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A cold front is the leading edge of a cooler mass of air at ground level that replaces a warmer mass of air and lies within a pronounced surface trough of low pressure.It often forms behind an extratropical cyclone (to the west in the Northern Hemisphere, to the east in the Southern), at the leading edge of its cold air advection pattern—known as the cyclone's dry "conveyor belt" flow.
On weather maps, the surface position of the cold front is marked by a blue line with triangles pointing in the direction where cold air travels and it is placed at the leading edge of the cooler air mass. [2] Cold fronts often bring rain, and sometimes heavy thunderstorms as well. Cold fronts can produce sharper and more intense changes in ...
The convergence line ahead of the low became known as either the steering line or the warm front. The trailing convergence zone was referred to as the squall line or cold front. Areas of clouds and rainfall appeared to be focused along these convergence zones.
Warm fronts are followed by extended periods of light rain and drizzle due to the fact that, after the warm air rises above the cooler air (which remains on the ground), it gradually cools due to the air's expansion while being lifted, which forms clouds and leads to precipitation. Cold fronts occur when an advancing mass of cooler air ...
Troughs may be at the surface, or aloft, at altitude. Near-surface troughs sometimes mark a weather front associated with clouds, showers, and a wind direction shift. Upper-level troughs in the jet stream (as shown in diagram) reflect cyclonic filaments of vorticity. Their motion induces upper-level wind divergence, lifting and cooling the air ...
The weather associated with an occluded front includes a variety of cloud and precipitation patterns, including dry slots and banded precipitation. Cold, warm and occluded fronts often meet at the point of occlusion or triple point. [28] A guide to the symbols for weather fronts that may be found on a weather map: 1. cold front 2. warm front
A shelf cloud is a low, horizontal, wedge-shaped arcus cloud attached to the base of the parent cloud, which is usually a thunderstorm cumulonimbus, but could form on any type of convective clouds. Rising air motion can often be seen in the leading (outer) part of the shelf cloud, while the underside can often appear as turbulent and wind-torn.
Outflow, in meteorology, is air that flows outwards from a storm system. It is associated with ridging, or anticyclonic flow. In the low levels of the troposphere, outflow radiates from thunderstorms in the form of a wedge of rain-cooled air, which is visible as a thin rope-like cloud on weather satellite imagery or a fine line on weather radar ...