CYCLONE FORECASTING

Subject: Geography

Concept:

• Over the years, India’s ability to track the formation of cyclones has improved significantly.
• There is a network of 12 doppler weather radars (DWR) along India’s coast if one were to begin counting from Kolkata and trawl up to Mumbai — there are 27 in all in the country.
• Depending on where a storm is forming, these radars send pulses of radio waves to gauge the size as well as the speed at which water droplets are moving. The earlier generation of radars was unable to track such progress in real time, but with DWRs, now the base standard of weather radars, it is usually possible to detect a potential storm at least four-five days in advance.
• The IMD also collaborates with similar international networks, such as the Japan Meteorological Agency, the U.S. National Hurricane Center, and the U.S. Central Pacific Hurricane Center, and these bodies constantly send warnings and forecasts about changes in the ocean weather.
• The near ubiquity of ocean-buoys that track changes in ocean sea surface temperatures as well as dedicated meteorological satellites improve the odds of early detection.
• The IMD follows a five-stage classification for cyclones, with the lowest a ‘cyclonic storm’ generating wind speeds of 62-87 kmph, and the highest a ‘super cyclonic storm’, generating winds over 222 kmph.

Cyclone Nivar :

• April-June and October-December are India’s cyclone seasons. The arriving monsoon, as well as its retreat, stir up the surrounding seas and generate cyclones.
• Though the Bay of Bengal is three times more likely to generate cyclones, the ones that originate in the Arabian Sea are trickier, as the cyclone, while ostensibly moving away from India’s western coast, can suddenly ‘recurve’ and move back in.
• There are also fewer radars along India’s west coast than the eastern coast, and all these reasons make the Bay of Bengal cyclones more tractable.
• In this context, Nivar, because it conformed to a fairly predictable trajectory and was not super cyclonic in intensity, gave State administrations in Puducherry, Tamil Nadu and Andhra Pradesh time to prepare, and was far less damaging than Amphan.
• However, the cyclone season is not yet over and more systems are likely to form in the coming weeks, according to the IMD.