Shannon and Weaver Model of Communication

Numerical code (called FM-12 by WMO) used for reporting weather observations made by manned and automated weather stations.


14 related topics


Low frequency

ITU designation for radio frequencies (RF) in the range of 30–300 kHz.

Atmospheric radio noise increases with decreasing frequency. At the LF band and below, it is far above the thermal noise floor in receiver circuits. Therefore, inefficient antennas much smaller than the wavelength are adequate for reception
An LF radio clock.
Low cost LF time signal crystal receiver using ferrite loop antenna.

A regular service transmitting RTTY marine meteorological information in SYNOP code on LF is the German Meteorological Service (Deutscher Wetterdienst or DWD).

Weather forecasting

Application of science and technology to predict the conditions of the atmosphere for a given location and time.

Forecast of surface pressures five days into the future for the North Pacific, North America, and the North Atlantic Ocean
The Royal Charter sank in an 1859 storm, stimulating the establishment of modern weather forecasting.
Weather map of Europe, December 10, 1887
BBC television weather chart for November 13, 1936
An example of 500 mbar geopotential height prediction from a numerical weather prediction model
Modern weather predictions aid in timely evacuations and potentially save lives and prevent property damage
Marestail shows moisture at high altitude, signalling the later arrival of wet weather.
An example of a two-day weather forecast in the visual style that an American newspaper might use. Temperatures are given in Fahrenheit.
Ash cloud from the 2008 eruption of Chaitén volcano stretching across Patagonia from the Pacific to the Atlantic Ocean
An air handling unit is used for the heating and cooling of air in a central location (click on image for legend).
Emblem of JTWC Joint Typhoon Warning Center

Stations either report hourly in METAR reports, or every six hours in SYNOP reports.

World Meteorological Organization

Specialized agency of the United Nations responsible for promoting international cooperation on atmospheric science, climatology, hydrology and geophysics.

German meteorologist Gerhard Adrian, president of the World Meteorological Organization, in 2019
WMO headquarters in Geneva, shared with the IPCC and the Group on Earth Observations
The member states of the World Meteorological Organization divided into the six regional associations, shown on a world map

The traditional code forms, such as SYNOP, CLIMAT and TEMP, are character-based and their coding is position-based.

Utility station

Used to describe fixed radio broadcasters disseminating signals that are not intended for reception by the general public .

Radioteletype tuning indicator

Weather information is often broadcast using RTTY and sending synoptic codes, or weather charts are sent using radiofax, which are used by mariners and others.

Data assimilation

Mathematical discipline that seeks to optimally combine theory with observations.

Lewis Fry Richardson
General Data Assimilation diagram (Alpilles-ReSeDA)

Stations either report hourly in METAR reports, or every six hours in SYNOP reports.

Station model

In meteorology, station models are symbolic illustrations showing the weather occurring at a given reporting station.

Station model as used in the United States plotted on surface weather analyses
Cloud classification by altitude of occurrence (towering vertical cumulus congestus not shown)
Common present weather symbols
Pressure tendency figures
Past weather symbols
Low étage (Sc,St) and upward-growing vertical (Cu, Cb)
Middle étage (Ac,As) and downward-growing vertical (Ns)
High étage (Ci,Cc,Cs)

Although the SYNOP code has no separate formal group classification for vertical or multi-level clouds, the observer procedure for selecting numerical codes is designed to give high reporting priority to those genera or species that show significant vertical development.


Okta is a unit of measurement used to describe the amount of cloud cover at any given location such as a weather station.

Scale of cloud cover measured in oktas (eighths) with the meteorological symbol for each okta.

In addition, in the SYNOP code there is an extra cloud cover indicator '9' indicating that the sky is totally obscured (i.e. hidden from view), usually due to dense fog or heavy snow.

Surface weather observation

Surface weather observations are the fundamental data used for safety as well as climatological reasons to forecast weather and issue warnings worldwide.

Weather station at Mildura Airport, Victoria, Australia.
ASOS sensors, located at Salinas, California
Station model used on surface weather maps
Different shapes and sizes of buoys

The reports are coded using the synoptic code, and relayed via radio or satellite to weather organizations worldwide.


Binary data format maintained by the World Meteorological Organization (WMO).

A Hasse diagram: representation of a Boolean algebra as a directed graph

BUFR was created in 1988 with the goal of replacing the WMO's dozens of character-based, position-driven meteorological codes, such as SYNOP (surface observations), TEMP (upper air soundings) and CLIMAT (monthly climatological data).

European Climate Assessment and Dataset

Database of daily meteorological station observations across Europe and is gradually being extended to countries in the Middle East and North Africa.

ECA&D project logo
Participating countries.
ECA&D data availability for precipitation. Green dots: data freely available; red dots: in database but ECA&D is not at liberty to distribute.
ECA&D data availability for snow depth. Green dots: data freely available; red dots: in database but ECA&D is not at liberty to distribute.
Station De Bilt, The Netherlands
Annual time series of the mean temperature at station De Bilt, The Netherlands.
Trend in the June maximum temperature from 1950–2009.
Anomaly in the number of wet days (precipitation sum greater than 1mm) for June, 2010 with respect to the normal period 1961–1990.
Climatology of mean temperature for the normal period 1961–1990.
E–OBS mean temperature for June, 2010.

In order to ensure that each station's time series are as complete as possible, the database contains an automated update procedure that relies on daily data from SYNOP (surface synoptic observations) messages that are distributed in near real-time over the Global Telecommunication System (GTS).