Tasmania in December 2009: A few very hot days after a cool start

After a generally cool month temperatures warmed in the final week, peaking on the 31st with many sites reaching into the mid to high 30s. On the evening of New Years Eve, Hobart was the warmest of all Australian capital cities and a spectacular lightning show ended the year. For the whole month it was wetter than usual in the west and parts of the east and southeast, but the remainder of the state was drier than usual.

A hot end to the year

A warm airmass ahead of an approaching cold front on the 31st made it the warmest day of the month, and for some sites, the year. Hobart reached 38.3 C and Bushy Park 38.4 C; there have only been 3 previous occurrences of December temperatures this high in Tasmania (the December record is 39.2 C at Hobart Airport in 1998). A few sites in the south had their hottest December day on record. Temperatures stayed high right into the evening; it was still 30.7 C in Hobart at 9 pm, easily the highest 9 pm New Year's Eve temperature ever recorded in the city and (for a few hours at least) making Hobart the warmest capital city in Australia. During the evening, a line of thunderstorms moved across the state giving a spectacular show of lightning, particularly in the southeast. Lightning strikes started several fires, mainly in the south.

Warm overall after a cool start

Daytime temperatures were mostly cooler than usual in the first three weeks, but a warm finish ensured mean maxima for the month were around a degree above average in the east and half a degree above average elsewhere. The 31st was the hottest day of the month for most sites but the 16th was also hot with a strong northerly airflow pushing temperatures over 30 C in most areas. In stark contrast, on the 17th temperatures struggled to reach 15 C in the west, south and east. The change was dramatic: very high to severe fire dangers on one day were replaced by rain and some snow on the higher peaks the next. Although large temperature changes are common with summertime cold fronts, this particular change was very marked. Several sites were 20 C cooler after the change: Campania fell from 36.3 C (the warmest in the state) on the 16th to 13.8 C on the 17th, and Hobart fell from 34.0 C (its second-hottest day of the year) to just 12.4 C (its coldest December day since 1992). The last time there was such a large fall in Hobart's temperature from one day to the next was in December 1945.

Some warm nights

Cool and warm nights were interspersed but averaged over the whole month minimum temperatures were mostly within half a degree of normal. There were three especially warm nights (the 17th, 24th and 31st) when minima were generally at least 5 degrees warmer than usual and a number of sites had their warmest December night since the early 2000s. Flinders Island had the warmest nights; after hovering near 27 C for most of the night on the 17th before the temperature cooled slightly after 5 am to a low of 20.5 C. It also didn't fall below 18 C on the 24th and 31st. The coldest night was -2.4 C at Liawenee on the 14th.

Some heavy rain but mostly drier than usual

Because winds were mostly westerly and several cold fronts crossed the state, most of the rain in December fell in the west. It rained in the west nearly every day for the first two weeks, and all of the highest daily totals were at Mount Read: 77 mm on the 12th, 55 mm on the 19th and 45 mm on the 10th. Rainfall extended statewide on the 3rd, 10th and 17th as weak low pressure systems formed on fronts crossing the state, and with a front on the 24th. There were some good falls in the east: on the 10th many parts received 10 to 20 mm and on the 17th falls of 25 to 40 mm were widespread. Of Hobart's 57 mm for the month, 32 mm fell on the 17th. The total is just slightly above the long-term average for December. For the whole month it was drier than usual in most areas except for the west coast and parts of the east and southeast. The wettest overall was 378.0 mm at Mount Read, whilst there was only 18.4 mm at Devonport Airport.

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Extremes in December 2009
Hottest day 38.4 C at Bushy Park on the 31st
Warmest days on average 23.3 C at Bushy Park and Campania
Coolest days on average 11.7 C at Mount Read
Coldest day 5.5 C at Mount Read on the 4th
Coldest night -2.4 C at Liawenee on the 14th
Coolest nights on average 3.3 C at Mount Wellington
Warmest nights on average 13.6 C at Swan Island
Warmest night 20.5 C at Flinders Island Airport on the 17th
Wettest overall 378.0 mm at Mount Read
Driest overall 18.4 mm at Devonport Airport
Wettest day 77.2 mm at Mount Read on the 12th
Highest wind gust 144 km/h at Mount Wellington on the 18th

Record highest December temperature

Highest temperature
in December 2009 (C)
Previous highest
for December
Years of
record
Average for
December
Cape Bruny Lighthouse 35.2 on the 31st 34.2 on the 12th in 1994 53 16.9
Mount Wellington 27.6 on the 31st 27.5 on the 11th in 1998 28 10.9
Geeveston (Cemetery Road) 37.0 on the 31st 36.6 on the 6th in 1994 24 19.9
Dover 37.3 on the 31st 36.1 on the 6th in 1994 20 19.0



