What made Cyclone Senyar a once-in-a-century weather anomaly in Malacca Strait

In an exceptionally rare meteorological development, Cyclone Senyar formed over the Malacca Strait in November, a basin where cyclonic systems are almost never observed.

According to Dr Mrutyunjay Mohapatra, Director General of the India Meteorological Department (IMD), this was the first cyclone recorded in the Strait in 135 years, with the previous instance dating back to 1886.

The Malacca Strait, bordered by Malaysia and Indonesia and known primarily for its crucial shipping routes, typically lacks the atmospheric and oceanic conditions required for cyclogenesis. “This is something we haven’t seen before in our monitoring activity,” said Dr Mohapatra, calling Senyar’s development a “rare weather occurrence.”

WHY SENYAR WAS RARE

The Strait is a virtually cyclone-free basin. It lies extremely close to the equator, where the Coriolis force, the deflection needed for storms to spin, is too weak to enable cyclone formation.

The last cyclone documented here was 135 years ago, making Senyar a historic anomaly in modern meteorological records.

Senyar’s formation was driven by a rare alignment of atmospheric factors, including back-to-back low-pressure systems, an active Inter-Tropical Convergence Zone (ITCZ), and supportive equatorial waves such as Kelvin and low-frequency waves.

These favourable triggers overlapped over the South Bay of Bengal and the equatorial maritime zone, allowing a marginal system to develop despite its proximity to the equator.

WEAK BUT NOTEWORTHY

Senyar reached about 35 knots, classifying it as a marginal system. While it never intensified into a severe cyclonic storm, its very emergence, rather than its strength, was the defining rarity.

Dr. Mohapatra noted that the IMD’s improved monitoring capabilities ensured early detection, with the forecast issued on November 13.

Senyar affected coastal areas of Malaysia and Indonesia, bringing rainfall and localised disruptions. Its life span remained restricted to the Strait, preventing significant intensification over the Bay of Bengal.

A YEAR OF UNUSUAL CYCLONE BEHAVIOUR?

November saw two cyclones: Senyar in the Malacca Strait and Ditwah near Sri Lanka and parallel to India’s east coast.

While Ditwah brought flooding and landslides to Sri Lanka before brushing past Tamil Nadu, it too remained marginal in strength. The IMD clarified that social-media claims of Ditwah becoming a “super cyclone” were inaccurate.

November recorded 42.9 per cent deficient rainfall across India, the 10th lowest since 2001, though temperatures stayed normal to below normal due to clear skies. The broader climate backdrop included a weakening La Nina expected in December and a negative Indian Ocean Dipole (IOD) transitioning toward neutral.

Although Senyar remained weak, its formation raises important questions about whether such rare meteorological coincidences could become more frequent amid broader climate transitions.

– Ends

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