Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Chapter 20.2 Fronts Formation of Fronts Air masses have different temperatures and different amounts of moisture depending on where they start. Also the characteristics can change as an air mass moves over a region. When 2 air masses meet, they form a front, a boundary that separates two air masses. Fronts form between any 2 different air masses. They also usually produce some sort of precipitation. Types of Fronts Fronts are classified by the temperature of the advancing front. 4 types of fronts: warm fronts, cold fronts, stationary fronts, and occluded fronts. Warm Fronts A warm front forms when warm air moves into an area formerly covered by cooler air. On a weather map it will be shown by a red line with red semicircles that point toward cooler air. The slope of a warm front is very gradual. As warm air rises, it cools to produce clouds, and precipitation. A warm front will be signified by cirrus clouds. The cirrus clouds will change into cirrostratus clouds and then altostratus clouds. This type of front will produce light-tomoderate precipitation over a large area for a long period of time. A slow increase of temperature will also take place. Cold Fronts A cold front forms when cold, dense air moves into an area occupied by warmer air. On a weather map the cold front will marked a blue line with blue triangles that point toward the warmer air mass. This front will become steeper and move faster. Those 2 things make the weather more violent. There are usually heavy downpours and gusty winds. Stationary Fronts In stationary fronts the surface position of the front does not move. On a weather map these fronts are shown by blue triangles on one side and red semicircles on the other side. Sometimes gentle to moderate precipitation occurs. Occluded Fronts When an active cold front overtakes a warm front an occluded front forms. This forces the warm front up. It may cause light precipitation. Middle-Latitude Cyclones Middle-latitude cyclones are large, low pressure centers that travel from west to east and cause stormy weather. This is the weather producers in the US. Most middle-latitude cyclones have a cold from and a warm front that moves from the center of the cyclone. Look at pg. 569 – explains how middle-latitude cyclones are made. The Role Of Airflow Aloft Most of the time air from high up in the atmosphere makes a middlelatitude cyclone. Most of the time cyclones and anticyclones will be found right next to one another.