Northern Territory in December 2011: A mix of wet & dry, hot & cool

Tropical Cyclone Grant brought heavy rains to the eastern Top End. Gove and Jabiru both recorded their wettest December on record while Darwin Airport and Alice Springs had below average rainfall.

Tropical Cyclone Grant

For several days numerical weather prediction models were consistently developing a low off the north coast, however the location and movement was unclear. On Wed 21st, a surface low was identified to the north of the Cobourg Peninsula by satellite observations. During the next few days, multiple vortices developed within a sharp shear line along the monsoon trough with initially, strong, southeast winds feeding in followed by a strengthening monsoon feeding in from the north. The system lacked persistent deep convection and did not develop to tropical cyclone strength for several days. On the 23rd, the low started showing signs of development in the cloud structure, however the system still struggled to maintain persistent development. Overnight on Saturday the 24th, further development occurred and TC Grant was named at 3:30am on Christmas Day, Sunday the 25th.

McCluer Island was the only station that reported gales. Gusts to 35kt were first observed at 4am on the 25th and mean winds of 35kt were first observed at 10am on 25th. These winds steadily increased and at 12pm, storm force winds of 51kt gusting to 61kt were reported. TC Grant then moved in a south southwest direction along the coast over the far eastern Van Diemen Gulf. It was weakening, but maintained as a Category 2 system until early on the 26th. At 6:30am it had crossed the coast again at the southeastern corner of the Van Diemen Gulf as a Category 1 system. By mid-day on the 26th it was downgraded to below TC strength.

Ex-TC Grant moved east over Arnhem Land and re-emerged over the Gulf of Carpentaria and continued eastward over the Cape York Peninsula and then into the Pacific Ocean but did not regain cyclone strength.

Flash Floods

On the 26th, Ex-TC Grant moved southwards, west of Jabiru, then slowed down as it gradually turned southeast and then east overnight on the 26th near Pine Creek. During this time rainfall of over 300 mm fell in the Edith, Cullen, Fergusson and Katherine River Catchments, including 385 mm at Edith River Ridge, resulting in flash flooding along those rivers.

Rainfall

Gove Airport already had above average rainfall for December when the monsoon trough moved over in the last few days of the month giving them their highest total December rainfall on record with 516.4 mm. Jabiru airport was similar, they had already received 378.2 mm of rainfall up to the 23rd of the month, including 87.2 mm on the 4th. And then as ex-TC Grant moved into the region an additional 71 mm fell on the 26th. By the end of the month a total of 459 mm had fallen passing the previous December record of 413.9 which fell in December 1977.

The wettest overall was Ngayawili with 607.8 mm, followed by Edith Falls Ridge with 566.4 mm, and then Warruwi with 559.8 mm.

The wettest single day was on the 27th as ex-TC Grant pushed inland. The highest rainfall totals from this event were Edith Falls Ridge with 385.0 mm, followed by Cullen River with 342.0 mm, and then Upper Seventeen Mile Creek with 311.2 mm.

Some sites, including Centre Island and Fergusson River, had their highest December daily rainfall on record.

Maximum temperature

Between the 3rd and 5th areas of The Barkly and northern Alice Springs districts experienced refreshingly cool days. Daily maximum temperatures were 8-12 degrees below the long term average. Alice Springs Airport measured a maximum temperature of only 26.2 °C on the 3rd which is 9 °C below their monthly average, Curtin Springs measured only 27 °C on the 4th, and Jervois saw a high of only 26.3 on the 4th which is 11.4 °C below their long term average. Temperatures quickly rebounded to near average temperatures for the remainder of the month.

The hottest day was at Yulara Aero with 44.3 °C on the 25th, followed by Ali Curung with 44.1 °C on the 31st, and then Walungurru with 43.2 °C on the 10th.

The warmest days on average were at Rabbit Flat and at Walungurru both with 37.8 °C, followed by Lajamanu with 37.7 °C, and then Ali Curung with 37.5 °C.

The coolest days on average were at Black Point with 32.1 °C, followed by Ngayawili with 32.2 °C, and then Alyangula Police and Central Arnhem Plateau which both had 32.4 °C.

The coldest day was at Tennant Creek Airport with 24.4 °C on the 3rd, and at Central Arnhem Plateau which also had 24.4 °C but on the 27th. These were followed by Papunya with 25.0 °C on the 14th, and then Tindal RAAF with 25.1 °C on the 26th, and Borroloola which also had 25.1 °C on the 27th.

