Unfortunately it appears that north-east NSW can not yet rest easy.....
ABC News, 16 August 2022:
The odds of there being a third sodden summer in a row have shortened now the Bureau of Meteorology has declared a La Niña alert.
Renewed cooling in the tropical Pacific Ocean and models indicating La Niña is likely during spring and early summer have prompted the BOM to raise the El Niño Southern Oscillation Index scale to "alert", the last step before an official La Niña.
Four of seven climate models it surveys suggest La Niña could return by early to mid spring. The remaining three suggest levels will remain neutral but close to the La Niña threshold through to the end of 2022.
If the climate driver is declared, it would be the third consecutive La Niña summer.
Triple-dip La Niñas are relatively rare, having only occurred twice since 1950, in 1973-76 and 1998-2001.
But with catchments already primed and water storages full, the third wet year could signal disaster.
National water storage levels are currently sitting at 71.3 per cent, up 5 per cent on last year, while the Murray-Darling Basin is sitting at 92.2 per cent, up 12.4 per cent on this time last year.
Many dams up and down the east coast are now sitting at or over capacity….
With catchments sodden, it won't take much before the water has nowhere to go…..
This year the rainfall is being further charged by a negative Indian Ocean Dipole (IOD), which has already been declared.
Much like a La Niña, a negative IOD means there is extra moisture available, this time in the north-west.
Frontal systems can then tap into that moisture and drag it across the country, typically bringing wetter than average conditions for south-eastern Australia in winter and spring until the monsoon moves down and breaks up the cycle in early summer.
All La Niñas and IODs are different and there are no guarantees when it comes to forecasting.
But even if the Bureau's official La Niña thresholds are not met this summer, above average sea surface temperatures will likely aid rainfall.
At this point, there is a strong chance of a third La Niña, acting on already primed catchments, with a complementary IOD, which is likely to bring more rounds of flooding rains this spring and summer....
Insurance News, 16 August 2022:
Flood fears increase as likelihood of rare triple-dip La Nina rises
The Bureau of Meteorology has today issued a La Nina alert, meaning there’s now a 70% chance that the flood-inducing climate driver will develop this year.
It would be the third La Nina in a row – something that has only happened twice since 1950 – leading to fears of more heavy rain along the already flood-hit east coast of Australia.....
Australian Bureau of Meteorology, ENSO Outlook An alert system for the El Niño–Southern Oscillation, 16 August 2022:
ENSO Outlook moves to La Niña ALERT
The ENSO Outlook has [moved] to La Niña ALERT. This means that even though the El Niño–Southern Oscillation is currently neutral, the chance of La Niña forming in the coming months has increased to around 70%. This is roughly three times the normal likelihood of an event forming in any year.
This status change follows a renewal of cooling in the tropical Pacific Ocean towards La Niña thresholds over recent weeks, as well as the persistence of the Southern Oscillation Index (SOI) at La Niña levels and strengthened trade winds at La Niña levels. Climate models indicate further cooling is likely, with four of seven models suggesting La Niña could return by early-to-mid southern hemisphere spring.
A La Niña ALERT is not a guarantee that La Niña will occur, rather it is an indication that most of the typical precursors of an event are in place. La Niña conditions increase the chance of above average spring and summer rainfall in northern and eastern Australia.
Bureau climatologists will continue to closely monitor conditions in the tropical Pacific as well as model outlooks for further signs of La Niña re-emergence.
"The chance of a La Niña developing in the coming season has increased. When these criteria have been met in the past, a La Niña event has developed around 70% of the time.".....
La Niña Alert
Any three of the following criteria need to be satisfied:
Sea surface temperature: A clear cooling trend has been observed in the NINO3 or NINO3.4 regions of the Pacific Ocean during the past three to six months.
Winds: Trade winds have been stronger than average in the western or central equatorial Pacific Ocean during any two of the last three months.
SOI: The two-month average SOI is +7 or higher.
Models: A majority of surveyed climate models show sustained cooling to at least 0.8 °C below average in the NINO3 or NINO3.4 regions of the Pacific Ocean by the late winter or spring.
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