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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

Freezing nights to come for Canberra

15:06 EST

Night-time temperatures will drop well below average in the Capital from Wednesday.

Warm oceans fuelling late end to big wet season

14:26 EST

Warmer-than-normal oceans have contributed to a late end to a big wet season across the southern hemisphere.

Great Barrier Reef: Making clouds brighter could help to curb coral bleaching, scientists say

14:21 EST

Marine scientists have upped the ante in their fight to save the Great Barrier Reef from the devastating effects of coral bleaching.