Appraisal of recent theories to understand cyclogenesis pathways of tropical cyclone Madi (2013)

Abstract

The present study aims to examine the new understanding of cyclogenesis by analyzing the genesis sequence of formation of a very severe cyclonic storm Madi (6–13 December 2013) that occurred over the Bay of Bengal. We have generated a high‐resolution (18 km, 6 km, and 2 km) analysis using three‐dimensional variational data assimilation technique and Weather Research and Forecasting model. The genesis sequence of Madi cyclone is analyzed using the concepts in the marsupial theory and other theories of tropical cyclone formation. Major results are as follows: the developed analysis is found useful for tracking the movement of westward moving parent disturbance from 15 days prior to the genesis; identifying developed pouch region in the Lagrangian frame of reference; understanding the evolution of the pouch and convection within the pouch region and for the study of intensification inside the pouch region. Also, large‐scale priming of environment concurs with the hypotheses of the marsupial theory of tropical cyclogenesis. The analysis of dynamical and thermodynamical processes within the pouch region showed gradual moistening, uplifting of moisture, diabatic heating causing buoyant convection in the vorticity‐rich environment followed by vortex tube stretching, development of convection, heavy precipitation, strengthening of lower level convergence, and hence spin‐up during a day or two preceding the genesis of Madi cyclone. In general, it is concluded that intensification within pouch region during the cyclogenesis phase followed the marsupial paradigm and bottom‐up mechanism.

Comparison of Reanalysis Data Sets to Comprehend the Evolution of Tropical Cyclones Over North Indian Ocean

“…Figures a–f show the composite structure of TCs in ERAI, GFS, JRA55, MERRA2, CFSR, and ERA5 data sets, respectively. The values captured in all reanalysis data sets are in range from −1.5 K(6 hr) −1 to +1.5 K(6 hr) −1 which are very low in comparison with the estimated value of (Wang, ; Rajasree, Kesarkar, Bhate, Singh, et al, ; Rajasree, Kesarkar, Bhate, Umakanth, et al, ). The pattern of increase in diabatic heating in the inner core region of TCs with intensification is represented more correctly in GFS analysis (Figure b) and CFSR (Figure e) followed by ERA5 (Figure f) data set compared to other data sets.…”

“…It is speculated that the majority of the errors in the spatiotemporal representation of development of TCs are mainly due to the coarse resolution of reanalysis data sets and unknown physical processes that contribute to the evolution of TCs and their parameterization in NWP. However, reanalyses developed based on high‐resolution mesoscale models are more in agreement with IMD best track data sets (Rajasree, Kesarkar, Bhate, Singh, et al, ; Rajasree, Kesarkar, Bhate, Umakanth, et al, ). Therefore, it can be said that there is a need to develop a high‐resolution global reanalysis data set that can represent the spatiotemporal evolution of TCs more appropriately.…”

“…The determination of the role of such environmental parameters on TCs structure and intensity changes is essential to enhance our understanding of TCs, which in turn improves the track and intensity prediction of TCs. High‐resolution simulations using mesoscale models and advanced data assimilation systems are recently being used for obtaining a better understanding of track, structure, and intensity variations of TCs (Montgomery et al, ; Rajasree, Kesarkar, Bhate, Singh, et al, ; Rajasree, Kesarkar, Bhate, Umakanth, et al, ). However, it is essential to know whether global reanalysis data sets are useful for understanding the evolution of TCs.…”

A comparative study on the genesis of North Indian Ocean tropical cyclone Madi (2013) and Atlantic Ocean tropical cyclone Florence (2006)

“…This paper is the second part of our study aimed to understand cyclogenesis pathways over the North Indian Ocean (NIO). Our previous study [ Rajasree et al ., ] examined the genesis pathway of tropical cyclone Madi that occurred over the Bay of Bengal (BoB) during 6–13 December 2013. This study showed that the genesis of tropical cyclone Madi follows the hypotheses of the marsupial paradigm even though the original formulation of the marsupial paradigm were based on the dynamics of easterly waves generated along the African Easterly Jet (AEJ) which move across the Atlantic Ocean (AO).…”

“…Rajasree et al . [] found that the precursor disturbance of tropical cyclone Madi originated from a Westward Moving Disturbance (WMD) embedded in the Intertropical Convergence Zone (ITCZ). The pouch region associated with the parent disturbance played a major role in the vorticity upscaling and aggregation of moisture inside it.…”