Northern Territory in October to April 2011-12: An average wet season?

  • Gove and Jabiru recorded their wettest December on record
  • Darwin had its equal longest dry spell in January
  • Yulara Aero and Curtain Springs recorded their coolest October to March period in over a decade

An average wet, full of extremes

The 2011-2012 wet season ended up as an average wet where extreme events antagonised each other. In terms of temperature there was a marked contrast between the north and south. In terms of rainfall, when compared with last years record-setting wet season this season seemed very dry. However, the 2011-2012 wet season will go down in history records as an average wet were long dry periods were interspersed by short but very wet, bursts.

Tropical cyclone Grant

After a few days where a tropical low over the Arafura Sea struggled to maintain persistent development, tropical cyclone Grant was named at 3:30am local time on Christmas Day, Sunday the 25th. The system reached maximum intensity on the 25th with sustained winds of 55 knots but was downgraded to below tropical cyclone strength on the following day. Ex-tropical cyclone Grant moved east over Arnhem Land bringing heavy rains to the eastern Top End. Both Jabiru and Gove, managed to end the month with very much above average rainfall, their wettest December on record. By the end of December the ex-tropical cyclone re-emerged over the Gulf of Carpentaria and continued eastwards towards Queensland. Tropical cyclone Grant was the only tropical cyclone to make landfall in the Northern Territory in the 2011-2012 tropical cyclone season. Despite only one tropical cyclone being named in the seas surrounding the Northern Territory, there were several tropical lows that did intrude further into land, contributing to rainfall across most of the Top End.

Longest January dry spell for Darwin Airport

Darwin Airport registered its equal longest dry spell for any January matching the one set in 1948, with 10 consecutive days from the 4th to the 13th, inclusive. However, this was followed by a vigorous active phase of the monsoon which dumped over 350 mm of rain at the end of the month. While long dry spells are normal for any given wet season, the monsoon breaks this season were usually followed by vigorous active phases of the North Australian Monsoon (NAM), allowing Darwin Airport to end up with above average rainfall for the wet season.. The 2011-2012 wet season had 116 rain days (the average being 106 days) and 96 dry days were no precipitation was recorded at Darwin Airport. This gives an average of 16.1 mm of rain per rainy day while the long-term average is 15.8 mm per rainy day.

Rainfall

Rainfall across most of the Northern Territory was average to very much above average from 1 October to 30 April, with the exception of some locations in the western Arnhem and northern Roper-McArthur. Area-averaged rainfall across the Northern Territory was 22% above normal with 614 mm. This makes the 2011-2012 wet season, the 17th wettest. There was however, a big contrast between the early wet season and the late wet season. Area-averaged, the Northern Territory had above average rainfall throughout October, November and December despite a dry start to October. Several stations recorded their wettest November on record primarily due to La Niña conditions in the Pacific Ocean.

Although this season experienced a slightly early onset of the NAM, 2012 saw the driest start to any year for most locations in the Northern Territory. However, a burst of an active monsoon half way through January brought totals back to average. Short after, the dry conditions seen in early January quickly returned and persisted throughout most of February with most stations north of Alice Springs receiving well below their average rainfall. Dum-in-Mirrie and Batchelor, recorded their second driest February on record while Gove Airport ended the wet season with a total rainfall of 1341.8 mm, 28.1 mm above average. With 85 rainy days, Gove was just two days shy of the average number of rain days for the wet season (87 days). On average, a rainy day in the wet season brings 15 mm of rain, while this season's was 16 mm per day.

Although many stations received over two meters of rain in the previous wet season and three even exceeded three meters, only two stations in the Northern Territory managed to break through the two meters mark this wet season. The wettest overall was Geriatric Park with 2202.0 mm, followed by Walker Creek with 2005.4 mm, followed by Majestic Orchids with 1924.5 mm. Over the eastern Top End, and despite receiving in excess of 150 mm of their average, Alyangula Police and Groote Eylandt Airport had their driest wet since 2004 with 919.7 mm and 1089.6 mm of rain respectively. The driest overall was Bond Springs Turnoff with 47.0 mm, followed by Wigley Gorge with 164.0 mm, and then Mount Lloyd with 166.0 mm.

