MART Vol. II MO/MP - NESA - Civil Air Patrol

• Make an immediate landing that might be extremely dangerous becauseof gusts and sudden wind shifts.The wind in a “high” blows in a clockwise spiral. When two highs areadjacent, the winds are in almost direct opposition at the point of contact. Sincefronts normally lie between two areas of higher pressure, wind shifts occur in alltypes of fronts, but they usually are more pronounced in cold fronts.If flight was continued, entrapment in a line of squalls and cumulonimbusclouds could occur. It may be disastrous to fly beneath these clouds; impossible,in a small plane, to fly above them. At low altitudes, there are not safe passagesthrough them. Usually there is no possibility of flying around them because theyoften extend in a line for 300 to 500 miles.3.3.5 Occluded FrontOne other form of front with which the pilot should become familiar is the“exclusion” or “occluded front.” This is a condition in which an air mass is trappedbetween two colder air masses and forced aloft to higher and higher levels until itfinally spreads out and loses its identity. An occluded front appears on weathermaps as shown in Figure 3-4.Occluded FrontCold FrontWarm FrontFigure 3-4Meteorologists subdivide occlusions into two types, but so far as the pilot isconcerned, the weather in any occlusion is a combination of warm front and coldfront conditions. As the occlusion approaches, the usual warm front indicationsprevail - lowering ceilings, lowering visibility, and precipitation. Generally the coldfront type, with squalls, turbulence, and thunderstorms, then follows the warmfront weather almost immediately.The first stage represents a boundary between two air masses, the cold andwarm air moving in opposite directions along a front. Soon, however, the coolerair, being more aggressive, thrusts a wedge under the warm air, breaking thecontinuity of the boundary. Once begun, the process continues rapidly to thecomplete occlusion. As the warmer air is forced aloft, it cools quickly and itsmoisture condenses, often causing heavy precipitation. The air becomesextremely turbulent, with sudden changes in pressure and temperature.53