Climate Change

Biporjoy: Depression forms over Arabian Sea, climate change making conditions conducive

Exceptionally warm Arabian Sea, weak monsoon onset and favourable Madden Julian Oscillation conditions favouring the cyclone, expert tells Down To Earth

By Rohini Krishnamurthy
Published: Tuesday 06 June 2023

A map released by the IMD on June 6.A map released by the IMD on June 6.

A depression formed in the southeast Arabian Sea at 5.30 am on June 6, 2023, about 920 kilometres (km) west-southwest of Goa, according to the India Meteorological Department (IMD).

The maximum wind speed is 45-55 km per hour (kmph), gusting to 65 kmph. By 5.30 pm, the depression is likely to intensify into a deep depression and by June 7, 2023, the system is likely to move nearly northwards and intensify into a cyclonic storm over the east-central Arabian Sea and adjoining southeast, it added.

A cyclonic storm will remain through the wee morning of June 8. The sustained wind speed is 80-90 kmph gusting to 100 kmph.

When the cyclone forms it will be named Biporjoy. “An exceptionally warm Arabian Sea, a weak monsoon onset, and favourable Madden Julian Oscillation (MJO) conditions are favouring this cyclone,” Roxy Mathew Koll, a climate scientist at the Indian Institute of Tropical Meteorology, wrote on Twitter.

The sea surface temperatures are 30-32 degrees Celsius. “This is above the climatological mean. This is clearly the climate change link, as Arabian Sea warming is favouring more intense cyclones,” Koll added in his tweet. High sea surface temperatures favour the formation of cyclones.

Further, MJO, an eastward-moving disturbance of clouds, rainfall, winds, and pressure that moves in the tropics, is active in the Indian Ocean, making conditions conducive for the formation of a cyclone, according to Koll.

MJO is different from El Nino-Southern Oscillation (ENSO), a recurring climate pattern involving changes in the temperature of waters in the central and eastern tropical Pacific Ocean.

The cyclonic storm is predicted to intensify into a severe cyclonic storm by 5.30 pm on June 8, with wind speeds of 90-100 kmph gusting to 110 kmph.

Most climate models “are indicating further intensification of the system into a severe cyclonic storm during the next 24 hours,” according to the IMD. It is likely to move nearly northwards in the next five days.

By June 10, the system will likely develop into a very severe cyclonic storm with wind speeds of 115-125 kmph gusting to 140 kmph. In the wee hours of June 11, the sustained wind speeds are expected to reach 125-135 kmph and gusts of upto 150 kmph

The European Centre for Medium-Range Weather Forecasts model as visualised by the software Windy shows that the system is moving towards the Pakistani province of Balochistan.

Another weather forecast model, Global Forecast System, shows that the system is moving towards Oman.

Koll said it’s too early to know where the system will make landfall as the background steering winds are evolving. “Now the system is in the central Arabian Sea. We know it is moving north-northwest direction. We need two-three days more to be certain about the track and landfall,” Koll told Down To Earth.

The system will delay the arrival of the southwest monsoon. “The system is driving moisture away from India and is hindering monsoon winds.  This could be a further cause of delay in the onset and progress of monsoon,” he added.

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