Earlier this class , U.S. scientists announced El Niño ’s comer , but described it as “ weak . ” Now , the Australian Bureau of Meteorology has move its own tracker status from alert to full - on El Niño , warning of widespread drouth and warmer temperatures .
We ’re calling it .
TheBureau ’s ENSO Tracker statushas be active from ALERT to EL NINO , signal the official declaration by the Bureau of Meteorology of El Niño 2015 .
El Niñois often associatedwith drought in Australia . It may be cold comfort for those toughing out the current dry in part of eastern Australia , but while El Niño certainly arouse the risk of infection of drought , it does n’t guarantee it . Of the 26 El Niño event since 1900 , 17 have resulted in far-flung Australian drought .
El Niño has been around for millennia , and is essentially a teddy in the climate patterns of the Pacific region driven by change in the sea . In the simplest terms , El Niño come when some of the warm ocean waters in the human race – northeast of Papua New Guinea , where the ocean can surpass 30C – change over east towards South America .
As the warmth slip east , so does the cloud and rainwater , and Australia becomes dominate by big , ironical , cloudless and rainless high - pressure systems .
So what are the criteria to announce El Niño , andwhy did it shift this time and not last year ?
Declaring an El Niño
The criteria for call El Niño are onour ENSO Tracker page , and in short we need to see at least three of the four survey things :
Tropical Pacific sea surface temperatures at least 0.8C above normal ( presently they are 1.1C above the mean value , and April averaged 0.82C above ) ;
Trade malarkey weaker than average ( generallyweak or even reversed since January 2015 ) ;
TheSouthern Oscillation Index(SOI ) below – 7 ( it has been electronegative pretty much since July 2014 ) ;
clime manikin are surefooted it will carry on ( all models we survey say ocean temperature will remain at El Niño levelsat least into late 2015 .
Why do we care about these four sea and atmospheric phenomena in particular ?
The modern definition of an El Niño centres on when the sea warming drives changes in the atm above it . Some of those changes in the aura ( such as a weakening of the trade air current ) actually help the ocean warm even more . This in number drives more changes in the atmosphere .
And around we go , in what ’s called a “ positivistic feedback ” loop . Once a convinced feedback loop topology is institute between the ocean and the atmosphere , we call them “ mate ” . And hence the El Niño is likely to be with us until the rude yearly cycle of ocean surface temperature ends the event betimes the next year .
Warmer and Drier Outlook
We speak about an increase of the betting odds for El Niño last year , but as Jaclyn Brown write last workweek , an El Niño never fully developed , and a declaration was never made .
Last year , sea temperatures along the equator warm up well-nigh everywhere , meaning little difference emerged between the east and west – and it ’s this difference which drives a lot of the changes in the atmosphere .
The conflict this time is that the western tropical Pacific Ocean is rest nerveless , and the lovesome area are further east , drive openhanded change in the atmosphere . We also started 2015 with strong body of water already in the tropical Pacific , whereas last yr it started from a cool stem .
Apart from increase the chance of drier precondition for many areas , El Niño can also bring higher daytime temperatures to the south , poorer snow seasons , lower streamflows , more heatwaves , longer freeze season ( cloudless night in natural spring ) , after onset of the northern rains and higher fire danger .
The shift in atmospheric patterns also means few tropical cyclones – estimable for the seashore but not so upright inland where they can impart summertime rainwater .
Right now , our outlook is actually for bedwetter than normal term in many areas – driven by warm water in the Indian Ocean . We excuse why in our May Climate and Water video .
However winter and bounce are the key clock time for Australia to receive El Niño impacts . Some areas are already in drought , particularly in Queensland and northern New South Wales , due to the failed northerly cockeyed season of 2012 - 13 and little recovery since . Western Victoria is also suffering long term rainfall deficiency .
Why El Niño?
The name comes from Peru , where every few years around Christmas ( the sentence of the nativity of Jesus “ the Boy Child ” , or “ El Niño ” in Spanish ) , the anchovy piscary would fail as warmer water supervene upon the normally coolheaded , anchovy - rich water along the South American coast .
So that ’s it in a nutshell – we have El Niño on our hands .
To keep yourself up to escort with the modish Bureau information about El Niño , see ourfortnightly ENSO Wrap Upsfor the latest word , sign up to our email list to get the latestclimate outlooks , and watch ourclimate and water supply videos .
Top image : Tim J Keegan / Flickr , CC BY - SA
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