The India Meteorological Department (IMD) is set to revamp its heatwave warning system for more effectively tracking severe weather, particularly in humid coastal areas using a new percentile-based alert approach.
The conditions under which a heatwave alert will be issued are part of the proposed framework, with one element being changes to what is deemed as a heatwave, where it would now be defined simply if the temperature exceeded the 95th percentile for the location (that is, the highest temperature that has ever been recorded at the location). Authorities state it will be a way to sense how humid it is on a given day, because many extreme humid days would feel much worse than what the temperature is.
The current threshold for defining a heatwave in plains, set by IMD, is when the temperatures are either 45°C or exceed by 4.5°C to 6.4°C from the normal. Generally, alerts in coastal regions are limited to temperatures above 37°C and much warmer than normal. The stated thresholds are not always applicable due to extreme humidities as found in southern and coastal areas of India, according to experts.
Moisture can contribute to severe heat stress even if temperatures don’t hit the ridiculously high levels of 44°C or 45°C, IMD Director General M Mohapatra commented in reference to the many coastal areas where it does not. With the new model, they will stop waiting until temperatures pass traditional thresholds if forecasts are for some time above the norm in the local 95th percentile.
The alert level system is based on a percentile approach and is already being used as a trial in some areas, and in highly eventful summers in the future around climate change can be used to enhance early warning, said officials.