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Severe Weather Threat Across the Central and Southern Plains Thursday; Hazardous Heat in South Texas and Florida

Severe thunderstorms are forecast across parts of the central and southern Great Plains Thursday afternoon through Thursday night, posing a risk for severe winds and large hail. Hazardous heat will continue across portions of South Texas and for much of the central and southern Florida Peninsula through the weekend. Daily high temperature records could be tied or broken. Read More >


Meteorological Character Codes

Why are there Meteorological Codes?

The efficient and timely movement of meteorological information is a fundamental requirement of modern meteorology. Observers record information about the environment and provide it to data processing centers so that forecast guidance products may be produced. Countries exchange information to enhance their forecasts and to produce global forecast models. The facility to move information quickly between centers, without regard to language, and in a format that may be processed by automated means is embodied in meteorological codes.

What are Meteorological Codes?

WMO Meteorological codes are defined by the World Meteorological Organization in WMO Manual No. 306. The codes are composed of a set of values defined in tables with reference to specific position within strings of information. These defined values make up a code form and binary codes are made up of groups of letters representing meteorological or other geophysical elements. Different code forms are used to represent different types of observations or products. In messages, these groups of letters are transcribed into figures indicating the value of state of the elements described.

The National Weather Service and other U.S. governmental agencies have developed additional codes and identification structures as supplements to the WMO codes and message identification systems. These are documented and made available through publications by the OFCM and other agencies as well as by the NWS. Some meteorological code documentation can be found via this server.

Changes to Codes and Coding Practices

The Working Group on Data Representation and Codes (WGDRC), which functions as a sub-group to the Commission for Basic Systems (CBS) of the World Meteorological Organization (WMO), meets on a regular basis to review the status of codes and coding practices. As a result of these meetings, changes to codes and coding practices are recommended to the Chairman of CBS. CBS, which meets semi-annually, reviews the changes, recommends adoption, and chooses the implementation date. The latest changes to the WMO codes can be found in the World Weather Watch ( WWW ) "Newsletters" documentation area of the WMO Web Server at WMO Secretariat in Geneva, Switzerland. The WMO Manual extracted code changes from the newsletters can also be found on the WMO server in Geneva.

User groups may recommend changes to codes or coding practices over which they have cognizance. An example of this would be the case whereby the Data Buoy Cooperation Panel recommended changes to FM 18 DRIFTR during CBS IX held in Oslo, Norway, in 1992. The changes, including a change in the name of the code to BUOY, were approved and implementation scheduled for November 1994.

In the case of aviation codes the International Civil Aviation Organization (ICAO), headquartered in Montreal, Canada, is responsible for defining and encouraging the provision of services which civil aviation requires. WMO is responsible for providing the technical methods and practices recommended for use in providing required meteorological services.

The WMO Member countries have a Commission for Basic Systems (CBS) meeting every two years, in which new code recommendation changes are approved. After approval these changes are entered into the WMO codes manual 306. The last meeting of CBS was held in Geneva, Switzerland.

The final report of the 2000 CBS (Twelfth Session) [1,025K] actions of the new reorganization of CBS working structure.

The current changes from CBS XIII, held in Geneva December 2000, can be found on the WMO server in their WWW-DDB FTP site. The Guide on Binary Codes & tables is available, containing the Identification of Originating/Generating Centre, Table C-1 of WMO Codes; Manual 306.