Subj : Weather Glossary (T)
To : All
From : Daryl Stout
Date : Mon Jan 21 2019 12:06 am
This weather glossary contains information on more than 2000 terms,
phrases and abbreviations used by the National Weather Service (NWS)...
the government agency who makes weather forecasts, and issues weather
advisories, watches, and warnings, for the United States, and its
territories.
Many of these terms and abbreviations are used by NWS forecasters to
communicate between each other and have been in use for many years and
before many NWS products were directly available to the public. It is the
purpose of this glossary to aid you in better understanding NWS products.
***
T
Thunderstorm
T Rolls
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.
TAF
Terminal Aerodrome Forecast
TAFB
Tropical Analysis and Forecast Branch (of the TPC)
Tail Cloud
A horizontal, tail-shaped cloud (not a funnel cloud) at low levels
extending from the 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
Slang for 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.
Tailwater Height
In hydrologic terms, height of water immediately downstream of the dam.
Target
Precipitation or other phenomena which produces echoes on a radar display.
TCU
Towering cumulus clouds
TD
Tropical Depression
TDA
Today
TDWR
Terminal Doppler Weather Radar
Teleconnection
Linkage between changes in atmospheric circulation occurring in widely
separated parts of the globe.
TEMP
Temperature- A measure of the internal energy that a substance contains.
This is the most measured quantity in the atmosphere.
Temperature
(Abbrev. TEMP)- The temperature is a measure of the internal energy that
a substance contains. This is the most measured quantity in the
atmosphere.
Temperature Inversion
(surface-based or elevated) : a layer of the atmosphere in which air
temperature increases with height. When the layer's base is at the
surface, the layer is called a surface-based temperature inversion; when
the base of the layer is above the surface, the layer is called an
elevated temperature inversion.
Temperature Recovery
The change in temperature over a given period of time. Generally, the
period between late evening and sunrise. Windy or cloudy conditions will
tend to produce slow temperature recovery, while clear, calm weather can
cause rapid recovery.
TEMPS
temperatures
Terminal Aerodrome Forecast
This NWS aviation product is a concise statement of the expected
meteorological conditions at an airport during a specified period
(usually 24 hours). Each country is allowed to make modifications or
exceptions to the code for use in each particular country. TAFs use the
same weather code found in METAR weather reports.
Terrain Forced Flow
An airflow that is modified or channeled as it passes over or around
mountains or through gaps in a mountain barrier.
Texas Hooker
Same as Panhandle Hook - low pressure systems that originate in the
panhandle region of Texas and Oklahoma which initially move east and
then "hook" or recurve more northeast toward the upper Midwest or Great
Lakes region. In winter, these systems usually deposit heavy snows
north of their surface track. Thunderstorms may be found south of the
track.
Thalweg
In hydrologic terms, the line of maximum depth in a stream. The thalweg
is the part that has the maximum velocity and causes cutbanks and
channel migration.
Theodolite
An instrument used in surveying to measure horizontal and vertical
angles with a small telescope that can move in the horizontal and
vertical planes. It used to track the movements of either a ceiling
balloon or a radiosonde.
Thermal
A relatively small-scale, rising air current produced when the Earth's
surface is heated. Thermals are a common source of low level turbulence
for aircraft.
Thermal Belt
A zone of high nighttime temperatures (and relatively low humidities)
that is often experienced within a narrow altitude range on valley
sidewalls, especially evident during clear weather with light winds.
Thermal High
Area of high pressure that is shallow in vertical extent and produced
primarily by cold surface temperatures.
Thermal Low
Area of low pressure that is shallow in vertical extent and produced
primarily by warm surface temperatures.
Thermal Wind
It is a theoretical wind that blows parallel to the thickness lines,
for the layer considered, analogous to how the geostrophic wind blows
parallel to the height contours. The closer the thickness isopleths,
the stronger the thermal wind. Cold air is always located to the left
of the thermal wind (as you face downstream) and the warm air is
located on the right. Since thickness contours are tighter on the cold
side of thermal wind, your lower thickness values will be found on the
left side of the thermal wind. The speed and direction of the thermal
wind are determined by vector geometry where the geostrophic wind at
the upper level is subtracted from the geostrophic wind at the lower
level.
Thermally Driven Circulation
A diurnally reversing closed cellular wind current resulting from
horizontal temperature contrasts caused by different rates of heating
or cooling over adjacent surfaces; includes along-slope, cross-valley,
along-valley, mountain-plain and sea breeze circulations.
