Weather forecasting

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A large window looking at a forested exterior, four hand-drawn blue raindrops, and a hand holding a phone displaying a pie chart showing a 60% chance of partly cloudy skies, and a 40% chance of rain.

A weather comparison for June 3, 2014, showing St. Louis as mostly cloudy with 84 degreesF and 60% humidity, and Chicago as sunny with 75 degreesF and 40% humidity, alongside a U.S. map of climate zones.

Evangelista Torricelli stands in a study, holding a glass tube upright in a dish while inventing the mercury barometer; books and scientific equipment are visible around him.

A five-panel diagram shows the evolution of a frontal wave cyclone, with blue indicating cold air and red indicating warm air. Arrows illustrate airflow as the system progresses from the initial stage, to wave development, cyclonic circulation, occluded front, and finally dissipation.

Hurricane Hyacinth

Know about the development of a thunderstorm prediction model that can run on a laptop

A cartoon tornado in a field populated by a farmhouse and other small buildings.

A three-dimensional Lorenz attractor graph with swirling blue lines forming a butterfly-shaped pattern, representing chaotic motion in a mathematical weather model, with labeled x, y, and z axes.

Understand meteorologist Edward Lorenz's chaos theory

At a Glance

Satellite image of Hurricane Katrina as a large, well-defined spiral with a clear eye over the Gulf of Mexico, approaching the southern United States coastline.

weather forecasting summary

Weather forecasting: Media

meteorology

Videos

A large window looking at a forested exterior, four hand-drawn blue raindrops, and a hand holding a phone displaying a pie chart showing a 60% chance of partly cloudy skies, and a 40% chance of rain.

What Does “Percentage of Rain” Actually Mean?

It's not an exact science, but we'd bring an umbrella just in case.

Video: Encyclopædia Britannica, Inc.

Know about the development of a thunderstorm prediction model that can run on a laptop

Know about the development of a thunderstorm prediction model that can run on a laptop

Learn about a thunderstorm prediction model that can be run on a laptop computer.

Video: © University of Melbourne, Victoria, Australia (A Britannica Publishing Partner)

A cartoon tornado in a field populated by a farmhouse and other small buildings.

How Do Tornadoes Form?

The average tornado has a short lifespan—but large potential for destruction.

Video: Encyclopædia Britannica, Inc.

Understand meteorologist Edward Lorenz's chaos theory

Understand meteorologist Edward Lorenz's chaos theory

Learn about meteorologist Edward Lorenz and his contribution to chaos theory.

Video: © Open University (A Britannica Publishing Partner)

Why the word tornado was banned from American weather forecasts

Why the word tornado was banned from American weather forecasts

Learn how the Tri-State Tornado of 1925 made meteorologists use the word tornado...

Video: Encyclopædia Britannica, Inc.

Satellite image showing three labeled hurricanes—Florence, Isaac, and Helene—across the Atlantic Ocean in September 2018.

How Do Hurricanes Form?

We have questions about hurricane season. Britannica editor John Rafferty has answers.

Video: Encyclopædia Britannica, Inc.

Images

Doppler radar

Doppler radar

Doppler radars, such as this one operated by the U.S. National Weather Service at...

Eric Kurth, NOAA/NWS/ER/WFO/Sacramento

A weather comparison for June 3, 2014, showing St. Louis as mostly cloudy with 84 degreesF and 60% humidity, and Chicago as sunny with 75 degreesF and 40% humidity, alongside a U.S. map of climate zones.

weather conditions

Comparing weather conditions for St. Louis and Chicago on a given day.

Encyclopædia Britannica, Inc.

Evangelista Torricelli stands in a study, holding a glass tube upright in a dish while inventing the mercury barometer; books and scientific equipment are visible around him.

Torricelli, Evangelista

Italian physicist and mathematician Evangelista Torricelli, inventor of the mercury...

Photos.com/Getty Images

A five-panel diagram shows the evolution of a frontal wave cyclone, with blue indicating cold air and red indicating warm air. Arrows illustrate airflow as the system progresses from the initial stage, to wave development, cyclonic circulation, occluded front, and finally dissipation.

cyclogenesis

Cyclogenesis: evolution of a wave (frontal) cyclone.

Encyclopædia Britannica, Inc.

Hurricane Hyacinth

Hurricane Hyacinth

The well-defined eye and the rain bands of Hurricane Hyacinth about 805 kilometres...

Courtesy of National Oceanic and Atmospheric Administration; photograph, AP/Wide World Photos

A three-dimensional Lorenz attractor graph with swirling blue lines forming a butterfly-shaped pattern, representing chaotic motion in a mathematical weather model, with labeled x, y, and z axes.

weather model of Edward Lorenz

The weather model of meteorologist Edward...

Encyclopædia Britannica, Inc.

Satellite image of Hurricane Katrina as a large, well-defined spiral with a clear eye over the Gulf of Mexico, approaching the southern United States coastline.

Hurricane Katrina

National Oceanic and Atmospheric Administration satellite image of Hurricane Katrina,...

NOAA

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