La Nina watch - might be another good Wet

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hobbsy
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Re: La Nina watch - might be another good Wet

Post by hobbsy » Thu Jul 29, 2021 7:43 pm

No complaints from me
Insanity is a good place to hide from reality!

It is not how long the fish is but how long you have fished & how long you've wished.......


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Matt Flynn
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Re: La Nina watch - might be another good Wet

Post by Matt Flynn » Sun Oct 03, 2021 1:46 am

From ... http://www.bom.gov.au/climate/enso/

"The El Niño–Southern Oscillation (ENSO) is currently neutral. However, recent model outlooks and cooling in the tropical Pacific Ocean mean the Bureau's ENSO Outlook status is at La Niña WATCH. In the past when La Niña WATCH has been reached, a La Niña event has subsequently developed around 50% of the time; this is approximately double the normal likelihood. La Niña events increase the chances of above-average rainfall for northern and eastern Australia during spring and summer.

Most oceanic and atmospheric indicators of ENSO remain within the ENSO-neutral range. However, sea surface temperatures in the central tropical Pacific Ocean have cooled over the past two to three months, supported by cooler than average waters beneath the surface. Climate models continue this cooling trend over the coming months, with three of the seven models surveyed by the Bureau meeting La Niña criteria, while two additional models briefly touch La Niña thresholds.

The negative Indian Ocean Dipole (IOD) event has weakened, with latest IOD values falling shy of negative thresholds. Should these values persist, it is likely that the negative IOD is near its end. However, the pattern of sea surface temperatures in the Indian Ocean remains likely to influence Australian rainfall over the coming months. A negative IOD increases the chances of above-average spring rainfall for much of southern and eastern Australia.

The Madden–Julian Oscillation (MJO) is currently weak, located over the western Maritime Continent, north of Australia. Most models forecast movement of the MJO towards the eastern Maritime Continent in the coming fortnight, but there is some disagreement between models as to the strength of the MJO during that period. Some models suggest a moderate strengthening while others maintain a weak MJO. If the MJO strengthens over the Maritime Continent region, it would encourage enhanced rainfall over the tropics to the north of Australia.

The Southern Annular Mode (SAM) index has mostly been positive for the past five weeks. It is forecast to remain positive for October to December. This forecast is supported by a combination of a strengthened polar vortex over Antarctica, as well as the likelihood of La Niña development. A positive SAM during spring typically brings wetter weather to eastern parts of Australia, but may be drier for western Tasmania.

Climate change continues to influence Australian and global climate. Australia's climate has warmed by 1.44 ± 0.24 °C over 1910–2019, while southern Australia has seen a reduction of 10–20% in cool season (April–October) rainfall in recent decades. Rainfall across northern Australia during its wet season (October–April) has increased since the late 1990s with a greater proportion of high intensity short duration rainfall events."

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Re: La Nina watch - might be another good Wet

Post by Matt Flynn » Tue Nov 23, 2021 1:29 pm

It's a La Nina ... BOM ENSO outlook today ...

The ENSO Outlook has been moved to LA NIÑA.

Key atmospheric and oceanic indicators of the El Niño–Southern Oscillation (ENSO) show an established La Niña. Tropical Pacific sea surface temperatures (SSTs) are close to La Niña thresholds, with models indicating further cooling is likely. Atmospheric indicators including the Southern Oscillation Index (SOI), trade wind strength, and equatorial cloudiness have demonstrated a response to this oceanic cooling and are typical of La Niña conditions. The latest 90-day SOI ending 21 November was +8.6.

The current model outlooks suggest this La Niña will persist until the late southern hemisphere summer or early autumn 2022. All models surveyed by the Bureau indicate SSTs will meet NINO3.4 La Niña thresholds in December and January with a majority also predicting thresholds will be met in February 2022.

Bureau climatologists will continue to closely monitor conditions in the tropical Pacific as well as model outlooks for further changes to this La Niña event.
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