Laserfiche WebLink
<br />v. The Mesohigh - A Special Form of Gravity Wave <br /> <br />The cold density current associated with a mesohigh is a form of <br />gravJty wave which is an important mesoscale triggering mE~chanism. <br />A mesohigh is a phenomenon associated with the development of a <br />thunderstorm in its mature and dissipating stages. It is created by <br />the downdraft induced by evaporative cooling of falling precipitation <br />and the downward advection of cold air aloft to the surface (see <br />Schlesinger, 1972, and Fujita et al., 1955). This results in a <br />local dome of cooler stable air having a mesohigh pressure at the <br />surface. The mesohigh produces a local gust front characterized by <br />a sudden pressure surge, gusty surface winds, rain, and tempey'ature <br />drop. Local intense convergence and convection occur at the inter- <br />section of a mesohighls outer boundary with other boundar'jes such as <br />fronts, squall lines, and other mesohighs or mountains and hills <br />(see Fujita, 1963). <br /> <br />Satellite imagery shows the mesohigh boundary as an arc-shaped line <br />of convective clouds advancing outward from the dissipating thunder- <br />storm area. Purdom (1973) has described the mesohigh which looks <br />like a weak arc-shaped line of convective clouds advancing outward <br />from the cumulonimbus (Cb) area. Cbls form along the boundary of <br />the mesohigh, especially at its intersection points. <br /> <br />7 <br />