[andyc (Andy)]

Looks like a useful paper on the STB and the Ghost here. Section 4 in the report text covers its origin:

Structured segment E arose in 2011, as a small cyclonic dark spot called DS4, and it developed into a pale, expanding feature which we call the ‘STB Ghost’. In its origin, appearance, and behaviour, it is an exact replica of the ‘STB Remnant’ of 2004-2009.

The origin as DS4 was described in our 2011/12 final report (see Section 5(ii) below), and was summarised in our long-term report [Ref.1], thus:

(E) Meanwhile another small v.d.s. (named DS4) appeared in 2011, in a small cyclonic faint blue patch, where there was also temporary disturbance of the SSTBn jet [ref. 2011/12 report]. It became remarkably dark in 2011 Nov., until 2012 Sep. Then it faded and turned white, within a faint cyclonic streak, just like other v.d.ss. have done, and we have predicted that it will become the next STB structured sector. (If it remains faint like the STB Remnant, we will suggest naming it the 'STB Ghost'.)