A
ACID RAIN – Refers to rain or cloud droplets that have become acidic due to pollutants such as nitrogen and sulfur oxides.
ADIABATIC – Refers to the cooling or warming of a parcel of air as it rises or descends in the atmosphere due to changes in pressure, without any exchange of heat with its surroundings.
ADDITIONALLY (ADNLY) – Refers to something that is being added or included in addition to what has already been mentioned.
ADVECTION – Refers to the horizontal movement or transport of air or atmospheric properties such as temperature or moisture.
ADVISORY – A weather advisory is issued for situations that could cause significant inconvenience or pose a risk to life if caution is not exercised, but do not meet the criteria for a warning.
ABOVE GROUND LEVEL (AGL) – Refers to the height or altitude above the ground surface.
AIR MASS – Refers to a large body of air with similar temperature and moisture characteristics in the horizontal direction.
ALERT – Automated Local Event Reporting in Real Time refers to a network of automatic rain gauges equipped with sensors that transmit data via VHF radio link in real-time.
ALBEDO – Refers to the percentage of light reflected by an object or surface.
ALTOCUMULUS (AC) – Refers to mid-level clouds with a cumuliform shape.
ALTOSTRATUS – Refers to mid-level clouds with a flat, sheet-like shape.
AMPLIFICATION (AMPLFCTN) – Refers to the strengthening or building of an upper-level high-pressure ridge or low-pressure trough.
ANABATIC – Refers to the wind that flows up an incline, such as up a hillside or mountainside.
ANEMOMETER – Refers to an instrument used to measure wind speed.
ANGULAR MOMENTUM – Refers to the energy of motion of a spinning body or mass of air or water.
ANTICYCLONE – Refers to a large area of high pressure around which the winds blow clockwise in the Northern Hemisphere.
ARCTIC AIR – Refers to a mass of very cold, dry air that originates over the Arctic Ocean north of Canada and Alaska.
ARCTIC HIGH – Refers to a very cold high-pressure system that originates over the Arctic Ocean.
AUTOMATED SURFACE OBSERVING SYSTEM (ASOS) – Refers to a system that observes and reports sky conditions, temperature, dew point, wind direction and speed, and barometric pressure.
ATMOSPHERE – Refers to the mass of air surrounding the Earth, held to it by gravitational attraction.
AT THE MOMENT (ATTM) – Refers to the current or present time.
ALASKA TSUNAMI WARNING CENTER (ATWC) – Refers to the center located in Palmer, AK, responsible for providing tsunami warnings and advisories for Alaska and the surrounding coastal areas.
AVALANCHE – Refers to a large mass of rapidly moving snow that slides down a steep mountain slope.
ADVANCED VERY HIGH RESOLUTION RADIOMETER (AVHRR) – Refers to the main sensor on U.S. polar-orbiting satellites used for monitoring weather and climate.
AVIATION MODEL (AVN) – Refers to a model generated every 12 hours by the National Centers for Environmental Prediction (NCEP) specifically for aviation purposes.
ADVANCED WEATHER INFORMATION PROCESSING SYSTEM (AWIPS) – Refers to the new computer system used by the National Weather Service (NWS) for integrating graphics, satellite, and radar imagery.
B
BACKING WINDS – A counterclockwise change in wind direction. Backing winds with height are indicative of cold air advection (CAA).
BAROCLINICITY– A cold air advection/warm air advection couplet that increases atmospheric instability. On analysis and forecast charts it is the isotherms crossing the height contours.
BAROTROPIC– Homogeneous atmosphere in which there are neither fronts nor any thermal advections.
BAROMETER – An instrument for measuring atmospheric pressure.
BEAUFORT SCALE – a scale that indicates the wind speed using the effect wind has on certain familiar objects.
BLACKBODY– A mass which absorbs and emits all wavelengths of radiation.
BLACK ICE – thin, new ice that forms on fresh water or dew covered surfaces; it is common on roadways during the fall and early winter and appears “black” because of its transparency.
BLIZZARD – A storm lasting about 3 hours or longer with sustained winds 35 mph or greater with frequent gusts to 35 mph or greater; and considerable falling and/or blowing snow frequently reducing visibilities to less than 1/4 mile.
BLOCKING PATTERN – A situation in which the upper tropospheric flow becomes highly meridional and stagnant. Two common blocking patterns are the omaga block and the rex block.
BLOWING DUST OR SAND – Small particles of dust or sand which are caused by strong winds blowing over dry ground, that has little or no vegetation.
BLOWING SNOW – Wind-driven snow which reduces surface visibility.