Thermistor
A resistor whose resistance changes with temperature. Because of the
known dependence of resistance on temperature, the resistor can be used
as a temperature sensor.
Thermocline
As one descends from the surface of the ocean, the temperature remains
nearly the same as it was at the surface, but at a certain depth
temperature starts decreasing rapidly with depth. This boundary is
called the thermocline. In studying the tropical Pacific Ocean, the
depth of 20�C water ("the 20�C isotherm") is often used as a proxy for
the depth of the thermocline. Along the equator, the 20�C isotherm is
typically located at about 50 m depth in the eastern Pacific, sloping
downwards to about 150 m in the western Pacific.
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.
Thermodynamic Diagram
Used interchangably with 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
In general, the relationships between heat and other properties (such as
temperature, pressure, density, etc.) In forecast discussions,
thermodynamics usually refers to the distribution of temperature and
moisture (both vertical and horizontal) as related to the diagnosis of
atmospheric instability.
Thermograph
An instrument that measures and records air temperature.
Thermometer
An instrument for measuring air temperature.
Thermosphere
The atmospheric shell extending from the top of the mesosphere to outer
space. It is a region of more or less steadily increasing temperature
with height, starting at 70 or 80 km.
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.
THETAE
Abbreviation for Theta-e; 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.
Thin Line Echo
A narrow, elongated, non-precipitating echo. It is usually associated with
thunderstorm outflows, fronts, or other density discontinuities. It is
also known as a Fine Line.
THK
Thick/Thickness
THN
Thin
Three-Hour Rainfall Rate
This WSR-88D Radar product displays precipitation total (in inches) of
the current and past two clock hours as a graphical image. It displays
hourly precipitation total (in inches) as a graphical image (polar
format with resolution 1.1 nm by 1 degree). It is updated once an hour.
It is used to:
1) Assess rainfall intensities and amounts over a longer viewing
interval; and
2) Possibly adjust flash flood guidance values since the product
corresponds to the timing of Flash Flood Guidance values.
Threshold Runoff
In hydrologic terms, the runoff in inches from a rain of specified
duration that causes a small stream to slightly exceed bankfull. When
available, flood stage is used instead of slightly over bankfull.
THRFTR
Thereafter
THRU
Through
THRUT
Throughout
THSD
Thousand
Thunder
The sound caused by rapidly expanding gases in a lightning discharge.
Thunderstorm
A local storm produced by a cumulonimbus cloud and accompanied by
lightning and thunder.
Tidal Cycle
The periodic changes in the intensity of tides caused primarily by the
varying relations between the earth, moon, and sun.
Tidal Piling
Occurs when unusually high water levels occur as the result of an
accumulation of successive incoming tides that do not completely drain
due to opposing strong winds and/or waves.
Tidal Wave
See TSUNAMI
TIDE
On a buoy report, the water level in feet above or below Mean Lower Low
Water (MLLW).
Tide Anomaly
Actual water level minus the prediction.
Tide Prediction
The computation of tidal highs and lows at a given location resulting
from the gravitational interactions between the earth and primarily the
moon and sun.
Tides
The periodic (occurring at regular intervals) variations in the surface
water level of the oceans, bays, gulfs, and inlets. Tides are the result
of the gravitiational attraction of the sun and the moon on the earth.
The attraction of the moon is far greater than the attraction of the sun
due to the close proximity of the earth and the moon. The sun is 360 times
further from the earth than the moon. Therefore, the moon plays a larger
role than the sun in producing tides. Every 27.3 days, the earth and the
moon revolve around a common point. This means that the oceans and other
water bodies which are affected by the earth-moon system experience a new
tidal cycle every 27.3 days. Because of the physical processes which
occur to produce the tidal system, there are two high tides and two low
tides each day. Because of the angle of the moon with respect to the
earth, the two high tides each day do not have to be of equal height. The
same holds true for the two low tides each day. Tides also differ in
height on a daily basis. The daily differences between tidal heights is
due to the changing distance between the earth and the moon. Scientists
use measurements of the height of the water level to examine tides and the
various phenomena which influence tides, such as hurricanes and winter
storms.
TIL
Until
Tilt
It describes a storm in which a line connecting the centroid of a mid
level storm component to the centroid of the lowest storm component is
to the right or the rear of the direction of motion.
Tilt Sequence
Radar term indicating that the radar antenna is scanning through a series
of antenna elevations in order to obtain a volume scan.
