Monthly Weather Review Northern Territory December 2012 Monthly Weather Review Northern Territory December 2012 The Monthly Weather Review - Northern Territory is produced twelve times each year by the Australian Bureau of Meteorology's Northern Territory Climate Services Centre. It is intended to provide a concise but informative overview of the temperatures, rainfall and significant weather events in Northern Territory for the month. To keep the Monthly Weather Review as timely as possible, much of the information is based on electronic reports. Although every effort is made to ensure the accuracy of these reports, the results can be considered only preliminary until complete quality control procedures have been carried out. Major discrepancies will be noted in later issues. We are keen to ensure that the Monthly Weather Review is appropriate to the needs of its readers. If you have any comments or suggestions, please do not hesitate to contact us: By mail Northern Territory Climate Services Centre Bureau of Meteorology PO Box 40050 Casuarina NT 0811 AUSTRALIA By telephone (08) 8920 3813 By email [email protected] You may also wish to visit the Bureau's home page, http://www.bom.gov.au. Units of measurement Except where noted, temperature is given in degrees Celsius (°C), rainfall in millimetres (mm), and wind speed in kilometres per hour (km/h). Observation times and periods Each station in Northern Territory makes its main observation for the day at 9 am local time. At this time, the precipitation over the past 24 hours is determined, and maximum and minimum thermometers are also read and reset. In this publication, the following conventions are used for assigning dates to the observations made: Maximum temperatures are for the 24 hours from 9 am on the date mentioned. They normally occur in the afternoon of that day. Minimum temperatures are for the 24 hours to 9 am on the date mentioned. They normally occur in the early morning of that day. Mean temperatures are the average of the daily maximum and daily minimum temperatures. Daily rainfall is for the 24 hours to 9 am on the date mentioned. This means a significant fraction of the rain may have occurred on the previous calendar day. Monthly rainfall is for the period from 9 am on the last day of the previous month to 9 am on the last day of this month. Maximum daily wind gusts are in the 24 hours from midnight to midnight. Climatological values The climatological averages shown in the text and tables are generally 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. Climatological extremes are generally taken from available observations from all available years of record. The number of years can vary substantially from site to site. Copyright © Commonwealth of Australia 2013 This work is copyright. You may download, display, print and reproduce this material in unaltered form only (retaining this notice) for your personal, non-commercial use or use within your organisation. Apart from any use as permitted under the Copyright Act 1968, all other rights are reserved. Requests and inquiries concerning reproduction and rights should be addressed to Commonwealth Copyright Administration, Attorney General’s Department, Robert Garran Offices, National Circuit, Barton ACT 2600 or posted at http://www.ag.gov.au/cca. Product code IDCKGC22R1. Prepared on 25 January 2013. ISSN 1836-392X Cover photograph Ormiston Gorge . Photograph by Gavin Heathertington-Tait, 19 December 2007. Used with permission. If you have a photo you think would make a good cover for the Monthly Weather Review, please contact us at the address above. Monthly Weather Review Northern Territory December 2012 Overview • Second hottest December on record at Darwin Significant weather Airport. • Little rainfall across the Top End. Sparse rainfall across the Top End • No sign of the Northen Australian Monsoon. On average the North Australian Monsoon sets onto the Top End around the last week of December. This year, however, the monsoon did not arrive in Extremes in December 2012 December and rainfall totals for the month were lower than average for the Top End. Adelaide River Hottest day Post Office, Pirlangimpi, Howard Springs Nature Park, (Highest daily maximum temperature) and Darwin Hospital all saw their driest December on 45.3 °C at Walungurru on the 24th record. Leanyer, Karama, and Wagait Beach all saw Warmest days on average their second driest December on record. (Highest mean daily maximum temperature) 40.1 °C at Walungurru Record low rainfall for Arnhem Land Coolest days on average In addition to the lack of monsoon activity, Arnhem (Lowest mean daily maximum temperature) Land was under the influence of a