though

[Fright Level]

Will they be hugely pessimistic compared to the actuals that turn up as well ;-)

[IO540]

There will be a mandatory PROB30 TEMPO +TSRA in every one :)

[bookworm]

Bear in mind that the 30 hour TAF will offer no more information than the current combination of short and long TAFs. Currently 24-hour long TAFs are available about 7 hours ahead of the start of validity. The new 24 and 30 hour TAFs will be available about 1 hour before. So overall, because fewer airports will have 30 hour TAFs than currently have long TAFs, we'll lose advanced planning information relative to the status quo on those airports that get 24 hour TAFs after Nov 5.

Met Office: Changes to Civilian TAF issue/validity times (http://www.metoffice.gov.uk/aviation/news/changes/civilian.html)

[NorthSouth]

Not only that, it will mean that at virtually all airports with a 30 hour TAF there will no longer be a 9 hour TAF. This means that the short-term forecast, which is by far the most important data source for VFR flying, will disappear. In some areas (notably most of Scotland) the introduction of 30 hour TAFs means that there will be no short-term forecasting for civil aerodromes whatsoever.

I predict this will lead to an even greater reduction in the accuracy and reliability of forecasts, leading to worse decision-making on whether the weather is flyable and potentially a greater likelihood of weather-related accidents to VFR traffic. The other side of the coin is that worse reliability also means more decisions not to fly when actually it's flyable. This will make the already virtually impossible economics of GA even worse.

NS

[BackPacker]

Not only that, it will mean that at virtually all airports with a 30 hour TAF there will no longer be a 9 hour TAF. This means that the short-term forecast, which is by far the most important data source for VFR flying, will disappear. In some areas (notably most of Scotland) the introduction of 30 hour TAFs means that there will be no short-term forecasting for civil aerodromes whatsoever.

I would assume that a 30-hour TAF would be just as accurate as the 9 hour TAF we have now, for the first 9 hours. Or, if the airport issues both a 9-hour and a 30-hour TAF simultaneously, that the first few bits of those TAFs (the ones that relate to the first 9 hour period) would be the same.

After all, it looks like the 30-hour TAF is nothing more than the combination of the traditional 9-hour TAF issued one hour before, and the 24-hour TAF that's issued 7 hours in advance. I can't see why the accuracy would diminish just because these two are combined.

[bookworm]

Not only that, it will mean that at virtually all airports with a 30 hour TAF there will no longer be a 9 hour TAF. This means that the short-term forecast, which is by far the most important data source for VFR flying, will disappear. In some areas (notably most of Scotland) the introduction of 30 hour TAFs means that there will be no short-term forecasting for civil aerodromes whatsoever.

I think you're misunderstanding the intention. As Backpacker says, the first part of a 24- or 30 hour TAF will be equivalent to the current short TAF. The only difference will be update frequency - every 6 hours instead of every 3, but the Met Office can issue an amendment if they need to.

[Legal Beagle]

I think the problem is that the 30 hour TAF is issued so far ahead of its validity period that things change! In practice the first part of the 30 hour TAF is not the same as the 9 hour TAF for precisely the reason that things have altered since the 30 hour TAF was issued.

In my opinion the disappearance of the 9 hour TAF from many airfields is a retrograde step and one that may prove to be detrimental to flight safety. How many of us routinely find the 9 hour TAF more reliable than the 30 hour one? (Accepting of course that the 9 hour TAF is not always reliable - it is a fiorecast after all!)

Given the notoriously fickle nature of our maritime climate, in which it is difficult to forecast the weather half an hour in advance let alone the best part of half a day in advance, I wonder why we didn't simply file a difference on this one and stick to 9 hour TAFs for airfields which have issued them until now?

[bookworm]

I think the problem is that the 30 hour TAF is issued so far ahead of its validity period that things change! In practice the first part of the 30 hour TAF is not the same as the 9 hour TAF for precisely the reason that things have altered since the 30 hour TAF was issued.

Like NS, I think you're missing a key aspect of the change.

In the current arrangement, long TAFs are issued 7 hours in advance of the start. And indeed by the time a 9-hour TAF is issued for the same period about an hour ahead of its start, things may have changed.

Under the new arrangement, the 24- and 30-hour will be issued an hour (or less) before their start. So the forecast for the start of the period will take into account recent reports and changes in what the weather is doing. They won't be advance guesses like the current long TAFs, they'll just roll the existing long and short TAFs together.

[Legal Beagle]

Thanks Bookworm. I had missed the change in issue times and now see that you are right, the 30 hour TAFs are to be issued 1 hour before validity time. It will be interesting to see how it works in practice.