A Synoptic Climatology of Frozen Precipitation Events in Central and Eastern North Carolina

Eastern North Carolina is shielded from frozen precipitation by its proximity to the warm waters of the Gulf Stream. Further inland in the Piedmont and Mountain regions of North Carolina frozen precipitation is much more common, with total snowfall more than 10 inches throughout the months of (DJF), when compared to just one inch at the coast (http://climate.ncsu.edu/climate/winter). In Eastern North Carolina frozen precipitation events (including sleet and freezing rain) occur at least a couple of times a year. On an event-by-event basis, forecasting frozen precipitation in Eastern North Carolina is complicated by the fact that during those events the rain/snow line is often within this region. In addition, a small displacement of the midlatitude-cyclone can completely change the rain/snow outcome. The goal of this project is to create a synoptic climatology of the midlatitude cyclones that produce frozen precipitation in the Piedmont and Coastal Plains Regions of North Carolina to provide guidance on the conditions that lead to frozen precipitation in each region. Ferreira and Hall (2015) created a synoptic climatology of the main track-based categories of midlatitude cyclones that affect the southeast United States. They found that the most common MLC’s to affect the Southeast United States during the winter are Rockies and Canadian Cyclones, followed by Gulf Lows and Hatteras Lows. In this project we will answer the following two questions: 1) what midlatitude cyclone types produce frozen precipitation in Central and Eastern North Carolina? and 2) what are the synoptic scale characteristics of the midlatitude cyclones that lead to frozen precipitation in each region? Our hypothesis is that snow events in the Piedmont are associated with Rockies cyclones while snow events in The Coastal Plains of North Carolina are associated with Gulf Lows or Hatteras Lows.

Our approach to answer these questions starts by using the (National Weather Service) NWS frozen precipitation reports from (http://www.weather.gov/rah/events) to catalogue the dates of frozen precipitation events in North Carolina between 1997 and 2015. Followed by using surface weather map analyses available at (http://www.wpc.ncep.noaa.gov/dailywxmap/index.html) to determine the tracks of midlatitude cyclones that produced frozen precipitation in Central and Eastern North Carolina.

Finally, following Ferreira et al. (2013) and Ferreira et al. (2015) we will create a synoptic climatology of midlatitude cyclones that produce frozen precipitation in the Piedmont and Eastern North Carolina. We will use (Grid Analysis and Display System) GRADs to make composites of sea-level pressure, temperatures, 850 mb and 200 mb winds, 1000-500 mb thickness, and 200 mb geo-potential from (North American Regional Reanalysis) NARR and precipitation from NASA’s TRMM (Tropical Rainfall Measuring Mission). We will also analyze atmospheric soundings from the University of Wyoming (http://weather.uwyo.edu/upperair/sounding.html) archive to determine the presence and characteristics of warm layers.

References

Nieto-Ferreira, R., L. Hall, and T. M. Rickenbach, 2013: A climatology of the structure, evolution, and propagation of midlatitude cyclones in the Southeastern United States. J. Climate, 26, 8406-8421.

Nieto-Ferreira, R., L. Hall, 2015: Midlatitude cyclones in the southeastern United States: frequency and structure differences by cyclogenesis region. Int. J. Climatol., doi:10.1002/joc.4247