Monday, 1 October 2012 - Monthly Climate Summary for Northern Territory - Product code IDCKGC12R0

Northern Territory in September 2012: "The Build Up"

The month of September is usually the last month of the dry season with increase in temperatures and humidity across the Northern Territory. Typically in September, the sub-tropical ridge weakens as troughs with associated moisture punch into the Territory and the climate begins the transition into the wet season. This month was strongly influenced by the sub-tropical ridge as no rainfall was recorded until the last two days of the month.

• Dry spell in Alice Springs District ends with 157 days without rain
• Bushfires char NT
• "Build Up" is felt in Top End

Extremes Maps Records Summaries Important notes the top

Dry spell in Alice Springs Airport ends

On September 29th, a record long dry spell of 157 days without rain at Alice Springs Airport, ended as 3.0 mm fell on the 29th and 0.8 mm on the 30th. The rain came as a result of a mobile trough that pushed across the Territory producing a northwest cloudband and brought light rain along with it.

Bushfires

Bushfires in the NT continued throughout the month due to the strong sub-tropical ridge. Dry, gusty southeast and northerly winds along with high fuel load raised the FDI's across the Territory, and several Fire Bans were imposed by the authorities. A total of 52 Fire Bans and 55 Fire Warnings were issued with a few 'extreme' FDI events recorded especially over the Top End.

The Build Up

During the month of September there was a gradual increase in temperatures and humidity indicative of the "build up"or transition into the wet season in the Territory. As an example, the monthly average dew point temperature at Darwin Airport for August was 14.6 °C while the average for September was 19.6 °C. The build up is often characterized as frequent thunderstorms from an hot and humid unstable atmosphere near the surface. While September was mostly dry, without thunderstorms, the first "build up" storm developed in the western Top End on the 30th.

Rainfall

On 29 and 30 September, a mobile trough moved slowly across the NT creating a northwest cloudband on the 29th which brought light rain to the Alice Springs District, ending Alice Springs' 157 day, record long, dry spell. The trough slowly moved north and by the time it reached the Top End, early on the 30th, it not only caused broad scale cloudiness and light rain, but also induced surface based convection in some areas causing significant rainfall which exceeded long term monthly mean for many locations. On the 30th, Channel Island had 31.8 mm, Darwin Airport recorded 23.0 mm, Middle Point measured 39.2 mm and Oenpelli had 20.0 mm. While none of these were records, they were all well above the September monthly mean. Two stations did measure their highest September daily rainfall on record on the 30th. These are Nutwood Downs and Channel Point. Nutwood Downs also measured their highest total September rainfall on record. There is a map of rainfall deciles below.

The wettest overall was Wongalara with 64.8 mm, followed by Nutwood Downs with 47.8 mm, and then Cdu Katherine Rural Campus with 47.0 mm.

The wettest single day was the 30th when the highest falls were at Wongalara with 64.8 mm, followed by Nutwood Downs with 47.8 mm, and then Cdu Katherine Rural Campus with 47.0 mm on the 30th.

Temperature

During the month of September, temperatures gradually increased as the sub-tropical ridge weakened and more solar exposure allowed for surface heating. The mean temperature for September across the Northern Territory was 23.64 °C, which is 1.14 °C warmer than the long-term average.

The warmest on average was Jabiru Airport with 28.8 °C, followed by Delamere Weapons Range with 28.3 °C,and then both Cape Don and Darwin NTC with 28.2 °C. The coolest on average was Arltunga with 18.9 °C, followed by Alice Springs Airport with 19.7 °C, and then Curtin Springs with 19.9 °C.

Maximum temperature

The maximum temperatures across the Northern Territory recorded about 1 to 3 °C greater than the September monthly maximum of 31.38 °C, except along the northwest coast which is just below the average due to the sea breeze. Increasing solar exposure increased the daily maximum temperatures especially across the central Australia (about 4 °C greater then September average) and sea breezes kept the northwest cooler. Some sites, such as Tindal RAAF, and had their highest September temperature on record, while Alice Springs Airport tied their highest September temperature on record. Jabiru had its highest September mean daily maximum temperature on record. There is a map of maximum temperature anomalies below.

The hottest day was at Lajamanu with 41.1 °C on the 23rd, followed by Bulman with 41.0 °C on the 27th, and then Daly Waters with 40.9 °C on the 27th.

The warmest days on average were at Douglas River with 38.0 °C, followed by Noonamah and Timber Creek both with 37.5 °C, and then Jabiru Airport and Middle Point with 37.4 °C.

The coolest days on average were at Arltunga with 28.1 °C, followed by McCluer Island with 29.2 °C, and then North East Island with 29.4 °C.

The coldest day was at Arltunga with 16.5 °C on the 29th, followed by Alice Springs Airport with 18.4 °C on the 29th, and then Jervois with 19.7 °C on the 29th.

Minimum temperature

The minimum temperatures across the Territory were below average for most of the month especially over the Top End. However, in the Alice Springs District the minimum temperatures were above average due to weak troughs with northerly wind flow ahead of the trough which moved across the area.

