24/7 Weather Glossary -- T Words
A | B | C | D | E | F | G | H | I | J and K | L | M | N | O | P | Q and R | S | T | U | V | W | X, Y and Z TAIL CLOUD
A horizontal, tail-shaped cloud (not a funnel cloud) at low levels extending from he precipitation cascade region of a supercell toward the wall cloud (i.e., it usually is observed extending from the wall cloud toward the north or northeast). The base of the tail cloud is about the same as that of the wall cloud. Cloud motion in the tail cloud is away from the precipitation and toward the wall cloud, with rapid upward motion often observed near the junction of the tail and wall clouds. Compare with beaver tail, which is a form of inflow band that normally attaches to the storm's main updraft (not to the wall cloud) and has a base at about the same level as the updraft base (not the wall cloud).TAIL-END CHARLIE
The thunderstorm at the southernmost end of a squall line or other line or band of thunderstorms. Since low-level southerly inflow of warm, moist air into this storm is relatively unimpeded, such a storm often has a higher probability of strengthening to severe levels than the other storms in the line.
TELECONNECTIONS
Information used by forecasters to determine what the weather might be elsewhere when compared with past weather conditions at the same degree of longitude.TEMPERATE CLIMATE
Climates with distinct winter and summer seasons, typical of regions found between the Tropics of Cancer and Capricorn and the Arctic and Antarctic Circles. Considered the climate of the middle latitudes.TEMPERATURE
The measure of molecular motion or the degree of heat of a substance. It is measured on an arbitrary scale from absolute zero, where the molecules theoretically stop moving. It is also the degree of hotness or coldness. In surface observations, it refers primarily to the free air or ambient temperature close to the surface of the earth.TERMINAL DOPPLER WEATHER RADAR (TDWR)
Doppler radar installed at major airports throughout the United States to detect microbursts.TERRESTRIAL RADIATION
Long wave radiation that is emitted by the earth back into the atmosphere. Most of it is absorbed by the water vapor in the atmosphere, while less than ten percent is radiated directly into space.TEXAS NORTHER
Local name in the south-central Great Plains for strong winter winds blowing north or northwest following a sharp cold front with dropping temperatures. Marked by a dark, blue-black sky.THAW
A warm spell of weather when ice and snow melt. To free something from the binding action of ice by warming it to a temperature above the melting point of ice.THEODOLITE
An optical instrument used to track the motion of a pilot balloon, or pibal, by measuring the elevation and azimuth angles.THERMAL LOW
Also known as heat low, it is an area of low pressure due to the high temperatures caused by intensive heating at the surface. It tends to remain stationary over its source area, with weak cyclonic circulation. There are no fronts associated with it. An example is the low that develops over southwestern United States and northwestern Mexico during the summer months.THERMOCLINE
A vertical negative temperature gradient in some layer of a body of water which is appreciably greater than the gradients above and below it. In the ocean, this may be seasonal, due to the heating of the surface water in the summer, or permanent.THERMODYNAMIC CHART
A chart containing contours of pressure, temperature, moisture, and potential temperature, all drawn relative to each other such that basic thermodynamic laws are satisfied. Such a chart typically is used to plot atmospheric soundings, and to estimate potential changes in temperature, moisture, etc. if air were displaced vertically from a given level. A thermodynamic chart thus is a useful tool in diagnosing atmospheric instability.THERMODYNAMICS
Study of the processes that involve the transformation of heat into mechanical work, of mechanical work into heat, or the flow of heat from a hotter body to a colder body.THERMOGRAPH
Essentially, a self-recording thermometer. A thermometer that continuously records the temperature on a chart.THERMOHALINE
In oceanography, it pertains to when both temperature and salinity act together. An example is thermohaline circulation which is vertical circulation induced by surface cooling, which causes convective overturning and consequent mixing.THERMOMETER
An instrument used for measuring temperature. The different scales used in meteorology are Celsius, Fahrenheit, and Kelvin or Absolute.THERMOSPHERE
A thermal classification, it is the layer of the atmosphere located between the mesosphere and outer space. It is a region of steadily increasing temperature with altitude, and includes all of the exosphere and most, if not all, of the ionosphere.THETA-E (or Equivalent Potential Temperature)
The temperature a parcel of air would have if a) it was lifted until it became saturated, b) all water vapor was condensed out, and c) it was returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Theta-e, which typically is expressed in degrees Kelvin, is directly related to the amount of heat present in an air parcel. Thus, it is useful in diagnosing atmospheric instability.THETA-E RIDGE
An axis of relatively high values of theta-e. Severe weather and excessive rainfall often occur near or just upstream from a theta-e ridge.THICKNESS
