A satellite based study of pre-monsoon thunderstorms (Nor’westers) over eastern India and their organization into mesoscale convective complexes

Abstract

Nor’wester studies have a long history of climatological, synoptic and radar observations. These studies have been briefly mentioned and the field programs for the study of Nor’westers implemented in India Meteorological Department (IMD) from 1931-1941 have been touched upon. Indian atmospheric science community organized a multi-year STORM program during 2007-2010 to understand the formation of these severe local storms and also understand their dynamics through modeling. An attempt is made to use INSAT Infrared and Visible imageries to document the convective cells which developed over Eastern and North-East (NE) Indian states and adjoining countries of Bangladesh, Bhutan and Nepal for the year 2009. Also convective cells which organized themselves into Mesoscale Convective Complexes (MCCs) for the four years period 2007-2010 have been studied. It is found that by and large Eastern India (Jharkhand, Orissa, Sub Himalayan West Bengal and Bangladesh) is responsible for the initiation of convection. Development occurs as the cells propagate over the neighbouring areas of Bangladesh and NE India. Important observations with regard to initiation, maturity and dissipation etc. of the MCCs are provided. It is suggested that half hourly to hourly monitoring of convection can be accomplished by using INSAT imagery, along with multiple overlapping radar coverages, which could help in nowcasting of convective cells. Synoptic and thermodynamic forcing can help as broad guidance. The only effective way for effective warning is nowcasting using satellite and multiple radar coverage.

Enhanced prediction of premonsoon thunderstorms over eastern India through assimilation of INSAT‐3D sounding data

“…During premonsoon, the eastern parts of India (Gangetic West Bengal, Assam, Odisha, Bihar, and Jharkhand) experience severe TS, locally known as Nor'westers or Kal-Baisakhi (Tyagi et al, 2012). This region is also identified as one of the most unstable (Convective Available Potential Energy, CAPE of ∼1500-3500 J⋅kg −1 ) and a suitable region to produce severe TS with intense rainfall (>7 mm⋅h −1 ) activity compared to other parts of India (Sahu et al, 2020;Sasanka et al, 2023;Tyagi et al, 2011Tyagi et al, , 2013Tyagi et al, 2012). The nonlinear nature of TS dynamics, coupled with their smaller spatial and temporal scales, makes predicting TS events a significant challenge (Osuri et al, 2017;Priya et al, 2021Priya et al, , 2022Rajeevan et al, 2010).…”

“…TS are a systematic natural process that transports heat, moisture, and momentum near the earth's surface to the upper level of the atmosphere to maintain the energy and moisture budget. During premonsoon, the eastern parts of India (Gangetic West Bengal, Assam, Odisha, Bihar, and Jharkhand) experience severe TS, locally known as Nor'westers or Kal-Baisakhi (Tyagi et al, 2012). This region is also identified as one of the most unstable (Convective Available Potential Energy, CAPE of ∼1500-3500 J⋅kg −1 ) and a suitable region to produce severe TS with intense rainfall (>7 mm⋅h −1 ) activity compared to other parts of India (Sahu et al, 2020;Sasanka et al, 2023;Tyagi et al, 2011Tyagi et al, , 2013Tyagi et al, 2012).…”

Spatio-temporal changes in the pre-monsoon thunderstorm activities of northeast India over the past four decades

“…(i) the east-west oriented region along the foothills of Himalaya and (ii) the northwest to southeast oriented region from sub-Himalayan West Bengal to Tripura. 5,6 Additionally, the monthly average of thunderstorm events is greater than 20 in Guwahati, Shillong, Imphal and Tezpur stations in April. Roy et al 7 showed that the number of thunderstorm days is highest in April and May throughout a zone spanning from the NE to West Bengal.…”

Thunderstorm detection from GPM IMERG rainfall: Climatology of dynamical and thermodynamical processes over India

“…As an alternative step, satellite‐derived information can be used to detect thunderstorms. For example, Tyagi et al (2012) used cloud top temperature from very high‐resolution radiometer of Kalpana‐1 satellite at a spatial resolution of 8 km in 1‐h intervals to study the premonsoon thunderstorm occurrences in 2009. Previous studies have also used feature‐tracking algorithms to study mesoscale convective systems across the globe (e.g., Da Silva & Haerter, 2023; Feng et al, 2021; Huang et al, 2018).…”