Satellites, oceanic tools help IMD shadow cyclones

The India Meteorological Department (IMD) has earned plaudits from home and abroad for its early warnings on the extremely severe cyclonic storm Fani that played a crucial role in the timely evacuation that eventually prevented thousands of casualties.

The progress on indigenous satellite imagery available for forecasting has been gradual, so has been the development of tools used to gauge oceanic conditions. However, the use of supercomputers that are at par with those used by other global meteorological bureaus and availability of images from foreign satellites have been attributed as two crucial modern tools that have enabled IMD to keep a closer watch on the cyclone's genesis, severity and its track.

To put things into perspective, foreign satellite images were not used for public forecasts until as recently as April 2018. Supercomputers with 8.0 petaflops have been put to use for forecasts, including dynamical monsoon forecasts, only since 2017.

Currently, the IMD gets cloud imagery, surface wind direction and wind speed from INSAT-3D and SCATSAT. Then, there are Eumetsat (EU satellite service), Meteosat, the Japanese satellite Himawari and even the Chinese Fengyun weather satellite, also known as FY series. These satellites provide images with resolutions ranging from 1km x 1km to 3km x 3km. The foreign satellite images are updated every 10-15 minutes.

IMD scientists, present and former, said that the ability to forecast cyclones was never in question. The heating of sea surface and winds fuel tropical cyclones. To track these two parameters, the quantum of data available has increased exponentially. Since last October, IMD has also been using the coupled ocean-atmospheric models to forecast and track the path of cyclones.

IMD Director General KJ Ramesh said right from the time a low-pressure area developed near the equatorial Indian Ocean on April 25, the data was fed into weather models, which threw up the possibility of the genesis of a cyclone and a forecast was issued stating the same. IMD also used the longer life-cycle of the cyclone to run more models.

IMD Director General KJ Ramesh explains, "With these satellites, we are able to track weather conditions over the Arabian Sea and Bay of Bengal with fast, near real-time updates on clouds and winds." He goes on to add, "Then, we have buoys, drifting ones and moored, and argo floats. INCOIS (Indian National Centre for Ocean Information Services) began putting them out in the sea from the turn of the century. The sum effect is that we have much more data to describe the atmosphere at a finer scale, that too as close as possible to the real conditions."

As part of this coupled model, cyclones are mapped from the outer wall and inward to their eye. This model, developed with the help of INCOIS, is run four times a day when a cyclone develops and accordingly its severity and path are updated.

Former IMD DG Ranjan Kelkar, who helmed the organisation during the 1999 Super Cyclone, said that with regards to technology, IMD's capabilities were not lacking much. Kelkar believes it was the utter lack of preparedness in terms of evacuation, flooding due to a massive storm surge and overall poor communication systems of the time that led to the widepsread destruction and death.

"The Paradip cyclone as it was termed had intensified rapidly and hit perpendicular to the Odisha coast after it originated from the Gulf of Thailand and then emerged into the Andaman Sea. We had INSAT satellite imagery available and a fairly accurate track was prepared. Yes, we did not have buoys and argo floats and there were fewer radars. However, some of my own personal advice to Railways to cancel trains was not heeded," Kelkar said.

He went on to add, "A cyclone does not emerge out of nothing. There is always a nascent disturbance. The Super Cyclone though led to two important developments. It led to the formation of the NDMA (National Disaster Management Authority) and a scheme was initiated to install more doppler weather radars, especially along the coast."