Definition of a cyclone and when a cyclone ends or reintensifies
3A Definition of a cyclone and when a cyclone ends or reintensifies
This regulation has effect for the purposes of the definitions of cyclone, end and reintensify in section 3 of the Act.
A cyclone is a non‑frontal low pressure system, of synoptic scale, that:
has developed over warm waters; and
has organised convection; and
has a maximum mean wind speed of 34 knots or greater that:
extends more than half‑way around near the centre of the system; and
has persisted for at least 6 hours.
This definition describes tropical cyclones, which in the Act and this instrument are referred to as cyclones.
A cyclone ends at the earliest time (the downgrade time) when the following conditions are satisfied:
the low pressure system concerned:
no longer satisfies the condition in paragraph (2)(b); or
no longer satisfies the condition in paragraph (2)(c);
and has been designated by the Bureau as an ex‑tropical cyclone or post‑tropical cyclone;
in the opinion of the Bureau, the likelihood that the system will intensify to such an extent as to again satisfy the conditions in paragraphs (2)(b) and (c) at some time within 48 hours after the downgrade time is less than the likelihood that it will not.
If a cyclone ends because of subregulation (3) or (5) but the low pressure system concerned later intensifies to such an extent as to again satisfy the conditions in paragraphs (2)(b) and (c), it again becomes a cyclone, and is taken to reintensify at the time when it again meets the conditions in paragraphs (2)(b) and (c).
A cyclone that has reintensified ends at the earliest time (also the downgrade time) after it reintensified when the conditions in paragraphs (3)(a) and (b) are satisfied.
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