The Bureau of Meteorology has – somewhat belatedly – officially announced that the El Nino climate driver has come into effect.
It comes comes amid soaring temperatures and extreme fire danger across parts of south-east Australia.
A meteorologist with the Bureau of Meteorology said now that the El Nino pattern is settling in, it increases the BoM’s confidence this pattern will last until the end of summer — meaning a continuation of warm and dry conditions.
“We are already seeing extreme conditions in some part of the continent, particularly in the duration of heat,” he said. “We’ve had an extended period of warm and dry weather to start spring, today we’ve had catastrophic conditions on the south coast of NSW just to underscore that risk.
“While we are different to leading into the black summer in 2019 where we had years of preceding drought, we do have a wetter landscape out there, it is drying out more rapidly than has occurred in recent years, and we are seeing that elevated risk now occurring in eastern NSW in particular and Sydney equalling its record so far today for temperatures for September.”
The BOM is months behind other meteorological agencies globally in calling El Nino. This is due to the fact the Bureau has a higher bar of when El Nino has come into effect.
There are fears El Nino will lead to a scorching spring and summer for Australia with lower than average rainfall as moisture that would otherwise wash over eastern Australia instead is sucked further out into the Pacific Ocean.
And its effects could be super-sized by a combination with another climate driver to Australia’s west.
The last El Nino contributed to 2016 being the hottest year on record.
El Nino is one extreme of a Pacific Ocean climate driver called the El Nino Southern Oscillation, or ENSO. At the other end of ENSO is La Nina.
During El Nino, the temperature of a specific area of the central and eastern Pacific – called Nino 3.4 in meteorological circles – rises.
This aids in the creation of clouds and rainfall further into the Pacific.
That lack of rainfall over Australia can lead to drier conditions and drought for the country.
Conversely, when a La Nina takes over sea surface temperatures fall which ups the likelihood of rain closer to Australia.
And it’s not just El Nino, another climate drive is also causing a ruckus.
The Indian Ocean Dipole (IOD) refers to an index that measures sea surface temperatures in the tropical Indian Ocean.
A positive IOD would reduce the amount of moisture flowing towards Australia from the northwest which would also suppress rainfall and increase daytime temperatures.
The El Nino conditions are worrying meteorologists, fire fighters and farmers – all of who fear punishing conditions and stronger bushfires aided by lots of growth following a wet few years.
BOM’s late El Nino call
In July, United Nations’ World Meteorological Organisation (WMO) announced El Nino had kicked in. That came a month after the US’ National Oceanic and Atmospheric Administration (NOAA) said the same.
But while BOM has been on “El Nino alert” for some time, it hadn’t yet called it.
The disparity in calling El Nino is down to the fact that the BOM has a slightly different definition of the climate driver and is stricter when it comes to the level sea surface temperatures have to reach.
NOAA announces El Nino when sea surface temperatures at Nino 3.4 are 0.5C warmer than normal with conditions expected to last for another five months at least.
The BOM needs it to be hotter – as much as 0.8C. It also needs a number of other factors to kick in too.
The Bureau has consistently said that over the past few months sea surface temperatures had indeed risen high enough to exceed the El Nino threshold.
But until now, other observations such as wind, clouds and broad scale pressure patterns hadn’t occurred.
Originally published as El Nino climate driver has kicked in – Bureau of Meteorology
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