Tropical cyclone formation require warm water and limited vertical wind shear

All hurricanes have a central eye, where no extreme weather occurs, surrounded by intense winds and thunderstorms.

Tropical cyclones consist of three main parts: the eye, the eyewall, and rainbands

The eye is a calm, clear central area surrounded by an eyewall of intense thunderstorms. Rainbands are spiral bands of clouds and thunderstorms extending from the eyewall.

How do hurricanes form?

Tropical cyclones, also called hurricanes and typhoons, cause catastrophic damage when they strike land. This four-minute video explores the life cycle of cyclones—how atmospheric conditions, ocean temperatures, and the Earth's rotation combine to create them, and how they are driven by winds and eventually weaken after moving over land.

Available data suggest that while hurricane frequency has not increased over the past century, average hurricane intensity has, a trend scientists attribute to rising air and ocean temperatures.

Tornado formation relies on wind shear to create a tube of rotating air

Once a horizontal vortex is created by air circulating between winds of different directions and speeds, an updraft, such as those seen in powerful thunderstorms, tilts the vortex vertically. The updraft then strengthens the vortex, which becomes a tornado upon touching the ground.

Lightning storms are more common in coastal and tropical regions

Water-abundant areas that receive increased solar radiation, such as those near the equator, experience increased rates of evaporation, which produce tall clouds as moisture rises, cools, and condenses. Mountain ranges can also steer air to higher altitudes, creating collisions between atmospheric particles that generate charge imbalances—the precursors to lightning.

Trade winds blow from east to west due to the Coriolis Effect

Warm air rises near the equator while cooler air sinks near the poles, creating circulation patterns that curve due to Earth's rotation. At the equator, doldrums—calm regions of no wind—build warm, moist air, creating storms.

Atmospheric processes amplify the strength of storms by coalescing clouds

Research has shown that turbulent mixing of air at the edges of clouds and other small-scale thermal activity beneath them help clouds group together, intensifying short bursts of rainfall, especially in tropical regions. Simulations reveal this produces more powerful storms than predicted by older models, though they may occur less frequently.

Fast-changing conditions during their formation make tornado forecasting difficult

The final steps of tornadogenesis—the process of forming a tornado—depend on near-surface details, such as local geography, which are difficult for radar to observe and affect how funnel clouds make contact with the ground. Inconsistencies in storm behavior have limited the amount of advance warning people receive before tornadoes touch down.

Though less common, tornadoes can form without the presence of thunderstorms

Supercell tornadoes involve rising warm air—updrafts—from the strongest type of thunderstorm—supercells—to help turn horizontally rotating tunnels of air into vertical columns. In non-supercell tornadoes, which are generally weaker as a result of forming within less energetic systems, vertical rotation is present from the start near ground level.

Tropical cyclones are called hurricanes, typhoons, and cyclones around the world

Tropical cyclones are named differently based on their region of origin due to historical traditions and cultural importance. These storms are called hurricanes in the Atlantic and northeast Pacific oceans, cyclones in the southwest Pacific and Indian oceans, and typhoons in the northwest Pacific Ocean.

Dust from the Sahel and Saharan regions makes northwest Africa a hurricane nursery

NASA’s Convective Processes Experiment—Cabo Verde studied the early stages of hurricane formation, identifying how dust interacts with clouds over the ocean to produce the rainy disturbances that become tropical cyclones.

Bomb cyclones can produce heavy rain, blizzard conditions, and intense winds

Known as "bombogenesis" in meteorology, these systems get their colloquial name from their rapid intensification over a 24-hour period—a phenomenon seen in some tropical cyclones. They occur most commonly along the coasts of the Northeast and Northwest US when there is a severe temperature difference between colliding air masses.

Hurricanes, which rely on air consistently spinning in the same direction, cannot cross the equator because air curves in opposite directions north and south of it.

Due to a local microclimate, a thunderstorm nicknamed Hector the Convector appears almost every day from September to March at around 3 pm off the northern coast of Australia.

Tornadoes, or twisters, have been seen on every continent but Antarctica

Because tornadoes require rising warm air to form, some meteorologists have suggested that urban environments—locations where human landscape modification has introduced materials that trap thermal energy—can enhance the conditions needed for tornado formation. Tornadoes have been reported to cause ear "popping" due to drastic changes in air pressure.

Rapid intensification is the increase in a hurricane's sustained wind speed by at least 35 miles per hour within 24 hours, which can strengthen it by up to two categories.

