Transition to new ICAO TAF Format from AvnFPS perspective

After 1800 UTC on 04 November 2008, forecasters using AvnFPS OB8.3.1 will notice that the software recognizes the significance of the next routine 0000 UTC TAF issuance.

Figure 1. TAF Editor showing guidance TAFs in new format for 0000 UTC 05 November 2008 issuance after 18Z TAF issuance

In Figure 1, the guidance TAFs start appearing in the new format when the 'Routine' button is active. Of course, the current 1800 UTC TAFs--either original or amended--still remain in their 'old' format in the TAF viewer and editor (upper text window in Figure 1). TAF KCVG (Covington, KY) becomes a 30-h long TAF at the same time the new format goes into effect. At this point, before the 0000 UTC initial issuance--for purposes of issuing any amendments on the 1800 UTC forecast--the TAF length should remain at 24 (hours) for KCVG.

As the 0000 UTC 5 November 2008 date approaches, aviation forecasters will begin to compose their new routine TAFs. You can:

Manually create the TAFs from scratch, using the 'blank sheet' approach.

Manually create the forecast from scratch using 0000 UTC TAF templates that you may have defined previously.

Use the 'AdjustTimes' tool on current TAFs originally issued for 1800 UTC 4 November 2008. This may be the most popular method that forecasters use to create the next set of routine TAFs.

If the forecaster loads the latest, current TAFs into the editor with the intent to use them for the 0000 UTC issuance with the 'Initialize From' option set to 'latest' or 'merge' and Forecast Type set to 'Routine', using the 'AdjustTimes' tool will remove expired change groups and reconstitute the TAFs into the new format as shown in the figure below. Please be aware that its not guaranteed that this tool will always select the correct day, particularly for the TEMPO and PROB30 groups. The next figure shows what happens with the TAFs in Figure 1 after the 'AdjustTimes' procedure is run:

Figure 2. After 'AdjustTimes' procedure is run on current TAFs in preparation for 0000 UTC 5 November issuance.

You will notice that Covington, KY TAF (KCVG) valid period is still 24 hours long instead of 30: "0500/0524". This is because the KCVG tafduration attribute was still set to 24 when this image was captured. If it was set to 30 (see here for instructions on how to change this), then the valid period would have been set to "0500/0606". But in the images that follow, let us continue to assume that tafduration for KCVG is set to 24 hours long and see how to get AvnFPS Syntax Check to accept a 30-h long TAF even with tafduration still set to 24. Knowing how to do this gives the forecaster maximum flexibility by allowing him/her queue up the 0000 UTC TAFs before they are scheduled to go out but still have the ability to issuance amendments on the 1800 UTC TAFs until the very last moment--just prior to the opening of the 0000 UTC TAF transmission window.

Let's go ahead and add another change group for KCVG for the last 6 hours. Remember in this scenario the tafduration is still set to 24 hours for KCVG.

New group for 30-h TAF with duration set to 24

Figure 3. Covington, KY (KCVG) TAF with a 30-h forecast valid from 0000 UTC 5 November to 0600 UTC on the 6th.

Pressing 'Syntax Check' will flag the FM060000 change group and valid period of KCVG TAF is changed back to "0500/0524". Figure 4 shows why: under the "Options" menu, the 'Update Times on Format' checkbox is active.

Figure 4. KCVG 30-h TAF with tafduration set to 24 (hrs) with 'Update Times on Format' option on

Unsetting the "Update Times on Format" option will allow a 30-h TAF to be checked for format errors even if tafduration is set to 24 and its duration in the editor is 30-h long. Notice that the FM060000 group is no longer flagged in this case:

Figure 5. KCVG 30-h TAF with tafduration set to 24 (hrs) with option off.

At this point, the forecaster can then proceed to queue up the 0000 UTC TAFs, nominally transmitted at 2320Z. But don't do this more than 3 hours ahead of time! The transmission server will move any pending product to the 'bad' directory if they sit in the pending queue too long (you can recover from this but explaining how to do that is way off tangent ;). If you need to check the 0000 UTC TAFs again before they're transmitted, use the 'Load' button and make sure the 'Forecast Type' option is set to 'Routine' on the Load GUI. By doing that, you will pull all of the 0000 UTC TAFs you've selected in the 'Load' dialog from the pending queue.

Once the aviation forecaster is confident that no more amendments on the 1800 UTC 04 November 2008 TAFs will be made, you can change the tafduration attribute for any of your affected TAF(s) to 30 hours. Certainly after the 0000 UTC 5 November 2008 issuance, the following TAFs should have their 'tafduration' attribute set to 30 (hrs):

KATL

KBDL

KBOS

KBWI

KCLE

KCVG

KDEN

KDFW

KDTW

KEWR

KIAD

KIAH

KIND

KJFK

KLAX

KMKE

KMSP

KOAK

KONT

KORD

KPHL

KPIT

KSAN

KSDF

KSEA

KSFO

KSLC

KSTL

KSWF

PANC

PAFA

PHNL

Table 1. 30-h TAFs beginning with 0000 UTC 5 November 2008 issuance