The thickness of a layer in the atmosphere is proportional to the mean temperature of that whole layer. The layer most often used in meteorology is between 1000 and 500 millibars. There can be different temperature profiles in the lowest layer of the atmosphere with the same 1000-500 millibar thickness value, depending on what is happening above that lowest layer. For example, if the lower levels are warming but higher levels are cooling, the overall mean temperature, the thickness, could remain the same. Likewise, on a sunny day, the amount of incoming solar radiation, affects the temperature right at the earth's surface, without necessarily having much effect on the thickness of the whole layer.THUNDER
The sound emitted by rapidly expanding gases along the channel of a lightning discharge. Over three-quarters of lightning's electrical discharge is used in heating the gases in the atmosphere in and immediately around the visible channel. Temperatures can rise to over 10,000 °C in microseconds, resulting in a violent pressure wave, composed of compression and rarefaction. The rumble of thunder is created as one's ear catches other parts of the discharge, the part of the lightning flash nearest registering first, then the parts further away.THUNDER SNOW
A wintertime thunderstorm from which falls snow instead of rain. Violent updrafts and at or below freezing temperatures throughout the atmosphere, from surface to high aloft, discourage the melting of snow and ice into rain. Intense snowfall rates often occur during these situations.THUNDERSTORM
Produced by a cumulonimbus cloud, it is a microscale event of relatively short duration characterized by thunder, lightning, gusty surface winds, turbulence, hail, icing, precipitation, moderate to extreme up and downdrafts, and under the most severe conditions, tornadoes.TIDE
The periodic rising and falling of the earth's oceans and atmosphere. It is the result of the tide-producing forces of the moon and the sun acting on the rotating earth. This propagates a wave through the atmosphere and along the surface of the earth's waters.TILT
The inclination to the vertical of a significant feature of the pressure pattern or of the field of moisture or temperature. For example, midlatitide troughs tend to display a westward tilt with altitude through the troposphere.TILTED STORM AND TILTED UPDRAFT
A thunderstorm or cloud tower which is not purely vertical but instead exhibits a lanted or tilted character. It is a sign of vertical wind shear, a favorable condition for severe storm development.TIROS
A series of Television InfraRed Observation Satellites that demonstrated the feasibility and capability of observing the cloud cover and weather patterns of earth from space. An experimental program, it was the first spaceborne system that allowed meteorologists to acquire information that was immediately put to use in an operational setting. The first U.S. weather satellite, TIROS I, was launched on April 1, 1960, and TIROS X, the last of the series, was launched on July 2, 1965.TORNADO
A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado, even in the total absence of a condensation funnel. Most tornadoes in the United States occur in the central plains, with the greatest likelihood of twisters in the southern plains around Kansas, Texas and Oklahoma. Colorado lies of the western fringe of "Tornado Alley", but our state still averages between 30 and 50 tornadoes per year. The peak season for tornadoes is in the spring and early summer. From March through June, about 70% of all the tornadoes in a year will occur. This is due to the fact that the weather patterns that are needed for tornado development are most common in the spring and early summer. Most tornadoes form from large rotating thunderstorms called "supercells". These monster storms tend to develop ahead of cold fronts that push southward from Canada across the central U.S. As the fronts sag into the warm and humid air that covers the southern plains, the colder air wedges under the warm air, creating lift. The lifted air rises up to form thunderstorms that can rapidly grow to heights of 40 to 50 thousand feet above the ground. The storm pushes high into the sky, reaching into the jet stream - the band or river of fast moving air that flows around the world. It is the increase in windspeed with height that causes the thunderstorm to begin a large, slow counterclockwise rotation. This rotating thunderstorm is what is classified as a "Supercell". Once the supercell storm develops, the best analogy for thinking about how the tornado forms is to think of a fugure skater doing a spin. The skater starts with their arms out, and is rotating rather slowly. As the skater brings their arms in, the rotation begins to speed up. In physics, this is called "the conservation of angular momentum". The rotation gets faster and faster as the size of the rotating column grows more narrow. This is a very simplistic description, but eventually this narrow rapidly rotating column of air will drop to the ground as a tornado. Tornadoes are classified by the wind damage that they cause. The tornado scale was developed by Dr. Ted Fujita from the University of Chicago. Dr. Fujita based his "F scale" on a 0 to 5 basis for tornadoes. The F0 is a weak tornado, while the F5 storms are the most powerful winds ever observed on Earth.
