Meteorological situations associated with significant temperature falls inBuenos Aires: an application to the daily consumption of residential natural gas

The synoptic situations associated with significant temperature decreases i n Buenos Aires are analysed. Knowledge of these situations for the winter s eason is very useful for the community, especially when they are related to the consumption of natural gas, which is one of the most important sources of energy in Argentina. The rotated principal component method is used to classify the synoptic situations. The significant temperature decreases in winter during the period 1980-1988 occur in five modes at 1000 hPa and thre e modes at 500 hPa. The relationship between the two levels identifies two dominant patterns. The first has a strong high-pressure system with a north west-southeast axis and a maximum strength near 80 degrees W, 40 degrees S; this pattern is related to south-southeast winds over Buenos Aires. The se cond type shows a high-pressure system at 105 degrees W, 48 degrees S and a minimum near 110 degrees W, 30 degrees-35 degrees S; this kind of pattern is associated with persistent blocking situations in the South Pacific whic h result in persistent winds from the south over Buenos Aires. In addition, a relationship between such situations and the resulting increases in the demand for natural gas in residential areas is shown. This will help in the forecasting of such events in the future.