Weather Glossary - U

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UKMET

A medium-range numerical weather prediction model operated by the United Kingdom METeorological Agency.

Ultraviolet radiation

Electromagnetic radiation with wavelengths shorter than visible light, but longer than x-rays. Exposure to too much UV radiation can cause skin cancer.

Unsettled

Changeable or variable weather.

Unstable air

Air in which static instability exists. This condition is determined by the vertical gradients of air temperature and humidity.

Updraft

A small-scale current of rising air. If the air is sufficiently moist, then the moisture condenses to become a cumulus cloud or an individual tower of a towering cumulus or Cb.

Updraft base

Alternate term for a rain free base.

Upper level

The portion of the atmosphere above the lower troposphere. It is generally applied to levels above 850 hPa.

Upper level system

A general term for any large-scale or mesoscale disturbance capable of producing upward motion (lift) in the middle or upper parts of the atmosphere. This term is sometimes used interchangeably with impulse or shortwave.

Upslope flow

Air that flows toward higher terrain, and hence is forced to rise. The added lift often results in widespread low cloudiness and stratiform precipitation if the air is stable, or an increased chance of thunderstorm development if the air is unstable.

Upslope fog

Fog that forms when warm moist air is forced up a slope by wind.

Upstream

Toward the source of the flow, or located in the area from which the flow is coming.

Upwelling

The rise of colder, deep ocean waters along a coast due to the movement of surface water away from the coast.

UTC

Abbreviation for Universal Time Coordinate. See also Zulu, GMT.

Display Your Local Weather

Weather News

Great looking week ahead for snow resorts

14:12 EST

A mix of sunny and warmer than average days and cold, snowy days will greet skiers and snowboarders at the resorts this week.

QLD forecast summary

12:22 EST

A weak low pressure trough will clip the southeast of Queensland tomorrow, although unlikely to generate any significant rain, with only a few isolated showers expected and mainly coastal.

Menindee jujube and grape growers halt season, while citrus hangs on amid drought and poor water conditions

08:19 EST

Tony Lombardo and his brother Charlie have been growing fruit and vegetables on their land in Menindee for decades.