Thursday, 12 October 2006

Two hot, dry and windy days in southern Tasmania

Tasmania, especially the southeast, has seen two days of high temperatures, separated by a very warm night, plus strong winds and very low humidities. Conditions are expected to change markedly for the weekend.

Note: it is quite possible that some of the maximum temperatures and wind gusts mentioned will have been exceeded since this statement was prepared.

Two hot days: It reached 33.1 °C in Hobart this (Thursday) afternoon, the third-warmest October day Hobart has ever had, and the warmest since the record high of 34.6 °C on the 31st in 1987.
Yesterday (Wednesday) Hobart's temperature reached 28.1 °C. Hobart normally sees two consecutive days over 28 °C once or twice each year, but only sees them in October about once every 20 years. The last time it happened in October was in 1977, when the temperature reached 28.7 °C on the 26th then 31.0 °C on the 27th. More recently, it reached 28.5 °C on 24 February this year and then 29.1 °C on the 25th.
Several sites, mostly in the southeast, recorded temperatures in the high 20s yesterday and the low 30s today. Today's highest temperature was 34 °C at Campania, the second-highest October temperature in Tasmania. Most sites in the south and east were over 30 °C today: Bull Bay (33.5), Hobart Airport(33.4), Hobart (33.1), Bushy Park (32.8), Flinders Island Airport (32.7), Friendly Beaches (32.7), Grove (32.2), Melton Mowbray (31.5), Grove (31.5), Swansea (31.2), Geeveston (31.0), Cape Bruny (30.5) and Tasman Island (30.5). Temperatures were generally lower in the north and west, but still above 20 °C.
Yesterday's warmest temperature was 29.0 °C at Bull Bay on Bruny Island.

A very warm night: Last night was also abnormally warm. Hobart's minimum temperature in the 24 hours from 9 am Wednesday to 9 am Thursday was 18.3 °C.  This temperature was actually recorded around 9 am on Wednesday; the overnight value was over 20 °C, but the Bureau does not have long-term statistics on "overnight" minima. Nonetheless, 18.3 °C is second only to the 20.3 °C on the 23rd in 1933 as the warmest October minimum in Hobart.
Strahan's minimum temperature last night of 19.2 °C and Bull Bay's 19.1 °C now fill the 3rd and 4th spots in the record book for high Tasmanian October minimum temperatures, behind the warm morning of the 28th in 1977 when Flinders Island Airport only fell to 20.6 °C and Rossarden only dropped to 20.0 °C.

Strong and gusty winds: It has also been very windy. Hobart's mean wind speed since Wednesday morning has been around 35 km/h, double the normal October value.
Several sites have recorded gusts well in excess of 100 km/h in the last two days, with Scotts Peak Dam reaching 135 km/h, Maatsuyker Island 128 km/h and Tasman Island 126 km/h. Hobart recorded a gust to 93 km/h at around noon on Thursday.

Low humidity: Along with the high temperatures and strong winds, Tasmania has also been experiencing very low humidity. The relative humidity in the southeast dropped below 10% on both Wednesday afternoon, and was again that low for much of Thursday. It is very rare to get such low humidities; the mean relative humidity at 3 pm in Hobart in October is 56%.

Extreme fire danger: High temperature, strong wind and low humidity increase the fire danger. The Fire Danger Rating reached "Extreme" at many sites in the southeast during Wednesday and Thursday, an very unusual occurrence for October. The measured Fire Danger Index at Hobart Airport was similar to that on the afternoon of 7 February 1967.

Colder weekend ahead: A weak cold front is expected to cross Tasmania from the west tonight, giving a cooler and less windy Friday with some showers in the west. A more significant front on Saturday will lead to a cool and showery weekend in the south and west, with some highland snow possible, although the north and east will be mostly fine. For the latest forecasts and warnings, check our web site.

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Further information

Ian Barnes-Keoghan
Meteorologist
Tasmania and Antarctica Climate Services Centre
Bureau of Meteorology
Phone (03) 6221 2043
Email climate.tas@bom.gov.au

Current forecasts and warnings

Regional Forecasting Centre (03) 6221 2000 (24 hours a day)
www.bom.gov.au/weather/tas

The Bureau of Meteorology's web site carries the most recent forecasts for Tasmania and Hobart. and other forecasts and warnings for Tasmania and the rest of Australia.