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Check Airman
8th May 2008, 16:43
I was on the National Weather Service website, and noticed that US TAFs will be changed to a 30hr forcast to "conform to international standards outlined in ICAO Annex 3". I've never seen a 30hr TAF before. Are there any countries currently using this format, or does everybody plan to change to a 30hr format come November?

http://aviationweather.gov/notice/taf30.php

tubby linton
8th May 2008, 17:09
Here is what the UK Met Office has to say:
http://secure.metoffice.com/aviation/news.jsp

Check Airman
8th May 2008, 19:03
Thanks Tubby. The site asks for a username and password though. What exactly does it say?

tubby linton
8th May 2008, 19:26
Practice as of 0001 UTC Wednesday 5 November 2008

In the fictitious forecast below, which is for 30 hours, the new date/time group format has been highlighted.
TAF for EGLL:
TAF EGLL 160505Z 1606/1712 13018KT 9999 BKN020 BECMG 1606/1608 SCT013CB BKN020
TEMPO 1608/1612 17025G45KT 3000 TSRA BKN008CB BECMG 1612/1614 20015KT FEW020
TEMPO 1703/1706 4000 BR TEMPO 1709/1712 BKN012=
The format of the issue time does not change.
The validity group should be read as 0600 UTC on the 16th of the month to 1200 UTC on the 17th of the month. The first BECMG group should be read as 0600 UTC on the 16th of the month, to 0800 UTC on the 16th of the month. The first TEMPO group should be read as from 0800 UTC on the 16th of the month to 1200 UTC on the 16th of the month. The last TEMPO should be read as 0900 UTC on the 17th of the month to 1200 UTC on the 17th of the month.
The example below illustrates the use of the FM group, as used regularly by some states:
TAF XXXX 160505Z 1606/1712 13018KT 9999 BKN020 BECMG 1606/1608 SCT015CB BKN020 TEMPO 1608/1612 17025G45KT 3000 TSRA SCT010CB BKN020 FM161230 15015KT 9999 BKN020 TEMPO 1703/1706 4000 BR TEMPO 1709/1712 BKN012=
The example above shows 'FM161230', which should be read as from 1230 UTC on the 16th of the month.
Not all TAFs will be 30 hours, but any TAFs of shorter duration will also follow the same format for indicating validity and change groups.
So, in the fictitious forecast below for a 9 hour TAF the new date/time group format has again been highlighted:
TAF for EGNH:
TAF EGNH 160805Z 1609/1618 13018KT 9999 BKN012 BECMG 1612/1615 FEW020 BECMG 1616/1618 3000 BR BKN007=
Note 1: The nominal validity time and nominal issue time of civilian TAFs will also change, so the example above is for a 0900 UTC to 1800 UTC standard 9 hour TAF for Blackpool, and not 1000 UTC to 1900 UTC as is the current practice. See separate notification for more detail.
Note 2: The Met Office cannot take responsibility for TAFs sourced from other countries/states. Therefore, after November 5th 2008 legacy formats may appear on our websites. However, TAFs produced by the Met Office and the majority of other countries/states will comply with the change.
Note 3: The lead time for 'Long TAFs' will change from ~7 hours to between 55 and 35 minutes before the start of the TAF. See changes to Civilian TAF issue and validity times (http://www.metoffice.gov.uk/aviation/news/changes/civilian.html).
Note 4: The practice of issuing 'Long TAFs' and 'Short TAFs' for the same airport will cease. Each airport will only receive one or the other. See separate notification for more detail.

Check Airman
8th May 2008, 21:42
Thanks Tubby. Seems everybody plans to change on the 5th.