BOW ECHO – An accelerated portion of a squall line of thunderstorms, taking on a radar indicated bow configuration, created by strong downburst winds.
C
CIRRUS – High-altitude clouds composed of ice crystals, often appearing thin and wispy.
COLD FRONT – The leading edge of a mass of cold air, characterized by cooler temperatures and often accompanied by precipitation and atmospheric instability.
CONVECTION – The transfer of heat through the vertical movement of air or other fluid due to differences in temperature and density.
CONVECTIVE AVAILABLE POTENTIAL ENERGY (CAPE) – A measure of the amount of energy available for thunderstorm development, indicating atmospheric instability.
CUMULONIMBUS (CB) – A type of cloud associated with thunderstorms, characterized by towering vertical development and often accompanied by heavy rain, lightning, and strong winds.
CUMULUS – Puffy, white clouds with a flat base and a rounded top, typically indicating fair weather conditions.
CYCLONE – A large-scale atmospheric circulation pattern characterized by inward spiraling winds around a low-pressure center. In the Northern Hemisphere, cyclones rotate counterclockwise.
CAPE VERDE HURRICANES – Hurricanes that form near the Cape Verde Islands in the eastern Atlantic Ocean and often track towards the Caribbean or the eastern coast of North America.
CELL – A small-scale convective storm characterized by updrafts and downdrafts, often associated with thunderstorms.
CHINOOK WIND – A warm, dry wind that descends from the mountains on the leeward side, leading to rapid temperature increases.
CLIMATE – The long-term average of weather conditions observed over a specific region or period.
CLOUD – Visible masses of water droplets or ice crystals suspended in the atmosphere.
COLD ADVECTION – The horizontal transport of colder air into a region, often associated with the passage of a cold front.
CONDITIONAL INSTABILITY – A state of atmospheric instability that requires the presence of a lifting mechanism to initiate widespread vertical motion.
CONVERGENCE – The coming together of airflows from different directions, leading to upward motion and potential cloud formation.
COUNTERCLOCKWISE – Rotating or turning in the opposite direction to the hands of a clock, typically referring to the circulation of winds around low-pressure systems in the Northern Hemisphere.
CUMULIFORM – Describing cloud formations that have a rounded, puffy shape, such as cumulus clouds.
CYCLONIC FLOW – Airflow characterized by a counterclockwise rotation around a low-pressure center in the Northern Hemisphere.
CEILING – The height of the lowest layer of clouds above the ground.
CHANCE OF PRECIPITATION (POP) – The probability or likelihood of precipitation occurring within a given area or time period.
CLIMATE CHANGE – Long-term shifts and alterations in global or regional climate patterns, typically attributed to human activities and the increase in greenhouse gas concentrations.
CORIOLIS EFFECT – The deflection of air and water currents caused by the rotation of the Earth, resulting in the clockwise rotation of winds around high-pressure systems and counterclockwise rotation around low-pressure systems in the Northern Hemisphere.
CUMULUS CLOUDS – Puffy, white clouds with a flat base and a rounded top, often associated with fair weather conditions.
CYCLONE – A large-scale atmospheric circulation pattern characterized by inward spiraling winds around a low-pressure center. In the Northern Hemisphere, cyclones rotate counterclockwise.
D
DENSE FOG – Fog with visibility of less than 1 kilometer (0.6 miles).
DEW – Moisture that forms on surfaces when the temperature cools and reaches the dew point.
DEW POINT – The temperature at which air becomes saturated with moisture, leading to the formation of dew or condensation.
DOWNBURST – A strong and localized downward rush of air from a thunderstorm, often associated with damaging winds near the ground.
DRIZZLE – Fine, light raindrops with a diameter less than 0.5 millimeters.
DROUGHT – An extended period of abnormally dry weather conditions, resulting in water shortages and adverse impacts on agriculture, ecosystems, and human activities.
DUST DEVIL – A small, rapidly rotating column of air that picks up dust or debris from the ground, often visible in dry and arid regions.
DYNAMIC – Referring to atmospheric processes or phenomena influenced by the motion and interaction of air masses and pressure systems.
E
EVAPORATION – The process by which liquid water changes into water vapor or gas, typically from the Earth’s surface or bodies of water.
EVAPOTRANSPIRATION – The combined process of evaporation from the Earth’s surface and transpiration from plants, resulting in the loss of water into the atmosphere.
EXTRATROPICAL – Referring to weather systems or cyclones that form outside the tropics, typically in the mid-latitudes.
EYE – The calm and relatively clear center of a tropical cyclone or hurricane, characterized by light winds and often a clear sky.
