Resonant interaction between shear Alfvén waves and energetic ions is one of the key burning plasma physics issues currently investigated at JET. A loss of the fast ion stabilisation effect on the n = 1 kink mode has previously been found to correlate with excitation of energetic particle-driven modes inside the q = 1 magnetic surface, either n = 1 fishbones or higher frequency so-called "tornado'' modes. The tornado modes were identified in as Toroidal Alfvén Eigenmodes (TAEs) inside the q = 1 magnetic surface. The loss of sawtooth stabilisation by fast ions can be understood as the possible effect of multiple-mode structures of tornado modes, observed prior to the sawtooth crashes, on the fast ion confinement. Bi-directional tornado modes with both positive and negative toroidal mode numbers n (i.e. propagating in both co-current and counter-current direction) were observed on JT-60U, but remain unexplained so far. In this paper, the first JET observations of bi-directional tornado modes are reported and explained. The spectroscopic analysis of the plasma equilibrium, which is performed with a suite of equilibrium and spectral MHD codes, verifies the observed evolution of tornado mode frequencies and is used to identify the temporal evolution of the safety factor inside q = 1 just before the sawtooth crashes. In order to understand the excitation mechanism of bi-directional tornado modes, we follow the idea and revisit the calculation of linear TAE growth rate due to ICRH-accelerated trapped ions in the small banana width limit [8] and identify a necessary velocity space anisotropy condition for a positive growth rate of bi-directional tornado modes.