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Purdue Univ.: "Impact of the 1997-98 El Nino event on synoptic-scale temperature and precipitation distributions over the Midwest"

Complete report not currently available online.

During El Niño events, the Midwest region is one of the more difficult areas in the United States to forecast trends in climatic patterns and especially their influence (or lack thereof) on synoptic-scale weather events. For example, during the 1982-83 El Niño the Midwest was located about midway between enhanced anticyclonic (cyclonic) flow to its north (south) and in a zone of weaker-than-normal westerly flow. Any slight shift in this mean seasonal circulation anomaly pattern, particularly in the north-south direction, would most likely change the weather conditions over the Midwest. In winter, this not only could alter the temperature and precipitation patterns, but it could cause the precipitation to change form from rain to snow, or vice versa. The overall goal of this project was to examine the effect the 1997-89 El Niño had on the anomalously low and/or high precipitation episodes that occurred across the Midwest during the winter season. The main work consisted of looking at individual case studies of the synoptic-scale circulation patterns, including the meandering of the jet stream, during both dry and wet periods.