Weather Glossary

Ever wonder what we're talking about? Here's a helpful Weather Glossary!

Cold Front

Zone in which a dense, cooler air mass advances toward a warmer air mass. Depicted on weather maps by a blue line and triangles.

Dew Point

A measure of the amount of moisture in the air. It is the temperature to which air must be cooled in order to reach saturation.

Dry Line

A boundary separating a dry and a moist airmass. The dry line is usually situated north-south separating the dry air from the southwestern states and the moist air from the Gulf of Mexico in the spring and summer months. The dry line is a focus point of thunderstorms as it moves eastward by a strong upper level storm system or by daytime heating. The dry line is generally represented on weather maps by a dashed grey line.

Enhanced Fujita Scale

A much more precise and robust way to assess tornado damage than the original Fujita Scale. It classifies EF0-EF5 damage as calibrated by engineers and meteorologists using a set of wind estimates (not measurements) based on damage. Its uses three-second gusts estimated at the point of damage based on a judgment of 8 levels of damage to the 28 indicators listed below. These estimates vary with height and exposure. Important: The 3 second gust is not the same wind as in standard surface observations. In the Enhanced F-scale, there are different, customized standards for assigning any given EF rating to a well built, well anchored wood-frame house compared to a garage, school, skyscraper, unanchored house, barn, factory, utility pole or other type of structure. There are no plans to systematically re-evaluate historical tornadoes using the Enhanced F-scale.

Heat Index

A temperature measured from how hot it really feels when the Relative Humidity (RH) is added to the actual air temperature.

High Pressure System

An area of a pressure maximum relative to its surroundings. A high pressure system has diverging winds which rotate clockwise in the Northern Hemisphere. Also known as an 'Anticyclone'.


An organized cyclone in the tropics with maximum sustained winds greater than 74 mph. Also called a Typhoon in the Eastern Pacific.

Jet Stream

Narrow stream of strong winds oriented in the upper portions of the atmosphere which shifts each day. The Jet Stream determines the general day-to-day weather pattern by driving different masses.

Low Pressure System

An area of a pressure minimum relative to its surroundings. A low pressure system has converging winds which rotate counterclockwise in the Northern Hemisphere. Also known as a 'Cyclone'.


An animated duck created by Weather Central often used by the on-air talent when conditions are rainy or are expected to be rainy. Puddleducky resembles a yellow "rubber-ducky" who splashes around in a water puddle while wearing rain boots and holding an umbrella.


Often recognized as a "Ridge of High Pressure". A ridge is an area of generally high atmospheric pressure. Ridges occur at all levels in the atmosphere. Upper level ridges represent fair weather. Upper level ridges are also favorable environments in the tropics for tropical storms to grow due to less amounts of shear.

Saffir-Simpson Hurricane Scale

A scale in which a hurricane's strength is determined by it's potential damage. The scale ranks from Category 1 (minimal damage, 74-95mph) to a Category 5 (Catastrophic, > 155mph). Unlike tornadoes, a hurricane's category fluctuates throughout its life cycle . For a landfalling hurricane, the landfalling category is finalized many months later in a report by the National Hurricane Center after inspections of damage.

Tropical Storm

An organized cyclone in the tropics with maximum sustained winds between 39 and 73 mph. Once tropical storm status has been reached, it is given a name.


Often recognized as a "Trough of Low Pressure". A Trough is an area of generally low atmospheric pressure. Troughs occur at all levels of the atmosphere. Upper level troughs drive air masses toward the southeast usually causing stormy weather. Surface troughs often precede cold fronts causing a lowering of pressure and a wind shift.

Warm Front

Transition zone in which warm air advances on a cooler airmass. Depicted on weather maps by a red line with half-circles.

Wind Chill

Temperature of what the air feels like due to increased wind speeds accelerating heat loss from exposed skin.

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