Glossary and Acronyms: T

TAFB:

Tropical Analysis and Forecast Branch. The Tropical Analysis and Forecast Branch is a group of highly trained meteorologists who specialize in marine meteorology, tropical meteorology, satellite imagery interpretation, and tropical weather analysis. TAFB products include but are not limited to the following:

High Seas Marine Forecasts over the tropics and subtropics,
Offshore Waters Marine Forecasts over the tropics and subtropics,
Tropical Weather Discussions over the tropics and subtropics, and
Surface weather analyses and forecasts over the tropics, subtropics, and mid-latitudes.

(Source: http://www.nhc.noaa.gov/)

TC:

Tropical Cyclone.See below.

TCC:

Tropical Cyclone Committee (TCC). This committee gathers the 15 Members of the Regional Association I (RA I) of the WMO> which can be hit directly or indirectly by tropical cyclones coming from the Southwest Indian Ocean. These Members are: Botswana, Comoros, France (La Réunion), Lesotho, Madagascar, Malawi, Mauritius, Mozambique, Namibia, Seychelles, South Africa, Swaziland, Tanzania, Zimbabwe. This committe meets each 2 years to adjust the "Tropical Cyclone Operational Plan for the South-West Indian Ocean", formulated in 1981. This Plan defines the forecasting and warning responsibilities of all cooperating Members. It also sets out the existing arrangements in the Region for provision of observational data and exchange of information and contains information on practices and procedures of regional significance.

TCP:

Tropical Cyclone Programm. The Tropical Cyclone Programme is a part of WMO's Weather and Disaster Risk Reduction Services Department tasked to establish national and regionally coordinated systems to ensure that the loss of life and damage caused by tropical cyclones are reduced to a minimum.
(Source: http://www.wmo.int/)

TCWC :

Tropical Cyclone Warning Centre (TCWC). The TCWCs have, geographically speaking, less responsiblity than the RSMCs. The Australian Centre in Perth is responsible for the Southeast Indian Ocean, the Indonesian Centre in Jakarta for the Northeast Indian Ocean.

TD:

Tropical Depression. A non-frontal synoptic-scale low pressure area originating over tropical waters with organized convection and definite cyclonic wind circulation in which the maximum of the average wind speed is estimated to be in the range 28 to 33 knots (51 to 62 km/h), wind force 7 in the Beaufort scale.

Tornado, twister:

A violently rotating storm of small diameter; the most violent weather phenomenon. It is produced in a very severe thunderstorm and appears as a funnel cloud extending from the base of a Cumulonimbus to the ground.

Trade winds:

persistent winds, mainly in the lower atmospheric levels, which blow over vast regions from a subtropical antcyclone towards the equatorial regions. Their predominant directions are north-east in the Northern Hemisphere and south-east in the Southern Hemisphere.
The trade-wind belt extends, depending on the season, from near the equator to 30-35° north and south of it.
The trade-wind inversion is the temperature inversion in the trade-wind belt caused by air subsiding from high levels; the inversion separates moist trade-wind air below from warm and very dry air above.
The anti-trade is an air current with a westerly component which, in various subtropical regions of the Northern or Southern Hemisphere, sometimes blows above the trade wind.

TRMM :

Tropical Rainfall Measuring Mission.

Tropical Cyclone:

In the South-West Indian Ocean, a TC is a tropical system in which the maximum 10-min average surface wind speed is above 63 kt [118 km/h]. We can then discriminate the intense tropical cyclone (90-115 knots) [166-212 km/h] and the very intense tropical cyclone (winds up to 116 knots [212 km/h]).
Be aware the word "cyclone" in the english litterature is often the generic name to designate a depression (or a low or a low-pressure area). This is the reason why a "tropical cyclone" is usually translated as a "tropical system". For further details, see FAQ A3

Tropical depression:

a tropical system in which the maximum average surface wind speed ranges from 28 to 33 knots [51-62 km/h]. Depressions have a closed circulation and the associated convection (cloudy mass) is better organised than in a tropical disturbance. (See FAQ A3)).

Tropical meteorology :

The tropical zone must not be reduced by the geographical zone bounded by the northern tropic (the tropic of Cancer, 23°27'N) and the southern tropic (the tropic of Capricorn, 23°27'S). The tropical zone is considered to be the part of the globe bounded by the axis of the subtropical anticyclones of the two hemispheres (located near 30N and 30S on an annual average), that is to say approximately a half of the globe surface. The tropical domain changes according to the seasons, since the position of these axis of the anticyclones follows the apparent movement of the sun. Easterly winds generally blow in the tropical troposphere, when westerly winds generally blow in the mid latitudes. Therefore, the line located between the easterly and the westerly winds in the mid troposphere is considered as the “meteorological border" between the tropical and the mid latitudes regions (temperate regions, baroclinic regions, westerly disturbed weather regions).

Tropical storm:

over the South-West Indian ocean, there are two stages for tropical storm; a tropical system in which the maximum average surface wind speed ranges from 34 kt to 47 kt [63-87 km/h] is a moderate tropical storm, and systems are usually named. A tropical system in which the maximum average surface wind speed ranges from 48 kt to 63 kt [88-17 km/h] is a severe tropical storm.
The convection in tropical storms is usually more concentrated near the center with outer rainfall organizing into distinct bands.

Tropopause:

boundary between the troposphere and the stratosphere, where an abrupt change in lapse rate usually occurs. It is defined as the lowest level at which the lapse rate decreases to 2°C km^-1 or less, provided that the average lapse rate between this level and all higher levels within 2 km does not exceed 2°C km^-1. Occasionnally, a second tropopause may be found if the lapse rate above the first tropopause exceeds 3°C km^-1.

Troposphere:

Lower part of the terrestrial atmosphere, extending from the surface up to a height varying from about 9 km at the poles to about 17 km at the equator, in which the temperature decreases fairly uniformly with height.

Through, trough line:

an elogated area or a line along which pressures are lower than in the surrounding and the cyclonic curvature of the isobars or contours is a maximum.

TS :

Tropical Storm. See above.

TUTT :

Tropical Upper Tropospheric Trough. Large-scale tilted trough in the upper troposphere over the middle and lower latitudes of most major oceans (particularly the North Pacific) during summer. In the Northern Hemisphere, it is usually oriented NNE-SSW and may contain one or more closed cyclonic circulations.

Twin tropical cyclogenesis:

symmetric cyclogenesis straddling the equator. Twin tropical cyclogenesis usually occur during interseasons, when environment is favourable to cyclogenesis in both hemispheres.

Typhoon:

Name given to a tropical cyclone in the western North Pacific.