ITCZ
I met an ITCZ once. Off the coast of Malasia, in one of HM finest twinjets. Without any 'cloud & clonk', we unknowingly entered it at FL330, and, notwithstanding full airbrakes and closed throttles, were finally spat out of the top at in excess of 55,000ft. Eye watering stuff. Having a beer that evening in the 'swill', someone remarked that we were lucky not to have been caught in the downdraught bit!