EYE WALL – The ring of intense thunderstorms surrounding the eye of a tropical cyclone, known for its strongest winds, heaviest rainfall, and severe weather.
ENDOTHERMIC – A process or reaction that absorbs heat energy from its surroundings, resulting in a decrease in temperature.
ENSO – El Niño-Southern Oscillation, a climate pattern characterized by the periodic warming (El Niño) and cooling (La Niña) of the eastern tropical Pacific Ocean, with widespread global impacts on weather patterns.
ENHANCED FUJITA SCALE (EF SCALE) – A scale used to measure the intensity of tornadoes based on the damage they cause, ranging from EF0 (weakest) to EF5 (most severe).
EXTENDED FORECAST – A weather forecast that covers a period beyond the usual 7-day forecast, providing an outlook for several weeks or months ahead.
EXCESSIVE HEAT WARNING – A warning issued by the National Weather Service when a prolonged period of dangerously hot weather is expected, with heat index values that may pose a significant risk to health and safety.
EXTRATROPICAL CYCLONE – A cyclone or low-pressure system that develops and operates outside the tropics, often associated with mid-latitude weather systems.
EXTRATROPICAL TRANSITION – The process by which a tropical cyclone or hurricane transforms into an extratropical cyclone, typically as it moves into higher latitudes and encounters cooler air masses.
EXPONENTIAL DECAY – A rapid decrease or decay in the intensity or magnitude of a weather phenomenon over time, often following an exponential or logarithmic curve.
EXPOSURE – The degree to which a location or object is exposed to the elements or weather conditions, such as wind, precipitation, or sunlight.
EXTREME WEATHER – Severe or unusual weather events that deviate significantly from the average or expected conditions, including intense storms, heatwaves, cold spells, hurricanes, tornadoes, etc.
EXTENDED OUTLOOK – A weather outlook or forecast that provides information beyond the typical 7-day forecast, giving an indication of weather trends and patterns for an extended period, usually up to 14 or 30 days.
EMBEDDED THUNDERSTORMS – Thunderstorms that are contained within a larger weather system, such as a squall line or frontal boundary, rather than existing as discrete individual storms.
F
FLASH FLOOD – A rapid and extreme flooding event that occurs within a short period, often as a result of intense rainfall or the sudden release of water, posing a significant threat to life and property.
FOG – A cloud in contact with the ground or water surface, formed by the condensation of water vapor in the air near the Earth’s surface, reducing visibility to less than 1 kilometer (0.6 miles).
FREEZING RAIN – Raindrops that freeze upon contact with surfaces that are at or below freezing temperature, creating a coating of ice and potentially hazardous conditions.
FRONTAL BOUNDARY – The transition zone between two air masses with different characteristics, such as temperature, humidity, or density, often associated with changes in weather conditions.
FUNNEL CLOUD – A tornado in its developing stage, appearing as a rotating, funnel-shaped cloud descending from a thunderstorm cloud but not reaching the ground.
G
GALE – Strong winds with sustained speeds of 39 to 54 knots (45 to 62 mph) on the Beaufort scale, often associated with stormy weather conditions.
GUST FRONT – The leading edge of cool air that rushes out ahead of a thunderstorm or squall line, often producing strong and gusty winds.
H
HAIL – Solid precipitation in the form of round or irregular pellets of ice, typically produced by strong thunderstorm updrafts that carry raindrops upward into extremely cold regions of the cloud.
HEAT INDEX – A measure of how hot it feels when relative humidity is factored in with the actual air temperature, indicating the perceived temperature or discomfort caused by the combination of heat and humidity.
HIGH PRESSURE – An area of atmospheric pressure that is higher than its surrounding areas, typically associated with fair weather conditions and descending air.
HUMIDITY – The amount of moisture or water vapor present in the air, often expressed as relative humidity (the percentage of moisture the air is holding relative to the maximum it could hold at that temperature) or dew point (the temperature at which air becomes saturated and condensation occurs).
HURRICANE – A large and powerful tropical cyclone with sustained winds of 74 miles per hour (119 kilometers per hour) or higher, typically accompanied by heavy rain, storm surge, and potential for significant damage.
HYDROMETEOR – Any atmospheric water or moisture substance, such as raindrops, snowflakes, or ice pellets, that falls from the atmosphere to the Earth’s surface.
HYDROSTATIC EQUILIBRIUM – A state in which the vertical pressure gradient force is balanced by the gravitational force, resulting in a stable atmosphere.
HYDROLOGY – The scientific study of water, including its occurrence, distribution, movement, and properties on the Earth’s surface, in the soil, and underground.
