Biporjoy is unusual because most models could not predict that it would intensify into an extremely severe cyclonic storm
Cyclone Biporjoy intensified into an extremely severe cyclonic storm at 5.30 am on June 11, 2023 and continues to remain so. It is likely to make landfall in Gujarat, according to the India Meteorological Department (IMD).
Till June 14, it is very likely to move northward and then cross Saurashtra, Kutch and adjoining coasts between Mandvi (Gujarat), Jakhau Port (Gujarat) and Karachi (Pakistan) around noon of June 15 as a very severe cyclonic storm.
Cyclone Biporjoy is now the strongest cyclone in the Arabian Sea after Tauktae according to both IMD and Joint Typhoon Warning Center (JTWC). But Biporjoy is unusual because most models could not predict that it would intensify into an extremely severe cyclonic storm.
One of the contributors to this unpredictability is the amount of wind shear, ie, the change of the wind with height. The shear towards the northern Arabian Sea has been weak and favourable for cyclone intensification.
Similarly the sea surface temperatures also have been favorable. The shear winds in the south increased as the monsoon strengthened. It is the progression of the monsoon and then the cyclone that is deciding the shear.
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.
Additionally, the upper air divergence helped the cyclone intensify. But now it is weakening, which would be among the factors to weaken the cyclone in the coming days.
When divergence occurs in the upper levels of the atmosphere, it leads to rising air. IMD forecasts indicate that cyclone Biporjoy might have a landfall as a severe cyclone but dissipate after landfall (in about six hours) to a deep depression.
In the satellite era (since 1982) Cyclone Biporjoy is now the 4th longest-lived cyclone (with winds at least 35 knots) during the pre-monsoon season in the Arabian Sea as per JTWC records.
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