These maps show the pattern of air pressure and wind direction during El Niño and La Niña phases of the Southern Oscillation. During the El Niño phase, pressures are high (H) to the north. Strong south-westerly winds bring drought to the north-east of the country. When La Niña is operating, there are high pressures over the South Island. These bring north-easterlies and rain to the north and east of the North Island.
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