I
ICE STORM – A weather event characterized by the accumulation of freezing rain or freezing drizzle, leading to a coating of ice on surfaces, such as trees, power lines, and roads, causing hazardous conditions.
INVERSION – A reversal of the normal vertical temperature distribution in the atmosphere, where a layer of cooler air is located near the surface with warmer air above, which can restrict vertical mixing and lead to poor air quality conditions.
ISOBAR – A line drawn on a weather map connecting points of equal atmospheric pressure, indicating areas of high and low pressure systems.
J
JET STREAM – A high-speed, narrow air current in the upper levels of the atmosphere, usually located around 9 to 16 kilometers (5 to 10 miles) above the Earth’s surface, where strong temperature gradients exist between air masses.
K
KNOT – A unit of speed equal to one nautical mile per hour, commonly used to measure wind speed and boat or aircraft velocities.
KATABATIC WIND – A downslope wind that occurs when cold, dense air flows down a slope or mountain due to gravity, often resulting in strong and gusty winds.
KELVIN – The SI unit of temperature, denoted by the symbol K, and used in scientific measurements. It is based on the Kelvin scale, where 0 K represents absolute zero, the point at which molecular motion ceases.
KONA WINDS – A local wind pattern in Hawaii, characterized by the flow of warm and humid air from the southwest, typically associated with unsettled weather and increased precipitation on the windward side of the islands.
KYOTO PROTOCOL – An international agreement adopted in 1997 to address global climate change by reducing greenhouse gas emissions, setting targets and timetables for industrialized countries to reduce their emissions.
L
LAKE EFFECT SNOW – A localized weather phenomenon that occurs when cold air passes over a relatively warm body of water, leading to the formation of snow showers or bands downwind of the lake.
LAND BREEZE – A local wind that blows from land to sea during the night or early morning, caused by the cooling of the land surface faster than the adjacent water.
LENS CLOUD – A cloud formation that resembles a lens or almond shape, often seen near mountainous regions and caused by the airflow being forced to rise over the terrain.
LIGHTNING – A sudden electrostatic discharge that occurs within a thunderstorm, resulting in the rapid expansion and heating of air, which produces a bright flash of light and the accompanying sound of thunder.
LOW PRESSURE – An area of atmospheric pressure that is lower than its surrounding areas, typically associated with unsettled weather conditions and ascending air.
M
MESOCYCLONE – A rotating updraft within a severe thunderstorm that often precedes tornado formation, characterized by a persistent, rotating updraft of air several kilometers in diameter.
MICROBURST – A localized column of sinking air within a thunderstorm, typically less than 4 kilometers in diameter, causing a sudden and strong downdraft of wind near the surface.
MIXED PRECIPITATION – A type of weather event that involves a combination of two or more forms of precipitation, such as rain, snow, sleet, or freezing rain, occurring simultaneously or alternating within a short period.
MONSOON – A seasonal wind pattern characterized by pronounced changes in wind direction and strength, typically occurring in tropical and subtropical regions. It often brings heavy rainfall during the wet season and dry conditions during the dry season.
N
NOCTURNAL – Relating to or occurring during the night.
NOR’EASTER – A type of intense extratropical cyclone that typically develops along the East Coast of North America, bringing strong northeasterly winds, heavy precipitation, and coastal storm surge.
O
OCCLUDED FRONT – A complex weather front formed when a cold front overtakes a warm front, lifting the warm air mass off the ground and creating a mixture of both warm and cold air, often associated with widespread precipitation.
OUTFLOW BOUNDARY – A boundary or gust front that forms when a downdraft from a thunderstorm spreads horizontally, pushing cooler air outward and away from the storm.
OVERCAST – A condition in which the sky is completely covered by clouds, resulting in little or no direct sunlight reaching the ground.
OVERSHOOTING TOP – A dome-shaped protrusion that extends above the anvil cloud of a severe thunderstorm, indicating a strong updraft and the potential for severe weather.
P
PRECIPITATION – Any form of water particles, liquid or solid, that falls from the atmosphere and reaches the Earth’s surface, including rain, snow, sleet, and hail.
PRESSURE GRADIENT – The rate of change in atmospheric pressure over a given distance, which determines the strength and direction of winds.
R
RADAR – An electronic instrument used to detect and track precipitation, such as rain, snow, and hail, by emitting radio waves and analyzing their reflections from the precipitation particles.
RADIATION – The transfer of heat energy through electromagnetic waves, including solar radiation from the sun and terrestrial radiation emitted by the Earth’s surface.
