Monday, 3 October 2011 - Monthly Climate Summary for Northern Territory - Product code IDCKGC12R0
Northern Territory in September 2011: Bushfires and the "Build up"
- Extreme fire weather across Territory
- "Build up" begins in the top end
- Darwin Area enjoys 5 nights below 20 °C
Bushfires in NT
The Northern Territory has had several dry months following a record-setting wet season. The lush biota has now become ample fuel for bushfires in the NT. In addition to a high fuel load, dry and gusty southeast winds raised the fire danger index (FDI) across the Territory. The FDI reached "catastrophic" levels on the 13th and 14th for the Darwin and Batchelor regions. Several Fire Bans were imposed by fire authoritiesthroughout the month. Several thousands of square kilometers have burned around the Alice Springs area. Local media at Alice Springs reported that an area greater than Tasmania has been burned by bushfires this month.
The "Build Up"
The "build up" is a colloquialism used by many Territorians in the Top End to describe the transition between the dry season and the wet season. It is usually marked by rising temperatures and humidity. The average relative humidity at Darwin Airport has been showing a gentle rise since the last week of August (although the 10th through the 16th of September saw an unusual dip in relative humidity as a burst of dry air pushed up from the south). The average monthly dew-point temperature for September was 18.0 °C with a maximum of 22.7 °C on the 25th. Another sign of the "build up" is the increase in thunderstorm activity as the lower atmosphere becomes more unstable. An early season thunderstorm brought 20.8 mm of rain to Mango Farm on the 22nd.
September is considered the last month of the dry season in the Top End. It is typically very dry, but it is not uncommon for a few isolated thunderstorms to form. From these isolated thunderstorms, the wettest single day was at Mango Farm with 20.8 mm on the 22nd. The next wettest days were at Bond Springs with 20.0 mm on the 8th and then Pirlangimpi with 12.0 mm on the 20th. The wettest overall for the month was Bond Springs with 29.0 mm, followed by Mango Farm with 20.8 mm, and then Pirlangimpi with 14.2 mm.
The Alice Springs District usually gets between 5 mm and 10 mm in September from frontal passages along the southern border. This month, however, persistent high pressure over central Australia prevented most of the cold fronts from moving into the Territory. Several locations, including Alice Springs Airport, did not receive any rainfall this month. Alice Springs Airport has now not recorded any rain since 16 July, and only 17.6 mm since mid-March.
When combining maximum and minimum temperatures throughout the month, the NT was cooler than average for September. Some locations, including Port Keats and Daly Waters, even measured their lowest mean September temperature on record with average monthly temperatures of 23.5 °C and 26.0 °C respectively. With a mean monthly temperature of 27.8 °C, Bradshaw had their second coolest September on record. Katherine Aviation Museum ranked as the third coolest September on record with an average monthly mean temperature of 25.9 °C, this is 2 °C below average and only 0.6 °C above the record set in September 2004.
The warmest on average was Jabiru Airport with 28.8 °C, followed by Bradshaw with 27.9 °C, and then Cape Don with 27.8 °C. The coolest on average was Arltunga with 17.1 °C, followed by Yulara with 18.2 °C, and then Alice Springs Airport with 18.4 °C.
There were no maximum temperature records set in the Northern Territory this month. Most stations finished the month within 1 °C of the average. Darwin Airport had a mean monthly maximum temperature of 32.8 °C which is 0.3 °C above average. The monthly mean maximum temperature at Alice Springs Airport this month was 27.6 °C which is 0.6 °C above average. Some stations including Bradshaw, Rabbit Flat, Alyangula Police and Port Keats measured their second coolest September on record. With an average maximum temperature of 35.2 °C, Batchelor had their third coolest September on record.
The hottest day was at Bradshaw with 39.7 °C on the 30th and 39.2 °C on the 27th, followed by Jabiru Airport with 39.1 °C on the 22nd, and then Timber Creek where the mercury rose to 39.0 °C on both the 19th and the 26th. The warmest days on average were at Bradshaw, Timber Creek and Noonamah all with and average monthly maximum temperature of 36.3 °C, followed by Jabiru Airport and with 36.2 °C, and then Middle Point with 35.9 °C.
The coolest days on average were at Arltunga with 27.1 °C, followed by Kulgera with 27.7 °C, and then Alice Springs Airport with 27.9 °C. The coldest day was at Jervois with 16.2 °C and Arltunga with 17.6 °C both on the 8th. The next coldest day was also at Arltunga with 18.2 °C on the 9th.
