By Akhil Srivastava, Scientist – D, India Meteorological Department, Delhi, India

The India Meteorological Department (IMD) follows a unified seamless system for monitoring and predicting heatwaves. This system spans from seasonal-range forecasts (three months in advance), followed by monthly forecasts (one month in advance) issued on the first day of the month, to extended-range forecasts (with a lead time of one to two- weeks) issued every Thursday, and medium range to short-range forecasts (with a lead time of seven days) issued daily and updated four times a day. The impact-based heatwave warning is issued twice daily (morning and evening) with validity for the next five days at the meteorological sub-division to district and station level. It contains observed heatwave conditions, warm nights, relative humidity, winds, percentile analysis, etc., and a warning for heatwaves, warm nights, and hot & humid weather conditions. The heatwave warnings are distributed to numerous stakeholders, including the Ministry of Home Affairs, National Disaster Management Authority (NDMA), State Disaster Management Authority (SDMA), Chief Secretaries, State Emergency Operation Centres (SEOC), district authorities, health and agriculture departments, power sector, Indian Railways, road transport authorities, as well as press and electronic media. Additionally, and Heat Action Plan (HAP) authorities at city, district, and state levels receive these warnings through websites, email, Common Alert Protocol & social media platforms such as WhatsApp, Facebook, X (formerly Twitter), and other channels. The heatwave forecast and warning services are used at the highest level of the government for anticipatory actions to mitigate the impact of heatwaves.

The forecast issued by IMD for different lead times invokes different anticipatory actions within IMD and with different stakeholders. The seasonal and monthly outlook issued by IMD anticipates preparatory and stock-taking actions from different stakeholders. The meetings are conducted by NDMA and different state governments for preparedness measures. The activation of HAPs, which are local government-based actions to tackle heatwaves, is anticipated upon the issuance of seasonal/monthly forecasts of increased temperatures and heatwaves. Within IMD, the issuance of seasonal and monthly outlook of increased temperatures and heatwaves initiates the meeting, and discussions among different forecasting offices of the region concerned for more rigorous monitoring and forecasting services aspects. Capacity-building measures are undertaken to update the officials for ensuing weather conditions which includes pre-season exercises and refresher courses. This also provides an opportunity to revisit the climatological dataset of extreme heat conditions. There could be mock drills by the concerned state and central authorities to ensure early action based on early warnings.

The extended range forecast further highlights the main regions for heatwaves during the coming two weeks along with the duration of the heatwave spell. This forecast anticipates on-ground actions with respect to making the arrangements required for interventions from different stakeholders for mitigating heatwave impacts. It triggers a pre-heatwave spell exercise for the region. The HAPs are activated. Within IMD extensive monitoring of the current state of temperatures, Numerical Weather Prediction (NWP) model analysis and their consensus, video conferencing among forecasters etc. continues to ensure the timely forecast of heatwaves and its dissemination to different stakeholders based on sectorial requirements.

The short to medium-range forecast (lead time up to seven days) with impact-based colour-coded warnings (for the next five days) at the district level are issued by IMD twice daily. These district-wise colour-coded impact-based warnings anticipate the immediate commencement of actions at the district level by different stakeholders as per the guidelines issued by the NDMA. The colour-coded warnings issued by IMD are GREEN COLOUR (No warning), YELLOW COLOUR (Be Updated), ORANGE COLOUR (Be Prepared) & RED COLOUR (Take Action). The daily dedicated sectorial bulletins with impact information are issued for anticipatory actions on the ground, for example, IMD issues a daily Heatwave Bulletin for Indian Railways and IMD also issues daily weather forecast bulletins constituency-wise with respect to the Lok Sabha elections of 2024.

Disclaimer: The views expressed in this piece are those of the author/s and do not necessarily reflect the views or policies of AIDMI.