The top priority of the World Meteorological Organization and its Members is to save lives through accurate forecasts and early warnings. A very successful example of this, in recent years, is improvements in Heat-Health Early Warnings and Heat Action plans, underpinned by strong collaborations between the meteorological, health, disasters management, and scientific communities.
WMO is aware of current interest in developing heatwave ranking and naming systems. As the UN specialized agency responsible for weather, climate and water, the WMO exercises a leadership role in coordinating globally recognized extreme weather naming conventions. The WMO Services Commission is therefore currently considering the advantages and disadvantages of naming heatwaves.
There is currently no agreed international system or protocol for naming or coordinating the naming of heatwave events.
International and regional naming protocols are used to support risk management of different types of storms, including tropical cyclones. Storm naming protocols and agreed intergovernmental coordination mechanisms are required to prevent misnaming and to coordinate the naming of transboundary or regional scale events.
However, what has been established for tropical cyclone events may not necessarily translate easily across to heatwaves. Caution should be exercised when comparing or applying lessons or protocols from one hazard type to another, due to the important differences in the physical nature and impacts of storms and heatwaves.
A heat wave is broadly defined as a period of statistically unusual hot weather persisting for a number of days and nights. Indices based on local climatological conditions are used to objectively characterize and declare a heat wave. In most countries only designated national agencies, such as weather services or public health agencies, have the national responsibility to issue official heat warnings. Independent practices to rank and name heatwaves which are not coordinated with the official warning systems, may risk disrupting civil protection protocols and coordination efforts, bring unintended negative consequences, or reduce the effectiveness of established heat advisory and response measures. Coordination of “pilot heatwave naming” activities with the official heat advisory systems in a country is suggested to prevent any confusion and interference with existing public messaging and designated operational procedures and protocols.
Heatwaves can be forecast up to 10 days in advance in many areas (mainly extra-tropics and high latitudes) but lack skill at 3-day lead-times in many regions (mainly tropics). Forecast-based naming creates additional challenges that named events might not actually take place, might turn out to be less severe, or occur in different localities. This could potentially undermine any benefits of raised awareness through naming and create false alarms.
To protect communities from avoidable heat related illness the public should be aware of actions to take during extreme heat events, as well as recognize their personal vulnerability factors, such as age, medications, or medical conditions which can make prolonged exposure to heat even below heatwave thresholds also deadly. Studies show heat related illness and death are also strongly associated with ‘mild’ hot days, occurring outside declared heatwave events, including hot nights, prolonged occupational heat exposures, and exertional heat stress.
WMO, working with the relevant partners, will continue to support the development of heat early warning systems, including the update of extreme heat related guidance and associated extreme heat risk communication strategies.
For further information on heat-health issues, consult the Global Heat Health Information Network, which is co-sponsored by WMO, WHO, and US NOAA and brings together the meteorological, health and scientific communities.