Summary statistics for December 2009

Maximum temperatures
for December
(C)
Minimum temperatures
for December
(C)
Rainfall
for December
(millimetres)
Mean for
December
2009
Diff
from
average
Highest for
December
2009
Mean for
December
2009
Diff
from
average
Lowest for
December
2009
Total for
December
2009
Average
for
December
Rank of
December
2009
Fraction of
December
average
Northern (district 91)
Bridport (Sea View Villas) 20.2 +0.1 26.0 31st 10.6 -0.5 1.5 30th 33.0 43.8 average 75%
Burnie (Round Hill) 20.1 +0.7 28.7 29th 12.0 +0.9 7.2 11th 20.4 62.9 low 32%
Cape Grim BAPS 17.7 +0.5 27.0 31st 12.0 +0.2 9.0 11th 40.0 45.7 average 88%
Cressy Research Station 23.2 +0.4 32.6 31st 8.8 +0.5 1.8 25th 26.8 42.4 average 63%
Devonport Airport 20.0 +0.5 27.2 29th 10.6 +0.1 4.9 9th 18.4 52.8 low 35%
Launceston (Ti Tree Bend) 22.8 +0.4 31.7 29th 11.3 +0.7 6.2 25th 22.2 45.5 low 49%
Launceston Airport 22.5   31.0 31st 9.1   3.8 9th 23.4


Low Head 18.8 0.0 21.6 31st 13.1 +0.4 10.0 1st 22.8 43.1 average 53%
Luncheon Hill (Forestry) 18.5 0.0 30.3 31st 8.8 +0.3 5.3 8th 82.0 93.5 low 88%
Marrawah 18.5 +0.2 28.8 31st 11.0 +0.4 7.2 20th 46.2 64.2 average 72%
Scottsdale (West Minstone Road) 21.3 +0.5 30.7 31st 9.4 +0.2 3.9 25th 35.2 67.1 low 52%
Sheffield School Farm 19.6 +0.1 29.6 29th 8.8 -0.1 4.0 9th 36.2 59.6 average 61%
Smithton Aerodrome 19.8 +0.4 26.8 31st 9.1 -0.5 3.6 21st 35.4 60.8 low 58%
Wynyard Airport 20.3 +0.9 28.7 29th 9.6 +0.1 3.3 9th 22.6 63.2 low 36%
East Coast (district 92)
Bicheno (Council Depot) 21.3 +1.3 32.7 31st 12.3 +0.8 8.3 18th 56.7 68.6 average 83%
Eddystone Point 21.8 +2.5 27.1 29th 12.4 +0.2 7.8 9th 23.4 59.8 low 39%
Fingal (Legge Street) 22.4 +1.0 34.4 31st 8.6 0.0 2.7 9th 27.4 49.6 average 55%
Friendly Beaches 22.0 +0.2 35.3 16th 12.0 +0.4 6.9 18th 50.4 37.9 high 133%
Lake Leake (Elizabeth River) 18.7 +1.2 29.3 31st 7.3 +0.4 2.4 25th 57.8 72.9 average 79%
Maria Island (Point Lesueur) 20.2   30.2 16th 12.1   9.0 18th 57.2


Orford (Aubin Court) 21.4 +1.0 34.8 31st 11.3 +0.8 6.8 18th 74.0 64.1 average 115%
Scamander 21.3 +1.0 35.1 31st 11.9 +0.6 8.4 18th 34.0 61.5 average 55%
St Helens Aerodrome 21.9   34.0 31st 11.8   7.9 9th 30.6


Swan Island 19.9   28.4 31st 13.6   10.1 1st 25.6


Swansea Post Office 22.0 +1.4 35.3 31st 10.7 +0.2 6.2 18th 58.6 59.9 average 98%
Midlands (district 93)
Ross (The Boulevards) 23.0 +0.4 32.9 31st 9.3 +0.8 3.3 25th 45.0 38.2 average 118%
Southeast (district 94)
Bull Bay (Lauriston) 20.6 +0.8 37.2 31st 10.9 +0.3 6.9 18th 48.2 62.9 average 77%
Campania (Kincora) 23.3   38.1 31st 10.0   5.1 2nd 55.6 36.6 high 152%
Cape Bruny (Cape Bruny) 19.3 +1.2 36.1 31st 10.6 0.0 7.6 20th 36.0 59.4 low 61%
Cape Bruny Lighthouse 18.7 +1.8 35.2 31st 10.7 +0.4 5.6 12th 43.0 76.7 low 56%
Dover 20.1 +1.1 37.3 31st 8.7 -0.2 2.9 20th 33.0 71.9 low 46%
Geeveston (Cemetery Road) 20.8 +0.9 37.0 31st 9.0 +0.4 3.5 20th 48.0 71.7 average 67%
Grove (Research Station) 21.3   37.1 31st 8.0   2.8 15th 55.6