About 70% of the annual average of 1000 tornadoes nationwide are classified as F0 or F1. About 28% of all tornadoes fall into the F2 or F3 category. Only about 2% of all tornadoes are classified as F4 or F5.Often a severe weather season will come and go without a single F5 tornado reported. However, about 80% of all tornadoes deaths are the result of the F3, F4 and F5 tornadoes. These storms are much less common, but much more dangerous. Tornadoes are not named like hurricanes are, but the strong or deadly tornadoes are usually remembered for the town or location that they affected. For instance, the infamous "Xenia Ohio Tornado" of April 1974, or in Colorado, the "Limon Tornado" in June of 1990. Perhaps the single worst tornado on record was the great "Tri-State Tornado" of March 1925. This huge tornado started in southeastern Missouri and tore a path of destruction all across Illinois, before ending in western Indiana. The twister covered a distance of 219 miles and was on the ground for over 3 hours. In the days before adequate warnings, the storm caught everyone off guard. The Tri-State Tornado killed 689 people, injured over 2,000 and caused 17 million dollars in damage - a very large figure in 1925! In Colorado, the peak season for tornadoes is in early June. At that time, the almost daily dose of thunderstorms can easily rise up to the jet stream level and begin to rotate into a supercell. These storms tend to form along the Front Range, roll over the Denver metro area and then really get severe over the eastern plains of the state. About 90% of all Colorado tornadoes occur east of I-25. Although tornadoes can form in the high country, the rough terrain tends to disrupt the rotation needed to form a supercell. Tornadoes have done some very unusual things. The powerful winds can pick up a railroad locomotive, lift a water tower off the ground, drive blades of grass into walls, just like a hammer and a nail. At the same time, there have been reports where tornadoes have picked a refridgerator off the ground, tossed it several hundreds of yards, dropped it back on the ground and not even broken an egg inside the refridgerator! Tornadoes usually form on the back edge of the thunderstorm cloud, menaing that most of the storm has already passed overhead. Often the rain, hail, thunder and lightning have mostly gone by and then the tornado occurs. That is why you will often see the sky looking very bright behind the tornado - a dramatic contrast to the very dark funnel. After the tornado, the sky often quickly clears as the storm moves away. There are, however, no hard and fast rules for tornados, so sometimes the twister occurs in the midst of a large area of thunderstorms, so after the tornado occurs, it just rains and rains.TORNADO ALLEY
A geographic corridor in the United States which stretches north from Texas to Nebraska and Iowa. In terms of sheer numbers, this section of the United States receives more tornadoes than any other.TORNADO WARNING
Issued by the National Weather Service when a tornado has been sighted either by an observer or Doppler radar.TORNADO WATCH
Issued by the National Sever Storm Laboratory in Kansas City when conditions are present in the atmosphere which may lead to the formation of tornadic thunderstorms.TORNADO FAMILY
A series of tornadoes produced by a single supercell, resulting in damage path segments along the same general line.TOTALS-TOTAL INDEX
A stability index and severe weather forecast tool, equal to the temperature at 850 b plus the dew point at 850 mb, minus twice the temperature at 500 mb. The total-totals index is the arithmetic sum of two other indices: the Vertical Totals Index (temperature at 850 mb minus temperature at 500 mb) and the Cross Totals Index (dew point at 850 mb minus temperature at 500 mb). As with all stability indices there are no magic threshold values, but in general, values of less than 50 or greater than 55 are considered weak and strong indicators, respectively, of potential severe storm development.TOWERING CUMULUS
Another name for cumulus congestus, it is a rapidly growing cumulus or an individual dome-shaped clouds whose height exceeds its width. Its distinctive cauliflower top often mean showers below, but lacking the characteristic anvil of a cumulonimbus, it is not a thunderstorm.TRACE
Generally, an unmeasurable or insignificant quantity. A precipitation amount of less than 0.005 inch.TRADE WINDS
Two belts of prevailing winds that blow easterly from the subtropical high pressure centers towards the equatorial trough. Primarily lower level winds, they are characterized by their great consistency of direction. In the Northern Hemisphere, the trades blow from the northeast, and in the Southern Hemisphere, the trades blow from the southeast.TRAJECTORY
The curve that a body, such as a celestial object, describes in space. This applies to air parcel movement also.TRANSLUCENT
Not transparent, but clear enough to allow light to pass through.TRANSMISSOMETER
An electronic instrument system which provides a continuous record of the atmospheric transmission between two fixed points. By showing the transmissivity of light through the atmosphere, the horizontal visibility may be determined.TRANSPARENT
A condition where a material is clear enough not to block the passage of radiant energy, especially light.TRANSPIRATION
The process by which water in plants is transferred as water vapor to the atmosphere.TRANSVERSE BANDS
Bands of clouds oriented perpendicular to the flow in which they are embedded. They often are seen best on satellite photographs. When observed at high levels (i.e., in cirrus formations), they may indicate severe or extreme turbulence. Transverse bands observed at low levels (called transverse rolls or T rolls) often indicate the presence of a temperature inversion (or cap) as well as directional shear in the low- to mid-level winds. These conditions often favor the development of strong to severe thunderstorms.TRANSVERSE ROLLS
Elongated low-level clouds, arranged in parallel bands and aligned parallel to the low-level winds but perpendicular to the mid-level flow. Transverse rolls are one type of transverse band, and often indicate an environment favorable for the subsequent development of supercells. Since they are aligned parallel to the low-level inflow, they may point toward the region most likely for later storm development. Sometimes known as a T-Roll.TRIPLE POINT
The point at which any three atmospheric boundaries meet. It is most often used to refer to the point of occlusion of an extratropical cyclone where the cold, warm, and occluded fronts meet. Cyclogenesis may occur at a triple point. It is also the condition of temperature and pressure under which the gaseous, liquid, and solid forms of a substance can exist in equilibrium.TROPICS/TROPICAL
