Monthly Weather Review Western Australia December 2008 Monthly Weather Review Western Australia December 2008 The Monthly Weather Review - Western Australia is produced twelve times each year by the Australian Bureau of Meteorology's Western Australia Climate Services Centre. It is intended to provide a concise but informative overview of the temperatures, rainfall and significant weather events in Western Australia 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 Western Australia Climate Services Centre Bureau of Meteorology PO Box 1370 WEST PERTH WA 6872 AUSTRALIA By telephone (08) 9263 2222 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 Western Australia 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 30 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 2009 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 IDCKGC21R1. This version prepared on 12 March 2009, revising an issue prepared on 22 January 2009. ISSN 1836-3032 Cover photograph Cumulus clouds over Mitchell Plateau near Port Warrander, Admiralty Gulf, North Kimberley, WA. Photograph by Kerrie Goodchild, 28 January 2003. Copyright © 2008 Kerrie Goodchild. 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 Western Australia December 2008 Overview A Cool and Wet Month for WA Extremes in December 2008 • Above average rainfall for WA. • Below average mean maximum temperature for Hottest day WA (Highest daily maximum temperature) • Near average mean minimum temperature for 45.7 °C at Marble Bar on the 19th WA. Warmest days on average The month of December in 2008 was generally cool (Highest mean daily maximum temperature) and wet in WA. The first cyclone to cross the WA 40.9 °C at Marble Bar coast for the 2008/2009 season occurred as Tropical Coolest days on average Cyclone Billy formed in the Joseph Bonaparte Gulf (Lowest mean daily maximum temperature) before making landfall near Wyndham as a category 20.7 °C at Albany two system. Rainfall was mostly above average for Coldest day the month, particularly in the northern Kimberley (Lowest daily maximum temperature) where several daily and monthly December records 16.2 °C at Jacup on the 10th were broken, mostly due to the passage of TC Billy. Coldest night Persistent thunderstorms kept daily maximum (Lowest daily minimum temperature) temperatures below normal through the Interior and 3.9 °C at Eyre on the 7th Kimberley, whilst parts of the south and west coasts Coolest nights on average also saw below average mean maxima, leading to a (Lowest mean daily minimum temperature) below average month across the state as a whole. 9.2 °C at Jarrahwood Overnight minima were below normal near the west Warmest nights on average coast and in the east and central Kimberley, but (Highest mean daily minimum temperature) above average in the far southeast, resulting in a 27.0 °C at Troughton Island near normal WA state mean minimum. (On the WA mainland) 26.4 °C at Bidyadanga 26.4 °C at Broome Airport Warmest night (Highest daily minimum temperature) 32.0 °C at Wittenoom on the 19th Wettest overall (Highest total rainfall) 697.8 mm at Oombulgurri Wettest day (Highest daily rainfall) 280.0 mm at Laurel Downs on the 26th Highest wind gust 94 km/h at Giles Meteorological Office on the 11th page 1 Monthly Weather Review Western Australia December 2008 Significant weather 23rd: Afternoon thunderstorms caused strong winds uprooting trees and downing power lines in Tropical Cyclones Kalgoorlie. Two trees fell on cars. 15th - 28th, Tropical Cyclone Billy: A tropical low formed in the Timor Sea, northwest of Darwin on the 26th: Strong winds during an afternoon 15th, initially moving to the southwest before thunderstorm caused some damage to a mine near tracking to the southeast on the 17th. The low Leinster in the northern Goldfields at 1445 WDT. moved into the Joseph Bonaparte Gulf on the 18th 30th: A severe thunderstorm in the Central West and intensified to a tropical cyclone north of district caused some damage with three houses roofs Wyndham. The slow moving system reached torn off and some broken tree branches and fences. category two intensity before moving to the west-southwest, crossing the coast near Wyndham Heavy Rainfall early on the 20th. TC Billy passed over Oombulgurri 10th/11th: The passage of a middle level trough and community at category 2 strength, causing tree moist low level southeasterly winds resulted in heavy damage and power outages before weakening to a rainfall over southern parts of the Southwest Land tropical low. Heavy rainfall caused flooding and road Division (SWLD) and southern Goldfields. A closures in the northeast Kimberley. The heaviest stormspotter reported that a thunderstorm rainfall was recorded at Wyndham, with 384.0 mm in (approximately 1230 WDT on the 10th) to the east of the 48 hours to 9am on the 21st. The low tracked Hyden produced 50 mm of rainfall in 30 minutes and west-southwest across the Kimberley, redeveloping hail up to 1.5cm in diameter. Crops were flattened to cyclone strength after moving off the northwest and paddocks were under water. In the 24hrs to 9am Kimberley coast near Kuri Bay on the 22nd. TC Billy on the 11th, Fitzgerald (Southeast Coastal) recorded then moved southwest along the coast, passing over 95.4 mm, Desert Fringe (Great Southern) 70 mm and the northern part of the Dampier Peninsula to the Bremer Bay (Southeast Coastal) 59 mm. Flooding and north of Broome overnight on the 22nd and in the road closures were reported near Tambellup. In morning of the 23rd. Broome Airport recorded a addition, a stormspotter at Kambalda reported wind gust of 91 km/h at 0922 WDT on the 23rd as TC 40 mm of rainfall in 20 minutes between Billy passed to the northwest of the town. TC Billy approximately 1030 WDT and 1100 WDT on the 11th rapidly intensified late on the 23rd and during the with the 24hr to 9am rainfall on the 12th recorded at 24th after moving westwards into open waters and Kambalda West of 42.4 mm. reached category four intensity late on the 24th, about 280 km north of Port Hedland. TC Billy then 21st: Heavy rainfall associated with an upper trough moved to the west-northwest away from the Pilbara caused damage to fruit and vegetable crops around coast, weakening from late on the 25th due to Pemberton and Northcliffe estimated in the millions increasing vertical wind shear. TC Billy eventually of dollars. The heaviest daily rainfall was 70 mm at weakened below TC intensity late on the 28th, about Karri Valley Resort. There were reports of severe 750 km north of Exmouth. winds that brought trees down and disrupted power supplies. Hail also contributed to the damage. Thunderstorms 3rd: Severe damage occurred at Laverton in the Goldfields at approximately 1530 WDT. Power poles were torn down and trees were ripped out by the roots. At the sports club, the caretaker's roof was torn off and dumped 150m away.