Synoptic and Mesoscale Aspects of an Appalachian Ice Storm Associated with Cold-Air Damming

A numerical investigation of a moderate coastal storm with intense precipitation

“…A pressure ridge extended southward along the eastern slope of the Appalachians, indicating the occurrence of a cold air damming. This is a common feature during the wintertime when a cold anticyclone propagates towards the northeastern U.S. (Forbes et al, 1987). Note that an inverted surface trough, accompanied by a warm front extending from northern Florida seaward, was situated over the warm Gulf Stream water and beneath an upper-level ridge.…”

A study on a snowband associated with a coastal front and cold-air damming event of 3–4 February 1998 along the eastern coast of the Korean Peninsula

“…At a low Fr, ranging from 0.5 to 2.3 (e.g., Kitabayashi, 1977;Mason and Skyes, 1978;Baines, 1979), the flow becomes blocked at low levels by the terrain. Forbes et al (1987) also showed in their study of an Appalachian ice storm associated with the cold-air damming that at a small Fr (about 0.3 to 0.4), the flow was blocked and was flowing mainly in the mountain-parallel direction. In our case, the calculated Froude number is about 0.3 to 0.4 at the early and mature stages of cold-air damming.…”

“…The effect of mountain blocking can be quantified by the Froude number, F r = U/(N H m ) (e.g., Forbes et al, 1987), where U is the speed of the component of the undisturbed wind normal to the mountain, and N is the Brunt-Väsälä frequency upstream of the mountain, and H m is the mountain height, which is about 900 m in this study. The square of Fr is proportional to the ratio of the kinetic energy of the air to the amount of potential energy that has to be raised for the air parcel to reach the mountain top.…”

“…In the latter region, cold, stable air from a surface high over New England or southeastern Canada flows southwestward and is channeled along the eastern slopes of the Appalachians. The mountains "dam" the air along the eastern slopes (Richwien, 1980;Forbes et al, 1987;Bell and Bosart, 1988;Stauffer and Warner, 1987). Furthermore, the cold-air advection associated with the damming intensifies the thermal contrast between the dammed air and that over the ocean, which has been warmed and moistened by the underlying sea (Sanders and Gyakum, 1980;Bosart, 1981).…”

“…Furthermore, the cold-air advection associated with the damming intensifies the thermal contrast between the dammed air and that over the ocean, which has been warmed and moistened by the underlying sea (Sanders and Gyakum, 1980;Bosart, 1981). This process enhances the baroclinic zone near the coastline, causing coastal frontogenesis (Bosart, 1975;Forbes et al, 1987;Stauffer and Warner, 1987), and such frontogenesis is usually restricted to the lower atmosphere.…”