20 results. (Showing 1 - 20)
1.
occluded front
A complex frontal system that occurs when a cold front overtakes a warm front. Also known as an occlusion.
2.
Occluded Mesocyclone
A mesocyclone in which air from the rear-flank downdraft has completely enveloped the circulation at low levels, cutting off the inflow of warm unstable low-level air.
3.
Office of Global Programs
(OGP )
The Office of Global Programs (OGP) sponsors focused scientific research, within approximately eleven research elements, aimed at understanding climate variability and its predictability. Through studies in these areas, researchers coordinate activities that jointly contribute to improved predictions and assessments of climate variability over a continuum of timescales from season to season, year to year, and over the course of a decade and beyond.
4.
Operational Products
Products and data that have been fully tested and evaluated that are produced on a regular and ongoing basis.
5.
Orographic
Related to, or caused by, physical geography (such as mountains or sloping terrain).
6.
Orographic Lift
Lifting of air caused by its passage up and over mountains or other sloping terrain.
7.
orographic uplift
The vertical forcing of air by terrain features such as hills or mountains. This can create orographic clouds and/or precipitation.
8.
Orphan Anvil
[Slang], an anvil from a dissipated thunderstorm, below which no other clouds remain.
9.
Oscillations
A shift in position of various high and low pressure systems that in climate terms is usually defined as an index (i.e., a single numerically-derived number, that represents the distribution of temperature and pressure over a wide ocean area, such as the El Niņo-Southern Oscillation, North Atlantic Oscillation, and Pacific Decadal Oscillation).
10.
outflow
Air that flows outward from a thunderstorm.
11.
Outflow Boundary
A storm-scale or mesoscale boundary separating thunderstorm-cooled air (outflow) from the surrounding air; similar in effect to a cold front, with passage marked by a wind shift and usually a drop in temperature. Outflow boundaries may persist for 24 hours or more after the thunderstorms that generated them dissipate, and may travel hundreds of miles from their area of origin. New thunderstorms often develop along outflow boundaries, especially near the point of intersection with another boundary (cold front, dry line, another outflow boundary, etc.; see triple point).
12.
Outgoing Longwave Radiation
(OLR )
Outgoing Longwave Radiation is a polar satellite derived measurement of the radiative character of energy radiated from the warmer earth surface to cooler space. This measurement provides information on cloud-top temperature which can be used to estimate tropical precipitation amounts which is important in forecasting weather and climate.
13.
overcast
Sky condition when 9/10 or 10/10 of the sky is covered.
14.
overhang
Radar term indicating a region of high reflectivity at middle and upper levels above an area of weak reflectivity at low levels. (The latter area is known as a weak-echo region, or WER.) The overhang is found on the inflow side of a thunderstorm (normally the south or southeast side).
15.
Overrunning
A weather pattern in which a relatively warm air mass is in motion above another air mass of greater density at the surface. Embedded thunderstorms sometimes develop in such a pattern; severe thunderstorms (mainly with large hail) can occur, but tornadoes are unlikely.
Overrunning often is applied to the case of warm air riding up over a retreating layer of colder air, as along the sloping surface of a warm front. Such use of the term technically is incorrect, but in general it refers to a pattern characterized by widespread clouds and steady precipitation on the cool side of a front or other boundary.
16.
overshooting top
A 'bubble' of cloud sticking up above the anvil of a thunderstorm, due to a vigorous updraft within the storm.
17.
Overshooting Top (or Penetrating Top)
A dome-like protrusion above a thunderstorm anvil, representing a very strong updraft and hence a higher potential for severe weather with that storm. A persistent and/or large overshooting top (anvil dome) often is present on a supercell. A short-lived overshooting top, or one that forms and dissipates in cycles, may indicate the presence of a pulse storm or a cyclic storm.
18.
ozone
A colorless gas with a pungent odor, having the molecular form of O3, found in two layers of the atmosphere, the stratosphere (about 90% of the total atmospheric loading) and the troposphere (about 10%). Ozone is a form of oxygen found naturally in the stratosphere that provides a protective layer shielding the Earth from ultraviolet radiation's harmful health effects on humans and the environment. In the troposphere, ozone is a chemical oxidant and major component of photochemical smog. Ozone can seriously affect the human respiratory system.
19.
ozone action day
A "heads-up" message issued by the Jefferson County Kentucky Air Pollution District if ozone levels may reach dangerous levels the next day. This message encourages residents to prevent air pollution by postponing the use of motor vehicles, boats, mowing the lawn, and filling their vehicle's gas tank; also recommends car pooling.
20.
Ozone Hole
A severe depletion of stratospheric ozone over Antarctica that occurs each spring. The possibility exists that a hole could form over the Arctic as well. The depletion is caused by a chemical reaction involving ozone and chlorine, primarily from human produced sources, cloud particles, and low temperatures.
