11 results. (Showing 1 - 11)

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

2. Ultraviolet (or Ultraviolet Radiation) (UV )
Ultraviolet radiation from the sun plays a role in the formation of the ozone layer by acting as a catalyst for a chemical reaction that breaks apart oxygen molecules which then recombine to form ozone. The absorption of UV by stratospheric ozone and atmospheric oxygen prevents very little ultraviolet radiation to reach earth's surfaces where it can detrimental effects on human health and property.

3. 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.

4. Updraft Base
Alternate term for a rain-free base.

5. 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 sometimes is used interchangeably with impulse or shortwave.

6. Upper-level (or upper air)
In weather observing, the term applies to the portion of the atmosphere that is above the lower troposphere, generally 850 hPa and above.

7. 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.

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

9. Upward Vertical Motion (UVM )

10. Upwelling
In ocean dynamics, the upward motion of sub-surface water toward the surface of the ocean. This is often a source of cold, nutrient-rich water. Strong upwelling occurs along the equator where easterly winds are present. Upwelling also can occur along coastlines, and is important to fisheries and birds in California and Peru.

11. urban and small stream flood advisory
Alerts the public to flooding which is generally only an inconvenience and does not pose a threat to life and/or property. Issued when heavy rain will cause flooding of streets and low-lying places in urban areas, or if small rural or urban streams are expected to reach or exceed bankfull.