Another burst of early spring warmth has begun across south-eastern Australia, with temperatures set to peak from Friday through to Monday.
A high-pressure system sitting over NSW is responsible for the warm, dry and settled weather that we will see over the next few days. This high-pressure system is squeezing cold fronts further south, with warm northwesterlies prevailing for the eastern states.
The warm north-westerly winds are set to strengthen from Friday for most of the capital cities, ahead of a stronger cold front expected on the weekend (figure 1).
Figure 1: ECMWF surface temperature at 1pm EST on Saturday, September 11.
Temperatures are likely to reach the mid-to-high twenties across most of SA, NSW, VIC and QLD during the next 4 days. Even the southern capital cities are going to be feeling the early-season warmth:
- Sydney could hit 30ºC on both days of the weekend, which is about 9ºC warmer than average for this time of year.
- Brisbane’s maximum temperature peaks on Friday, with 29ºC on the forecast, which is just over 3ºC the September average.
- Adelaide’s predicted top of 27ºC on Friday would be almost 9ºC above average for September
- Melbourne’s forecast of 25ºC on Saturday is around 7ºC above average for this early in spring.
While the forecast of 28-30ºC for Sydney over the weekend seems like it could be a record for early spring, Sydney’s highest recorded September temperature was 34.6ºC on September 26, 1965.
After this early-spring warmth, temperatures will plummet as a cool change sweeps through between Saturday and Monday (figure 2).
Figure 2: ECMWF surface temperature at 1pm EST on Sunday, September 12, showing warm air ahead of the cold front and a cool change behind.
The change should reach Adelaide on Saturday evening, Melbourne Sunday morning, Sydney Sunday evening and Brisbane by Monday evening. Temperatures are likely to drop by around 6-12ºC in the wake of this change.
Looking ahead, temperatures will stay on the cooler side early-to-mid next week, with cool southerly winds, cloud, and showers all on the forecast. Daytime maximums will stay 2-5ºC below average for the south-eastern capital cities for about three days following the cool change.
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