non-frontal synoptic scale low pressure area originating in the tropics or sub-tropics with enhanced convection and light surface winds.
generic term for a non-frontal synoptic scale low pressure area, originating over tropical or sub-tropical waters with organized convection and definite cyclonic surface wind circulation (wind estimated to be not exceeding 27 knots (50 km/h, force 6 in the Beaufort scale)).
tropical disturbance in which the maximum average surface wind speed ranges from 28 to 33 knots (51 to 62 km/h, force 7 in the Beaufort scale).
tropical system in which the maximum average surface wind speed ranges from 34 kt to 47 kt [63-87 km/h, gale or strong gale force winds, Beaufort scale 8 or 9]. At this level, systems are usually named.
tropical disturbance in which the maximum average surface wind speed ranges from 48 kt to 63 kt [88-17 km/h, storm or violent storm force winds, Beaufort scale 10 or 11]. The convection in tropical storms is usually more concentrated near the center with outer rainfall organizing into distinct bands.
tropical disturbance in which the maximum average surface wind speed ranges from 64 kt to 89 kt [118-165 km/h, hurricane force winds, Beaufort scale 12].
tropical disturbance in which the maximum average surface wind speed ranges from 90 kt to 115 kt [166-212 km/h].
tropical disturbance in which the maximum average surface wind speed above 115 kt [212 km/h].
synoptic scale low pressure area outside of the tropics or former tropical disturbance having lost its tropical characteristics.
synoptic scale low pressure area having during its life, characteristics
which could belong to both tropical and extra-tropical depressions.
In the South West Indian Ocean,
the genesis of such system is regularly observed over the South of Mozambique Channel.