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It is important that there should be one report containing all data from the ascent, although there can be earlier partial reports (particularly up to 100 hPa) for timeliness reasons.
Usually these BUFR reports are produced by the software from the radiosonde manufacturers. (Attempts to convert alphanumeric TEMP reports to BUFR are very problematic, and do not provide the higher resolution that WMO GBON will require shorthly.)
Ideally there should be an overlap of 2-6 months between good quality BUFR made available over the GTS and the withdrawal of TAC reports - with notification of these changes via https://community.wmo.int/news/operational-newsletter .
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