Channel Point and Port Keats Aero both measured their highest December temperature on record. A few other temperature records include Tindal RAAF and Borroloola which had their coldest December day (lowest maximum temperature) on record. Alyangula Police their lowest December mean daily maximum temperature on record.

Minimum temperature

Minimum temperatures were average to above average along the north coast and in the Alice Springs District, but were below average across central NT. When averaged across the Territory, the monthly mean minimum temperature was 17.4 °C which is 1.1 °C below average. Black point had their lowest December temperature on record with 20.1 °C on the 27th breaking the old record of 21.2 set on the 30th in 1996. Channel Point tied their highest December mean daily minimum temperature on record with 25.8 °C which ties their record set in December 2000. Four sites, including Rabbit Flat and Timber Creek, had their lowest December mean daily minimum temperature on record.

The coldest night was at Kulgera with 10.5 °C on the 2nd, followed by Arltunga with 12.0 °C on the 7th, followed by Kulgera with 12.8 °C on the 1st.

The coolest nights on average were at Arltunga and Kulgera which both had an average minimum temperature of 18.9 °C. The next coolest places were Alice Springs Airport and Yulara Aero which both had 19.1 °C, and then Curtin Springs with 19.2 °C.

The warmest nights on average were at Cape Don with 27.5 °C, followed by Centre Island with 26.8 °C.

The warmest night was at Ngayawili with 29.9 °C on the 10th followed by Centre Island with 29.8 °C on the 11th.

Wind

The strongest wind gust was at McCluer Island with 126 km/h as TC Grant made landfall on the 25th, followed by Rabbit Flat with 107 km/h on the 11th, followed by Yulara Aero with 98 km/h on the 21st.

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Extremes in December 2011
Hottest day 44.3 °C at Yulara Aero on the 25th
Warmest days on average 37.8 °C at Rabbit Flat
37.8 °C at Walungurru
Coolest days on average 32.1 °C at Black Point
Coldest day 24.4 °C at Tennant Creek Airport on the 3rd
24.4 °C at Central Arnhem Plateau on the 27th
Coldest night 10.5 °C at Kulgera on the 2nd
Coolest nights on average 18.9 °C at Arltunga
18.9 °C at Kulgera
Warmest nights on average 27.5 °C at Cape Don
Warmest night 29.9 °C at Ngayawili on the 10th
Warmest on average overall 30.9 °C at Walungurru
Coolest on average overall 26.6 °C at Arltunga
Wettest overall 607.8 mm at Ngayawili
Wettest day 385.0 mm at Edith Falls Ridge on the 27th
Highest wind gust 126 km/h at McCluer Island on the 25th

Record highest December daily rainfall
Highest daily rainfall
in December 2011 (mm)
Previous wettest
for December
Years of
record
Centre Island 146.0 on the 28th 137.0 on the 26th in 2000 44
Mary River Rangers 192.8 on the 27th 155.1 on the 28th in 1993 23
North East Island 95.0 on the 23rd 94.0 on the 12th in 1993 21
Cape Wessel 148.8 on the 24th 66.0 on the 21st in 2003 20
Nitmiluk Rangers 184.6 on the 27th 157.0 on the 22nd in 2003 15
Fergusson River 144.4 on the 27th 96.8 on the 22nd in 2010 12
Seventeen Mile Creek 184.5 on the 27th 127.5 on the 22nd in 2003 12



Record highest total December rainfall
Total rainfall
for December 2011 (mm)
Previous wettest
for December
Years of
record
Average for
December
Gove Airport 516.4 372.6 in 1999 35 174.1
Jabiru Airport 459.0 413.9 in 1977 33 227.0
Yirrkala Tropical Gardens 549.0 338.0 in 1992 22 136.4
North East Island 419.6 283.0 in 1993 19 76.8
Ngayawili 607.8 574.0 in 2003 11 249.4





Record highest December temperature
Highest temperature
in December 2011 (°C)
Previous warmest
for December
Years of
record
Average for
December
Channel Point 35.7 on the 25th 35.4 on the 16th in 2004 16 32.3
Port Keats Aero 38.9 on the 25th 37.9 on the 6th in 2006 10 33.4



