Central 12-month Rainfall Forecast

10 5 0
Nov 17
Dec 17
Jan 18
Feb 18
Mar 18
Apr 18
May 18
Jun 18
Jul 18
Aug 18
Sep 18
Oct 18
Rainfall deciles
10 Well above normal
8-9 Above normal
4-7 Near normal
2-3 Below normal
1 Well below normal

Issue Notes

ENSO status: Neutral (La Nina Watch)
Indian Ocean Dipole (IOD): Neutral

Sea surface temperatures (SSTs) and atmospheric indicators across the equatorial Pacific Ocean remain within neutral ENSO boundaries.

The Nino3.4 value remained at -0.3 in October, despite some cooling through the month. The Southern Oscillation Index (SOI) recorded a value of 9.1 during the same month.

Current consensus continues to suggests La Nina side of neutral is likely throughout the Austral summer. All eight international models are indicating a cooler side of neutral (La Nina) with all but one model reaching La Nina thresholds in January. At least six models maintain La Nina thresholds for at least three months, bringing a moderate-to-high risk of a weak La Nina.

Across the far eastern Indian Ocean SSTs are now warmer than average. The current SST pattern across the eastern Indian Ocean and the equatorial Pacific is now looking more La Nina-like, as cooler SSTs now extend from the Dateline across the equator to South America.

Climate forecasts are favouring slightly above average rainfall for parts of western Australia and central Australia. Given the recent evolution of ENSO conditions across the Pacific, the forecast is a bit trickier for the eastern states. Average-to-slightly below average rainfall is favoured for QLD, VIC and TAS through the tail end of spring. Based on the current Nino3.4 outlook, models are leaning towards the return of average rainfall values during the early summer with increased risk of a wetter than normal end to the season.

Warming SSTs across northern and eastern Australia maintain the risk of an earlier onset of the wet season across Australia‚??s tropical north. Along the eastern seaboard, warmer than average SSTs could lead to intense but localised rainfall events over the coming months. During neutral ENSO years, SE QLD and NE NSW tend to see above average thunderstorm activity during the warmer months.

Issued Nov 10

Forecast Explanation

Notes on the concept of deciles

If all the data in a record are ranked from lowest to highest they can then be divided into 100 equal blocks. These blocks are known as percentiles. The values that fall into the lowest 10% range (from 0 to 10%) are said to be in the first decile, those in the group 10+% to 20% are in the second decile, and so on. Those in the group 90+% to the maximum value recorded are in the 10th decile. The 50% value is a special one known as the 'median'. It is noteworthy since there is the same number of records above and below its value.

Deciles have been found to be very useful for analysing rainfall in particular as its distribution is not the normal bell-shape distribution but is skewed towards many low values with only a few high values. The deciles can be described in qualitative terms. A table is provided in the accompanying results.

Site search

Enter a postcode or town name for local weather, or text to search the site. » advanced search

Eastern Australia's missing heat challenges records in Tasmania, Victoria

09:45 AEDT Australia's eastern seaboard is experiencing a notably cool November this year, while a spell of late-spring heat is challenging records in the nation's southeast.

Help with Farmonline Weather