A hurricane gets its energy from heat. Water vapor that cools and condenses back into liquid water releases latent heat. That heat powers the hurricane. Cold water and land do not give off much evaporated water, so they cannot feed a hurricane the way warm ocean can. A hurricane is a low-pressure system, so it pulls air toward its center. Earth's Coriolis effect comes from different parts of the Earth moving at different speeds. It bends the moving air. This bending of the air, the Coriolis deflection, is what makes tropical cyclones spin. Tornadoes can be spawned by hurricanes. They most often form in the right-front part of the hurricane, where wind shear is greatest.

A tornado has a different parent. A supercell is a long-lived, organized thunderstorm with a tilted, rotating updraft, a rising current of air. Tornadoes that come from supercell thunderstorms are the most common kind, and they start with a rotating updraft. When Doppler radar detects the rotation inside a supercell, scientists call it a mesocyclone. The tornado itself is a very small extension of the much larger rotation inside the storm.

Tornadoes come in other kinds. Some tornadoes form along lines of strong thunderstorms. These are called QLCS tornadoes. A landspout is a tornado with a narrow, rope-like funnel. There are two kinds of waterspout, fair weather waterspouts and tornadic waterspouts. A tornadic waterspout is a tornado that forms over water or moves from land to water. Fair weather waterspouts are generally not linked to thunderstorms.

Hurricanes got their scale from an engineer. Saffir made a hurricane scale because there was no scale for storms like the well-known earthquake scales. The scale was conceived in 1969 by engineer Herbert Saffir. He showed it to Robert Simpson, director of the National Hurricane Center. Simpson began using the scale in 1973. The Saffir-Simpson Hurricane Wind Scale is a 1 to 5 rating based only on maximum sustained wind speed. Category 3, the first major category, means sustained winds of 111 to 129 mph. Category 5, the top of the scale, is sustained winds of 157 mph or higher. A hurricane's size is not a sign of how strong it is.

Tornado ratings work differently. Enhanced Fujita wind speeds are estimates, not measurements. They come from damage. A tornado's size or shape does not tell you how strong it is. Enhanced Fujita ratings EF0 and EF1 are called weak, EF2 and EF3 strong, and EF4 and EF5 violent. Weak tornadoes usually last less than 10 minutes and have winds less than 100 mph (160 kph). As of November 2026, EF4 and EF5 tornadoes make up only about 2% of all tornadoes. As of November 2026, tornadoes have traveled about 3.5 miles along the ground on average, based on path length records since 1950.

How do scientists measure a storm they cannot touch? Doppler radar shows wind motion. Red is a target moving away from the radar and green is a target moving toward it. A radiosonde is a small, expendable instrument package that hangs below a weather balloon and weighs 60 to 80 grams. It reports pressure, temperature, humidity and GPS position every second, and it can rise higher than 35 km (about 115,000 feet). GOES satellites orbit 22,236 miles above Earth's equator at the speed of Earth's rotation, so each keeps watching the same area. Polar-orbiting satellites fly over a storm about twice a day at a lower altitude than the satellites that stay in view.

Some scientists fly into storms. The history of hurricane hunting starts in 1943, when Colonel Joe Duckworth of the Army Air Forces flew a single-engine trainer plane through a hurricane for the first time and showed it could be done. After that flight, interest in flying into storms grew. The Army Air Force became the Air Force, and the Air Force took over the military side of hurricane flying. Hurricane hunter missions fly to locate the center of the storm and measure its central pressure and surface winds. NASA's HS3 mission used the Global Hawk, a high-altitude long-endurance aircraft able to fly for 26 hours, to study hurricanes. A Hurricane Hunter mission in a P-3 plane typically lasts 8 to 10 hours.

Words to know

• latent: hidden
• Coriolis: spin effect
• mesocyclone: rotating updraft
• waterspout: tornado over water
• radiosonde: balloon instrument
• deflection: a bend