Subj : Wx Terms (T)(4)
To   : All
From : Daryl Stout
Date : Sat Oct 21 2017 12:04 am

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.



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