Relationships between synoptic-scale circulation features and antecedent upstream air trajectories associated with winter storms in central North Carolina

Recent research (Fuhrmann and Konrad 2013) has shown that air parcel trajectory analyses are useful for assessing the ingredients and meteorological processes that come together to produce heavy winter storms. While the details of the trajectory motions and characteristics have been shown to influence the type of precipitation that accumulates (i.e. snow or freezing rain), examination of a sufficiently large sample of storms of varying intensities is needed to better establish climatologically robust relationships between the trajectories and resulting precipitation characteristics. In addition, because air parcel trajectories have been shown to be good indicators of synoptic-scale circulation regimes, it is likely that various features of the large-scale circulation, such as the position and orientation of troughs and ridges, as well as the tracking and intensity of surface cyclones and anticyclones, are useful in predicting those trajectory motions tied to specific precipitation characteristics.

In this follow-up study, we have added an additional 30 winter storms (i.e. snowstorms and ice storms) of varying intensities across central North Carolina to the original sample of 15 winter storms, increasing the total sample to 45 storms for the period 1997 to 2013. This new sample of mostly lighter storms also includes events involving precipitation-type transitions (e.g. snow to freezing rain). As in Fuhrmann and Konrad (2013), we use the Hybrid Single-Particle Lagrangian Integrated Trajectory (HYSPLIT) tool to calculate 72-hour backward, or upstream, air parcel trajectories for each storm from three critical vertical levels: the near-surface level, the elevated warm layer zone, and the dendritic growth zone. Comparisons of composite trajectories and meteorological properties of air parcels (e.g. temperature, moisture, vertical velocity) are made between storms of varying intensities at each of the three critical levels. To determine the synoptic-scale circulation patterns associated with these storms and their trajectory characteristics, composite plots of the lower and middle-tropospheric circulation are analyzed using data from the North American Regional Reanalysis.

Reference: Fuhrmann, C.M. and C.E. Konrad (2013) A trajectory approach to analyzing the ingredients associated with heavy winter storms in central North Carolina. Weather and Forecasting, 28, 647-667.