The wettest single day was at Edith Falls Ridge with 385.0 mm on 27 Dec 2011 as tropical cyclone Grant moved south over the base of the Top End, followed by Cullen River with 342.0 mm and by Upper Seventeen Mile Creek with 311.2 mm all on the same day. Some sites registered their highest October to April daily rainfall on record.

Temperature

Area-averaged, the mean minimum temperature for the Northern Territory during the 2011-2012 wet season was 21.4 °C, 0.6 °C below the norm making it the equal 7th coolest wet season nights. Similarly, the mean maximum temperature for the Territory was 34.4 °C, 0.6 degrees below the norm and the 12th coolest on record. Combining both minimum and maximum temperatures, the average temperature was 27.9 °C, 0.6 degrees below the norm making it the equal 10th coolest wet season on record. To that note, November 2012 was particularly cold with below average temperatures Territory-wide. Central parts of the Northern Territory recorded mean temperatures 1 °C to 3 °C below average, making it the 5th coolest on record.

Although, the Northern Territory was below average as a whole, there was a contrast between the Top End and the south. The mean temperature (both maximum and minimum temperatures combined) for Gove Airport was 28.2 °C, the second warmest on record which stands at 28.3 set in 1987. The warmest on average for the Territory was Timber Creek with 30.0 °C, followed by Centre Island with 29.8 °C and then by Cape Don and Jabiru Airport with 29.7 °C. Over the south, both Curtin Springs and Yulara Aero recorded their lowest wet season mean temperature since 2001 with 25.4 °C and 25.2 °C respectively. The coolest on average was Arltunga with 24.4 °C, followed by Alice Springs Airport with 25.1 °C and then by Yulara Aero with 25.2 °C. Aslo worth mentioning was Borroloola in the Gulf of Carpentaria which recorded a mean temperature of 28.6 °C, its third coolest wet season since records began in 1994.

Maximum temperature

Maximum temperatures where generally below average across the lower half of the Northern Territory, south of Katherine. Over the north, decreased cloud activity due to long break periods in the NAM and warm Sea Surface Temperatures across northern Australia led to above average temperatures over most of the Top End. Temperatures were very much above average over the Gove Peninsula, Greater Darwin Area and Tiwi Islands. Gove Airport's mean maximum temperature over this period was 32.4 °C, 0.6 °C above the average making it the second hottest wet season when it comes to daytime temperatures. Pirlangimpie ended up at 33.1 °C for the mean maximum, also 0.6 °C above average and their 3rd hottest on records. In Darwin, the period from 1 December 2011 through to 29 February 2012 recorded a mean maximum temperature of 32.8 °C, 0.9 °C above average and the 3rd hottest 'summer' period on record. The previous December to February record was 33.0 °C, which was set in 1969.

Over the southern districts cooler days prevailed throughout most of the wet season. During January, Yulara registered a mean maximum temperature of 36.2, their coolest January since records began in 1984. Borroloola with a mean maximum temperature of 34.6 °C for the wet season had its 4th coolest, 0.4 °C below their average. However, early April was very warm in the Alice Springs District, with several locations measuring above 36 °C during the first five days, including three days above 38 °C. As such, several sites had their highest April temperature on record including Yuendumu, Rabbit Flat and Papunya.

The hottest day was at Yulara Aero with 44.3 °C on 25 Dec 2011, followed by Walungurru with 44.2 °C on 16 Feb 2012 and then by Ali Curung with 44.1 °C on 31 Dec 2011.

The warmest days on average were at Kidman Springs with 36.6 °C, followed by Rabbit Flat with 36.6 °C and then by Timber Creek with 36.5 °C.

The coolest days on average were at Arltunga with 31.8 °C, followed by Kulgera with 32.2 °C and by Ngayawili with 32.3 °C.

The coldest day in the NT this season was 21 November, 2011, when the daily maximum temperature at Kulgera was only 14.7 °C, Curtin Springs got up to only 14.9 °C and Yulara Aero had 15.3 °C.

Some sites had their highest October to April temperature on record. Some sites had their coldest October to April day (lowest maximum temperature) on record.

