The Unusual Long Track and Rapid Intensification of Very Severe Cyclone Ockhi

Abstract

Cyclone Ockhi in November 2017, was the first very severe cyclone to form over the Lakshadweep Sea since 1925, resulting in a death toll of 844 in India and Sri Lanka.The distance travelled, duration and accumulated cyclone energy were significantly larger for cyclone Ockhi, in comparison with the climatological cyclone records.It intensified rapidly from a depression to a cyclone in a span of 9 h and further to a very severe cyclone in 24 h.The present study shows that the Madden-Julian Oscillation and warm oceanic conditions provided favourable dynamic and thermodynamic conditions for the genesis of cyclone Ockhi.The favourable thermodynamic conditions due to warm sea-surface temperature over southeast Arabian Sea also helped in the intensification of the cyclone during its early and mature stages.Meanwhile, the unusual long track was steered by upper-level winds.The vital role of ocean temperature in the genesis and rapid intensification of the cyclone highlights the need for efficiently incorporating the coupled oceanatmospheric conditions in cyclone forecast models.The Arabian Sea needs to be closely monitored for future storms since climate projections indicate that the rapid warming in the basin will continue into the future.