9A.3
An investigation of cold-air cyclogenesis along the East Coast of the United States
Christopher J. Warren, Plymouth State Univ., Plymouth, NH; and E. G. Hoffman
A ten-year climatology of East Coast cold-air cyclogenesis was developed to determine significant atmospheric conditions associated with these rather unique events. In the literature, a few case studies have examined these small-scale synoptic low-pressure systems in the midlatitudes that form within arctic airmasses as cold air moves offshore. Some of the characteristics of these storms have been shown to be similar to “polar lows”. The goals of this study are to: 1) determine how frequently these systems occur; 2) examine conditions that are favorable for their development; and 3) find similarities or differences between these storms and other East Coast cyclones and polar lows.
In order to identify cases of cold air cyclogenesis, all cyclone events along the East Coast (within a bounded region at 45°N by 70°W and 62.5°W, and at 30°N by 85°W and 72.5°W), were identified using the North American Regional Reanalysis (NARR). Cyclone events were counted when at least one closed sea-level pressure isobar (plotted at 2 hPa intervals) was present in the region of interest. Cyclogenesis was determined to have occurred when the sea-level pressure in the center of circulation decreased by at least 2 hPa/6-hrs at least twice in a 24 hour period (not necessarily consecutively). Finally, cyclogenesis events were classified as cold-air events if the gridpoint values of the mean daily 1000-500 hPa thickness from the National Centers for Environmental Protection/National Center for Atmospheric Research (NCEP/NCAR) Reanalysis near and immediately surrounding the storm were below -0.5 standard deviations from a 32 year (1975-2006) mean.
These storms were examined before, during, and after development and the results were used to generate composite analyses of various atmospheric features and typical storm tracks. These features include the position of upper-level and low-level jets, 500 hPa troughs, storm intensity, location of surface high pressure systems, presence of shallow baroclinic zones, and importance of imbedded mesoscale vortices.
Recorded presentationSession 9A, General Climate Studies: Climate Dynamics
Wednesday, 23 January 2008, 8:30 AM-10:00 AM, 215-216
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