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Aviation Glossary :: Occluded Front  Aviation Glossary :: Occluded Front FAA Written Test Preparation
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At Dauntless, our editorial staff maintains the web's largest unified glossary of aviation terms. This glossary is built from a combination of official, quasi-official, and proprietary sources (including original material that we develop oursselves). Uniquely, we often provide multiple definitions of a given term so that you can find that which best applies to you. In order to maximize your learning efficiency, this glossary (and similar ones for our international users) is incresingly fully integrated into our aviation learning apps, including our FAA written test prep and FAA practical test prep software and apps. If you like this glossary, you'll love them with their polished learning environments and world's best and clearest content (please do give them a try.).

Occluded Front
Occluded Front
A composite of two fronts as a cold front overtakes a warm front or quasi-stationary front.
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source: FAA Aviation Weather for Pilots (AC 00-6A)

The front formed by a cold front overtaking a warm front and lifting the warm air above the earth’s surface. An occlusion (or frontal occlusion) forms when an air mass is trapped between two colder air masses and is forced to higher and higher levels.
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source: FAA Parachute Rigger Handbook (FAA-H-8084-17)

The front formed by a cold front overtaking a warm front and lifting the warm air above the earth’s surface. An occlusion (or frontal occlusion) forms when an air mass is trapped between two colder air masses and is forced to higher and higher levels.
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source: FAA Pilot Guide: Flight in Icing Conditions (AC 91-74A)

A composite of two fronts, formed as a cold front overtakes a warm or quasi-stationary front. Two types of occlusions can form depending on the relative coldness of the air behind the cold front to the air ahead of the warm or stationary front. A cold occlusion results when the coldest air is behind the cold front and a warm occlusion results when the coldest air is ahead of the warm front.
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source: NOAA National Weather Service Glossary

An occluded front is formed during the process of cyclogenesis when a cold front overtakes a warm front. When this occurs, the warm air is separated (occluded) from the cyclone center at the Earth's surface. The point where the warm front and the occluded front meet (and consequently the nearest location of warm air to the center of the cyclone) is called the triple point.

The trowal (short for TROugh of Warm air ALoft) is the projection on the Earth's surface of the tongue of warm air aloft formed during the occlusion process of the depression.

Occluded fronts usually form around mature low pressure areas. There are two types of occlusion, warm and cold:

  • In a cold occlusion, the air mass overtaking the warm front is cooler than the cool air ahead of the warm front, and plows under both air masses.
  • In a warm occlusion, the air mass overtaking the warm front is not as cool as the cold air ahead of the warm front, and rides over the colder air mass while lifting the warm air.

The occluded front symbol should thus be plotted at the position where the cold air is intersecting the surface, as on the image to the right. It thus varies between warm and a cold occlusions. The trowal on the other hand, being the projection of the warm air trough aloft, is at the same position in both cases. The position of the occluded front is often misplaced with the associated weather on a weather map but this is the position of the trowal.

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source: Wikitionary / Wikipedia and Related Sources (Edited)


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Disclaimer: While this glossary in most cases is likely to be highly accurate and useful, sometimes, for any number of editorial, transcription, technical, and other reasons, it might not be. Additionally, as somtimes you may have found yourself brought to this page through an automated term matching system, you may find definitions here that do not match the cotext or application in which you saw the original term. Please use your good judgement when using this resource.


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