• On the dynamics of cyclogenesis, rapid intensification and recurvature of the very severe cyclonic storm, Ockhi

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      https://www.ias.ac.in/article/fulltext/jess/129/0194

    • Keywords

       

      Tropical cyclone; easterly waves; rapid intensification; recurvature; upper ocean thermal energy; tropical dynamics.

    • Abstract

       

      A very severe cyclonic storm (VSCS), ‘Ockhi’ started its journey from southwest Bay of Bengal (BoB) over Comorin area (7.5$^{\circ}$N–77.5$^{\circ}$E) as a low-pressure area on 28 November, 2017. Initially it moved north-westwards across Lakshadweep Islands without hitting Tamil Nadu or Kerala coast, then moved north-eastward over the Arabian Sea and dissipated upon hitting south Gujarat coast on 06 December, 2017. Rapid intensification (RI), clockwise recurvature and a longer track were the major features of the VSCS, Ockhi. In the present study, an attempt has been made to understand the mechanism of cyclogenesis, RI and recurvature of the Ockhi using satellite and reanalysis datasets. Initially, role of easterly waves (EW) and Madden Jullian Oscillations (MJO) on the cyclogenesis of tropical cyclone Ockhi is addressed. Our analysis suggests that the EW (MJO) played a seminal (insignificant) role in preconditioning the atmosphere for the cyclogenesis of the Ockhi. Our detailed analysis using various oceanic parameters indicate that, the passage of the cyclonic storm over the regions of high thermal energy, especially warmer ocean mean temperature (OMT) at 100 m depth, was instrumental in its rapid intensification. Further, we addressed the recurving feature of the VSCS Ockhi using steering flow analysis. It is found that strong north-eastward steering winds, embedded in subtropical westerlies with deep southward extent, favoured the recurving of the Ockhi towards north-eastward by suppressing the conventional westward (north-westward) track movement.

      $\bf{Highlights}$

      $\bullet$Easterly wave activity facilitated the cyclogenesis.

      $\bullet$Upper ocean thermal energy contributed in rapid intensification.

      $\bullet$Trough in upper level westerlies facilitated in recurvature of the VSCS Ockhi.

    • Author Affiliations

       

      SANAP S D1 MOHAPATRA M2 ALI M M3 4 PRIYA P5 VARAPRASAD D6

      1. India Meteorological Department, Ministry of Earth Sciences, Office of the Climate Research and Services, Shivajinagar, Pune 411 005, India.
      2. India Meteorological Department, Ministry of Earth Sciences, Office of the Director General of Meteorology, Mausam Bhavan, Lodi Road, New Delhi 110 003, India.
      3. Centre for Ocean-Atmospheric Prediction Studies, Florida State University, Tallahassee, USA.
      4. Present address: Andhra Pradesh Disaster Management Authority, Kunchanapalli, Andhra Pradesh, India.
      5. Centre for Climate Change Research (CCCR), Indian Institute of Tropical Meteorology, Ministry of Earth Sciences, Pashan, Pune 411 008, India.
      6. National Remote Sensing Centre (NRSC), Hyderabad 500 037, India.
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