  Paper I described the normal features of the North Equatorial Belt (NEB) in
recent years, especially the large dark formations which are thought to
represent waves in the prograde jet on the NEB south edge (NEBs, 7N), and the
NEB expansion events (NEEs) in which the belt broadens to the north at
intervals of 3 to 5 years. Here I describe an exceptional set of apparently
coordinated changes which occurred in 2011-12, after more localised precursors
in 2008 and 2010. (1) The large NEBs dark formations progressively disappeared
until none remained. (2) In the sectors of NEBs thus vacated, smaller dark
features all moved with unprecedented super-fast speeds, which were modulated
by the few normal features as long as they lasted, and then accelerated
further, reaching 139-151 m/s. (3) Rifts (expanding systems of convective white
clouds) also disappeared from the NEB. (4) The NEB north half progressively
faded (whitened) until there was only a narrow, southerly NEB, narrower and
fainter than it had been for nearly a century. These changes have several
profound implications for understanding the dynamics of the region. First, the
NEBs took on the same appearance, dynamics, and speed, as the equivalent jet at
7S (SEBn), supporting the view that the two jets are essentially symmetrical,
with an underlying jet in the range 150-170 m/s. Secondly, the manifestation of
this jet at the surface is normally suppressed by the presence of large
slow-moving formations, which are probably Rossby waves. Thirdly, the loss of
the large dark formations and the narrowing of the belt may have been promoted
by the decline of convective rift activity. Fourthly, these changes seem to
represent a reversion to the situation that existed before 1912, when such
appearances were common and were followed cyclically by vigorous NEB Revivals.
Indeed, just such a Revival would ensue in 2012.