Tilted Storm
A thunderstorm or cloud tower which is not purely vertical but instead
exhibits a slanted or tilted character. It is a sign of vertical wind
shear, a favorable condition for severe storm development.
Tilted Updraft
A thunderstorm updraft which is not purely vertical but instead exhibits
a slanted or tilted character. It is a sign of vertical wind shear, a
favorable condition for severe storm development.
Tipping-Bucket Rain Gage
A precipitation gage where collected water is funneled into a two
compartment bucket; 0.01, 0.1 mm, or some other designed quantity of rain
will fill one compartment and overbalance the bucket so that it tips,
emptying into a reservoir and moving the second compartment into place
beneath the funnel. As the bucket is tipped, it actuates an electric
circuit.
TKE
Turbulent Kinetic Energy
TMW
Tomorrow
TNDCY
Tendency
TNGT
Tonight
Toe of Dam
(Upstream and Downstream) : The junction of the face of a dam with the
ground surface.
TOP
Cloud Top
Topography
The shape of the land.
TOR
Tornado (or) Tornado Warning
Tornado
A violently rotating column of air, usually pendant to a cumulonimbus,
with circulation reaching the ground. It nearly always starts as a funnel
cloud and may be accompanied by a loud roaring noise. On a local scale,
it is the most destructive of all atmospheric phenomena.
Tornado Family
A series of tornadoes produced by a single supercell, resulting in damage
path segments along the same general line.
Tornado Vortex Signature
An image of a tornado on the Doppler radar screen that shows up as a small
region of rapidly changing wind speeds inside a mesocyclone. The
following velocity criteria is normally required for recognition:
velocity difference between maximum inbound and outbound (shear) is
greater than or equal to 90 knots at less than 30 nmi and is greater than
or equal to 70 knots between 30 and 55 nmi. It shows up as a red upside
down triangle on the Storm Relative Velocity Display. Existence of a TVS
strongly increases the probability of tornado occurrence, but does not
guarantee it; therefore, the feature triggering it must be examined
closely by the radar operator. A TVS is not a visually observable feature.
Tornado Warning
This is issued when a tornado is indicated by the WSR-88D radar or sighted
by spotters; therefore, people in the affected area should seek safe
shelter immediately. They can be issued without a Tornado Watch being
already in effect. They are usually issued for a duration of around 30
minutes.
A Tornado Warning is issued by your local National Weather Service office
(NWFO). It will include where the tornado was located and what towns will
be in its path. If the tornado will affect the nearshore or coastal
waters, it will be issued as the combined product--Tornado Warning and
Special Marine Warning. If the thunderstorm which is causing the tornado
is also producing torrential rains, this warning may also be combined
with a Flash Flood Warning. If there is an ampersand (&) symbol at the
bottom of the warning, it indicates that the warning was issued as a
result of a severe weather report.
After it has been issued, the affected NWFO will followed it up
periodically with Severe Weather Statements. These statements will
contain updated information on the tornado and they will also let the
public know when the warning is no longer in effect.
Tornado Watch
This is issued by the National Weather Service when conditions are
favorable for the development of tornadoes in and close to the watch area.
Their size can vary depending on the weather situation. They are usually
issued for a duration of 4 to 8 hours. They normally are issued well in
advance of the actual occurrence of severe weather. During the watch,
people should review tornado safety rules and be prepared to move a place
of safety if threatening weather approaches.
A Tornado Watch is issued by the Storm Prediction Center (SPC) in Norman,
Oklahoma. Prior to the issuance of a Tornado Watch, SPC will usually
contact the affected local National Weather Forecast Office (NWFO) and
they will discuss what their current thinking is on the weather
situation. Afterwards, SPC will issue a preliminary Tornado Watch and
then the affected NWFO will then adjust the watch (adding or eliminating
counties/parishes) and then issue it to the public. After adjusting the
watch, the NWFO will let the public know which counties are included by
way of a Watch Redefining Statement. During the watch, the NWFO will keep
the public informed on what is happening in the watch area and also let
the public know when the watch has expired or been cancelled.
Total-Totals Index
A stability index and severe weather forecast tool, equal to the
temperature at 850 mb 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
A large cumulus cloud with great vertical development, usually with a
cauliflower-like appearance, but lacking the characteristic anvil of a
Cb. (Often shortened to "towering cu," and abbreviated TCU.)
TPC
(Tropical Prediction Center) - An NCEP center which produces marine
offshore and high seas forecasts south of 30N in the Eastern Pacific,
Gulf of Mexico and Caribbean.