RAINBOW – A meteorological phenomenon caused by the reflection, refraction, and dispersion of light in water droplets, appearing as a circular arc of colors in the sky.
RELATIVE HUMIDITY – The amount of moisture present in the air compared to the maximum amount the air can hold at a particular temperature, expressed as a percentage.
P
PRECIPITATION – Any form of water particles, liquid or solid, that falls from the atmosphere and reaches the Earth’s surface, including rain, snow, sleet, and hail.
PRESSURE GRADIENT – The rate of change in atmospheric pressure over a given distance, which determines the strength and direction of winds.
R
RADAR – An electronic instrument used to detect and track precipitation, such as rain, snow, and hail, by emitting radio waves and analyzing their reflections from the precipitation particles.
RADIATION – The transfer of heat energy through electromagnetic waves, including solar radiation from the sun and terrestrial radiation emitted by the Earth’s surface.
RAINBOW – A meteorological phenomenon caused by the reflection, refraction, and dispersion of light in water droplets, appearing as a circular arc of colors in the sky.
RELATIVE HUMIDITY – The amount of moisture present in the air compared to the maximum amount the air can hold at a particular temperature, expressed as a percentage.
S
SATELLITE – An artificial or natural object orbiting the Earth that is used to observe and collect data on weather patterns, cloud cover, and other atmospheric conditions.
SEVERE WEATHER – Weather phenomena that pose a significant threat to life and property, including strong storms, tornadoes, hurricanes, blizzards, and extreme heat or cold.
SQUALL – A sudden, brief, and intense burst of strong winds, often accompanied by heavy rain or snow showers, typically lasting for a few minutes to an hour.
STORM SURGE – The abnormal rise in seawater level along a coastline during a storm, primarily caused by strong onshore winds and low atmospheric pressure, often resulting in coastal flooding.
STRATOCUMULUS – Low- to mid-level clouds characterized by a lumpy or globular appearance, often appearing in a layer or patches and sometimes associated with fair weather.
STRATOSPHERE – The layer of the Earth’s atmosphere located above the troposphere and below the mesosphere, characterized by increasing temperature with altitude and containing the ozone layer.
SUNSPOT – A dark, relatively cool region on the surface of the Sun, associated with intense magnetic activity and often occurring in pairs or groups.
SUPERCCELL – A severe thunderstorm characterized by a persistent rotating updraft known as a mesocyclone, often producing strong winds, large hail, and tornadoes.
SYNOPTIC – Referring to a broad-scale weather system or analysis that considers the overall weather conditions over a large area, typically covering several hundred kilometers.
T
THERMAL – Pertaining to heat or temperature, often used to describe rising air currents caused by temperature differences.
THUNDER – The sound produced by the rapid expansion and contraction of air surrounding a lightning bolt, typically heard as a loud rumbling or crashing noise.
TORNADO – A violent, rotating column of air that is in contact with both the surface of the Earth and a cumulonimbus cloud, often appearing as a funnel-shaped cloud and capable of causing significant damage.
TROPOPAUSE – The boundary between the troposphere and the stratosphere, where a temperature inversion typically occurs, causing a change in the lapse rate.
TROPOSPHERE – The lowest layer of the Earth’s atmosphere, extending from the surface up to the tropopause, where most weather phenomena occur.
U
UPDRAFT – A current of rising air within the atmosphere, often associated with convective activity such as thunderstorms and cumulus clouds.
V
VISIBILITY – The distance at which objects can be seen and identified in the atmosphere, often affected by factors such as fog, precipitation, and atmospheric conditions.
W
WARM FRONT – The boundary between advancing warm air and retreating cooler air, characterized by a gradual slope and often associated with steady precipitation and a change from cooler to warmer temperatures.
WIND CHILL – The perceived decrease in air temperature caused by the combination of actual air temperature and wind speed, resulting in a “feels like” temperature that is lower than the actual temperature.
WIND SHEAR – A sudden change in wind direction or speed over a short distance in the atmosphere, often associated with hazardous conditions for aviation, such as turbulence and microbursts.
WINDWARD – The side or direction from which the wind is blowing, typically referring to the side of a mountain or an object that faces the oncoming wind.
X
X-RAYS – Electromagnetic radiation emitted by the Sun, often studied in solar physics to understand the Sun’s energy output and solar activity.
Y
YARDANG – A streamlined, elongated ridge of sand or rock formed by wind erosion, often found in arid or desert regions.
Z
ZONAL FLOW – A weather pattern characterized by west-to-east airflow in the middle latitudes, typically associated with more frequent and less extreme weather conditions compared to meridional flow patterns.
