Friday, 1 October 2010 - Monthly Climate Summary for New South Wales - Product code IDCKGC15R0

New South Wales in September 2010: La Niña brings a wet and cold start to Spring

• Wettest September since 1998 for the MDB, since 2005 for NSW
• Lowest September average maximum temperature since 1998
• 6th consecutive September with above average minimum temperatures for NSW

Details Extremes Maps Records Summaries Important notes the top

Rainfall

Above average rainfall was recorded for much of the state during September, with very much above average rainfall recorded in areas of northern and central NSW. Average rainfall was recorded along much of the coast and Great Dividing Range, with the exception of small regions along the central and southern coast. A small area of very much below average rainfall was recorded on the Victorian border. The statewide average rainfall for September was 50.1mm which is above the historical average of 34.7mm. This is the wettest September for NSW since 2005 (58.0mm).

It was Australia's wettest September on record (see Special Climate Statement 22) associated with a moderate to strong La Niña event, now well established in the Pacific Ocean. The rainfall distribution across NSW during the month (wet in the west, drier in the east) is typical of that experienced during a La Niña event. Long-range models surveyed by the Bureau of Meteorology suggest the central Pacific will continue to exceed La Niña thresholds through spring, with the majority indicating the La Niña event will continue into at least early 2011. For routine updates and comprehensive discussion on any developments regarding El Niño and La Niña, please see the ENSO Wrap-Up.

Much of the rainfall experienced by the state resulted from four main rainfall events. On the 4th/5th September a complex low pressure system developed over South Australia and moved over western Victoria. This brought heavy rainfall over much of NSW, with the heaviest rainfall experienced over the southwestern slopes of the southern ranges and adjacent inland. Mid month low pressure troughs and associated cloud bands generated rain for most of the state, and from the 20th to the 26th a lingering low pressure trough brought isolated showers to the northeastern corner of the state.

The Murray Darling Basin recorded a basin-wide average of 60.6mm which is above the historical average of 34.0mm. This is the wettest September in 12 years for the MDB and the 10th highest September MDB monthly rainfall on record.

Some sites had their highest total September rainfall on record.

See a map of rainfall deciles.

Temperature

Areas west of the Divide experienced below average to very much below average maximum temperatures during September, with some areas experiencing mean maximum temperatures of up to 3°C below average. All areas east of the Divide experienced average to above average temperatures. This pattern of maximum temperature distribution is directly related to the incidence of rainfall experienced across the state. The wet conditions west of the divide contributed to the below average to very much below average maximum temperatures and the dry conditions east of the divide contributed to the average to above average temperatures. The overall statewide average maximum temperature for NSW during September was 20.0°C which is 0.6°C below the historical average of 20.6°C. This is the lowest September average maximum temperature on record for NSW since 1998, and the second consecutive month with below average day time temperatures in NSW.

The northeastern half of NSW experienced above average to very much above average minimum temperatures, with the far northeastern corner of the state experiencing its highest minimum temperatures on record. The southwestern half of the state experienced average to very much below average minimum temperatures. The overall statewide average minimum temperature for NSW during September was 7.7°C which is 0.6°C above the historical average of 7.1°C. This is the 6th consecutive September with above average minimum temperatures for NSW.

NSW experienced average temperatures during September, with a statewide average mean temperature of 13.8°C.

Some sites had their highest September temperature on record.

See a map of maximum temperature anomalies.

Some sites had their highest September mean daily minimum 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