Melbourne Metropolitan Area and Environs in September 2010: Cool and cloudy with slightly less rainfall than usual

  • Cool days
  • Average rainfall
  • Normal nights

Summary

Across the Melbourne Metropolitan Area, September 2010 was a cool and cloudy month, with slightly below average precipitation at most places. This was on account of persistent southwesterly flow with high pressures centred to the south of Western Australia bringing cool, moist air to Victoria.

The cloud acted as a "blanket" and overnight temperatures, therefore, were generally near to those usually experienced. However, the southern origin of the airmass meant that daytime temperatures at most localities were cooler than those registered in the past. A major frontal passage early in the month, resulted in a very wet couple of days in Melbourne, but total rainfall for September was generally slightly less than that usually recorded, on account of the subsequent frontal passages being relatively weak. The air following the front which moved across Victoria on the 28th was extremely cold, leading to snow flurries and near-zero temperatures on the Dandenongs during the morning of the 29th.

Details

Rainfall

High rainfalls were recorded in the first week of the month, with several stations registering daily totals of 10 to 20mm on the 4th. In fact, this was the wettest single day in the Central district, with 25.0 mm recorded at Avalon Airport.

Melbourne Airport was the driest location in September receiving just 40.2 mm, 6 mm below average. Melbourne Regional Office was also below its climatological average of 58 mm, observing just 49.6 mm. In fact, approximately 40 mm of this total was received in the first week of the month. Weak frontal systems meant that drizzle and weak rain accompanied persistent cloud cover but did not result in substantial rainfall totals.

Avalon Airport, Coldstream and Ferny Creek were the only stations to record slightly above average rainfall this month. In contrast, Scoresby and Bundoora were particularly low, receiving 30% less rainfall than usual for September.

Temperature

Maximum temperature

Warm days were few and far between this month, with maximum temperatures across the Central district, on average, more than 1.5C below normal. Overcast conditions and cool, moist south-westerly flow frequently kept daytime temperatures below 16C. Several sites also recorded their lowest average daytime September temperatures since the early 1990's this month.

A slow moving high pressure system brought sunny spring-like conditions to Melbourne for the AFL Grand final weekend, with 22.1C recorded at the Melbourne Regional Office on the 26th. This ended a long stretch of sub 20C temperatures at the Melbourne Regional Office; with 138 consecutive days making it the fourth longest such stretch since 1855.

Interestingly the coldest day at the Melbourne Regional Office this month was the 1st, reaching just 13.3C after a mild night (11.1C). This occurred as a result of the passing of a cold front which brought widespread rainfall and cloudy conditions.

Minimum temperature

Night-time temperatures were very close to average with frequent cloud cover preventing significant overnight cooling. The coldest nights were the 3rd, with clear skies bringing temperatures close to zero at Coldstream, and the 8th when most of the Central district experienced frosty temperatures of just 2C.

The warmest nights on average at 9.1C were experienced at the Melbourne Regional Office which was over 1C lower than normal. This site, not surprisingly, also observed the warmest night of the month (12.8C) for the Central district on the 27th.

Wind gusts

The strongest wind gust was 102 km/h at Laverton RAAF on the 5th, associated with the intensification of the tropical low pressure system which caused widespread flooding in northern Victoria.

Further information

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Extremes in September 2010
Hottest day 22.1 C at Melbourne Regional Office on the 26th
Warmest days on average 16.5 C at Melbourne Regional Office
Coolest days on average 10.4 C at Ferny Creek (Dunns Hill)
Coldest day 7.4 C at Ferny Creek (Dunns Hill) on the 10th
Coldest night 0.3 C at Coldstream on the 3rd
Coolest nights on average 4.9 C at Ferny Creek (Dunns Hill)
Warmest nights on average 9.1 C at Melbourne Regional Office
Warmest night 12.8 C at Melbourne Regional Office on the 27th
Wettest overall 99.8 mm at Ferny Creek (Dunns Hill)
Driest overall 40.2 mm at Melbourne Airport
Wettest day 25.0 mm at Avalon Airport on the 4th
Highest wind gust 102 km/h at Laverton RAAF on the 5th