Trace
In hydrologic terms, a hydrograph or similar plot for an extended-range
time horizon showing one of many scenarios generated through an ensemble
forecast process.
Track
The path that a storm or weather system follows.
Trade Winds
Persistent tropical winds that blow from the subtropical high pressure
centers towards the equatorial low.
Training
Repeated areas of rain, typically associated with thunderstorms, that
move over the same region in a relatively short period of time and are
capable of producing excessive rainfall totals. Train(ing) echoes can
frequently be a source of flash flooding.
Transmitter
The radar equipment used for generating and amplifying a radio
frequency (RF) carrier signal, modulating the carrier signal with
intelligence, and feeding the modulated carrier to an antenna for
radiation into space as electromagnetic waves. Weather radar
transmitters are usually magnetrons or klystrons.
Transpiration
Water discharged into the atmosphere from plant surfaces.
Transport Wind
The average wind over a specified period of time within a mixed layer
near the surface of the earth.
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.
Trapper
A valley or basin in which cold air becomes trapped or pooled.
Travel Time
In hydrologic terms, the time required for a flood wave to travel from
one location to a subsequent location downstream.
Triple Doppler
Since any wind has three components (say, in the x, y and z directions),
and a single radar measures in only one direction (radial), a single
radar cannot give the 3D winds everywhere it samples. However, if three
different radars view a storm from three different locations, the 3
measured radial velocities can be transformed into the actual 3D wind
field.
Triple Point
The intersection point between two boundaries (dry line, outflow
boundary, cold front, etc.), often a focus for thunderstorm development.
Triple point also may refer to a point on the gust front of a supercell,
where the warm moist inflow, the rain-cooled outflow from the forward
flank downdraft, and the rear flank downdraft all intersect; this point
is a favored location for tornado development (or redevelopment).
TROF
Trough
TROP
Tropopause
Tropical Advisory
Official information issued by tropical cyclone warning centers
describing all tropical cyclone watches and warnings in effect along
with details concerning tropical cyclone locations, intensity and
movement, and precautions that should be taken. Advisories are also
issued to describe:
(a) tropical cyclones prior to issuance of watches and warnings and
(b) subtropical cyclones.
Tropical Analysis and Forecast Branch
One of three branches of the Tropical Prediction Center (TPC). It
provides year-round products involving marine forecasting, aviation
forecasts and warnings (SIGMETs), and surface analyses. The unit also
provides satellite interpretation and satellite rainfall estimates for
the international community. In addition, TAFB provides support to NHC
through manpower and tropical cyclone intensity estimates from the
Dvorak technique.
Tropical Cyclone
A warm-core, non-frontal synoptic-scale cyclone, originating over
tropical or subtropical waters with organized deep convection and a
closed surface wind circulation about a well-defined center.
Tropical Cyclone Associated High Winds
High winds that occur a few hundred miles or so inland from the coast
of a landfalling tropical cyclone.
Tropical Cyclone Plan of the Day
A coordinated mission plan that tasks operational weather
reconnaissance requirements during the next 1100 to 1100 UTC day or
as required, describes reconnaissance flights committed to satisfy
both operational and research requirements, and identifies possible
reconnaissance requirements for the succeeding 24-hour period.
Tropical Cyclone Position Estimate
The National Hurricane Center issues a position estimate between
scheduled advisories whenever the storm center is within 200 nautical
miles of U.S. land-based weather radar and if sufficient and regular
radar reports are available to the hurricane center. As far as is
possible, the position estimate is issued hourly near the beginning of
the hour. The location of the eye or storm center is given in map
coordinates and distance and direction from a well-known point.
Tropical Cyclone Update
This brief statement is issued by the National Hurricane Center in
lieu of or preceding special advisories to inform of significant
changes in a tropical cyclone or the posting or cancellation of
watches and warnings.
Tropical Depression
A tropical cyclone in which the maximum 1-minute sustained surface
wind is 33 knots (38 mph) or less.
Tropical Disturbance
A discrete tropical weather system of apparently organized convection--
generally 100 to 300 mi in diameter--originating in the tropics or
subtropics, having a nonfrontal migratory character and maintaining its
identity for 24 hours or more. It may or may not be associated with a
detectable perturbation of the wind field.
Tropical Storm
A tropical cyclone in which the maximum 1-minute sustained surface wind
ranges from 34 to 63 knots (39 to 73 mph) inclusive.