Record lowest December daily maximum temperature
Lowest daily maximum
temperature
in December 2011 (°C)
Previous coolest
for December
Years of
record
Average for
December
Larrimah 26.0 on the 27th 26.1 on the 6th in 2000 44 36.8
Tindal RAAF 25.1 on the 26th 26.1 on the 22nd in 2003 22 35.6
Borroloola 25.1 on the 27th 26.1 on the 31st in 2001 16 36.5
McCluer Island 28.9 on the 22nd = 28.9 on the 11th in 2009 11 32.1
Ngayawili 27.3 on the 23rd 28.7 on the 28th in 2007 11 32.7



Record lowest December mean daily maximum temperature
Mean daily maximum
temperature
for December 2011 (°C)
Previous coolest
for December
Years of
record
Average for
December
Alyangula Police 32.4 = 32.4 in 2000 28 33.9




Record lowest December temperature
Lowest temperature
in December 2011 (°C)
Previous coolest
for December
Years of
record
Average for
December
Black Point 20.1 on the 27th 21.2 on the 30th in 1996 18 26.2



Record highest December mean daily minimum temperature
Mean daily minimum
temperature
for December 2011 (°C)
Previous warmest
for December
Years of
record
Average for
December
Channel Point 25.8 = 25.8 in 2000 16 25.0



Record lowest December mean daily minimum temperature
Mean daily minimum
temperature
for December 2011 (°C)
Previous coolest
for December
Years of
record
Average for
December
Timber Creek 24.4 24.6 in 2000 29 25.4
Borroloola 24.2 = 24.2 in 2000 16 25.4
Rabbit Flat 22.4 22.6 in 2000 14 23.7
Port Keats Aero 24.8 = 24.8 in 2006 10 25.7




