The Fast Break – Victoria

Seasonal climate risk information for Victoria

Volume 19 | Issue 11 | 26 November 2024

Rainfall has curtailed grain harvest and hay baling for the time being, but the south west and far east Gippsland remains atypically dry with around a third of November rainfall to date. Soil moisture is drier than normal south of the Great Divide. But storms have increased moisture at depth in a few locations. Southern pastures are using soil water with west Gippsland showing water use more akin to December.

The Pacific Ocean is confused. Cooler temperatures in the NINO3.4 region have backed off and returned to a close to zero anomaly. This has been due to no reversed trade wind activity during most of November. A large slug of cooler water still exists under the Pacific that could upwell cooler. Cloud patterns at the dateline are like La Niña but closer to Australia show no La Niña like signal. In the last week, stronger wind is occurring in the western Pacific which is likely to warm temperatures further in the Coral Sea as an increased moisture source. This has also seen a week-long change to a more La Niña like Southern Oscillation Index (SOI) value. Most (but not all) models still predict a La Niña can form, but after this month’s regression there is much more work to be done to achieve it.

The Indian Ocean is also a dynamic beast. The warming off Indonesia last month has cooled somewhat and the Dipole Mode Index (DMI) has declined but remains at a negative Indian Ocean Dipole (-IOD) like value. This is still being based on Sumatran warmth rather than African cooling. Stronger winds and greater cloud off Sumatra are probably more associated with the passing phase of the Madden Julian Oscillation rather than coupling of the atmosphere with the ocean. Regardless, this is likely to warm ocean temperatures off Indonesia. The big change this month is the appearance of record warmth off the Kimberley coast of up to 3 °C warmer. The Indian Ocean is also primed as a better moisture source. All models predict the ocean to our northwest to remain warmer than normal.

The Southern Annular Mode (SAM) has been mainly positive over November. Spring is a transition time for SAM between its winter and summer behaviour. In summer a positive SAM would often mean more moisture flow into Eastern Victoria.

The Madden Julian Oscillation (MJO) has been over Africa during November and is currently positioned in the central Indian Ocean. It is predicted to be north of Australia as a moisture source during mid-December. The MJO has historically affected Victoria’s winter and spring rainfall to a greater extent.

Pressure has become more favourable for moisture transport but also for greater heat, as high pressure has spent a large amount of time in the Tasman Sea, causing more northerly winds.

My assessment of 12 climate models for Victoria is split between increased chances of being wetter and neutral (anything could happen). Temperatures are likely to be warmer for the next 3 months.

Soil moisture

Compared to 30 days earlier than 25 November 2024

The BoM Australian Water Outlook decile (AWO) deciles for perennial pasture rank drier south of the Great Divide and much drier at decile 1 in the Pyrenees, eastern south-west, west Gippsland and far east Gippsland. Far north-east Victoria is also slightly drier but much of the northern country and western north-east is close to average.  The Mallee is much wetter at decile 8–10 and some areas around Ouyen and the western Millewa are ranked close to wettest on record. Checking the soil moisture probe values storms have increased moisture at some sites, but most southern pastures are decreasing. Longwarry is using water 2 to 3 weeks earlier than normal. The Ouyen site increased 18 percentage points from 70 to 88% and the Cann River pasture decreased 44% from 94 to 50%.

Soil moisture probe data can be accessed in real time at Agriculture Victoria’s soil moisture monitoring website.

Probes from Agriculture Victoria, Dookie Land Management Group, Gecko Clan, Perennial Pasture Systems, Gippsland Agriculture Group, Murrayville Landcare and Riverine Plains Inc. networks.

Model distribution summary for the next 3 months

Predicted rainfall: December 2024 to February 2025

Predictions for December 2024 to February 2025 – the outlook from 12 global model forecasts is split between likely wetter and neutral across Victoria.

Model distribution summary for Victoria

Predicted temperature: December 2024 to February 2025

Predictions for December 2024 to February 2025 – the outlook from 11 global model forecasts is for likely warmer across Victoria.

Model distribution summary for the next 4 to 6 months

Predicted rainfall: March to May 2025

Predictions for March to May 2025 – the outlook from nine global model forecasts is neutral with sniffs of wetter across Victoria.

Predicted temperature: March to May 2025

Predictions for March to May 2025 – the outlook from 9 global model forecasts is for likely warmer across Victoria.

Model consensus forecast for the next 6 months

Current outlook (26 November)

Previous outlook (28 October)

Sea surface temperature (SST) anomalies

The equatorial Pacific Ocean surface stopped cooling and started to warm back to normality during November. The oceanic values for NINO3 and NINO3.4 were −0.05 and −0.14 °C respectively (26 November). Both these values are normal as a La Niña value would be cooler than −0.8oC. Ocean temperatures are warmer in the Coral Sea as a better moisture sources. Most models still predict a La Niña can form in the central Pacific, a flavour of La Niña called a ‘Modoki’. With the Equatorial Pacific warming instead of cooling this month there is a lot of work for it to do to get to this state.

The Indian Ocean has warmed to an extremely warm 3 degrees above normal off the north-west coast of Australia. The Dipole Mode Index is currently −0.54 °C (26 November), a negative IOD like value but not in the classic pattern. It now very late for a −IOD to form.