Tropical Storm Summary
Written by the Hydrometeorological Prediction Center* (HPC) after
subtropical and names tropical cyclones have moved inland and advisories
have been discontinued. These advisories will be terminated when the
threat of flash flooding has ended or when the remnants of these storms
can no longer be distinguished from other synoptic features capable of
producing flash floods. Storm summaries will not be issued for storms
that enter the coast of Mexico and do not pose an immediate flash flood
threat to the coterminous United States. They will be initiated when and
if flash flood watches are posted in the United States because of an
approaching system. Storm summaries will continue to be numbered in
sequence with tropical cyclone advisories and will reference the former
storm's name in the text. Summaries will be issued at 0100, 0700, 1300,
and 1900 Eastern Daylight Time (EDT). The only exception will be the
first one in the series may be issued at a nonscheduled time.
Tropical Storm Warning
A warning for sustained surface winds, associated with a tropical
cyclone, within the range of 34 to 63 knots (39 to 73 mph), expected
in a specified coastal area within 24 hours.
Tropical Storm Watch
An announcement that a tropical storm poses or tropical storm conditions
pose a threat to coastal areas generally within 36 hours. A tropical
storm watch should normally not be issued if the system is forecast to
attain hurricane strength.
Tropical Wave
(formerly known as inverted trough) - A trough or cyclonic curvature
maximum in the trade wind easterlies. The wave may reach maximum
amplitude in the lower middle troposphere or may be the reflection of
an upper tropospheric cold low or an equatorward extension of a
mid-latitude trough.
Tropical Weather Discussion
These messages are issued 4 times daily by the Tropical Analysis and
Forecast Branch (TAFB) to describe significant synoptic weather
features in the tropics. One message will cover the Gulf of Mexico,
the Caribbean, and the Atlantic between the equator and 32 degrees
North and east of 140 degrees West. Plain language is used in these
discussions.
Tropical Weather Outlook
This outlook normally covers the tropical and subtropical waters,
discussing the weather conditions, emphasizing any disturbed and
suspicious areas which may become favorable for tropical cyclone
development within the next day to two. In the Atlantic, the outlook
is transmitted daily at 0530, 1130, 1730, and 2230 Eastern local time.
In the eastern Pacific, it is transmitted daily at 0100, 0700, 1300,
and 1900 Eastern local time. For the Central Pacific, transmission
times are 1000 and 2200 UTC. Existing tropical and subtropical cyclones
are mentioned, as are depressions not threatening land. Given for each
system are its location, size, intensity, and movement. For the first
24 hours of a depression or tropical cyclone, the outlook includes a
statement identifying the AFOS and World Meteorological Organization
(WMO) headers for the advisory on it.
Tropical Weather Summary
The National Hurricane Center issues a monthly summary of tropical
weather is included at the end of the month or as soon as feasible
thereafter, to describe briefly the past activity or lack thereof
and the reasons why.
Tropics
Areas of the Earth within 20� North and South of the equator.
Tropopause
The upper boundary of the troposphere, usually characterized by an
abrupt change in lapse rate from positive (decreasing temperature
with height) to neutral or negative (temperature constant or
increasing with height).
Tropopause Jet
Type of jet stream found near the tropopause. Examples of this type
of jet are the subtropical and polar fronts.
Troposphere
The layer of the atmosphere from the earth's surface up to the
tropopause, characterized by decreasing temperature with height
(except, perhaps, in thin layers - see inversion, cap), vertical
wind motion, appreciable water vapor content, and sensible weather
(clouds, rain, etc.).
Trough
An elongated area of relatively low atmospheric pressure, usually not
associated with a closed circulation, and thus used to distinguish
from a closed low. The opposite of ridge.
TRPCL
Tropical
TRRN
Terrain
True Wind
Wind relative to a fixed point on the earth. Wind relative to a moving
point is called APPARENT or RELATIVE WIND.
TS
Tropical Storm
TSRA
Thunderstorms with rain
TSTM
Thunderstorm
Tsunami
A series of long-period waves (on the order of tens of minutes) that are
usually generated by an impulsive disturbance that displaces massive
amounts of water, such as an earthquake occurring on or near the sea
floor. Underwater volcanic eruptions and landslides can also cause
tsunami. The resultant waves much the same as waves propagating in a
calm pond after a rock is tossed. While traveling in the deep oceans,
tsunami have extremely long wavelengths, often exceeding 50 nm, with
small amplitudes (a few tens of centimeters) and negligible wave
steepness, which in the open ocean would cause nothing more than a
gentle rise and fall for most vessels, and possibly go unnoticed.