Minimum temperature

On average, milder minimum temperatures were observed across the Territory during the wet season when compared to maximum temperatures. Similar to the maximum temperatures, above average minimum temperatures prevailed over the Top End, while below average minimum temperatures prevailed over central parts of the Northern Territory and the southern Alice Springs District. Over the northeast, Groote Eylandt Airport registered a mean miminum temperature of 23.7 °C, their 3rd highest on record. Similarly, over the opposite side of the Top End, Pirlangimpi recorded a minimum temperature of 24.4 °C their 3rd hottest on record.

Further south, rainy days and clear nights allowed Batchelor to register a mean night-time temperature of 23.2 °C, their 3rd lowest on record. Timber Creek with a mean minimum temperature of 23.5 °C had its 4th coolest wet season since records began in 1981. By the end of April, the Norther Territory had a taste of the dry season to come as a dry surged spread across the Territory. On 29 April, just two days before th official end of the wet season, the minimum temperature at Darwin Airport dropped to 18.8 °C, their lowest April night-time temperature in 43 years. Finally, Borroloola managed to register a mean night-time temperature of 22.5 °C, 1.0 °C below average and its lowest October to April mean daily minimum temperature on record.

The coldest night was at Alice Springs Airport with 4.4 °C on 26 Apr 2012 and by Kulgera with 4.5 °C on 12 Apr 2012.

The coolest nights on average were at Arltunga with 17.0 °C, followed by Alice Springs Airport with 17.1 °C and then by Kulgera with 17.4 °C.

The warmest nights on average were at Cape Don with 26.7 °C, followed by North East Island with 26.3 °C and then by Centre Island with 26.2 °C.

The warmest night was at Jervois with 30.5 °C on 7 Jan 2012.

Some sites had their lowest October to April temperature on record. Some sites had their lowest October to April mean daily minimum temperature for at least 10 years.

Wind

The strongest wind gust registered over the wet season was at McCluer Island with 126 km/h on 25 Dec 2011, the day tropical cyclone Grant was named over the Arafura Sea. Tennant Creek Airport registered a maximum wind gust of 117 km/h on 23 Jan 2012, followed by Rabbit Flat with 107 km/h on 11 Dec 2011.

 

Further information

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Extremes in October to April 2011-12
Hottest day 44.3 °C at Yulara Aero on 25 Dec 2011
Warmest days on average 36.6 °C at Kidman Springs
36.6 °C at Rabbit Flat
Coolest days on average 31.8 °C at Arltunga
Coldest day 14.7 °C at Kulgera on 21 Nov 2011
Coldest night 4.4 °C at Alice Springs Airport on 26 Apr 2012
Coolest nights on average 17.0 °C at Arltunga
Warmest nights on average 26.7 °C at Cape Don
Warmest night 30.5 °C at Jervois on 7 Jan 2012
Warmest on average overall 30.0 °C at Timber Creek
Coolest on average overall 24.4 °C at Arltunga
Wettest overall 2202.0 mm at Geriatric Park
Driest overall 47.0 mm at Bond Springs Turnoff
Wettest day 385.0 mm at Edith Falls Ridge on 27 Dec 2011
Highest wind gust 126 km/h at McCluer Island on 25 Dec 2011

Maps


Maps
Observed Anomaly Decile rank
Total
rainfall
Map of Rainfall totals Map of Percentage of normal rainfall Map of Rainfall deciles

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

Month by month
Rainfall rankMaximum temperature rankMinimum temperature rank
October
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
November
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
December
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
January
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
February
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
March
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
April
Map of decile rank of rainfall Map of Decile rank of mean maximum temperature Map of Decile rank of mean minimum temperature
Rainfall rankMaximum temperature rankMinimum temperature rank

Record highest October to April daily rainfall
Highest daily rainfall (mm) Previous wettest
for October to April
Years of
record
Cdu Katherine Rural Campus 255.0 on 25 Dec 2011 250.0 on 11 Jan 2002 37
Mallapunyah 287.0 on 26 Jan 2012 282.0 on 29 Jan 2010 43
Yambah 107.4 on 1 Mar 2012 98.0 on 18 Mar 1983 43
Gilnockie 143.4 on 1 Mar 2012 135.6 on 16 Feb 1991 22




