DPIRD drought  forecast

DPIRD’s drought forecast shows that the most likely outcome through to 28 February 2025 is for most of NSW to be in the Non-Drought category with the area in Drought Affected category likely to increase for some areas of NSW.

• For most of NSW, Non-Drought or Drought Affected are the most likely CDI drought categories forecast, with moderate to high agreement (50% to above 75%) across the model ensemble.
• The Riverina and Murray LLS regions are forecast to continue to experience drought conditions and remain in the Drought or Drought Affected CDI categories. Drought conditions are likely to expand into the western part of the Murray LLS region.
• Parts of the South East LLS region including the southern Monaro and South Coast are forecast to transition from the Non-Drought to Drought Affected category during the forecast period.
• The historical accuracy of the drought forecast ranges from low (below 40%) to high (60 - 80%) over the forecast period depending on region.

DPIRD’s drought forecast uses the Bureau of Meteorology seasonal climate model ensemble to determine the NSW-CDI for the coming forecast period. The drought forecast figure shows the most frequent (mode) drought category in the 99-member model ensemble at the end of the forecast period (February 2025).

Forecast releases

• The end of month Drought Forecast maps are provided below.
• A mid-month update of the current drought forecast (using more recent information) is released around the 20^th of the month and can be viewed here. The forecast could be different to the figure below.

Understanding the DPIRD drought forecast figures

Most Likely CDI Category

The DPIRD drought forecast for NSW presents the ‘Most Likely’ Combined Drought Indicator (CDI) category for the forecast period. The Most Likely CDI category is determined by identifying the 'mode' of the CDI. The mode is the category that appears most frequently across all possible forecast outcomes in the ensemble run. It is the most common prediction for drought conditions in the forecast period based on the model's simulations.

This map can be used alongside the most current CDI map to observe current conditions and the most likely conditions in three months’ time.

Ensemble Agreement

Ensemble agreement refers to the level of consensus on the mode among the ensemble members. When there is high agreement, it means that most of models are predicting a similar CDI category, suggesting greater confidence in the forecast. If the agreement is low, it suggests that there is a wide range of possible outcomes, leading to greater uncertainty in the forecast.

Past Accuracy

Past accuracy refers to how the mode of previous forecasts matched the actual CDI categories that occurred for every forecast month in the historical record (1981 –2018), allowing an assessment of the reliability of the current forecast. If the model has consistently provided accurate predictions, there is more confidence in its current output. However, if past accuracy is low, it might suggest a need for more caution in interpreting the forecast, especially when ensemble agreement is low.

Overview of the DPIRD drought forecast

The seasonal drought forecast have been developed as a drought early warning system to prepare for drought events, mitigate drought impacts, and better aid farm and Government management decisions.

The DPIRD drought forecast has been generated by forcing the NSW DPI Enhanced Drought Information System (EDIS) with calibrated forecast variables from the Bureau’s seasonal prediction system, ACCESS-S to produce an ensemble of drought indicators. A 99-member lagged ensemble is used to determine the drought forecast.

A technical description of the DPIRD drought forecast, including a full analysis of the systems skill, is being prepared for public release in the Spring of 2024.

Find out more information about the drought forecast here.

Provide feedback

To provide feedback on the DPIRD Drought forecast, please email seasonal.conditions@dpird.nsw.gov.au

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