Mesoscale analysis of nor'easter of December 9, 2005

Between December 9 and December 10 of 2005, a small, intense nor'easter developed off the coast of New Jersey, moved north as it strengthened, and reached Nova Scotia. During this period, the storm experienced rapid development, and produced heavy snow over coastal New England with the accompaniment of thunder and lightning. The heavy snow fell on a Friday afternoon, causing massive traffic jams, as many folks tried in vain to “get home early”. By early evening, the sky had cleared completely.

The operational forecasts for this storm were good, but the nature of the storm development made it particularly difficult for businesses and schools to be able to react to the deterioration of the road conditions in time to prevent the traffic snarls. The mesoscale details of the development proved to be interesting and important in terms of the impact on the region.

Because this storm was so small and intense, much can be learned about the mesoscale influences contributing to the storm evolution. The sea level pressure in the center of the storm dropped a total of 26 hPa in less than 24 hours, with 17 hPa of this fall occurring in one six hour period. The convective precipitation appears to be due to an elevated region of instability, and later in the storm evolution, it appears that a tropospheric fold developed which allowed high velocity winds to be carried down to the surface, causing some structural damage. The Figure 1 shows the storm at 1800 UTC, December 9, 2005, when the precipitation over eastern Massachusetts was very heavy.

Using the Rapid Update Cycle analyses as verification, high resolution modeling of this storm brings out the mesoscale variability in this storm, and provides some insight into the predictability of the mesoscale details, given the operational constraints on the resolution of the our forecast models.