The region of the earth located between the Tropic of Cancer, at 23.5 degrees North latitude, and the Tropic of Capricorn, at 23.5 degrees South latitude. It encompasses the equatorial region, an area of high temperatures and considerable precipitiation during part of the year.TROPICAL AIR MASS
An air mass that forms in the tropics or subtropics over the low latitudes. Maritime tropical air is produced over oceans and is warm and humid, while continental tropical air is formed over arid regions and is very hot and dry.TROPICAL CYCLONE
A warm core low pressure system which develops over tropical, and sometimes subtropical, waters, and has an organized circulation. Depending on sustained surface winds, the system is classified as a tropical disturbance, a tropical depression, a tropical storm, or a hurricane or typhoon.TROPICAL DEPRESSION
A tropical cyclone in which the maximum sustained surface winds are 38 miles per hour (33 knots) or less. Characteristically having one or more closed isobars, it may form slowly from a tropical disturbance or an easterly wave which has continued to organize.TROPICAL DISTURBANCE
An area of organized convection, originating in the tropics and occasionally the subtropics, that maintains its identity for 24 hours or more. It is often the first developmental stage of any subsequent tropical depression, tropical storm, or hurricane.TROPICAL PREDICTION CENTER (TPC)
A division of the National Centers for Environmental Prediction, the Center issues watches, warnings, forecasts, and analyses of hazardous weather conditions in the tropics for both domestic and international communities. The National Hurricane Center is a branch. For further information, contact the TPC, located in Miami, Florida.TROPICAL STORM
A tropical cyclone in which the maximum sustained surface winds are from 39 miles per hour (34 knots) to 73 miles per hour (63 knots). At this point, the system is given a name to identify and track it.TROPICAL WAVE
Another name for an easterly wave, it is an area of relatively low pressure moving westward through the trade wind easterlies. Generally, it is associated with extensive cloudiness and showers, and may be associated with possible tropical cyclone development.TROPIC OF CANCER
The most northern point on the earth where the sun is directly overhead, located at approximately 23.5 degrees North latitude.TROPIC OF CAPRICORN
The most southern point on the earth where the sun is directly overhead, located at approximately 23.5 degrees South latitude.TROPOPAUSE
The boundary zone or transition layer between the troposphere and the stratosphere. This is characterized by little or no increase or decrease in temperature or change in lapse rate with increasing altitude.TROPOSPHERE
The lowest layer of the atmosphere located between the earth's surface to approximately 11 miles (17 kilometers) into the atmosphere. Characterized by clouds and weather, temperature generally decreases with increasing altitude.TROUGH
An elongated area of low atmospheric pressure that is associated with an area of minimum cyclonic circulation. The opposite of a ridge. Sometimes abbreviated TROF on a weather map.TSUNAMI
An ocean wave with a long period that is formed by an underwater earthquake or landslide, or volcanic eruption. It may travel unnoticed across the ocean for thousands of miles from its point of origin and builds up to great heights over shallower water. Also known as a seismic sea wave, and incorrectly, as a tidal wave.TULE FOG
Ground fog in the central valley of California and the leading cause of weather-related casualties in that state. It forms at night and in the early morning when the ground cools, lowering the air temperature near the ground to or below its initial dew point.TURBULENCE
The irregular and instantaneous motions of air which is made up of a number of small of eddies that travel in the general air current. Atmospheric turbulence is caused by random fluctuations in the wind flow. It can be caused by thermal or convective currents, differences in terrain and wind speed, along a frontal zone, or variation in temperature and pressure.TURKEY TOWER
A narrow, individual cloud tower that develops and falls apart rapidly. The sudden development of turkey towers from small cumulus clouds may signify the breaking of a cap.TWILIGHT
Often called dusk, it is the evening period of waning light from the time of sunset to dark. The time of increasing light in the morning is called dawn. Twilight ends in the evening or begins in the morning at a specific time and can be categorized into three areas of decreasing light. Civil twilight is the time in the evening when car headlights need to be turned on to be seen by other drivers. Nautical twilight is when the bright stars used by navigators have appeared and the horizon may still be seen. Astronomical twilight is when the sunlight is still shining on the higher levels of the atmosphere, yet it is dark enough for astronomical work to begin. During dawn, the reverse order occurs until full daylight.TWISTER
A slang term used in the United States for a tornado.TYPHOON
The name for a tropical cyclone with sustained winds of 74 miles per hour (65 knots) or greater in the western North Pacific Ocean. This same tropical cyclone is known as a hurricane in the eastern North Pacific and North Atlantic Ocean, and as a cyclone in the Indian Ocean.TVS
Tornadic Vortex Signature. Doppler radar signature in the radial velocity field indicating intense, concentrated rotation - more so than a mesocyclone. Like the mesocyclone, specific criteria involving strength, vertical depth, and time continuity must be met in order for a signature to become a TVS. Existence of a TVS strongly increases the probability of tornado occurrence, but does not guarantee it. A TVS is not a visually observable feature. A | B | C | D | E | F | G | H | I | J and K | L | M | N | O | P | Q and R | S | T | U | V | W | X, Y and Z
A horizontal, tail-shaped cloud (not a funnel cloud) at low levels extending from he precipitation cascade region of a supercell toward the wall cloud (i.e., it usually is observed extending from the wall cloud toward the north or northeast). The base of the tail cloud is about the same as that of the wall cloud. Cloud motion in the tail cloud is away from the precipitation and toward the wall cloud, with rapid upward motion often observed near the junction of the tail and wall clouds. Compare with beaver tail, which is a form of inflow band that normally attaches to the storm's main updraft (not to the wall cloud) and has a base at about the same level as the updraft base (not the wall cloud).TAIL-END CHARLIE
The thunderstorm at the southernmost end of a squall line or other line or band of thunderstorms. Since low-level southerly inflow of warm, moist air into this storm is relatively unimpeded, such a storm often has a higher probability of strengthening to severe levels than the other storms in the line.