Record highest October to April temperature
Highest temperature (°C) Previous warmest
for October to April
Years of
record
Average for
October to April
Black Point 36.4 on 15 Nov 2011 36.1 on 19 Oct 2009 16 32.0




Record lowest October to April temperature
Lowest temperature (°C) Previous coolest
for October to April
Years of
record
Average for
October to April
Channel Point 16.5 on 30 Apr 2012 17.0 on 27 Apr 2008 18 24.6
Bradshaw 13.5 on 28 Apr 2012 14.0 on 26 Apr 2008 14 24.5
Dum In Mirrie 18.0 on 30 Apr 2012 18.2 on 26 Apr 2008 14 25.4
Middle Point 13.8 on 29 Apr 2012 15.1 on 27 Apr 2008 11 23.5



Record lowest October to April mean daily minimum temperature
Mean daily minimum
temperature
for October to April 2011-12 (°C)
Previous coolest
for October to April
Years of
record
Average for
October to April
Borroloola 22.5 22.8 in 2010 17 23.4



Summary statistics for October to April 2011-12
Maximum temperatures
for October
to April
(°C)
Minimum temperatures
for October
to April
(°C)
Rainfall
for October
to April
(millimetres)
Mean for
October
to April
2011-12
Diff
from
average
Highest for
October
to April
2011-12
Mean for
October
to April
2011-12
Diff
from
average
Lowest for
October
to April
2011-12
Total for
October
to April
2011-12
Average
for
October
to April
Rank of
October
to April
2011-12
Fraction of
October
to April
average
Darwin-Daly (district 14GA)
Batchelor Aero 33.8 -0.3 38.6 18 Oct 2011 23.2 -0.2 13.5 29 Apr 2012 1431.8 1565.9 average 91%
Cape Don 32.7   35.4 17 Jan 2012 26.7   22.6 18 Feb 2012 1190.4 1225.9 average 97%
Central Arnhem Plateau 32.7   37.7 13 Jan 2012 22.5   13.9 29 Apr 2012 1210.2
Darwin Airport 32.8 +0.4 35.8 27 Nov 2011 24.7 -0.1 18.8 29 Apr 2012 1869.6 1686.7 high 111%
Delamere Weapons Range 35.5 +0.2 42.3 13 Jan 2012     14.1 27 Apr 2012 686.2 882.4 low 78%
Jabiru Airport 34.9 0.0 39.2 31 Oct 2011 24.5 +0.1 18.3 29 Apr 2012 1567.2 1533.2 average 102%
Mango Farm 34.9 +0.1 39.5 12 Oct 2011 23.0 -0.2 14.2 29 Apr 2012 1494.4 1418.6 average 105%
Middle Point 34.4 -0.2 39.8 14 Oct 2011 23.2 -0.3 13.8 29 Apr 2012 1484.6 1421.5 average 104%
Pirlangimpi 33.1 +0.6 36.7 31 Oct 2011 24.4 +0.5 17.8 29 Apr 2012 1907.2 1947.6 average 98%
Port Keats Aero 33.7 +0.2 38.9 25 Dec 2011 24.3 -0.1 15.6 29 Apr 2012
Tindal RAAF 35.2 +0.1 40.7 12 Oct 2011 23.4 -0.3 12.3 29 Apr 2012 797.2 1061.8 low 75%
Arnhem (district 14BC)
Gove Airport 32.4 +0.6 37.6 11 Dec 2011 23.9 +0.2 18.7 2 Oct 2011 1341.8 1313.7 average 102%
Groote Eylandt Airport 33.4 +0.1 39.1 11 Oct 2011 23.7 +0.1 15.3 3 Oct 2011 1089.6 1349.2 low 81%
Ngayawili 32.3 +0.3 36.7 27 Nov 2011 24.8 +0.2 19.1 29 Apr 2012 1554.6 1519.6 average 102%
