Gujarat floods: What's behind heavy August downpour and erratic rain patterns

Image source: IMD

The India Meteorological Department (IMD) has predicted extremely heavy rains in isolated parts of Gujarat today, warning that Saurashtra and Kutch regions will experience heavy rainfall, with red and yellow alerts issued over the next few days. The torrentials rains have claimed 26 lives in Gujarat over the past three days and around 17,800 people have been evacuated from flood-affected areas.

As the flood situation in rain-battered coastal districts has worsened, here’s an analysis of the factors that may have contributed to the unusually intense rainfall in the region:

Gujarat, situated on the Tropic of Cancer, typically experiences a tropical dry climate, with the majority of its annual rainfall occurring between June and September. During this period, the state receives rain from the Arabian Sea branch of the southwest monsoon, which gathers moisture as it moves over the Indian Ocean.

However, the current downpour, attributed to a deep depression over the coastal region, is unusual. It's a land-based deep depression and such low pressure systems active over land rarely get enough moisture for heavy precipitation.

The Gujarat Institute of Disaster Management did a study on the variability in Gujarat rains during the summer monsoon and observed the erratic precipitation over years. "Rainfall variability study over Gujarat in 2022" study done by the institution in 2022 observed that heavy rainfall days are increasing and creating flood-like situations over the state.

The long-term trends over Gujarat according to "Observed Rainfall Variability and Changes Over Gujarat State" published by IMD in January 2020 suggested that 19 districts have shown an increasing trend in overall rainfall. The IMD also studied the rainfall variablity in the state over the last 30 years.

Deep depression over Saurashtra and Kachchh moved slowly during past 6 hours and about 60 km N-NW of Bhuj (Gujarat). To move W-SW and emerge into NE Arabian Sea and intensify into a cyclonic storm on 30th August. pic.twitter.com/snauAJl6wT

India Meteorological Department (@Indiametdept) August 29, 2024

IMD's release on Wednesday highlights rain intensity across Gujarat:

- Monsoon was active over Gujarat region and vigorous over Saurashtra-Kutch.

- Exceptionally heavy rainfall occurred at in districts of Saurashtra namely in Dwarka and Jamnagar.

- Extremely heavy rainfall at isolated in districts of at isolated in districts of Saurashtra-Kutch region namely Dwarka, Jamnagar, Rajkot and in Porbandar.

- Very heavy rainfall occurred at a few places; in the districts of Saurashtra-Kutch namely Jamnagar, Junagadh, Morbi, Porbandar and Rajkot,

- Heavy rainfall occurred at a isolated places in Kheda district of North Gujarat region; in the districts of Saurashtra-Kutch Amreli, Botad, Gir-Somnath, Junagadh, Morbi, Rajkot and in Kutch.

- Rainfall occurred at most places over Gujarat region and Saurashtra-Kutch.

- Gujarat weather warning for today (Thursday): Extremely heavy to exceptional heavy rainfall at isolated places very likely in the Saurashtra-Kutch region. Heavy to Very heavy rains at a few places with isolated extremely heavy falls very in all the district of Saurashtra-Kutch namely Surendranagar, Rajkot, Jamnagar, Porbandar, Junagadh, Amreli, Bhavnagar, Morbi, Dwarka, Gir Somnath, Botad, Kutch and in Diu.

IMD's predictions on Gujarat weather studied: If we study the IMD's observations and predictions of the past few days, the reason behind the ongoing heavy rain is the depression that has moved from Madhya Pradesh to Rajasthan, Maharashtra and Gujarat.

August 29: A deep depression over Saurashtra and Kachchh has moved slowly during past six hours and about 60 km N-NW of Bhuj (Gujarat). To move W-SW and merge into NE Arabian Sea and intensify into a cyclonic storm on August 30.

August 28: The deep depression is likely to move slowly west-southwestwards across Saurashtra & Kachchh region and reach Saurashtra & Kachchh and adjoining areas of Pakistan coasts by morning of August 29.

August 27: Deep depression over east Rajasthan and adjoining west Madhya Pradesh lay centered over north Gujarat in the morning (0830 hours IST) of today.

August 26: A depression over northwest Madhya Pradesh and adjoining east Rajasthan intensified into a deep depression.

August 25: A deep depression lay centred near 70 km south-southeast of Chittorgarh, Rajasthan. This system is expected to move west-southwest, affecting South Rajasthan, and Gujarat, and reaching Saurashtra, Kutch, and parts of Pakistan by August 29.

Deep depressions formed over land masses (and not the sea waters), however, rarely get enough moisture to bring heavy rains of this scale. One of the probable reasons behind the high moisture in the atmosphere during this time could be the rain-soaked soil from the earlier prcipitations.

According to a detailed report published by the Down to Earth magazine, only six land-based deep depressions have formed over India in the last decade.

The IMD's prediction of a land-based tropical cyclone on August 30 makes it the first since 2008 and only the 15th land cyclone since 1891. Before 2008, the last such land cyclone had occurred in 1976, the report said.