|
|
Information used by forecasters to determine what the weather might be elsewhere when compared with past weather conditions at the same degree of longitude.TEMPERATE CLIMATE
Climates with distinct winter and summer seasons, typical of regions found between the Tropics of Cancer and Capricorn and the Arctic and Antarctic Circles. Considered the climate of the middle latitudes.TEMPERATURE
The measure of molecular motion or the degree of heat of a substance. It is measured on an arbitrary scale from absolute zero, where the molecules theoretically stop moving. It is also the degree of hotness or coldness. In surface observations, it refers primarily to the free air or ambient temperature close to the surface of the earth.TERMINAL DOPPLER WEATHER RADAR (TDWR)
Doppler radar installed at major airports throughout the United States to detect microbursts.TERRESTRIAL RADIATION
Long wave radiation that is emitted by the earth back into the atmosphere. Most of it is absorbed by the water vapor in the atmosphere, while less than ten percent is radiated directly into space.TEXAS NORTHER
Local name in the south-central Great Plains for strong winter winds blowing north or northwest following a sharp cold front with dropping temperatures. Marked by a dark, blue-black sky.THAW
A warm spell of weather when ice and snow melt. To free something from the binding action of ice by warming it to a temperature above the melting point of ice.THEODOLITE
An optical instrument used to track the motion of a pilot balloon, or pibal, by measuring the elevation and azimuth angles.THERMAL LOW
Also known as heat low, it is an area of low pressure due to the high temperatures caused by intensive heating at the surface. It tends to remain stationary over its source area, with weak cyclonic circulation. There are no fronts associated with it. An example is the low that develops over southwestern United States and northwestern Mexico during the summer months.THERMOCLINE
A vertical negative temperature gradient in some layer of a body of water which is appreciably greater than the gradients above and below it. In the ocean, this may be seasonal, due to the heating of the surface water in the summer, or permanent.THERMODYNAMIC CHART
A chart containing contours of pressure, temperature, moisture, and potential temperature, all drawn relative to each other such that basic thermodynamic laws are satisfied. Such a chart typically is used to plot atmospheric soundings, and to estimate potential changes in temperature, moisture, etc. if air were displaced vertically from a given level. A thermodynamic chart thus is a useful tool in diagnosing atmospheric instability.THERMODYNAMICS
Study of the processes that involve the transformation of heat into mechanical work, of mechanical work into heat, or the flow of heat from a hotter body to a colder body.THERMOGRAPH
Essentially, a self-recording thermometer. A thermometer that continuously records the temperature on a chart.THERMOHALINE
In oceanography, it pertains to when both temperature and salinity act together. An example is thermohaline circulation which is vertical circulation induced by surface cooling, which causes convective overturning and consequent mixing.THERMOMETER
An instrument used for measuring temperature. The different scales used in meteorology are Celsius, Fahrenheit, and Kelvin or Absolute.THERMOSPHERE
A thermal classification, it is the layer of the atmosphere located between the mesosphere and outer space. It is a region of steadily increasing temperature with altitude, and includes all of the exosphere and most, if not all, of the ionosphere.THETA-E (or Equivalent Potential Temperature)
The temperature a parcel of air would have if a) it was lifted until it became saturated, b) all water vapor was condensed out, and c) it was returned adiabatically (i.e., without transfer of heat or mass) to a pressure of 1000 millibars. Theta-e, which typically is expressed in degrees Kelvin, is directly related to the amount of heat present in an air parcel. Thus, it is useful in diagnosing atmospheric instability.THETA-E RIDGE
An axis of relatively high values of theta-e. Severe weather and excessive rainfall often occur near or just upstream from a theta-e ridge.THICKNESS
The thickness of a layer in the atmosphere is proportional to the mean temperature of that whole layer. The layer most often used in meteorology is between 1000 and 500 millibars. There can be different temperature profiles in the lowest layer of the atmosphere with the same 1000-500 millibar thickness value, depending on what is happening above that lowest layer. For example, if the lower levels are warming but higher levels are cooling, the overall mean temperature, the thickness, could remain the same. Likewise, on a sunny day, the amount of incoming solar radiation, affects the temperature right at the earth's surface, without necessarily having much effect on the thickness of the whole layer.THUNDER
