BBC's Alex Deakin presenting a weather report.

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.

An example of a long-range forecast

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.

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 (http://www.geocities.com/capetropics/asi_index.html)

See also: Meteorology, Weather control, Afghanistan Meteorological Authority, TV Nova; AccuWeather