Sea surface temperatures are the key to the world’s rainfall. For more information on how they are measured, maps created and how to read them, check out our eLearn

National Oceanic and Atmospheric Administration (NOAA) Coral Reef Watch Daily 5 km SST Anomalies (Version 3.1) 24 November 2024.

Equatorial Pacific subsea temperature anomalies

Analysis done 25 November 2024

The Pacific Ocean Equatorial sub-surface temperature stayed at a similar size, in a pre-Niña like pattern. Less cooler water is upwelling at the surface than a month ago.

Southern Oscillation Index (SOI)

30-day moving SOI: 24 November 2024

The SOI has slowly started to rise during November but remains at a neutral value. The SOI is currently at +5.1 (as of 24 November 2024). The tropical atmosphere has been showing little interest in La Niña, where values above +8 would be more like La Niña. The last 8 days have seen more La Niña like values so expect to see the SOI rise further.

© Copyright Commonwealth of Australia 2024. Bureau of Meteorology. Climatology period 1933–92.

Dipole Mode Index (DMI)

Latest weekly value to 24 November 2024

The DMI is the difference between the temperature of the west and east boxes of ocean monitored for the IOD. The IOD is at a negative-IOD like value (currently −0.54 °C on 24 November). The majority of this signal is coming from a warmer eastern box.

© Copyright Commonwealth of Australia 2024. Bureau of Meteorology.

Pacific Ocean surface wind anomalies

Wind direction and strength anomalies for the last 30 days

Operational data: Surface winds (m/s) 30-day anomaly for Sunday 27 October to Monday 25 November 2024.

There has been no support for La Niña formation from the trade winds for most of November. In the last week, a stronger burst of easterly wind in the western Pacific might be expected to warm the ocean more to the north of Australia. In the Indian Ocean, a burst of stronger westerly wind across the eastern half would be expected to be causing greater warmer water to pile up around Sumatra.

(NCEP Operational climatology data: 1985–96, smoothed with 5-day running mean.) Source: NOAA.

World cloudiness anomalies

OLR anomalies: Average of 25 October to 24 November 2024

Cloud at the junction of the Date Line is less than normal, which is more like a La Niña. A buildup of cloud to the north of Australia is not apparent but would be more common in La Niña. In the eastern Indian Ocean an ‘eye’ of greater cloud exists south of the Equator, looking negative IOD like, but this is possibly linked to the position of the MJO.

Source: Bureau of Meteorology.

Southern Annular Mode (SAM)

AAO: Observed and GFS forecasts

29 July to 25 November 2024

The Southern Annular Mode (SAM) or Antarctic Oscillation (AAO) has spent November in weak to moderate positive territory. A positive SAM in summer can lead to more moisture flow into the east of Victoria. In the next 14 days BoM predicts a sustained weak positivity, and NOAA predicts a return to neutrality.

Source: NOAA.

Madden–Julian Oscillation (MJO)

MJO phase diagram for 18 October to 24 November 2024

For November the MJO cloud band crossed Africa and is moving across the Indian Ocean currently mid-way. Positions 5 and 6 are the more critical to Victoria as a moisture source. The BoM ACCESS model predicts the MJO to get to positions 5 and 6 around mid-December with some strength.

Source: Bureau of Meterology.

Air pressure

Last 30 days air pressure

Sea level pressure (mb) 30-day mean for Sunday 27 October to Monday 25 November 2024.

In the past 30 days the Sub Tropical Ridge of High Pressure (STR) has returned to a normal latitude for spring centred over Adelaide. Victoria has been situated between the dominant high off Perth and an occasionally persistent high in the Tasman Sea. This has meant both northerly winds and moisture troughing down.

Source: NOAA.

Air pressure anomalies

Last 30 days air pressure anomaly

Sea level pressure (mb) 30-day anomaly for Sunday 27 October to Monday 25 November 2024.

The Sub Tropical Ridge was slightly higher in pressure over Victoria during November, but the pressure was much higher off Western Australia and in the Tasman Sea. This meant Victoria spent a lot of time in the troughing zone between high pressure systems, bringing both hot northerly wind and tropical moisture. Pressure was slightly higher at Darwin and higher at Tahiti. This is why the SOI is not strongly positive and like La Niña. A La Niña would normally have much lower pressure at Darwin.

(NCEP Operational climatology data: 1985–96, smoothed with 5-day running mean.) Source: NOAA.

Climate definitions

Read a list of climate acronyms and explanations.

Modelled climate and ocean predictions for Victoria from November 2024-run models

Twelve climate models show their predictions for the next 6 months for the Pacific Ocean, Indian Ocean, rainfall and temperature for Victoria.

View a colour-coded version of this table (WORD - 77.1 KB)

Our e-learning module How to read the Fast Break table explains this table.

Four coupled global circulation model forecasts

*DJF = December, January, February; FMA = February, March, April; MAM = March, April, May

Four coupled global circulation model forecasts

*DJF = December, January, February; FMA = February, March, April; MAM = March, April, May

Three ensembles and a statistical model forecast

Image references

Original images used in this document are sourced from the Bureau of Meteorology under a Creative Commons 3.0 licence and from the NOAA which has a public domain policy. Annotations highlighting areas of interest have been added by Dale Grey.