Explanation of the most important terms relating to extreme weather

Hurricane Beryl is sweeping through Texas on Monday after devastating parts of Mexico and the Caribbean.

The storm regained hurricane strength over the weekend as it moved across the Gulf of Mexico. It had previously been downgraded to a tropical storm as it weakened over land.

So what is the difference between a hurricane and a tropical storm? What about a typhoon or a cyclone?

Here is a breakdown of some commonly used weather terms and their definitions, based on material from the National Weather Service:

atmospheric river – Long and broad plumes of moisture that form over an ocean and flow through the sky over land.

Blizzard – Winds of 35 miles per hour or more and significant snowfall and/or flurries with visibility of less than a quarter mile for three or more hours.

Cyclone – A storm with strong winds circling around a moving center of low pressure. In the United States, the word is sometimes used to mean a tornado, and in the Indian Ocean, it is used to mean a tropical cyclone such as a hurricane.

Derecho – A widespread and usually fast-moving, straight-line storm. It is usually more than hundreds of miles long and more than 100 miles in diameter.

El Niño, La Niña – El Niño is a naturally occurring climate phenomenon that begins with unusually warm water in the central and eastern equatorial Pacific and then changes the weather worldwide. The flip side of El Niño is La Niña, an occasional but natural cooling of the equatorial Pacific that also changes the weather worldwide.

Hurricane or typhoon – A warm-core tropical cyclone in which the minimum sustained surface winds are 75 mph (120 km/h) or more. Hurricanes form in the North Atlantic and the central and eastern North Pacific. Typhoons develop in the northwest Pacific. In the Indian Ocean and the South Pacific, they are called cyclones.

Microburst – Occurs when a mass of cooled air flows downward from a thunderstorm, hits the ground, and flows outward in all directions.

Polar Vortex – Usually refers to the giant circular weather pattern in the upper layer of the Arctic air that envelops the North Pole (but can also apply to the South Pole). It is a normal pattern that is stronger in winter and keeps some of the coldest weather near the North Pole. The jet stream usually holds the polar vortex in place and keeps it to the north. However, sometimes part of the vortex can break away or move south, allowing unusually cold weather to move south and warmer weather to move north.

Snow squall – An intense but short-lived period of moderate to heavy snowfall, with strong winds and possible lightning.

Storm surge – An abnormal rise in water above normal tide caused by a storm.

Tornado – A violently rotating column of air that forms a trailer, usually from a cumulonimbus cloud, and touches the ground. On a local scale, it is the most destructive of all atmospheric phenomena. Tornadoes can occur from any direction, but in the U.S. most move from the southwest to the northeast. Measured on the F-scale from EF0 to EF5, which accounts for 28 different types of damage to buildings and trees. An EF2 or higher is considered a significant tornado.

Tornado Warning – The National Weather Service warns the public of an impending tornado.

Tornado Warning – Warns the public of the possibility of tornado formation.

Tropical Depression – A tropical cyclone in which the maximum sustained wind speed at the Earth’s surface is 38 mph (33 knots) or less.

Tropical Storm – A warm-core tropical cyclone with maximum sustained surface winds ranging from 39 to 73 miles per hour (34 to 63 knots).

Tsunami – A large ocean wave or seismic wave caused by an underwater disturbance such as an earthquake, landslide, or volcanic eruption.

Nor’easter – The term used by the National Weather Service for storms that are either dissipating or moving north along the East Coast, generating northeasterly winds.

Waterspout – A tornado over water.

Wind chill factor – A calculation that describes the combined effect of wind and cold temperatures on exposed skin.

Wind shear – A sudden change in wind direction and/or speed.