Relationships between Mid-Tropospheric Flow Patterns and January Precipitation Totals in the Southeastern United States

Abstract

We systematically examine relationships between mid-tropospheric flow patterns and precipitation totals in the southeastern United States. While many have examined relationships between 700 hPa and 500 hPa geopotential heights and precipitation directly, the use of zonal and meridional indices to specify precipitation has not been used as frequently. For the mid-winter month of January we use a 24-year record of 500 hPa heights to calculate four zonal and six meridional indices. These values are then correlated with monthly precipitation totals at 60 climatic divisions in the contiguous United States, and the resultant patterns are mapped. Relationships between height differences and precipitation totals were strongest at sites close to one another. Strong and consistent relationships were found throughout the lower Mississippi Valley, which experiences frequent cyclogenesis in winter. By examining relationships between zonal and meridional indices it was possible to identify teleconnected patterns such as the prevailing mid-winter Pacific-North American teleconnection pattern. We conclude that variations in 500 hPa heights along discrete profiles (i.e., zonal and meridional indices) can be used to examine spatial variability in the control of precipitation.