North East Island 32.6   35.8 13 Jan 2012 26.3   23.0 9 Mar 2012 836.0 818.3 average 102%
Warruwi 32.6 +0.4 36.3 15 Oct 2011 25.5 -0.1 22.1 30 Apr 2012 1018.6 1129.7 average 90%
Roper-Mcarthur (district 14DE)
Borroloola 34.6 -0.4 40.7 11 Oct 2011 22.5 -0.9 10.9 30 Apr 2012 1048.2 944.4 average 111%
Centre Island 33.3 0.0 38.2 14 Oct 2011 26.2 -0.1 19.2 26 Apr 2012 1229.4 1047.4 high 117%
Daly Waters 35.6 -0.3 41.7 12 Oct 2011 22.1 -0.6 13.0 3 Oct 2011 761.2 650.9 high 117%
Larrimah 35.1 -0.6 41.2 11 Oct 2011 22.4 -0.7 11.1 27 Apr 2012 754.9 844.8 average 89%
McArthur River Mine 35.7 -0.8 41.6 11 Oct 2011 23.4 0.0 13.2 29 Apr 2012 1047.1 752.3 high 139%
Ngukurr 35.8 -0.2 42.3 11 Oct 2011     17.0 26 Apr 2012 758.1 754.7 average 100%
Wollogorang     40.3 11 Oct 2011 22.2 -0.4 11.9 3 Oct 2011 811.5 936.8 average 87%
Victoria (district 14F)
Kidman Springs 36.6 -0.1 43.0 13 Oct 2011 23.8 -0.1 11.9 28 Apr 2012 658.6 736.2 average 89%
Lajamanu 36.4 0.0 43.1 15 Feb 2012 21.8 -0.4 8.7 27 Apr 2012 499.2 485.6 average 103%
Timber Creek 36.5 0.0 43.6 12 Oct 2011 23.5 -0.6 11.9 27 Apr 2012 901.5 961.1 average 94%
Victoria River Downs 36.2 -0.2 42.9 12 Oct 2011 23.2 -0.3 9.6 29 Apr 2012 777.4 641.7 high 121%
Wave Hill 36.3 -0.4 42.3 11 Oct 2011     9.7 28 Apr 2012 841.3 672.0 high 125%
Barkly (district 15A)
Brunette Downs 35.6 -0.8 42.9 5 Feb 2012 22.0 -0.7 10.5 27 Apr 2012 465.5 393.8 high 118%
Tennant Creek Airport 34.4 -0.8 43.2 5 Feb 2012 22.7 -0.6 12.0 26 Apr 2012 562.2 444.1 average 127%
Alice Springs (district 15B)
Alice Springs Airport 33.1 -0.1 42.7 4 Jan 2012 17.1 -0.8 4.4 26 Apr 2012 194.4 219.6 average 89%
Arltunga 31.8 -1.1 40.9 6 Jan 2012 17.0 -1.5 4.6 28 Apr 2012 234.6 241.4 average 97%
Curtin Springs 32.9 -1.3 43.1 17 Feb 2012 17.7 -0.6 6.2 26 Apr 2012 390.8 172.6 v high 226%
Jervois 34.5 -0.7 43.6 30 Jan 2012 19.4 +0.2 6.7 2 Oct 2011 195.6 240.8 average 81%
Kulgera 32.2 -0.7 42.3 17 Feb 2012 17.4 -1.0 4.5 12 Apr 2012 234.9 198.2 average 119%
Rabbit Flat 36.6 -0.5 43.3 17 Feb 2012 21.1 -0.4 8.9 27 Apr 2012 262.1 448.9 low 58%
Territory Grape Farm 34.1 -0.4 41.6 30 Jan 2012 19.4 +0.4 7.0 26 Apr 2012 258.4 245.7 average 105%
Walungurru 35.8   44.2 16 Feb 2012 22.2   12.6 27 Apr 2012 264.8 221.8 average 119%
Yulara Aero 32.8 -1.8 44.3 25 Dec 2011 17.6 -1.3 6.1 26 Apr 2012 427.4 226.9 high 188%

Notes

A Seasonal Climate Summary is prepared to list the main features of the weather in Northern Territory 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 3 pm on Monday 30 April 2012. 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
(03) 9669 4057
Enquiries