The coldest night was at Arltunga with -0.4 °C on the 10th, followed by Arltunga with 0.0 °C on the 2nd, and then Arltunga again on the 3rd with 0.5 °C.

The coolest nights on average were at Arltunga with 9.4 °C, followed by Alice Springs Airport with 9.6 °C, and then Curtin Springs with 10.2 °C.

The warmest nights on average were at Darwin NTC and McCluer Island with 24.5 °C, followed by Cape Don with 24.3 °C, and then Cape Wessel with 24.0 °C.

The warmest night was at Timber Creek with 26.3 °C on the 30th, followed by Darwin NTC with 26.0 °C on the 27th, followed by Cape Don with 26.0 °C on the 30th, and then McCluer Island on the 13th and Darwin NTC on the 24th with both recorded 25.8 °C.

There is a map of minimum temperature anomalies below.

Wind

The strongest wind gust was at Central Arnhem Plateau with 72 km/h on the 29th, followed by Walungurru with 70 km/h on the 13th, and then both Ngayawili on the 12th and Territory Grape Farm on the 28th with 67 km/h

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Extremes in September 2012
Hottest day	41.1 °C at Lajamanu on the 23rd
Warmest days on average	38.0 °C at Douglas River
Coolest days on average	28.1 °C at Arltunga
Coldest day	16.5 °C at Arltunga on the 29th
Coldest night	-0.4 °C at Arltunga on the 10th
Coolest nights on average	9.4 °C at Arltunga
Warmest nights on average	24.5 °C at Darwin NTC AWS
Warmest night	26.3 °C at Timber Creek on the 30th
Warmest on average overall	28.8 °C at Jabiru Airport
Coolest on average overall	18.9 °C at Arltunga
Wettest overall	64.8 mm at Wongalara
Wettest day	64.8 mm at Wongalara on the 30th
Highest wind gust	72 km/h at Central Arnhem Plateau on the 29th

Extremes Maps Records Summaries Important notes the top

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Maps
	Observed	Anomaly	Decile rank
Total rainfall
Mean daily maximum temperatures
Mean daily minimum temperatures

Click on a map to show it full size in a pop-up window

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Record highest September daily rainfall
	Highest daily rainfall in September 2012 (mm)		Previous wettest for September		Years of record
Nutwood Downs	47.8	on the 30th	40.8	on the 24th in 1998	75
Channel Point	34.6	on the 30th	17.0	on the 18th in 2002	22

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Record highest total September rainfall
	Total rainfall for September 2012 (mm)	Previous wettest for September		Years of record	Average for September
Nutwood Downs	47.8	40.8	in 1998	75	3.9

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Record highest September temperature
	Highest temperature in September 2012 (°C)		Previous warmest for September		Years of record	Average for September
Alice Springs Airport	38.8	on the 22nd	= 38.8	on the 22nd in 2003	71	27.2
Daly Waters AWS	40.9	on the 27th	40.0	on the 26th in 2003	44	34.6
Tindal RAAF	40.0	on the 27th	39.9	on the 28th in 1992	25	35.7
Territory Grape Farm	38.2	on the 27th	38.0	on the 22nd in 2003	20	30.2

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Record highest September mean daily maximum temperature
	Mean daily maximum temperature for September 2012 (°C)	Previous warmest for September		Years of record	Average for September
Jabiru Airport	37.4	= 37.4	in 2009	34	36.2

