Using the monthly classification of global SSTs and 500 HPA height to predict temperature and precipitation regimes one to two season in advance for the Mid-Mississippi Region

Abstract

Using the results from previous studies of the interannual variability of local mean monthly temperature and precipitation by this group, long range forecasts were generated for summer and winter season temperatures and precipitation four to five months in advance using analogs and/or contingency tables. These forecasts also included information about El Niño phase and east Pacific region blocking events. Summer and winter season forecasts of temperature and precipitation are of interest to the local and regional media as well as the agricultural communities in the mid- Mississippi River Valley. A simple forecast verification scheme was borrowed and used to score the long range forecasts, and skill scores were used to compare and evaluate the forecasts against climatology. The results show that these forecasts have been better than climatology, in general, especially in the summer season and for seasonal temperature forecasts. The research results used here have demonstrated that Pacific region SSTs and SST anomalies can be separated into seven general synoptic classifications (“clusters”, A-G). Some of these clusters are shown to have a distinct impact on the barotropic component of the mean tropospheric height distributions as well. Clusters A, B, E, and G (C, D, and F) have been shown to be representative of La Niña (El Niño) type SST distributions by previous studies. Further, an analysis of the SST patterns from 1955 - 2007 demonstrated that certain clusters were prominent from 1955 - 1977, and from 1999 to the present; others dominated the period in between. This shift in prominent patterns during 1977 and 1999 corresponded roughly with a change in phase of the Pacific Decadal Oscillation (PDO). Some SST anomalies were correlated with warmer or cooler than normal conditions in the mid-Mississippi region, while others did not produce definitive results.