T
Section of the Earth's crust which moves in relation to the other plates. The amount of movement is usually measured in centimetres each year.
How hot or cold something is, measured with a thermometer.
A harmonic constituent with three periods in a constituent day. See also species.
A layer in which the temperature decreases significantly (relative to the layers above and below) with depth. The principal ones are designated diurnal, seasonal, and main thermocline. A common feature of thermoclines is the presence of internal tides.
The layer of the atmosphere located between the mesosphere and outer space. It is a region of increasing temperature with height, and includes all of the exosphere and most of the ionosphere.
The sound emitted by rapidly expanding gases along the channel of a lightning discharge.
A day on which thunder is heard at least once in a location.
Thunderstorms are cumulonimbus clouds with lightning and thunder. They often come with rain and hail, are usually short-lived and affect a relatively small area.
For terms describing thunderstorms in forecasts see:
Thunderstorms are associated with convective clouds (cumulonimbus) and are more often accompanied by precipitation. They are often short-lived and usually occur over localised areas. Aviation hazards associated with thunderstorms include wind shear, loss of visibility, low cloud, lightning strikes and possible large hail. In aviation forecasts and reports it is coded as TS.
Rain with thunder. An area of rain that contains thunderstorms.
A level of the sea defined by some phase of the tide, from which depths of water and heights of tide are calculated.
In relation to a watercourse, the maximum upstream location on that watercourse at which a tidal variation in water level is observed.
The various tidal water levels, such as low water or mean sea level for example, are known collectively as tidal planes. Also known as tidal datums, tidal levels, tidal elevations or datum planes.
Tidal planes are defined at the tide gauge – a specific location – but for practical purposes they are considered points on a continuous surface. The full list of tidal planes is extensive and different countries define the tidal planes differently. For legal definitions, the appropriate regulatory authority or document should be consulted.
Where the tide moves up and down the lower reaches of a river, a volume, known as the tidal prism, of fresh water is displaced each tidal cycle.
The tidal prism takes its name from the fact that the front between fresh and salt water is often inclined to the vertical, with the downstream edge of the fresh water riding over the salt.
This term is used in various contexts, including:
- Coastal aquifers – in this case, the rise and fall of the tide is often accompanied by a delayed and reduced oscillation of water level in nearby wells.
- The bringing of nutrient-rich offshore water into the shallower regions – this usually involves a relatively large flood tide bringing water up and into a bay or other semi-enclosed area, where it mixes with water from previous high tides before draining more slowly back to the open ocean. Submarine canyons across the continental shelf may also cause a rectified flow with a net increase of nutrients in the upper layer.
A generic term for a type of large-scale wave generated by the gravitational forces of the Sun and Moon on the ocean. Sometimes this term is used incorrectly as a synonym for tsunami.
A device for measuring sea level.
Timings refer to local time in each state/territory.
Early in the morning
Expected before 7 am
In the morning
Expected between 1 am and 11 am
In the late morning
Expected between 9 am and noon
During early afternoon
Expected between noon and 4 pm
During the afternoon
Expected between 1 pm and 9 pm
In the evening
Expected between 6 pm and midnight
Later in the evening
Expected after 9 pm
Tall, rapidly rotating column of wind 5–1000 m in diameter. Tornadoes are attached to the base of a cumulonimbus or large cumulus cloud and can cause damage on the ground. They may form water spouts when they happen over water.
See also Funnel cloud.
In relation to a water sample, the total concentration of all forms of nitrogen found in the water sample. This includes nitrate, nitrite, ammonia-N and organic forms of nitrogen.
Ozone concentration in the atmosphere above a point.
In relation to a water sample, the total concentration of all forms of phosphorus found in it.
In relation to a water sample, the measure of the particles mixed in it.
Combined height of the sea and the swell that mariners experience on open waters. Refers to the average height of the highest third of the waves.
Also known as combined sea and swell, or significant wave height.
A vertically developed cumulus cloud, often a precursor to cumulonimbus. In aviation forecasts and reports it is coded as TCU.
Rainfall observers report a trace of rain when a little water can be seen in the rain gauge, but there is less than 0.1 mm in total.
This is often reported as 'tce' or 'tr' in rainfall bulletins.
Rainfall amounts between 0.1 mm and 0.2 mm are reported as 0.2 mm in rainfall bulletins.
Predicted path of the centre of a tropical cyclone.
East to southeasterly winds (in the southern hemisphere) which affect tropical and subtropical regions, including the northern areas of Australia. During the monsoon season in northern Australia, the easterly trade winds are replaced by moist northwesterly (monsoonal) winds from the Indian Ocean and southern Asian ocean waters.
In the northern hemisphere the trade winds blow east to northeasterly.
So in both hemispheres, they tend to blow from the east to the west and towards the equator.
Located at 23.5 degrees north, it is the most northern point on the earth where the sun is directly overhead (on 21 June).
Located at 23.5 degrees south, it is the most southern point on the earth where the sun is directly overhead (on 22 December).
At latitudes near the maximum declination of the Moon (which varies between 18.3° and 28.6° latitude north and south over the course of the nodal cycle) the diurnal tides are greatest when the moon is near maximum declination.
These so-called tropic tides are the equivalent of the more common spring tides, with the beat frequencies being diurnal instead of semi-diurnal. The range (peak to peak distance between high and low tide) at the time when these diurnal tides are greatest is known as the tropic range.
An air mass that forms in the tropics or subtropics. Maritime tropical air is produced over oceans and is warm and humid, while continental tropical air is formed over arid land and is very hot and dry.
Very intense low pressure system that forms over warm ocean waters in the tropics (low latitudes). It brings damaging winds, torrential rain, large waves and storm surges.
An area of organized convection, originating in the tropics or occasionally the subtropics, that maintains its identity for 24 hours or more, but has no closed wind circulation. It is often the first developmental stage of a tropical cyclone.
The region of the earth located between the Tropic of Cancer, at 23.5 degrees north and the Tropic of Capricorn, at 23.5 degrees south.
The boundary zone or transition layer between the troposphere and the stratosphere.
The lowest layer of the atmosphere. Is characterised by clouds, weather and a decrease in temperature with increasing altitude.
Elongated area of low pressure. On a weather map a trough shows as a dashed line, which often extends outward from a low-pressure centre.
Generally, the wind changes direction as you cross from one side of a trough to the other.
The measure of the light-scattering properties of water. This is an indicator of the presence of suspended solids.
Irregular fluctuations occurring in fluid motions.
Term used in the northwestern Pacific for a tropical cyclone.