Aëtius ii 20.1 (DK 12A21) 

Aëtius ii 25.1 (DK 12A22), on the moon, is similar, ending 
It is generally supposed that
is the nozzle of a bellows; but G. E. R. Lloyd, Polarity and analogy 313 ff. is doubtful of this interpretation, pointing out that only one, doubtful, parallel can be cited for this meaning of πρηστήρ, and that the nozzle of a bellows does not emit fire. He concludes, however, that if πρηστήρ has its normal, meteorological, sense, ‘it seems impossible to interpret … αὐλός … for this must surely refer to some sort of pipe or tube and this seems quite inappropriate to such phenomena as lightning or whirlwinds … “Bellows” … appears to give the best sense for this difficult phrase’.
My purpose here is to show that
has a good meteorological sense. According to Aristotle Mete. 371a15 ff., the πρηστήρ is a variant of the τυφῶν, which is a whirlwind (370b22) which forms within a cloud (ib. 28), and, being unable to separate itself from the cloud, descends to the earth, bringing the cloud with it (371a9, ff., and especially 11 ff.
). This seems to be the ‘tornado’ or the ‘waterspout’ of modern meteorology. A tornado is ‘a very intense, progressive whirl, of small diameter … From the violently-agitated main cloud-mass above there usually hangs a writhing funnel-shaped cloud …’ The ‘funnel-shaped cloud’ is presumably the cloud which Aristotle's whirlwind ‘draws down with it’.