Climate Change

Biporjoy: Here is why track of very severe cyclone is unclear

Biporjoy is the fourth-strongest cyclone that occurred in June in the Arabian Sea

By Rohini Krishnamurthy
Published: Friday 09 June 2023

An IMD map showing the track of BiporjoyAn IMD map showing the track of Biporjoy

The track of Biporjoy, the very severe cyclonic storm, is unclear as different climate models are making diverging forecasts. But experts warn that India should be alert.

With wind speeds reaching 70 knots (129.64 kmph), the very severe cyclone Biporjoy is the fourth-strongest cyclone that occurred in June in the Arabian Sea. The 2007 Cyclone Gonu, with wind speeds reaching 145 knots, was the strongest, followed by the 1998 Gujarat or Kandla cyclone (105 knots), and the 2019 Cyclone Vayu (100 knots).

Gonu, the 1998 Gujarat cyclone and Vayu struck in El Nino years. National Oceanic and Atmospheric Administration announced the arrival of El Nino on June 8, 2023. Previously, in May 2023, the World Meteorological Organization predicted that there was a 60 per cent chance of an El Nino during May-July 2023.

What are the models saying?

The India Meteorological Department (IMD) has predicted as on June 9, 8.30 am that the cyclone will move north-northeastwards towards India in the next 48 hours and then move north-northwestwards in the subsequent three days.

IMD’s previous forecast on June 8 predicted that the system would move north-northwestwards.

The European Centre for Medium-Range Weather Forecasts (ECMWF) model as visualised by the software Windy shows that the landfall will occur in the Sindh province of Pakistan on June 16.

Wind speeds could reach 77 kmph on June 15 a few hours before the cyclone makes landfall.

Another weather forecast model, Global Forecast System (GFS), predicts a different track. Data visualised by climate website Windy shows that it will likely make landfall in Balochistan province of Pakistan on June 16.

Wind speeds could reach 102 kmph on June 16 before it makes landfall.

On June 8, the GFS model predicted that the landfall will likely occur in Oman by June 14-15.

“Areas from Oman to coastal Pakistan and Gujarat should be prepared for possible impacts next week,” Jason Nicholls, senior meteorologist and manager of International Forecasting at website AccuWeather said on Twitter.

Akshay Deoras, a research scientist at the University of Reading in the United Kingdom explained that models typically show variance. But this time, the variations are quite stunning.

There are two reasons. One is that the wind profile is not ideal. “The wind shear is high. For example, you have strong winds moving in one direction at the top and weak winds from another direction at the bottom, there is a tilt, which does not favour tropical cyclones,” he explained.

The second unfavourable condition is dry air in Pakistan and West Asia, which is a poison for tropical cyclones. “As the cyclones move further, they will suck dry air from different regions,” he highlighted. The sea surface temperatures are high, which works in favour of the cyclones.

As a result, models, according to Deoras, are struggling to predict the exact intensity and location of the tropical cyclone and the track.

If this tropical cyclone remains over the Arabian Sea and conditions continue to be unfavourable, it could die over the Sea or form a weak system.

But if it can maintain intensity, it could bring more rainfall. “If it comes towards Pakistan or northern Gujarat, it will dump rain but I don’t think it will bring any storm surge,” he added. 

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