A strong area of low pressure will have many isobars encircling it on a surface chart and several height contours encircling it on the 850 mb and 700 mb level progs. The isobars or height contours will create a "oval" shaped pattern (kinking of contours occurs in association with warm and cold front boundary). The thickness pattern will have an "S" shaped appearance (or side-ways S pattern). This occurs due to strong WAA in the warm sector of the mid-latitude cyclone raising heights and CAA in the cold sector lowering heights. This same "S" pattern will be noticeable for low-level temperature and dewpoint also. link to UNISYS MODELS A well-amplified trough will show up at the 500 millibar and 300 millibar levels. In a well-developed cyclone, the region of lowest heights will tilt with height in the troposphere. This occurs because of cold dense air located to the west and northwest of the low-level cyclone. A mass of cold dense low-level air and its associated CAA will result in lowering heights above this air. A deep mid-latitude cyclone will have well defined fronts and a well-defined synoptic scale precipitation pattern surrounding the low and along the fronts. A strong low has in association with it, these uplift mechanisms: low level convergence due to fronts and friction, low level WAA, possible moisture advection in warm sector, shortwaves ( also see pressure troughs) along well developed frontal boundaries, curvature and shear vorticity, and jet streaks developed by a strong thermal gradient. The release of latent heat will enhance the low pressure's development. Most of the UVV action takes place to the right of the 700-mb trough axis since this region experiences the low level WAA, frontal uplift, and PVA. Since a deep low pressure is cold cored and thus has rising air throughout most of the troposphere, RH (850 to 500 mb RH) values will be relatively high. Watching a strong mid-latitude cyclone develop on the model progs truly is pure enjoyment! |