Various types of tornadoes are distinguished by their shape, size, and location

Waterspouts form over water as long, thin columns of mist and air, while elephant trunks are tornadoes that elongate vertically as they become tilted during their formation, resembling the mammal's appendage. Wedge tornadoes are among the most powerful, often spanning a mile or more in width.

By absorbing 90% of the thermal energy trapped by greenhouse gases, oceans are providing increasingly more energy to power the rapid strengthening of hurricanes.

Rising wildfire smoke can create 'fire clouds'—towering clouds that can help combat fires through downbursts of rain or complicate firefighting efforts by triggering new fires via lightning strikes.

In a tornado outbreak, a single severe weather system can spawn multiple twisters

By maintaining the ingredients for tornadoes—differences in wind speed and direction across altitudes, moisture, and rising air—for long periods of time as it moves across a region, a severe thunderstorm can continuously produce tornadoes by lifting multiple columns of horizontally rotating air.

The risk of tornadoes and storm surges is greatest on the 'dirty side' of a hurricane

Winds in the right-front quadrant of the storm are amplified by the hurricane's motion and its rotation, which both move air in the same direction. Upon making landfall, these winds pull water from the Gulf and Atlantic onto land, creating storm surges. Tornadoes can also be generated from large differences in wind speed and direction at various heights.

The way hurricanes are categorized may mislead the public to their dangers

The Saffir-Simpson scale categorizes hurricanes based on wind speed, but tropical cyclones' main dangers are storm surges and heavy rainfall. To better communicate risks to the public, a new system that incorporates hurricane size, water content, and other complexities should be developed.

Why aren’t there hurricanes in Europe?

Despite their proximity to the Atlantic Ocean, the effects of the subtropical jet stream make tropical storms and hurricanes unlikely to reach Europe at full strength. Their remnants, however, can combine with other weather systems to create powerful storms.

Hurricanes can grow by replacing their eyewall

A second outer eyewall can form around the primary eyewall surrounding a hurricane's eye. During an eyewall replacement cycle, the outer wall can weaken, collapse, and replace the inner wall, temporarily weakening the storm before it strengthens and grows.

Hurricane conditions are created in a University of Miami wind-wave tank

The SUrge-STructure-Atmosphere INteraction Wind Wave Laboratory contains a 38,000-gallon wave pool connected to a wind tunnel that can generate air currents of up to 155 mph. SUSTAIN allows scientists to study how the atmosphere interacts with the ocean in extreme weather.

Nor'easters can produce thundersnow—lightning in blizzard conditions

Although thunderstorms typically require warm air to rise in updrafts and collide with heavier soft hail, which creates charge separation and eventual electrical discharge, these cyclones can replicate these conditions by churning the atmosphere through strong winds. Rarely, especially warm lakes can similarly help generate thunderstorms during the winter.

Most tornadoes occur during the afternoon and evening hours

While there is no official national tornado season as with Atlantic hurricanes, many tornadoes form in the presence of thunderstorms, which are fueled by solar heating and the energy released by the condensation of water vapor. The airflow instabilities created from this energy build throughout the day until the sun sets.

Cloud formation requires water vapor and condensation nuclei to build from

The nuclei—particles like dust, salt, and smoke—act like jumpstarts that water molecules can start to accumulate onto to form clouds. Condensation nuclei are about 1/100th the size of cloud droplets, which are mostly water.

The ingredients that make up severe weather

A seven-minute video illustrating how a storm is made. These factors—moisture, instability, lift, and shear—are explained through a series of data sets and creative, descriptive diagrams.

How does climate change impact hurricanes?

Statistical relationships between sea surface temperature and hurricanes, analysis of century-scale Atlantic tropical storm and hurricane records, analysis of other observed Atlantic hurricane metrics, and more.

The top several meters of the world's oceans can hold as much thermal energy as the entire atmosphere.

As of 2025, the world's largest tropical cyclone spanned half the continental US

Typhoon Tip traveled across the western Pacific Ocean in 1979, achieving winds of 300 kilometers per hour. Though it weakened significantly before making landfall in Japan, its rainfall produced over 600 mudslides and killed 42 people.

An overview of Earth's atmospheric cells and how they distribute Earth's uneven heating

The Hadley, Ferrel, and Polar cells are circulation patterns that act like gears, moving warmer air from the equator to the poles. The rising and falling of air currents within these patterns creates semi-persistent regions of low and high pressure, which contribute to the formation of regional climates, such as tropical zones.