Summary statistics for December 2011
Maximum temperatures
(°C)
Minimum temperatures
(°C)
Rainfall
(millimetres)
Mean Diff
from
average
Highest Mean Diff
from
average
Lowest Total Average
Rank Fraction of
average
Darwin-Daly (district 14GA)
Batchelor Aero 34.3 +0.6 36.8 10th 24.2 +0.1 20.6 2nd 149.2 280.6 low 53%
Black Point 32.1 -0.3 34.4 7th 26.3 +0.1 20.1 27th 498.6 208.8 v high 239%
Bradshaw 36.5 0.0 39.6 1st 24.9 -0.6 21.4 2nd 89.0 170.4 average 52%
Cape Don 32.9   35.1 16th 27.5   23.3 12th 311.2 265.4 average 117%
Central Arnhem Plateau 32.4   36.9 14th 23.3   20.9 27th 212.0
Channel Point 33.3 +1.0 35.7 25th 25.8 +0.8 22.0 2nd 67.8 331.9 v low 20%
Darwin Airport 33.3 +0.7 35.0 28th 25.7 +0.4 22.4 2nd 234.2 250.4 average 94%
Delamere Weapons Range 35.4 -0.3 38.7 31st 24.0 -0.5 20.7 4th 156.8 175.2 average 89%
Douglas River 35.0 0.0 37.5 14th 24.3 +0.7 22.5 2nd 170.6 204.2 average 84%
Dum In Mirrie AWS 33.2 +0.8 34.5 21st 26.4 +0.3 23.0 2nd 159.8 288.2 low 55%
Jabiru Airport 34.2 -0.8 37.1 10th 25.0 +0.1 23.2 14th 459.0 227.0 highest 202%
Mango Farm 35.5 +0.7 38.4 31st 24.1 +0.3 21.9 15th 167.0 243.7 average 69%
Middle Point AWS 34.7   36.7 14th 24.1   22.6 4th 213.6
Noonamah AWS 35.0   36.9 14th 24.2   22.6 5th 365.6
Oenpelli 34.0 -0.9 36.8 14th 24.7 +0.2 22.1 26th 484.0 224.6 v high 215%
Pirlangimpi 33.3 +0.7 35.7 4th 25.2 +0.5 22.1 13th 427.4 350.4 high 122%
Point Stuart AWS 32.7   34.8 11th 25.0   22.6 2nd 178.4 205.5 average 87%
Port Keats Aero 34.8 +1.4 38.9 25th 24.8 -0.9 22.3 5th 132.8 146.4 average 91%
Tindal RAAF 35.3 -0.3 38.9 14th 24.6 -0.2 21.7 27th 218.0 201.3 high 108%
Arnhem (district 14BC)
Alyangula Police 32.4 -1.5 35.6 11th     21.5 31st 376.8 163.3 v high 231%
Cape Wessel 33.3   36.2 14th     24.3 25th 385.8 121.6 v high 317%
Gove Airport 33.0 +0.1 37.6 11th 24.9 +0.3 23.4 23rd 516.4 174.1 highest 297%
Groote Eylandt Airport AWS 33.4 -0.9 36.8 30th 25.1 0.0 23.3 6th 304.8 189.0 v high 161%
Ngayawili 32.2 -0.5 34.7 4th 25.9 +0.3 23.2 5th 607.8 249.4 highest 244%
North East Island 32.9   35.7 16th 26.7   23.9 23rd 419.6 76.8 highest 546%
Warruwi 32.8 -0.4 34.6 15th 25.9 -0.3 23.7 12th 559.8 191.9 v high 292%
Roper-Mcarthur (district 14DE)
Borroloola 34.5 -2.0 38.8 10th 24.2 -1.2 19.7 4th 316.8 127.2 high 249%
Centre Island 33.7 -0.9 37.1 10th 26.8 -0.6 22.7 4th 466.2 124.1 v high 376%
Daly Waters AWS 35.3 -2.0 39.0 31st 23.2 -1.1 17.8 30th 89.2 104.9 average 85%
Larrimah 35.1 -1.7 38.2 10th 23.8 -0.7 20.5 4th 147.0 137.7 average 107%
McArthur River Mine 36.0 -1.8 40.3 10th 24.8 -0.1 19.6 4th 194.6 119.3 high 163%
Ngukurr 35.8 -2.2 39.6 10th 25.5 0.0 22.1 4th 152.0 130.0 average 117%
Wollogorang 35.6 -1.2 39.5 14th 23.4 -0.8 20.0 9th 66.6 162.1 low 41%
Victoria (district 14F)
Kidman Springs 36.6 -0.9 40.3 25th 25.0 -0.4 21.5 3rd 94.7 137.9 low 69%
Lajamanu 37.7 -0.3 41.6 31st 23.6 -0.6 19.4 4th 87.6 75.3 average 116%
Timber Creek 36.4 -0.8 39.5 25th 24.4 -1.0 21.0 4th 148.9 177.7 average 84%
Victoria River Downs 36.4 -1.4 40.7 31st 24.5 -0.6 21.6 3rd 115.2 117.2 average 98%
Wave Hill 36.9 -1.3 41.2 31st 23.6 -0.9 18.8 30th 89.1 117.2 average 76%
Barkly (district 15A)
Brunette Downs 36.9 -1.6 40.4 31st 23.6 -0.8 19.3 5th 37.4 67.1 average 56%
Elliott 35.9 -2.8 39.4 31st 23.8 -0.6 18.5 30th 136.9 95.4 high 144%
Tennant Creek Airport 35.4 -1.9 39.9 11th 23.6 -1.3 17.8 4th 105.0 67.4 high 156%
Alice Springs (district 15B)
Ali Curung 37.5 -0.3 44.1 31st     17.5 5th 22.6 63.8 low 35%
Alice Springs Airport 36.4 +1.0 42.2 25th 19.1 -1.1 13.2 5th 3.6 37.1 low 10%
Arltunga 34.6 +0.3 40.6 10th 18.9 -1.5 12.0 7th 21.8 40.0 average 55%
Curtin Springs 35.6 -0.7 42.9 25th 19.2 -1.3 13.0 5th 22.5 29.8 average 76%
Jervois 36.6 -1.2 41.4 10th 21.1 -0.2 15.8 5th 28.8 38.7 average 74%
Kulgera 34.9 -0.1 42.3 25th 18.9 -1.5 10.5 2nd 12.7 34.5 average 37%
Papunya 35.2   40.5 31st 21.1   15.0 4th 63.3 33.0 high 192%
Rabbit Flat 37.8 -0.6 42.5 11th 22.4 -1.3 16.6 4th 73.8 79.5 average 93%
Territory Grape Farm 36.5 +0.2 41.2 10th 22.1 +1.1 17.6 4th 57.6 45.0 average 128%
Walungurru 37.8   43.2 10th 23.9   16.8 4th 57.0
Yulara Aero 35.4 -0.9 44.3 25th 19.1 -1.6 13.9 6th 57.8 43.5 average 133%
Offshore Islands (district 200)
Northern Endeavour 34.1 +0.6 36.0 6th 28.1 0.0 25.0 11th

Notes

A Monthly 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 12 pm on Tuesday 3 January 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 the years 1800 to 2009. They are not shown for sites with less than 10 years of record in that time, 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