Wednesday, 1 September 2010 - Seasonal Climate Summary for New South Wales - Product code IDCKGC25R0

NSW: Coldest winter in over a decade

• Wettest winter since 2005 for NSW and the Murray Darling Basin
• Coldest winter since 1998 for statewide average maximum temperatures
• 16th coolest winter on record
• Slightly above average minimum temperatures

Details Extremes Maps Records Summaries Important notes the top

Rainfall

NSW experienced its wettest winter since 2005. Despite the dry start to the season, with just 30.2 mm of rainfall recorded in June, above average rainfall in July (66.0 mm) and August (40.7 mm) lifted the statewide winter average to 136.9 mm, which is above the historical winter average¹of 115.97 mm. This is the first time NSW has experienced above average winter rainfall since 2005, when 180.7 mm was recorded.

Northern inland regions of NSW received above to very much above average rainfall during winter, predominantly during July and August. Elsewhere in the state about average rainfall was recorded, with only a small region on the far southeast coast recording below to very much below average rainfall. The above average rainfall experienced in the latter part of winter can, in part, be attributed to two main climate influences - the La Niña event in the Pacific Ocean and the Indian Ocean Dipole (IOD). The IOD moved into sustained negative mode during July and August, contributing to the enhanced rainfall across NSW during these months. La Niña events are usually, but not always, associated with enhanced rainfall across eastern Australia, particularly inland regions. For more about La Niña and the IOD please refer to the ENSO Wrap Up.

As with NSW, the Murray Darling Basin (MDB) experienced a dry start to winter, with June recording just 23.6 mm of rainfall (basin-wide average). However, above average falls in July (60.1 mm) and August (51.4 mm) offset this dry month, resulting in a basin-wide winter average of 135.1 mm, which is above the historical winter average of 111.1 mm. This was the first time the MDB has experienced above average winter rainfall since 2005, when 170.2 mm of rainfall was recorded.

Temperature

NSW experienced it's coldest winter since 1998 for statewide average maximum temperatures, with below to very much below average temperatures recorded across much of NSW. Interestingly, winter did not begin cold - above average temperatures were recorded in both June and July. However, day-time temperatures plummetted in August, bringing the overall winter average to 15.9°C, which is 0.3 °C below the historical average of 16.2 °C. This is the first time NSW has experienced below average winter maximums since 1998 (15.9 °C) and is the 16th coolest winter on record for NSW.

The cool day-time temperatures experienced during August were, in part, due to the passage of winter cold fronts across southern Australia during the month. The late appearance of these cold fronts can be attributed to the Southern Annular Mode (SAM). In it's positive mode since late May, it effectively inhibited the passage of westerlies and cold fronts across southern Australia during much of winter. However, during August, the SAM turned negative, allowing westerlies and cold fronts to again pass through southern Australia, bringing cold, wet conditions.

Minimum temperatures showed little variation during winter, with close to average night-time temperatures recorded in June, July and August. However, July was the warmest of the three months, with an average maximum temperature 0.7 °C above the average. These consecutive months of near average temperatures resulted in a winter statewide average minimum temperature of 4.6 °C, which is just 0.3 °C above the historical winter average of 4.3 °C. This is the fourth consecutive winter with above average minimum temperatures for NSW.

The statewide average mean temperature for winter was 10.2 °C which equals the historical average of 10.2 °C.

Some sites had their coldest winter day (lowest maximum temperature) on record.
See a map of maximum temperature anomalies.
Some sites had their lowest winter temperature on record.
See a map of minimum temperature anomalies.

Details Extremes Maps Records Summaries Important notes the top

Details Extremes Maps Records Summaries Important notes the top

Details Extremes Maps Records Summaries Important notes the top