Surface ocean currents are primarily driven by wind, tides, and Earth's rotation, while deep-ocean currents are driven by differences in temperature and salt concentration.

Hurricanes spin due to differences in air and ground speed as they move across Earth

The movement of an object across latitudes causes it to take a curved trajectory because its speed no longer matches that of the ground beneath it. This phenomenon, called the Coriolis effect, explains why hurricanes spin counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere.

How jet streams, which reside in the troposphere, shape and confine pockets of atmospheric air

These fast-flowing ribbons of air are hundreds of kilometers wide and typically travel from west to east due to Earth's rotation, with the polar front and subtropical jets serving as major drivers of global circulation. Warmer air near the equator pushes the polar front jets toward the poles, which can buckle and deform them as they contain frigid polar vortex systems.

Storm surges, not winds, are the leading cause of hurricane-related fatalities

A storm surge is an abnormal rise in water levels generated by a storm that exceeds predicted tides. It is particularly dangerous in coastal regions, where it can generate extreme flooding well before the hurricane makes landfall.

The first known instance of a fire tornado occurred in 2003

During pyro-tornadogenesis, many processes that create thunderstorms from wildfires, such as rising hot air and steam from evaporated water in forests, fuel the formation of a fire tornado. The increasing rates of wildfires due to climate change are expected to make this phenomenon and other extreme weather more common.

Hail forms in freezing temperatures thousands of feet above the ground

Even if surface temperatures are well above freezing during the summer, updrafts during thunderstorms can push raindrops high into the atmosphere, where they can freeze and form hail. Giant hailstones the size of softballs require updrafts of close to 100 mph.

Turbulence is crucial to the formation of stars in molecular clouds

Within simulations of these clouds, gravity, jets, supernovae, and galactic motion-induced stirring have been shown to develop turbulence that creates shocks. These turbulent shocks move quickly in low-density regions and slow in high-density areas, forming lumps of matter with sufficient gravitational force to collapse and initiate fusion, birthing a star.

Differences in pressure and temperature between atmospheric gases create wind

Because Earth's surface is not uniformly heated by the sun at all times, pockets of warmer and cooler air will form and interact. Warmer pockets of less dense air will rise, leaving gaps for cooler, denser air to move in. Wind is this movement of air from high-pressure to low-pressure areas.

The Arctic warms more quickly than the rest of the planet because of the loss of surface ice, a lack of vertical air circulation, and the release of thermal energy as water vapor condenses.

A breakdown of Earth's atmospheric layers, including why it can get colder or hotter with altitude

Gases in the troposphere—the atmosphere's lowest layer—cool with increasing height as they get farther from the thermal energy emitted by Earth's warm surface. In the next layer—the stratosphere—ozone is increasingly heated by the sun's ultraviolet radiation with height. Because cooler air sinks and hotter air rises, the cooler troposphere and hotter stratosphere form a natural boundary keeping Earth's weather in the lowest layer.

Juno has revealed Jupiter’s polar cyclones, complex atmosphere, and diffuse core

The continent-sized cyclones at Jupiter’s poles generate strong winds and ammonia-laden storms. The spacecraft has also collected data on Jupiter’s unique magnetic field, which resembles a blend of Earth’s and Uranus/Neptune's.

How salt, sunlight, and wind drive ocean currents

The Atlantic Meridional Overturning Circulation plays a critical role in regulating earth's climate, but is threatened by climate change. Explore the effects of temperature, density, and salinity on ocean currents in this 13-minute PBS video.

Every tropical storm is named from one of six predetermined lists maintained by the World Meteorological Organization.

What is a heat dome?

The world is seeing regular heat waves with multiple causes, including so-called "heat domes," a term rising in use in recent years. A heat dome occurs when the atmosphere traps hot ocean air like a lid or cap, creating stifling conditions and resulting in extended periods of heat. See an illustration of this phenomenon and read how it works with this brief explainer.

Climate change is increasing the frequency and intensity of severe turbulence

Severe turbulence over the North Atlantic has increased by 55% over the past 40 years, driven by strengthened jet streams and storm systems. Ongoing increases in global temperatures, which fuel these changes, may triple severe turbulence incidents in the coming decades.

Watch how scientists learn about hurricanes by flying into them

A specialized fleet of Air Force planes is built to fly into hurricanes and gather critical data from inside the storm. Beyond radar and microwave sensors, the planes are equipped with dropsondes—small instruments dropped into storms to measure pressure, temperature, and wind.