Extremes Maps Records Summaries Important notes the top

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Summary statistics for September 2012
	Maximum temperatures for September (°C)				Minimum temperatures for September (°C)				Rainfall for September (millimetres)
	Mean for September 2012	Diff from average	Highest for September 2012		Mean for September 2012	Diff from average	Lowest for September 2012		Total for September 2012	Average for September	Rank of September 2012	Fraction of September average
Darwin-Daly (district 14GA)
Batchelor Aero	36.5	+0.5	38.4	23rd	19.6	-1.1	15.9	3rd	11.6	6.6	high	176%
Black Point	32.1	+0.5	34.2	15th	22.3	-0.8	19.9	2nd	0	1.0	lowest	0%
Cape Don	32.1		33.5	16th	24.3		23.2	8th	0.2	6.5	average	3%
Central Arnhem Plateau	34.9		38.3	27th	17.8		14.2	10th	15.0
Darwin Airport	33.8	+1.2	36.2	9th	21.9	-1.1	19.4	10th	23.0	15.7	high	146%
Darwin NTC AWS	31.9		34.6	10th	24.5		21.6	30th
Delamere Weapons Range	36.7	+1.1	39.5	22nd	20.0	-0.8	13.8	17th	1.0	3.4	average	29%
Douglas River	38.0	+1.4	40.2	23rd	16.8	-1.9	11.7	2nd	5.0	4.4	high	114%
Dum In Mirrie AWS	31.6	-0.1	35.6	10th	21.8	-1.4	18.8	2nd	4.0	13.8	average	29%
Jabiru Airport	37.4	+1.2	39.8	27th	20.4	-1.2	16.0	20th	0.4	6.3	average	6%
Katherine Country Club	37.3		40.4	28th	18.5		12.5	17th	26.6
Mango Farm	37.1	+0.8	40.0	24th	16.7	-2.7	12.0	3rd	3.4	8.3	average	41%
McCluer Island	29.2	0.0	31.8	1st	24.5	-0.2	22.2	1st	0	0.3	v low	0%
Middle Point AWS	37.4	+1.2	38.8	24th	17.1	-2.2	13.7	3rd	39.2	19.9	high	197%
Noonamah AWS	37.5		39.3	24th	18.2		12.8	10th	24.8
Pirlangimpi	34.6	+1.5	36.8	23rd	20.8	-0.5	18.1	3rd	0.6	27.4	low	2%
Port Keats Aero	33.6	0.0	36.4	16th	19.5	-1.6	15.2	16th	0.6	3.0	average	20%
Arnhem (district 14BC)
Cape Wessel	31.5		32.3	25th	24.0		22.9	7th	0	6.9	lowest	0%
Gove Airport	30.8	+0.5	33.5	18th	18.7	-1.1	16.0	17th	0	5.8	lowest	0%
Groote Eylandt Airport AWS	32.8	+0.2	35.5	27th	17.8	0.0	14.3	19th	0.4	2.9	average	14%
Maningrida Aero	32.4		34.9	9th	19.9		16.2	3rd	0.2
Milingimbi AWS	31.7		34.3	9th	21.0		18.7	3rd	0	4.5	v low	0%
Ngayawili	31.9	+0.2	33.7	19th	20.2	-0.4	18.0	19th	1.0	7.3	high	14%
North East Island	29.4		31.9	27th	22.5		21.0	17th	2.6	0.8	high	325%
Warruwi	31.7	+0.8	33.9	17th	23.3	-0.3	20.2	1st	0	1.0	lowest	0%
Roper-Mcarthur (district 14DE)
Borroloola	35.9	+1.0	38.2	25th	17.4	-0.3	12.0	3rd	22.6	2.4	v high	942%
Bulman AWS	36.7		41.0	27th	15.7		11.0	2nd	35.8	3.8	v high	942%
Centre Island	31.1	+0.6	33.6	17th	22.1	-0.1	19.6	4th	1.2	1.4	average	86%
Daly Waters AWS	36.8	+2.2	40.9	27th	14.5	-2.5	7.6	17th	1.0	1.9	high	53%
McArthur River Mine	36.4	+1.2	39.3	27th	17.0	-0.2	10.5	3rd	21.8	5.3	v high	411%
Ngukurr AWS	36.5		40.2	27th	18.0		12.5	17th	13.2
Wollogorang	35.2	+0.8	38.6	26th	14.2	-1.7	9.5	17th	0	3.9	lowest	0%
Victoria (district 14F)
Lajamanu	35.7	+1.4	41.1	23rd	15.9	-0.7	8.3	16th	0	4.4	lowest	0%
Timber Creek	37.5	+1.0	40.3	25th	18.7	-1.9	11.8	4th	0	5.7	lowest	0%
Victoria River Downs	36.5	+1.0	40.3	23rd	14.8	-3.4	9.4	17th	0	4.2	lowest	0%
Wave Hill			36.8	13th	16.5	-1.4	10.2	10th	0	8.8	lowest	0%
Barkly (district 15A)
Elliott	36.1	+0.7	39.4	26th	16.3	-1.1	10.8	4th	7.8	6.0	high	130%
Tennant Creek Airport	32.9	+1.4	38.7	23rd	18.4	0.0	13.3	9th	8.8	7.9	average	111%
Alice Springs (district 15B)
Alice Springs Airport	29.6	+2.4	38.8	22nd	9.6	-0.7	1.0	1st	3.8	8.5	average	45%
Arltunga	28.1	+0.4	37.0	27th	9.4	-1.6	-0.4	10th	8.2	6.8	high	121%
Curtin Springs	29.5	+1.8	37.4	27th	10.2	+0.2	2.3	8th	3.4	10.0	average	34%
Jervois	30.3	+0.6	40.3	20th	11.6	+0.3	2.4	2nd	14.2	8.8	high	161%
Papunya	31.3	+0.2	37.5	27th	13.6		7.0	6th	6.8	7.2	high	94%
Rabbit Flat	35.3	+1.0	40.7	23rd	14.4	-0.1	6.0	10th	0	6.5	v low	0%
Territory Grape Farm	31.1	+0.9	38.2	27th	11.0	-1.0	4.7	9th	1.8	10.9	average	17%
Walungurru	32.9		39.0	27th	17.5		12.9	6th	1.8	10.0	high	18%
Yulara Aero	29.9	+1.3	38.0	27th	10.3	-0.4	1.0	6th	3.2	8.4	average	38%

Extremes Maps Records Summaries Important notes the top

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