Subj : Wx Terms (T)(3)
To   : All
From : Daryl Stout
Date : Sat Oct 21 2017 12:04 am

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public know when the warning is no longer in effect.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.



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