broad-scale area 32.7 °C at McCluer Island of very dry air which extended into the middle layers Coldest day of the atmosphere for most of the month. This dry (Lowest daily maximum temperature) air prevented gulf lines from initiating convection 27.1 °C at Kulgera on the 9th over land. As gulf lines approached Nhulumbuy from Coldest night the east, they quickly dissipated leaving the eastern (Lowest daily minimum temperature) Arnhem Land without the usual precipitation. Gove 13.0 °C at Watarrka on the 19th Airport had its second driest December on record Coolest nights on average with only only 6.4 mm for the month, the long-term (Lowest mean daily minimum temperature) December average is 181.2 mm. Maningrida, 21.0 °C at Kulgera Milingimbi and Ngayawili all had their lowest rainfall Warmest nights on average on record and Groote Eylandt Airport had its third (Highest mean daily minimum temperature) driest December on record. 28.1 °C at McCluer Island Warmest night Record hot Days in the NT (Highest daily minimum temperature) Darwin Airport measured their seconded hottest 31.2 °C at Walungurru on the 25th December on record this year with a mean daily Warmest on average overall maximum temperature of 34.2 °C (the record is (Highest mean temperature) 34.4 °C set in December 2002). Middle Point, 33.4 °C at Walungurru Pirlangimpi, and Jabiru Airport saw a record high Coolest on average overall mean daily maximum temperature this year. In the (Lowest mean temperature) Arnhem Land, Ngayawili set a new temperature 28.6 °C at Kulgera record with a mean daily maximum temperature of Wettest overall 34.1 °C. The primary reason for these high (Highest total rainfall) temperatures was the lack of cloud cover at a time 374.8 mm at Geriatric Park when the North Australian Monsoon usually cools Driest overall the land through the combined effects of cloud cover (Lowest total rainfall) and rainfall. Most of December saw high humidity 0 mm at Gilnockie and very direct sunlight, specially over the Top End.. 0 mm at Milingimbi Wettest day (Highest daily rainfall) 114.6 mm at Kidman Springs on the 19th Highest wind gust 93 km/h at Victoria River Downs on the 2nd 93 km/h at Tindal RAAF on the 8th 93 km/h at Bulman on the 25th page 1 Monthly Weather Review Northern Territory December 2012 Synoptic summary The month started with a slow moving trough pushing northwest from Western Australia. As the trough slowly creeped northwards, it brough some rain over the southwestern corner of the Alice Springs Distric at the western Victoria River Distric. By the 5th, the trough managed to reach the base of the Top End as a broad area of high pressure over the Bight strengthened. By then the trough dissipated, failing to bring any precipitation further north. As the second week of the month began, another quasi-stationary trough emerge over the central NT and by the 9th, an area of low pressure extended as far south as Victoria. The systrem, brough precipitation to the central NT until about the 13th with some areas receiving 24h totals of up to 25 mm. About half way through the month, the pressure gradient across the NT was week with a poorly organised trough sitting over the northern Alice Springs Distric. On the 13th, with the passage of a vigorous low pressure system over Tasmanian latitudes, an area of low pressure developed extending the trough across most of the country. From about the 16th, warm and moist air originating over the Indian Ocean was directed by this trough over the central NT leading to widespread rainfall across the region. Over the second half of December, the pressure gradient across the NT rtemained weak with no sign of the North Australian Monsoon development. A series of weak low pressure trough continued to skirt the Territory (particularly south and west) but little rainfal eventuated from these systrems. From the 21st to about the 23rd, however, a low pressure system gradually formed over the southern Gulf of carpentaria and moved west over the Top End leading to widespread showers on the 22nd and 23rd. By the end of the month, a weak monsoon trough developed to the north of Australia over southern Indonesia and New Guinea with a low pressure over the Coral Sea which later became tropical cyclone Freda and a low off the northwestern coast of Australia which later became tropical cyclone Mitchel. The last four days of the year, were marked by a strong and slow moving trough in the Bight, which directed hot and humid easterly winds across the nothern NT and lead to speckled storms over the Top End. page 2 Monthly Weather Review Northern Territory December 2012 Daily mean sea level pressure analyses 1 December 2012 2 December 2012 3 December