Monthly Weather Review Victoria September 2010 Monthly Weather Review Victoria September 2010 The Monthly Weather Review - Victoria is produced twelve times each year by the Australian Bureau of Meteorology's Victoria Climate Services Centre. It is intended to provide a concise but informative overview of the temperatures, rainfall and significant weather events in Victoria 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 Victoria Climate Services Centre Bureau of Meteorology PO Box 1636 Melbourne VIC 3001 AUSTRALIA By telephone (03) 9669 4956 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 Victoria 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. 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 2010 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 IDCKGC26R1. Prepared on 25 October 2010. ISSN 1836-3016 Cover photograph Flood waters across Egan's Bridge Road, Wanalta. Photograph by Margaret McLean, 5 September 2010. 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 Victoria September 2010 Overview Daytimes in Victoria were generally cooler than usual Significant weather this September with mean maximum temperatures up to 3 °C below normal across the state. Night-time Widespread flooding across the north temperatures were generally close to average. A major rain event affected the north of Victoria on Rainfall patterns were normal for most of the state the weekend of the 4th and 5th as a low pressure except parts of Gippsland, that were drier, and parts system over South Australia deepened and moved of the Great Dividing Range, that were wetter than into Bass Strait, with an associated trough extending usual. There was major flooding in the north of the north into NSW. Rain began falling on the 3rd and by state at the start of the month. 9 am on the 4th a large proportion of the state had received in excess of 25 mm, with some areas Extremes in September 2010 receiving as much as 80 mm. Rainfall continued during the 4th with the highest 24 hour totals to 9 am on the 5th centred over the northeast ranges Hottest day (Highest daily maximum temperature) with some places receiving in excess of 130 mm. The 24.6 °C at Bairnsdale Airport on the 4th highest rainfall totals for the event were 242.8 mm 24.6 °C at Orbost (Comparison) on the 4th at Falls Creek, 216.4 mm at Whitlands and 181 mm 24.6 °C at Lakes Entrance (Eastern Beach Road) on at Myrrhee. Significant riverine flooding occurred the 27th over the ensuing days as flood waters made their way into the states river systems. Major flood Warmest days on average (Highest mean daily maximum temperature) warnings were issued for many river systems 18.3 °C at Mildura Airport including the Avoca, King, Ovens, Goulburn and Wimmera Rivers with many homes and business Coolest days on average (Lowest mean daily maximum temperature) affected in towns such as Creswick, Charlton, 2.5 °C at Mount Hotham Wangaratta and Shepparton. Every river basin north of the Great Divide experienced Major flooding Coldest day (Lowest daily maximum temperature) except for the Campaspe which saw areas of −2.6 °C at Mount Hotham on the 16th Moderate flooding. A total of 331 flood warnings (110 Major) were issued for the duration of the Coldest night (Lowest daily minimum temperature) event. New record flood peaks were recorded at 10 −7.6 °C at Mount Hotham on the 8th forecasting locations in northern Victoria. Coolest nights on average Strong winds also affected southern and elevated (Lowest mean daily minimum temperature) areas of the state from late on the 4th and overnight −2.5 °C at Mount Hotham into the 5th as the low moved into the Tasman Sea. Warmest nights on average The strongest recorded gust was 137 km/h at Falls (Highest mean daily minimum temperature) Creek, while away from the Alpine areas the 9.4 °C at Cape Nelson Lighthouse strongest gusts were 122 km/h at Colac and Wilsons 9.4 °C at Gabo Island Lighthouse Promontory and 118 km/h at Cape Otway. In the Warmest night Melbourne area 104 km/h was the strongest wind (Highest daily minimum temperature) gust, recorded at St Kilda. The Victorian SES received 13.3 °C at Orbost on the 5th over 2000 requests for assistance across the duration Wettest overall of the event. (Highest total rainfall) 334.4 mm at Falls Creek (Rocky Valley) Tornados Driest overall Two separate tornado reports were also received for (Lowest total rainfall) the month. One was reported on the afternoon of 0.2 mm at Mount Useful the 4th just east of Broadford to the north of Wettest day Melbourne. A storm spotter reported a damage path (Highest daily rainfall) around 100 m wide and 4km long with numerous 135.2 mm at Whitlands (Burder's Lane) on the 5th trees damaged and roof tiles removed from one Highest wind gust house. The other reported tornado sighting was on 139 km/h at Falls Creek on the 4th the 13th in the Miram/Diapur area in the North Wimmera District, however there were no reports of damage. page 1 Monthly Weather Review Victoria September 2010 Synoptic summary September started with a trough extending from the northwest corner of the state through to West Gippsland. Behind the trough was a cold front that delivered rainfall to most districts on the 1st and 2nd. A high pressure system moved across Bass Straight on the 3rd, clearing away most of the rain before a deep low pressure system passed to the south of the state in the following days. Widsepread rainfall associated with the low pressure system contributed more than 50 mm to some parts of the state on the 4th and 5th. This rainfall went on to produce significant flooding in the north of the state and was the largest rainfall event for the month. A high pressure system centred over the state on the 7th made way for another cold front that came in from the west on the 9th. Rainfall associated with the front was recorded in most districts on the 10th. The next few days were dominated by a high pressure system before another low pressure system tracked eastward across the north of the state on the 14th. Rainfall associated with the low pressure system was focused over the North Mallee District. Trailing behind the low pressure system, a cold front swept across southern parts of the state on the 15th but delivered less than 10 mm to most parts. Over the following days the synoptic pattern over Victoria did not change much. A strong high pressure system in the Southern Ocean remained almost stationary for three days before it began to slowly move east into the Great Australian Bight. This set up a south-westerly wind pattern across most of the state until the 21st, with rainfall confined to the coastal districts excluding East Gippsland.