Monthly Weather Review Northern Territory September 2012 Monthly Weather Review Northern Territory September 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 2012 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 24 October 2012. ISSN 1836-392X Cover photograph Darwin Met Building. Photograph by Brittany Tanner Lisonbee. 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 September 2012 Overview The month of September is the last month of the dry Significant weather season and usually begins a transition to higher September bushfires temperatures and humidity across the Northern On the 1st and 2nd, several fires between Berry Territory. Typically in September, the sub-tropical Springs and Darwin River Dam threatened houses, a ridge weakens as troughs with associated moisture service station and mango orchards, fueled by a punch into the Territory and the climate begins the burst of dry SE winds across the Top End. transition into the wet season. This month was strongly influenced by the sub-tropical ridge as no Beginning around the same time, another fire rainfall was recorded until the last two days of the burned for seven days in the area around the Black month. Alice Springs Airport saw the end of its Jungle Conservation Reserve, in Darwin's rural area, longest dry spell on record with 157 days with no burning parts of the nature reserve and flood plains rain recorded since 24 April this year. and threatening 15 homes in the area. On the 19th, a fire near Girraween in Darwin's rural Extremes in September 2012 area, fueled by hot, dry, east to southeast winds threatened approximately 53 homes. Fire fighters Hottest day used aerial suppression and on-ground resources to (Highest daily maximum temperature) battle the blaze. All homes were saved. 41.1 °C at Lajamanu on the 23rd Warmest days on average Also on the 19th, another fire near Ban Ban Springs, (Highest mean daily maximum temperature) north of Adelaide River, burned for two days, no 37.9 °C at Douglas River structures were burnt, but 153 sq km of pasture Coolest days on average were lost to the fire. (Lowest mean daily maximum temperature) During the 26th and 27th a number of fires 27.9 °C at Arltunga developed around the Marrakai region of the NW Coldest day Darwin-Daly District burning pasture and threatening (Lowest daily maximum temperature) a number of rural properties. 16.5 °C at Arltunga on the 29th Coldest night (Lowest daily minimum temperature) Synoptic summary −0.4 °C at Arltunga on the 10th The month started with a weak ridge over the Coolest nights on average Northern Territory, the ridge gradually eased as a (Lowest mean daily minimum temperature) shallow trough developed over the western boarder 9.4 °C at Arltunga and moved across on the 5th. On the 6th, another Warmest nights on average high pressure system centred over the southern (Highest mean daily minimum temperature) Indian Ocean extends a ridge over the continent with 24.5 °C at Darwin Harbour a cool southeast change and showers were Warmest night contracted along the northern coast of the Top End. (Highest daily minimum temperature) The high moved eastwards and was located over the 26.3 °C at Timber Creek on the 30th Tasman Sea on the 11th ahead of a developing Warmest on average overall shallow weak trough over the western boarder. A (Highest mean temperature) southeast wind flow affected the Territory until 15th 28.9 °C at Jabiru Airport as the high moved over to southeast Australia. A Coolest on average overall series of troughs developed on the 16th with (Lowest mean temperature) increase humidity in the area until the 22nd, ahead 18.7 °C at Arltunga of another high that developed over the southern Wettest overall Indian Ocean. The high pressure system ridged over (Highest total rainfall) Australia until the 24th before another weak and 75.3 mm at Mainoru Outstation Store shallow trough developed over the western boarder Wettest day on the 25th and propagated eastwards with not (Highest daily rainfall) much precipitation. 75.3 mm at Mainoru Outstation Store on the 30th On the 28th a trough pushed into the Territory Highest wind gust 72 km/h at Central Arnhem Plateau on the 29th bringing rain for the first time in the month. (See the rainfall section for more information on this rainfall event). The trough pushed to the east as a strong ridge replaced it. As the high pressure moved to the northeast it provided a lifting mechanism that initiated convection within a heat-trough that was situated over the Top End. page 1 Monthly Weather Review Northern Territory September 2012 Daily mean sea level pressure analyses 1 September 2012 2 September 2012 3 September 2012 4 September 2012 5 September 2012 6 September 2012 7 September 2012 8 September 2012 9 September 2012 10 September 2012 11 September 2012 12 September 2012 13 September 2012 14 September 2012 15 September 2012 16 September 2012 17 September 2012 18 September 2012 page 2 Monthly Weather Review Northern Territory September 2012 19 September 2012 20 September 2012 21 September 2012 22 September 2012 23 September 2012 24 September 2012 25 September 2012 26 September 2012 27 September 2012 28 September 2012 29 September 2012 30 September 2012 page 3 Monthly Weather Review Northern Territory September 2012 Temperatures Temperatures gradually increased across the Territory during the September month due to more solar exposure and weakening of the sub-tropical ridge. The mean temperature (average of daily maximum and minimum) for Northern Territory in September 2012 was 24.7 °C, which is 1.1 °C above the long-term average. The warmest on average was Jabiru Airport with 28.9 °C, followed by Delamere Weapons Range with 28.3 °C, and then both Cape Don and Darwin NTC with 28.2 °C respectively. The coolest on average was Arltunga with 18.7 °C, followed by Alice Springs Airport with 19.5 °C, and then Curtin Springs with 19.8 °C. New temperature records Record highest September daily maximum temperature Years New record Old record of record Alice Springs Airport 38.8 on 22nd = 38.8 on 22nd in 2003 70 Daly Waters AWS 40.9 on 27th 40.0 on 26th in 2003 42 Tindal RAAF 40.0 on 27th 39.9 on 28th in 1992 24 Territory Grape Farm 38.2 on 27th 38.0 on 22nd in 2003 20 page 4 Monthly Weather Review Northern Territory September 2012 Maximum temperatures Anomalies of mean daily maximum temperature in September 2012 Maximum temperatures were mostly above average across the Territory.