Record lowest September mean daily maximum temperature
Mean daily maximum
temperature
for September 2010 (C)
Previous lowest
for September
Years of
record
Average for
September
Coldstream 15.1 15.7 in 2004 15 17.2
Viewbank (ARPANSA) 15.5 16.4 in 2004 10 17.8

Lowest September mean daily maximum temperature for at least 10 years
Mean daily maximum
temperature
for September 2010 (C)
Most recent September
this low or lower
Years since
lower
Average for
September
Laverton RAAF 15.6 14.1 in 1992 18 17.0
Melbourne Airport 15.1 13.7 in 1992 18 16.6
Scoresby Research Institute 15.1 14.1 in 1992 17 16.4
Bundoora (Latrobe University) 15.6 15.2 in 1994 16 16.9
Cerberus 14.8 14.7 in 1994 16 16.3
Cranbourne Botanic Gardens 14.8 14.6 in 1994 16 16.4
Ferny Creek (Dunns Hill) 10.4 10.2 in 1994 16 12.6
Melbourne Regional Office 16.5 16.0 in 1994 16 17.2
Moorabbin Airport 15.1 =15.1 in 1994 16 16.8
Avalon Airport 15.9 =15.9 in 1997 13 17.7



Summary statistics for September 2010
Maximum temperatures
for September
(C)
Minimum temperatures
for September
(C)
Rainfall
for September
(millimetres)
Mean for
September
2010
Diff
from
average
Highest for
September
2010
Mean for
September
2010
Diff
from
average
Lowest for
September
2010
Total for
September
2010
Average
for
September
Rank of
September
2010
Fraction of
September
average
Avalon Airport 15.9 -1.8 19.7 26th 6.6 0.0 1.3 8th 54.0 46.1 average 117%
Bundoora (Latrobe University) 15.6 -1.3 21.2 26th 7.7 +0.5 2.2 8th 43.8 58.9 low 74%
Cerberus 14.8 -1.5 18.1 25th 7.8 +0.4 1.9 3rd 63.0 66.5 average 95%
Coldstream 15.1 -2.1 20.9 26th 6.0 +0.6 0.3 3rd 72.6 69.5 average 104%
Cranbourne Botanic Gardens 14.8 -1.6 17.9 4th 7.6 -0.1 3.0 3rd 68.9 86.0 average 80%
Essendon Airport 15.4 -1.2 20.9 26th 7.1 +0.6 1.5 8th 42.2 50.8 average 83%
Ferny Creek (Dunns Hill) 10.4 -2.2 16.9 26th 4.9 -1.1 0.9 29th 99.8 92.0 average 108%
Laverton RAAF 15.6 -1.4 19.3 25th 6.9 +0.3 1.3 8th 41.6 49.6 average 84%
Melbourne Airport 15.1 -1.5 21.2 26th 6.8 -0.2 1.9 14th 40.2 46.1 average 87%
Melbourne Regional Office 16.5 -0.7 22.1 26th 9.1 +1.2 5.2 8th 49.6 58.0 average 86%
Moorabbin Airport 15.1 -1.7 19.3 26th 8.3 +0.4 2.2 8th 57.2 65.6 average 87%
Scoresby Research Institute 15.1 -1.3 20.8 26th 7.0 -0.5 1.0 8th 56.0 84.6 low 66%
Viewbank (ARPANSA) 15.5 -2.3 21.1 26th 7.6 -0.1 2.5 14th 52.4 53.7 average 98%

Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Melbourne Metropolitan Area and Environs using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 11 am on Friday 1 October 2010. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages are long-term means based on observations from all available years of record, which vary widely from site to site. They are not shown for sites with less than 10 years of record, as they cannot then be calculated reliably.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Media
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Enquiries