THE WA STORMSPOTTER

Welcome to the 2005 edition of the WA Stormspotter newsletter. There have already been a couple of significant events affecting parts of the Southwest Land Division. In this edition we feature the severe weather event that spawned the tornadoes that caused significant damage to parts of Perth and the Southwest on 16 May 2005.

There are currently 281 registered storm spotters throughout Western Australia. We thank all the spotters who sent us reports of severe thunderstorms in their area either by phone or by post. Even if you hear of severe thunderstorms in your general area we welcome that information as well. We are keen to recruit new storm spotters in two areas: North of Perth in the Gingin, Lancelin, Badgingarra area for early detection of potential supercells that may affect the Perth Metropolitan area in the warmer months; and coastal areas between Lancelin and Albany for severe cool season thunderstorms/tornadoes.

Cool Season Tornadoes

A tornado is a violently rotating column of air, in contact with the ground, either pendant from a cumuliform cloud or underneath a cumuliform cloud, and often (but not always) visible as a funnel cloud.

Tornadoes, particularly cool season tornadoes, have become a popular topic amongst the media and public in recent times. On average there are 6 tornado events each year over an area mainly southwest from Lancelin to Albany. Cool season tornadoes are fast moving, last only a short time and have very localised effects. They are often associated with cold fronts but do not necessarily occur on the leading edge of the front; they may occur ahead of or behind the front. Significant tornadoes in the past include; 22 September 1993 in Mandurah, 25 August 1999 in Fremantle, 17 October 2003 when several tornadoes were reported through the southwest of Western Australia and 11 August 2004 in Bunbury.

National Storm Spotters Website

In July 2005, the Bureau of Meteorology will be launching a National Storm Spotters Website. The website will be introduced in the "feature of the month" section of the Bureau's website. The website will contain a wealth of information including: Duties of storm spotters, what storm spotters report, how to join the storm spotters network and storm spotter links. The links section include the storm spotters handbook, spotter safety information, national warnings page and significant weather summaries. The links section also include report forms and the storm spotters newsletters, both of which wll require a user id and password for access. These are provided to registered storm spotters.
For more information please visit the Bureau's website at www.bom.gov.au.

Tornadoes, 16 May 2005

Overview

Damage Reports

In Perth the most serious damage was to a primary school in Bicton. Several rooms in the school were demolished by a tornado. Other damage included several roofs completely lifted off and a significant amount of tree, fence and roof tile damage. 100 000 homes were reported to have lost power during the event. The SES reported 800 calls for assistance.

In Bunbury a tornado caused a trail of damage along the main street of the CBD. The most significant damage was the destruction of the rear section of the ABC studio as a result of a falling crane. Businesses along the main street were badly damaged with 3 or 4 older buildings unable to be repaired. Bunbury SHS was also closed following building damage.

Radar

The front was very fast moving. From radar and satellite imagery it was measured to be travelling at around 100 km/h.

The highest rainfall recorded in the 24hrs to 9am on 16 May was 89mm at Acton Park in the southwest. Other notable falls included 82mm at Nannup and 80mm at Shannon.

Severe Wind Gusts

Forecast Performance

The first Severe Weather Warning for locally destructive winds and flash flooding was issued on Sunday at 2:15pm, some 15 hours before the first reported severe wind gust at Abrolhos Island.

Figure 1. Leading edge of cold front: 5:50am.

Sustained strong N'ly winds led to a storm surge in the Busselton area. A storm surge of 0.773m was recorded at Busselton at 8:15am 16 May (data courtesy of the Department of Planning and Infrastructure).

The maximum pressure gradient recorded between Geraldton and Albany was 17.8hPa at 0945 WST. On average the Geraldton to Albany pressure gradient exceeds 20hPa only once every 5 years.

Storm Safety: mobile and cordless phones

You've probably heard that telephones should not be used in storms because of the risk of electric shocks from lightning striking the telephone line and travelling along it. You may be wondering then if it's OK to use mobile or cordless phones. A report by Bondarenko & Associates (Surge Testing and Protection Consultants) December 2002, has found that it depends on where you are.

If you are outdoors, a mobile phone is much like any other metallic object such as an umbrella or a golf club. It is advised that such objects should not be carried outdoors in a thunderstorm, as they may attract a strike. So avoid using your mobile outside in a storm!

Indoors is a different matter. It is safe to use a mobile or cordless phone indoors provided all other recommended safety measures are observed: Don't stand near open doors or windows, and avoid touching metallic objects and electrical appliances, including the base station of a cordless phone. All of these are shock risks.

It has been found that using mobile and cordless phones is also safe in a car with a metallic roof, as long as it is stationary, and there are no electrical connections between the handset and the car. You should also wind up the windows and avoid touching any metallic parts of the car, whether you're using a phone or not. So in summary, a mobile or cordless phone is safe to use indoors or in a car, provided that all other safety precautions are followed, but outdoors it might act as a lightning rod, so don't use it!

Latest statistics on the Internet

From June 2004 to May 2005, the Bureau of Meteorology website registered 2,308,732,139 hits. March 2005 recorded the highest monthly total with 297,043,335 hits.

All enquires regarding the Western Australian Storm Spotter Network can be directed to Joe Courtney, Kevin Smith or Andrew Burton on 08 9263 2222 or write to us: Severe Weather Section, Bureau of Meteorology, PO Box 1370, West Perth 6872.
E-mail address :- sevwx_wa@bom.gov.au

Severe Weather Summary January to May 2005

Maximum Wind Gusts in Western Australia

The highest recorded non-cyclonic wind gust was 193 km/h at Forrest during a thunderstorm on 20 November 1959. During the cooler months vigorous fronts and intense low pressure systems affect the Southwest Land Division and result in severe wind gusts. Perth recorded a wind gust of 156 km/h on 23 August 1963 and Esperance 152 km/h on 28 May 1993.

The highest recorded wind gusts for the Perth Metropolitan area are listed below: