arry = numpy.fromfile(file, dtype='float, S2')
col1 = arry['f0']
diff = col1 - numpy.roll(col1, 1)
idxs = numpy.where(diff < 0)[0]
strts = idxs
stops = list(idxs[1:]) + [None]
groups = [data[strt:stop] for strt, stop in zip(strts, stops)]
Split array at value in numpy