El Niño is characterised by unusually warm ocean surface temperatures in the central and eastern tropical Pacific. Whilst many models indicate that an El Niño may develop around the middle of the year, it is still too early to assess the strength of any such event.
During El Niño events, the eastward shift of thunderstorm activity from Indonesia into the central Pacific can result in abnormally dry conditions over northern Australia, Indonesia and the Philippines. Drier than normal conditions are also often seen over southeastern Africa and northern Brazil, during the northern winter season.
During the northern summer season, Indian monsoon rainfall tends to be less than normal, especially in northwest India where crops are adversely affected. Wetter than normal conditions are observed along the west coast of tropical South America, and at subtropical latitudes of North America (Gulf Coast) and South America (southern Brazil to central Argentina).
The impact of El Nino events on wheat production in New South Wales are well documented.
During an El Niño event in winter, mid-latitude low pressure systems tend to be more vigorous than normal in the region of the eastern North Pacific.
These systems pump abnormally warm air into western Canada, Alaska and the extreme northern portion of the contiguous United States. Storms also tend to be more vigorous in the Gulf of Mexico and along the southeast coast of the United States resulting in wetter than normal conditions in that region.
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