The Structure of a Winter Storm Producing Heavy Precipitation over Nova Scotia

Abstract

On 22 February 1986 Nova Scotia experienced heavy precipitation in the form of snow, freezing precipitation, and rain from a storm having a central pressure no lower than 99.3 kPa. Using observations obtained during the Canadian Atlantic Storms Program (CASP) field project, the mesoscale structure of this storm was investigated. Throughout much of the storm, the lowest 1?3 km of the atmosphere over the coastline was near 0°C as a result of the diabatic process of melting and refreezing. Convergent flow aloft and the trajectories of particles undergoing terminal velocity changes contributed to enhanced precipitation near the coastline that was sometimes detected by radar as a precipitation band straddling the coastline. A mesoscale circulation, driven by melting and forced to remain linked to the coastline between the warm ocean and the cold land, is consistent with the observations.