The most significant weather occurs on fronts, since that is where the air is rising fastest.Fronts are the boundary between two air masses.Fronts form as the result of ‘conflict’ between warm and cold air.There are also particularly strong gusts of wind in the showers As with fronts, the wind tends to back ahead of the trough and to veer immediately behind it. Pressure begins to fall as the trough approaches and often rises sharply once it has passed. Whereas fronts separate air masses, which are different in temperature, troughs generally develop in cold air and are characterised by an increase in the frequency and intensity of showers. Fig 6: The point of occlusionĬloud lifts and breaks after the front has moved through and there may be a change in temperature and a veer in the wind, though these tend to be small. The characteristics of an occlusion are similar to those of a cold front in that the rain belt is narrow. Fig 5: An occluded front in diagrammatic form This causes the warm air to be undercut and lifted up from the surface. They occur because cold fronts travel more quickly than warm fronts and eventually this results in the cold front ‘catching up’ with the warm front. Occlusions are slightly more complex than warm or cold fronts. On the other hand, in some cases, pressure will rise rapidly after a cold front has passed and this causes there to be few, if any, showers. Sometimes the showers may become heavy, perhaps even accompanied by hail and thunder. The passage of the front is usually marked by a sharp change from falling to rising pressure and a veer in the wind.Īs the rain dies away, the cloud lifts and breaks and, although there is sunshine, the air temperature falls.Īfter a time, cumulus clouds begin to form, often bringing showers. In some cases, there may also be hail and thunder. This is often accompanied by an increase in and a backing of the wind. Pressure begins to fall increasingly rapidly as the front approaches and rain usually starts not long before it arrives, becoming heavy for a short time. Warm air is thus replacing cold air at the surface. This is because the warm air is ‘lighter’ or less dense, than the colder air. The presence of a warm front means that the warm air is advancing and rising up over the cold air. Warm frontĪ warm front marks the leading edge of a warm air mass. Three types of front can be identified warm fronts, cold fronts and occluded fronts. Consequently, fronts tend to be associated with cloud and rain. At a front, the heavier cold air undercuts the less dense warm air, causing the warm air to rise up over the wedge of cold air.Īs the air rises there is cooling and condensation, thus leading to the formation of clouds and rainfall. In our latitudes a front usually separates warm, moist air from the tropics and cold, relatively dry air from polar regions.įronts move with the wind, so in the UK this is normally from west to east because our prevailing winds are from the west or southwest. A front is the boundary between two different types of air mass.
0 kommentar(er)
