How El Niño will affect you

HOTTER days, less rain and more pain for our farmers. We have officially entered an El Nino. This is what it means for Australia.

AUSTRALIA has officially entered an El Niño. That means hotter days, less rain and more pain for our farmers.

El Niño is generally the precursor for drought, as it causes reduced rainfall in winter and spring in the eastern states.

It also causes warmer than average daytime temperatures over the southern half of the country.

Sea surface temperatures have been at, or near, El Niño thresholds since spring last year, save for a brief dip soon after Christmas.

In April, the bureau raised its El Nino Southern Oscillation (ENSO) tracker to the “alert” level, raising to 70 per cent or greater its expectation an El Niño would form in the Pacific in the winter or spring of 2015.

Wide areas of Queensland, NSW, Victoria and South Australia are in severe drought going back more than two years.

David Jones, of the bureau’s climate information services branch, says El Niño does not always mean drought in Australia but since 1900 it has been a strong indicator of drier times ahead.

“We know that 17 of the last 26 El Ninos have seen reasonably extensive drought conditions over Australia,” he said.

“So while below-average rainfall is not guaranteed, there is a strong weighting and assistance towards below-average rainfall and increased risk of drought, which obviously isn’t good for those people already in drought.”

WHAT IS AN EL NINO?

* A warming of sea surface temperatures in the eastern and central Pacific Ocean that disrupts weather patterns across the Pacific.

* Can cause a corresponding cooling of the ocean in the western Pacific and around Northern Australia

* Cooler seas near Australia, Papua New Guinea and Indonesia reduces convection — moist air at the surface that is heated, rises, cools and condenses into rain-bearing clouds.

* Convection migrates towards the eastern Pacific and can deliver increased rain to the west coast of North and South America * El Niño can disrupt the trade winds that, in the southern tropical Pacific, blow moisture-laden air towards eastern Australian coast.

How El Nino makes Australia drier

WHAT ARE THE EFFECTS OF AN EL NINO IN AUSTRALIA?

LOWER RAINFALL:

* El Niño increases chances of below-average rainfall through winter and spring in much of Australia, especially the north and east

* El Niño does not always mean drought but nine out of the 10 driest winter/spring periods happened in El Niño years

* Australia’s severest droughts — 1982/83, 1994, 2002 and 2006 were all associated with El Nino * Since 1900, El Ninos delivered winter/spring rainfall 28 per cent lower than the long-term average

Farmers can expect drought conditions to continue

TEMPERATURE EXTREMES:

* Warmer-than-average weather, particularly in southern Australia and particularly in the second half of the year.

Decreased cloud cover increases surface heating and assists to keep rainfall low

* Background warming of the atmosphere has made El Niño years warmer since the 1950s, the Bureau of Meteorology says

* In warmer months, El Niño can cause fewer slow-moving “blocking” high pressure systems, worsening heat extremes for cities such as Adelaide and Melbourne with an increase in extreme hot days and heatwaves further north

* Frost increases in El Niño years in cooler months in eastern Australia because clearer skies contain less daytime heat and lead to reduced minimum temperatures

* Between 15 and 30 per cent more frost days in El Niño years than average in northern Victoria and southern NSW, affecting agriculture

* Australia’s record low temperature of -23C at Charlotte Pass, NSW, on June 29, 1994, occurred during a strong El Niño.

Satellite image of planet earth showing the lack of cloud around northern Australia characteristic of the El Nino weather pattern.

INCREASED BUSHFIRE RISK:

* El Niño droughts dry the bush and have led to disasters including the 1983 Ash Wednesday bushfires that killed 75 people in Victoria and South Australia.

DISRUPTED TROPICAL WEATHER:

* Fewer tropical cyclones, especially for Queensland

* Later onset of northern monsoon rains

* Below-average wet season rains early in the season, with average rain later in the season.

REDUCED WINTER SNOWFALL:

* The four lowest recorded peak snow depths in Australia’s alpine country occurred in El Niño years, including severe drought.

Originally published as How El Niño will affect you