Tsunami travel at very high speeds, sometimes in excess of 400 knots.
Across the open oceans, these high-speed waves lose very little
energy. As tsunami reach the shallow waters near the coast, they begin
to slow down while gradually growing steeper, due to the decreasing
water depth. The building walls of destruction can become extremely
large in height, reaching tens of meters 30 feet or more as they reach
the shoreline. The effects can be further amplified where a bay,
harbor, or lagoon funnels the waves as they move inland. Large tsunami
have been known to rise to over 100 feet! The amount of water and
energy contained in tsunami can have devastating effects on coastal
areas.
Tsunami Advisory
An advisory issued to coastal populations within areas not currently
in either warning or watch status when a tsunami warning has been issued
for another region of the same ocean. A Tsunami Advisory indicates that
an area is either outside the current warning and watch regions or that
the tsunami poses no danger to that area.
Tsunami Warning
A warning issued when the imminent threat of a tsunami from a large
undersea earthquake or following confirmation that a potentially
destructive tsunami is underway. They may initially be based only on
seismic information as a means of providing the earliest possible
alert. Warnings advise that appropriate actions be taken in response
to the tsunami threat. Such actions could include the evacuation of
low-lying coastal areas and the movement of boats and ships out of
harbors to deep water. Warnings are updated at least hourly or as
conditions warrant to continue, expand, restrict, or end the warning.
Tsunami Watch
An advance alert to areas that could be impacted by destructive tsunami
waves based on seismic information without confirmation that a
destructive tsunami is underway.
Tule Fog
Radiation fog in the Central Valley of California. It forms during night
and morning hours in late fall and winter months following the first
significant rainfall. A leading cause of weather related casualties in
California.
Turbidity
The thickness or opaqueness of water caused by the suspension of matter.
The turbidity of rivers and lakes increases after a rainfall.
Turbulence
Irregular motion of the atmosphere, as indicated by gusts and lulls in
the wind.
Turkey Tower
Slang for 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.
Turning Point
In hydrologic terms, a temporary point whose elevation is determined by
additions and subtractions of backsights and foresights respectively.
TVL
Travel
TVS
Tornado 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.
TWD
Toward
TWEB
Transcribed Weather Broadcasts - This NWS aviation product is similar to
the Area Forecast (AF) except information is contained in a route format.
Forecast sky cover (height and amount of cloud bases), cloud tops,
visibility (including vertical visibility), weather, and obstructions to
vision are described for a corridor 25 miles either side of the route.
Cloud bases and tops are always Mean Sea Level (MSL) unless noted.
Ceilings are always above ground level.
Twilight
The average time of civil twilight, which is the time between civil dawn
and sunrise in the morning, and between sunset and civil dusk in the
evening.
Twister
In the United States, a colloquial term for a tornado.
Two-Ribbon Flare
In solar-terrestrial terms, a flare that has developed as a pair of
bright strands (ribbons) on both sides of the main inversion ("neutral")
line of the magnetic field of the active region.
Type I, II, III, IV
(In solar-terrestrial terms) -Emissions of the sun in radio wavelengths
from centimeters to dekameters, under both quiet and disturbed
conditions.
Type I. A noise storm composed of many short, narrow-band bursts in the
metric range (300 - 50 MHz).
Type II. Narrow-band emission that begins in the meter range (300 MHz)
and sweeps slowly (tens of minutes) toward deka- meter wavelengths
(10 MHz). Type II emissions occur in loose association with major
FLAREs and are indicative of a shock wave moving through the solar
atmosphere.
Type III. Narrow-band bursts that sweep rapidly (seconds) from decimeter
to dekameter wavelengths (500 - 0.5 MHz). They often occur in groups and
are an occasional feature of complex solar ACTIVE REGIONs.
Type IV. A smooth continuum of broad-band bursts primarily in the meter
range (300 - 30 MHz). These bursts are associated with some major flare
events beginning 10 to 20 minutes after the flare maximum, and can last
for hours.
Typhoon
A tropical cyclone in the Western Pacific Ocean in which the maximum
1-minute sustained surface wind is 64 knots (74 mph) or greater.
Typhoon Season
The part of the year having a relatively high incidence of tropical
cyclones. In the western North Pacific, the typhoon season is from
July 1 to December 15. Tropical cyclones can occur year-round in any
basin.
--- SBBSecho 3.06-Win32
* Origin: RadioWxNet: The Thunderbolt BBS tbolt.synchro.net (801:1/2)
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