Hobart (Ellerslie Road) 21.9 +1.6 38.3 31st 11.4 +0.6 8.0 18th 57.2 56.9 average 101%
Hobart Airport 21.8 +1.2 37.1 31st 11.3 +0.6 7.4 18th 54.4 53.7 average 101%
Maatsuyker Island Lighthouse 16.4 +0.7 30.4 31st 10.4 +0.8 8.2 4th 95.4 90.4 average 106%
Melton Mowbray (North Stockman) 22.0 +0.2 36.2 31st 8.8 -0.2 3.2 14th 39.2 37.9 average 103%
Mount Wellington 12.8 +1.9 27.6 31st 3.3 +0.5 -0.9 4th 63.0 87.7 average 72%
Tasman Island 17.1   31.1 31st 9.8   7.1 8th 68.2


Tunnack Fire Station 19.3 -0.3 30.1 31st 7.6 +0.2 1.5 14th 38.4 51.0 low 75%
Derwent Valley (district 95)
Bushy Park (Bushy Park Estates) 23.3 +1.3 38.4 31st 8.7 -0.4 4.4 15th 27.6 50.6 low 55%
Maydena Post Office 19.8 +0.1 35.2 31st 7.4 0.0 2.6 20th 71.5 88.6 average 81%
Ouse Fire Station 23.2 +0.2 37.3 31st 8.5 -0.1 2.2 14th 21.6 35.7 average 61%
Tarraleah Village 18.6 +0.9 32.1 31st 6.0 -0.1 1.9 8th 50.1 91.4 low 55%
Central Plateau (district 96)
Butlers Gorge 17.2 +0.6 31.0 31st 4.7 -0.8 -0.8 8th 99.6 127.0 average 78%
Lake St Clair National Park 17.5 +0.3 31.0 31st 4.3 -0.7 -1.0 1st 116.2 133.7 average 87%
Liawenee 16.9   28.0 16th 3.7   -2.4 14th 33.0 65.0 low 51%
West Coast (district 97)
Hartz Mountain (Keoghs Pimple) 14.6 -0.2 30.9 31st 5.2 +0.2 1.3 4th 80.4 81.0 average 99%
Mount Read 11.7 +0.1 25.0 31st 3.8 0.0 -0.5 4th 378.0 292.4 high 129%
Scotts Peak Dam 18.7 +0.4 34.4 31st 7.8 -0.1 3.2 20th 139.6 153.9 average 91%
Strahan Aerodrome 19.3 -0.4 34.5 31st 9.8 +0.2 4.6 20th 123.4 79.9 high 154%
Strathgordon Village 17.0 -0.2 29.0 30th 7.6 -0.7 4.0 20th 250.7 202.4 high 124%
Warra 17.3   33.1 31st 6.6   1.1 20th 118.4


King Island (district 98)
King Island Airport 19.8 +1.3 35.2 31st 10.9 0.0 5.6 26th 33.6 50.6 average 66%
Flinders Island (district 99)
Flinders Island Airport 21.1 +1.0 34.6 16th 11.9 +0.1 4.9 21st 28.8 58.1 low 50%
Hogan Island 20.7   33.8 31st 13.1   10.0 11th 38.6


Antarctica and Macquarie Island (district 300)
Macquarie Island 8.2 +0.3 9.7 24th 4.2 -0.1 1.3 14th 67.0 77.2 average 87%

Notes

A Monthly Climate Summary is prepared to list the main features of the weather in Tasmania using the most timely and accurate information available on the date of publication; it will generally not be updated. Later information, including data that has had greater opportunity for quality control, will be presented in the Monthly Weather Review, usually published in the fourth week of the month.

This statement has been prepared based on information available at 9 am on Tuesday 5 January 2010. Some checks have been made on the data, but it is possible that results will change as new information becomes available.

Averages are 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.
The median is sometimes more representative than the mean of long-term average rain.

The Rank indicates how rainfall this time compares with the climate record for the site, based on the decile ranking (very low rainfall is in decile 1, low in decile 2 or 3, average in decile 4 to 7, high in decile 8 or 9 and very high is in decile 10).
The Fraction of average shows how much rain has fallen this time as a percentage of the long-term mean.

Further information

Media
(03) 9669 4057
Enquiries