The sound emitted by rapidly expanding gases along the channel of a lightning discharge. Over three-quarters of lightning's electrical discharge is used in heating the gases in the atmosphere in and immediately around the visible channel. Temperatures can rise to over 10,000 °C in microseconds, resulting in a violent pressure wave, composed of compression and rarefaction. The rumble of thunder is created as one's ear catches other parts of the discharge, the part of the lightning flash nearest registering first, then the parts further away.THUNDER SNOW
A wintertime thunderstorm from which falls snow instead of rain. Violent updrafts and at or below freezing temperatures throughout the atmosphere, from surface to high aloft, discourage the melting of snow and ice into rain. Intense snowfall rates often occur during these situations.THUNDERSTORM
Produced by a cumulonimbus cloud, it is a microscale event of relatively short duration characterized by thunder, lightning, gusty surface winds, turbulence, hail, icing, precipitation, moderate to extreme up and downdrafts, and under the most severe conditions, tornadoes.TIDE
The periodic rising and falling of the earth's oceans and atmosphere. It is the result of the tide-producing forces of the moon and the sun acting on the rotating earth. This propagates a wave through the atmosphere and along the surface of the earth's waters.TILT
The inclination to the vertical of a significant feature of the pressure pattern or of the field of moisture or temperature. For example, midlatitide troughs tend to display a westward tilt with altitude through the troposphere.TILTED STORM AND TILTED UPDRAFT
A thunderstorm or cloud tower which is not purely vertical but instead exhibits a lanted or tilted character. It is a sign of vertical wind shear, a favorable condition for severe storm development.TIROS
A series of Television InfraRed Observation Satellites that demonstrated the feasibility and capability of observing the cloud cover and weather patterns of earth from space. An experimental program, it was the first spaceborne system that allowed meteorologists to acquire information that was immediately put to use in an operational setting. The first U.S. weather satellite, TIROS I, was launched on April 1, 1960, and TIROS X, the last of the series, was launched on July 2, 1965.TORNADO
A violently rotating column of air in contact with the ground and extending from the base of a thunderstorm. A condensation funnel does not need to reach to the ground for a tornado to be present; a debris cloud beneath a thunderstorm is all that is needed to confirm the presence of a tornado, even in the total absence of a condensation funnel. Most tornadoes in the United States occur in the central plains, with the greatest likelihood of twisters in the southern plains around Kansas, Texas and Oklahoma. Colorado lies of the western fringe of "Tornado Alley", but our state still averages between 30 and 50 tornadoes per year. The peak season for tornadoes is in the spring and early summer. From March through June, about 70% of all the tornadoes in a year will occur. This is due to the fact that the weather patterns that are needed for tornado development are most common in the spring and early summer. Most tornadoes form from large rotating thunderstorms called "supercells". These monster storms tend to develop ahead of cold fronts that push southward from Canada across the central U.S. As the fronts sag into the warm and humid air that covers the southern plains, the colder air wedges under the warm air, creating lift. The lifted air rises up to form thunderstorms that can rapidly grow to heights of 40 to 50 thousand feet above the ground. The storm pushes high into the sky, reaching into the jet stream - the band or river of fast moving air that flows around the world. It is the increase in windspeed with height that causes the thunderstorm to begin a large, slow counterclockwise rotation. This rotating thunderstorm is what is classified as a "Supercell". Once the supercell storm develops, the best analogy for thinking about how the tornado forms is to think of a fugure skater doing a spin. The skater starts with their arms out, and is rotating rather slowly. As the skater brings their arms in, the rotation begins to speed up. In physics, this is called "the conservation of angular momentum". The rotation gets faster and faster as the size of the rotating column grows more narrow. This is a very simplistic description, but eventually this narrow rapidly rotating column of air will drop to the ground as a tornado. Tornadoes are classified by the wind damage that they cause. The tornado scale was developed by Dr. Ted Fujita from the University of Chicago. Dr. Fujita based his "F scale" on a 0 to 5 basis for tornadoes. The F0 is a weak tornado, while the F5 storms are the most powerful winds ever observed on Earth.
