Evaluation process

The evaluation process starts with an initial assessment of a new potential extreme and available evidence by the Services Commission Rapporteur of Weather and Climate Extremes, followed by the establishment of an ad-hoc evaluation committee of international atmospheric scientists and other subject matter experts, as appropriate, in consultation by the rapporteur and the leadership of the Commission and the Secretariat. In the years since its inception, scientists from dozens of countries have been members of evaluation committees.

The members of these committees are selected for a range of specific expertise, including local climate knowledge, understanding of factors contributing to an extreme occurring at a particular location, metrology, or understanding of specific climate phenomena for the world in general. The Rapporteur, in conjunction with a committee member from the local area of the potential extreme and others, constructs a background report of the available information (metadata) and data regarding the extreme observation.

This report includes:

  • The exact geographic location of the observation;
  • The type of equipment used to make the observation (along with its model, serial number and specifics on its calibration, maintenance and operation);
  • The synoptics of the event and around the event, regional weather including all available climatological, synoptical and/or meteorological aerodrome reports and remote sensing data like satellite and radar images and other data; and
  • Any notable, unusual or unique information concerning the event. 
     

The committee reviews the report and discusses all aspects of the potential extreme, addressing the key questions.

The actions and procedures conducting a detailed rigorous evaluation have become more and more codified into seven distinct steps:

  1. Initial Contact
  2. Creation of Evaluation Committee
  3. First Session of the Committee
  4. Background Report
  5. Deliberations
  6. Formal Verdict
  7. Dissemination of Committee Results

New records and relevant documentation associated with the Record extremes are posted on this website following the Rapporteur's decision.

This website contains all accepted and verified record extremes (with corresponding metadata).

Records that are addressed primarily are:

  • Observed by instrumentation at the location of the event, such as thermometers in meteorological instrument shelters or rain gauges.
  • Instantaneous observations, such as the highest air temperature recorded at a station, even if it was only momentarily warm, as long as the thermometer registered that air temperature.
  • Data collected by that station over certain periods of time, such as total precipitation over 24 or 48 hours.
  • Records at global, hemispheric or continental scale. 
  • Sometimes multiple categories are required, for example, highest wave height determined by both ship or buoy observations as their measurement methodologies are somewhat different (e.g.: smallest tropical cyclone’s eye; highest weather-associated mortality; longest tornado transport; longest lightning flash).
     

For more information: Guidelines for the WMO Evaluation of Records of Weather and Climate Extremes (WMO-No. 1317)