Been looking at that ADDS thing a bit more. There's something seriously wrong with that algorithm. The interpretation is done correctly, as is the presentation. But then the wrong bits of TAF are associated with the presentation bits. Everything is well (excellent, actually) up to the PROB30 bit.
Then comes the following line:
Text: PROB30
And some text suggesting it interprets that line. But what that piece of text actually interprets is
Text: PROB30 TEMPO 1920 4000 +SHRA +TSRA BKN008CB
which is correct, as this is one "block".
The next "block" then seems to interpret the line
Text: BECMG 2023 7000 BKN008
But this line is listed after the block it interprets. Because the line preceding it is the "TEMPO 1920 ..." line which should have been on the PROB30 line.
So past the PROB30 bit, all the content of the "Text:" lines need to be shifted up one block to make things fit. And even then the interpretation block doesn't neatly interprets what's on the "Text:" line, since the interpretation also looks through the rest of the TAF for anything that precedes or supersedes this bit of "Text:" line.
Just guessing what happened: A smart programmer wrote an algorithm to make a linear interpretation of a TAF, from hour to hour, and present it in text form. Which worked flawlessly. And this is no mean feat, because to interpret what the weather is going to be at the end of the period may mean going backwards in the TAF a few "blocks", and to interpret how long the initial weather is going to last may mean going forward in the TAF.
Then a customer request comes along to have the actual TAF text inbetween the interpretation. Which isn't possible in this case since a TAF isn't necessary linear, but the algorithm linearizes the results. So the smart programmer refuses, tries to explain this to his non-understanding management or non-understanding customers, and moves on.
Anyway, request persists, so a less intelligent programmer comes along, willing to take the job (after all, a TAF is in ALL CAPS so it can't be difficult), finds he doesn't understand the code programmer #1 has written so he writes his own algoritm that breaks the TAF into blocks. And then injects these blocks into the blocks that the original algorithm spews out. A quick test by management finds no flaws with this so the thing goes into production.
And the worst thing is that that second programmer probably made a lot of money. First for taking on a job that everybody said was impossible, and secondly for getting it through acceptance testing. In less time than expected.
(Is it true you turn into a cynic after working in the same field for 10 years?
)