- F0 - up to 72 mph - light damage F1 - 73 to 112 mph - moderate damage F2 - 113 to 157 mph - considerable damage F3 - 158 to 206 mph - severe damage F4 - 207 to 260 mph - devastating damage F5 - above 261 mph - incredible damage
About 70% of the annual average of 1000 tornadoes nationwide are classified as F0 or F1. About 28% of all tornadoes fall into the F2 or F3 category. Only about 2% of all tornadoes are classified as F4 or F5.Often a severe weather season will come and go without a single F5 tornado reported. However, about 80% of all tornadoes deaths are the result of the F3, F4 and F5 tornadoes. These storms are much less common, but much more dangerous. Tornadoes are not named like hurricanes are, but the strong or deadly tornadoes are usually remembered for the town or location that they affected. For instance, the infamous "Xenia Ohio Tornado" of April 1974, or in Colorado, the "Limon Tornado" in June of 1990. Perhaps the single worst tornado on record was the great "Tri-State Tornado" of March 1925. This huge tornado started in southeastern Missouri and tore a path of destruction all across Illinois, before ending in western Indiana. The twister covered a distance of 219 miles and was on the ground for over 3 hours. In the days before adequate warnings, the storm caught everyone off guard. The Tri-State Tornado killed 689 people, injured over 2,000 and caused 17 million dollars in damage - a very large figure in 1925! In Colorado, the peak season for tornadoes is in early June. At that time, the almost daily dose of thunderstorms can easily rise up to the jet stream level and begin to rotate into a supercell. These storms tend to form along the Front Range, roll over the Denver metro area and then really get severe over the eastern plains of the state. About 90% of all Colorado tornadoes occur east of I-25. Although tornadoes can form in the high country, the rough terrain tends to disrupt the rotation needed to form a supercell. Tornadoes have done some very unusual things. The powerful winds can pick up a railroad locomotive, lift a water tower off the ground, drive blades of grass into walls, just like a hammer and a nail. At the same time, there have been reports where tornadoes have picked a refridgerator off the ground, tossed it several hundreds of yards, dropped it back on the ground and not even broken an egg inside the refridgerator! Tornadoes usually form on the back edge of the thunderstorm cloud, menaing that most of the storm has already passed overhead. Often the rain, hail, thunder and lightning have mostly gone by and then the tornado occurs. That is why you will often see the sky looking very bright behind the tornado - a dramatic contrast to the very dark funnel. After the tornado, the sky often quickly clears as the storm moves away. There are, however, no hard and fast rules for tornados, so sometimes the twister occurs in the midst of a large area of thunderstorms, so after the tornado occurs, it just rains and rains.TORNADO ALLEY
A geographic corridor in the United States which stretches north from Texas to Nebraska and Iowa. In terms of sheer numbers, this section of the United States receives more tornadoes than any other.TORNADO WARNING
Issued by the National Weather Service when a tornado has been sighted either by an observer or Doppler radar.TORNADO WATCH
Issued by the National Sever Storm Laboratory in Kansas City when conditions are present in the atmosphere which may lead to the formation of tornadic thunderstorms.TORNADO FAMILY
A series of tornadoes produced by a single supercell, resulting in damage path segments along the same general line.TOTALS-TOTAL INDEX
A stability index and severe weather forecast tool, equal to the temperature at 850 b plus the dew point at 850 mb, minus twice the temperature at 500 mb. The total-totals index is the arithmetic sum of two other indices: the Vertical Totals Index (temperature at 850 mb minus temperature at 500 mb) and the Cross Totals Index (dew point at 850 mb minus temperature at 500 mb). As with all stability indices there are no magic threshold values, but in general, values of less than 50 or greater than 55 are considered weak and strong indicators, respectively, of potential severe storm development.TOWERING CUMULUS
Another name for cumulus congestus, it is a rapidly growing cumulus or an individual dome-shaped clouds whose height exceeds its width. Its distinctive cauliflower top often mean showers below, but lacking the characteristic anvil of a cumulonimbus, it is not a thunderstorm.TRACE
Generally, an unmeasurable or insignificant quantity. A precipitation amount of less than 0.005 inch.TRADE WINDS
Two belts of prevailing winds that blow easterly from the subtropical high pressure centers towards the equatorial trough. Primarily lower level winds, they are characterized by their great consistency of direction. In the Northern Hemisphere, the trades blow from the northeast, and in the Southern Hemisphere, the trades blow from the southeast.TRAJECTORY
The curve that a body, such as a celestial object, describes in space. This applies to air parcel movement also.TRANSLUCENT
Not transparent, but clear enough to allow light to pass through.TRANSMISSOMETER
An electronic instrument system which provides a continuous record of the atmospheric transmission between two fixed points. By showing the transmissivity of light through the atmosphere, the horizontal visibility may be determined.TRANSPARENT
A condition where a material is clear enough not to block the passage of radiant energy, especially light.TRANSPIRATION
The process by which water in plants is transferred as water vapor to the atmosphere.TRANSVERSE BANDS
Bands of clouds oriented perpendicular to the flow in which they are embedded. They often are seen best on satellite photographs. When observed at high levels (i.e., in cirrus formations), they may indicate severe or extreme turbulence. Transverse bands observed at low levels (called transverse rolls or T rolls) often indicate the presence of a temperature inversion (or cap) as well as directional shear in the low- to mid-level winds. These conditions often favor the development of strong to severe thunderstorms.TRANSVERSE ROLLS
Elongated low-level clouds, arranged in parallel bands and aligned parallel to the low-level winds but perpendicular to the mid-level flow. Transverse rolls are one type of transverse band, and often indicate an environment favorable for the subsequent development of supercells. Since they are aligned parallel to the low-level inflow, they may point toward the region most likely for later storm development. Sometimes known as a T-Roll.TRIPLE POINT
