Frontogenesis and Symmetric Stability in a Major New England Snowstorm

Abstract

Abstract Synoptic and Doppler radar data are used to study the roles of large-scale frontogenetical forcing and of moist symmetric instability in the New England snowstorm of 5–6 December 1981, associated with an explosively intensifying cyclone offshore. Radar reflectivity patterns showed a tendency toward banded structure, particularly near the leading (northwestern) edge of the storm. Only a minor portion of the snowfall, however, was associated with this pronounced bandedness. From a set of constant-pressure analyses, the frontogenetical forcing was measured from the variation along the temperature gradient of the geostrophic wind component in the direction of this gradient. Over southeastern New England maximum forcing, found near 500 mb at the outset of the storm, descended to the layer between 850 and 700 mb 24 h later. Magnitudes were (3–7) × 10−10 deg m−1 s−1. Observed rates of strengthening of temperature gradient were less than half this value, implying relative adiabatic cooling in the rising ...