If you're looking for the revolutionary communist Weather Underground Organization, see Weathermen

Weather forecasting is the science of making predictions about general and specific weather phenomena for a given area based on observations of such weather related factors as atmospheric pressure, wind speed and direction, precipitation, cloud cover, temperature, humidity, frontal movements, etc.

Meteorologists use several tools to help them forecast the weather for an area. These fall under two categories: tools for collecting data and tools for coordinating and interpreting data.

• Tools for collecting data include instruments such as thermometers, barometers, hygrometers, rain gauges, anemometers, wind socks and vanes, Doppler radar and satellite imagery (such as the GOES weather satellite).

• Tools for coordinating and interpreting data include weather maps and computer models in the form of Numerical Weather Predictions.

In a typical weather-forecasting system, recently collected data are fed into a computer model in a process called assimilation. This ensures that the computer model holds the current weather conditions as accurately as possible before using it to predict how the weather may change over the next few days.

Weather forecasting involves processing a lot of data, but interpretation can be difficult because of the chaotic nature of the factors that affect the weather. These factors can follow generally recognized trends, but meteorologists understand that many things can affect these trends. With the advent of computer models and satellite imagery, weather forecasting has improved greatly. Since lives and livelihoods depend on accurate weather forecasting, these improvements have helped not only the understanding of weather, but how it affects living and nonliving things on Earth.

The chaotic nature of the atmosphere imposes a limit on the predictability of the weather. The predictability limit is estimated to be about two weeks. Predictions beyond this limit are necessarily statistical rather than deterministic. Current operational weather prediction has not yet reached this predictability limit.

Below is a sample Hurricane Warning issued by the Cape Cod Hurricane Center:

EXTREMELY DANGEROUS HURRICANE ISABEL UPDATED

As of the 5PM advisory, Hurricane Isabel has been updated 
to a category 5 on the Saffir-Simpson Intensity Scale.  
Isabel's position is at 21.6N and 55.3W with maximum 
sustained winds at 155 KTS (160 MPH.)

The exact track of Isabel is still very uncertain past 
the 5th day.  The GFDL has Isabel heading in the Long 
Island direction.  Most of the models agree on a slow but 
steady WNW to NW turn over the next 3 days.  All interests 
on the Eastern Seaboard should monitor this extremely 
dangerous threat.  It is still too early to determine the 
exact track of Isabel.  If Isabel does indeed head up the 
Eastern Seaboard I am expecting the possible strike area 
will be from Cape Hatteras to Block Island.

Repeating the 5PM advisory, Hurricane Isabel is at 21.6N 
and 55.3W with maximum sustained winds at 155 KTS.

Forecaster Bryant
Cape Cod, Mass.

• The Cape Cod Hurricane Center

History

Historically, the two men most credited with the birth of forecasting as a science were Francis Beaufort (remembered chiefly for the Beaufort scale) and his protegé Robert Fitzroy (developer of the Fitzroy Barometer). Both were influential men in British Naval and Governmental circles, and though ridiculed in the press at the time, their work gained scientific credence, was accepted by the British Navy and formed the basis for all of today's weather forecasting knowledge.

Television weather reporters have sometimes used gimmicks to attract viewers. One trend that started in the 1970s was "backyard" weather where the forecaster would stand in an outdoor setup while making predictions. WNEP-TV in Scranton, Pennsylvania has been doing this since 1978.

See also

• Meteorology
• Weather control
• Afghanistan Meteorological Authority
• TV Nova
• AccuWeather