The point at which any three atmospheric boundaries meet. It is most often used to refer to the point of occlusion of an extratropical cyclone where the cold, warm, and occluded fronts meet. Cyclogenesis may occur at a triple point. It is also the condition of temperature and pressure under which the gaseous, liquid, and solid forms of a substance can exist in equilibrium.TROPICS/TROPICAL
The region of the earth located between the Tropic of Cancer, at 23.5 degrees North latitude, and the Tropic of Capricorn, at 23.5 degrees South latitude. It encompasses the equatorial region, an area of high temperatures and considerable precipitiation during part of the year.TROPICAL AIR MASS
An air mass that forms in the tropics or subtropics over the low latitudes. Maritime tropical air is produced over oceans and is warm and humid, while continental tropical air is formed over arid regions and is very hot and dry.TROPICAL CYCLONE
A warm core low pressure system which develops over tropical, and sometimes subtropical, waters, and has an organized circulation. Depending on sustained surface winds, the system is classified as a tropical disturbance, a tropical depression, a tropical storm, or a hurricane or typhoon.TROPICAL DEPRESSION
A tropical cyclone in which the maximum sustained surface winds are 38 miles per hour (33 knots) or less. Characteristically having one or more closed isobars, it may form slowly from a tropical disturbance or an easterly wave which has continued to organize.TROPICAL DISTURBANCE
An area of organized convection, originating in the tropics and occasionally the subtropics, that maintains its identity for 24 hours or more. It is often the first developmental stage of any subsequent tropical depression, tropical storm, or hurricane.TROPICAL PREDICTION CENTER (TPC)
A division of the National Centers for Environmental Prediction, the Center issues watches, warnings, forecasts, and analyses of hazardous weather conditions in the tropics for both domestic and international communities. The National Hurricane Center is a branch. For further information, contact the TPC, located in Miami, Florida.TROPICAL STORM
A tropical cyclone in which the maximum sustained surface winds are from 39 miles per hour (34 knots) to 73 miles per hour (63 knots). At this point, the system is given a name to identify and track it.TROPICAL WAVE
Another name for an easterly wave, it is an area of relatively low pressure moving westward through the trade wind easterlies. Generally, it is associated with extensive cloudiness and showers, and may be associated with possible tropical cyclone development.TROPIC OF CANCER
The most northern point on the earth where the sun is directly overhead, located at approximately 23.5 degrees North latitude.TROPIC OF CAPRICORN
The most southern point on the earth where the sun is directly overhead, located at approximately 23.5 degrees South latitude.TROPOPAUSE
The boundary zone or transition layer between the troposphere and the stratosphere. This is characterized by little or no increase or decrease in temperature or change in lapse rate with increasing altitude.TROPOSPHERE
The lowest layer of the atmosphere located between the earth's surface to approximately 11 miles (17 kilometers) into the atmosphere. Characterized by clouds and weather, temperature generally decreases with increasing altitude.TROUGH
An elongated area of low atmospheric pressure that is associated with an area of minimum cyclonic circulation. The opposite of a ridge. Sometimes abbreviated TROF on a weather map.TSUNAMI
An ocean wave with a long period that is formed by an underwater earthquake or landslide, or volcanic eruption. It may travel unnoticed across the ocean for thousands of miles from its point of origin and builds up to great heights over shallower water. Also known as a seismic sea wave, and incorrectly, as a tidal wave.TULE FOG
Ground fog in the central valley of California and the leading cause of weather-related casualties in that state. It forms at night and in the early morning when the ground cools, lowering the air temperature near the ground to or below its initial dew point.TURBULENCE
The irregular and instantaneous motions of air which is made up of a number of small of eddies that travel in the general air current. Atmospheric turbulence is caused by random fluctuations in the wind flow. It can be caused by thermal or convective currents, differences in terrain and wind speed, along a frontal zone, or variation in temperature and pressure.TURKEY TOWER
A narrow, individual cloud tower that develops and falls apart rapidly. The sudden development of turkey towers from small cumulus clouds may signify the breaking of a cap.TWILIGHT
Often called dusk, it is the evening period of waning light from the time of sunset to dark. The time of increasing light in the morning is called dawn. Twilight ends in the evening or begins in the morning at a specific time and can be categorized into three areas of decreasing light. Civil twilight is the time in the evening when car headlights need to be turned on to be seen by other drivers. Nautical twilight is when the bright stars used by navigators have appeared and the horizon may still be seen. Astronomical twilight is when the sunlight is still shining on the higher levels of the atmosphere, yet it is dark enough for astronomical work to begin. During dawn, the reverse order occurs until full daylight.TWISTER
A slang term used in the United States for a tornado.TYPHOON
The name for a tropical cyclone with sustained winds of 74 miles per hour (65 knots) or greater in the western North Pacific Ocean. This same tropical cyclone is known as a hurricane in the eastern North Pacific and North Atlantic Ocean, and as a cyclone in the Indian Ocean.TVS
Tornadic Vortex Signature. Doppler radar signature in the radial velocity field indicating intense, concentrated rotation - more so than a mesocyclone. Like the mesocyclone, specific criteria involving strength, vertical depth, and time continuity must be met in order for a signature to become a TVS. Existence of a TVS strongly increases the probability of tornado occurrence, but does not guarantee it. A TVS is not a visually observable feature. A | B | C | D | E | F | G | H | I | J and K | L | M | N | O | P | Q and R | S | T | U | V | W | X, Y and Z
Copyright 2005 by TheDenverChannel.com. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.
