Mesoscale Structure in the Megalopolitan Snowstorm, 11–12 February 1983. Part II: Doppler Radar Study of the New England Snowband

Abstract

Abstract A major snowstorm in eastern Massachusetts, 11–12 February 1983, was associated with a persistent mesoscale band of high reflectivity observed at MIT. The band was strengthened, then weakened, by the propagation of a high-amplitude gravity wave through it, without permanent disruption of either entity. Transformation of a single band to a group of three accompanied rotation from zonal to northeast-southwest, as the storm passed eastward out of radar range. An RHI cross section normal to the band at the inception of breakup showed a shallow layer of strong transverse (warm-to-cold) velocity components, evidently due to large-scale frontogenetical forcing, separating ascending air with small hydrostatic and symmetric stability above from descending air with large stability below. Band breakup was associated with a prominent small-scale oscillation along transverse jet Vertical motions calculated from a velocity azimuth display time series showed descent in the layer from 1.5 to 2.5 km throughout th...