The minimum temperatures around the Territory were average to a little below average for most of the month. Minimum temperatures at Darwin Airport dropped below 20 °C five times in the month. In an average September the minimum temperature at Darwin Airport will drop below 20 °C only once. The most September nights below 20 °C is seven, in 2004 and in 2006. Daly Waters had their lowest September temperature on record, with 4.3 ° on the 13th, and tied their lowest September mean daily minimum temperature on record with 12.8 °C. Yuendumu also tied their lowest September temperature on record, with 3.1 °C on the 13th
The coldest nights were all at Arltunga with -0.5 °C on the 15th, -0.4 °C on the 13th and -0.3 °C on the 11th. It is no surprise then that the coolest nights on average were at Arltunga with 6.9 °C. The next coolest nights on average were at Yulara with 8.4 °C followed by Alice Springs Airport with 8.9 °C.
The warmest nights on average were at Cape Don with 24.2 °C, followed by Warruwi with 23.3 °C and then Black Point with 22.7 °C. The warmest nights were all at Cape Don with 25.7 °C on the 30th, 25.3 °C on the 22nd, and 25.1 °C on the 19th.
Dry, gusty winds across southern NT fanned already extreme fire conditions. The strongest wind gust was at Yulara Aero with 78 km/h on the 27th, followed by Walungurru with 69 km/h on the 8th, followed by Jervois with 65 km/h on the 28th.
|Extremes in September 2011|
39.7 °C at Bradshaw on the 30th|
|Warmest days on average||
36.3 °C at Noonamah |
36.3 °C at Bradshaw
36.3 °C at Timber Creek
|Coolest days on average||27.2 °C at Arltunga|
|Coldest day||16.2 °C at Jervois on the 8th|
|Coldest night||-0.5 °C at Arltunga on the 15th|
|Coolest nights on average||6.9 °C at Arltunga|
|Warmest nights on average||24.2 °C at Cape Don|
|Warmest night||25.7 °C at Cape Don on the 30th|
|Warmest on average overall||28.8 °C at Jabiru Airport|
|Coolest on average overall||17.1 °C at Arltunga|
|Wettest overall||29.0 mm at Bond Springs|
|Wettest day||20.8 mm at Mango Farm on the 22nd|
|Highest wind gust||78 km/h at Yulara Aero on the 27th|
|Record lowest September temperature|
in September 2011 (°C)
|Daly Waters||4.3||on the 13th||6.0||on the 5th in 2003||37||17.0|
|Yuendumu||3.1||on the 13th||= 3.1||on the 8th in 1975||41||13.0|
|Record lowest September mean daily minimum temperature|
Mean daily minimum
for September 2011 (°C)
|Daly Waters||12.8||=12.8||in 1976||37||17.0|
|Summary statistics for September 2011|
|Darwin-Daly (district 14GA)|
|Batchelor Aero||35.2||-0.8||37.4||26th||20.1||-0.4||16.4||14th||0||5.2||v low||0%|
|Cape Don||31.5||34.3||14th||24.2||22.4||12th||0||2.3||v low||0%|
|Central Arnhem Plateau||33.2||36.0||27th||18.3||12.7||12th||0|
|Delamere Weapons Range||34.1||-1.5||37.4||19th||18.2||-2.5||11.0||12th||0||3.7||v low||0%|
|Katherine Aviation Museum||34.7||-1.2||37.4||27th||17.3||-2.7||8.8||12th||0||6.4||lowest||0%|
|Mango Farm||35.5||-0.8||38.2||27th||18.3||-1.0||13.0||15th||20.8||7.7||v high||270%|
|Port Keats Aero||32.6||-0.9||36.1||20th||19.5||-1.5||13.3||2nd||0.4||3.0||average||13%|
|Arnhem (district 14BC)|
|Groote Eylandt Airport||32.0||-0.6||36.1||27th||17.6||0.0||12.1||11th||0||1.8||v low||0%|
|North East Island||28.5||30.7||27th||22.6||21.6||11th||0.8||0.7||v high||114%|
|Roper-Mcarthur (district 14DE)|
|McArthur River Mine||35.0||-0.2||38.0||24th||16.9||-0.2||7.7||13th||0||5.1||lowest||0%|
|Victoria (district 14F)|
|Victoria River Downs||35.2||-0.3||38.7||19th||15.1||-3.1||6.8||12th||0||4.3||lowest||0%|
|Barkly (district 15A)|
|Tennant Creek Airport||30.8||-0.8||36.5||28th||17.1||-1.3||10.5||11th||0||8.0||lowest||0%|
|Alice Springs (district 15B)|
|Alice Springs Airport||27.9||+0.6||35.8||27th||8.9||-1.5||1.5||11th||0||8.1||lowest||0%|
|Rabbit Flat||32.5||-2.2||38.8||27th||10.8||-3.9||4.0||14th||0||5.9||v low||0%|
|Territory Grape Farm||29.9||-0.6||37.3||28th||9.2||-3.0||1.1||10th||0.4||7.9||average||5%|
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 10 am on Friday 30 September 2011. 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
(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.