Tasmania in December 2010: Cool with severe thunderstorms and heavy rain in the north

Severe thunderstorms were a prominent feature in December, affecting the state on several days during the first half of the month. Overall, rainfall was above average in the north and Midlands but below average in the southeast around Hobart and the Derwent Valley. Both maximum and minimum temperatures were cooler than usual in most areas, making it one of the few cooler than usual months of 2010. 

  • Several severe thunderstorms with flash flooding
  • 86 mm in a day at Erriba
  • Many cool days with some mountain snow on the 26-27th

Severe thunderstorms, mainly in the north

Several severe thunderstorms affected Tasmania during December, causing localised flash flooding. Affected areas included the southeast on the 3rd, the northeast on the 4th, the northwest around Wynyard, Preolenna and Wilmot on the 8th, the north including Launceston on the 11-12th, Scamander on the 15th and Devonport on the 17th. The worst reported damage occurred in Devonport on the 17th, with several businesses and roads affected.

Wet in the north, dry in the southeast

Troughs, low pressure systems, thunderstorms and fronts all contributed to a very wet December in the north. Most northern sites had over 100 mm, and inland areas between Sheffield and Scottsdale had at least double their normal December rainfall. Barrington, with 177 mm, had its wettest December on record and a few other sites, including Launceston, had their wettest December for at least 20 years. The Midlands and parts of the east were also wetter than usual, having been affected by thunderstorms on the 3rd and 20th, but only a fraction of this rain managed to reach the south. Consequently, December was drier than usual in most of the south and especially in the southeast around Hobart and the Derwent Valley. The driest site for the month was Hermitage with 21.6 mm.

The heaviest rainfall occurred on the 7-8th as a trough crossed the state. Erriba had 86 mm in one day, followed by Mole Creek with 58 mm. This rain caused flooding of the Meander, Mersey, Forth and Macquarie river basins. Despite the heavy rain in the north, Mount Read was still the wettest site with 294 mm. Erriba and Mount Barrow were not far behind, with totals of 239 mm and 227 mm respectively.

A cool start to summer

Summer had a slow start with many December days recording much cooler than usual temperatures. Averaged over the month, maximum temperatures were around a degree cooler than usual, and near two degrees cooler than usual at some sites in the Midlands. There were many cool to cold days between the 5th and 27th. Of note were the 5th, 10th, 21st and 26-27th, when temperatures struggled to reach 20 C. There was even some mountain snow in the south just after Christmas. The coldest day was 2.9 C at Mount Wellington on the 21st.

There were a few exceptions to the cool conditions: temperatures reached the high 20s in the north on the 4th and in the southeast on the 8th and 31st. It was also warm in the west for the first 9 days of the month as easterly winds blew over the state. The hottest day was 29.4 C at St Helens on the 4th. On the same day Wynyard reached 28.8 C, its highest December temperature since 1998.

Nights: warm at the start, then cool

From the 1st to the 10th nights were warmer than usual as moist air from the Tasman Sea was directed over Tasmania much of the time, restricting overnight cooling. The 3rd, 4th and 8th were especially warm, with extensive fog that persisted into the afternoon in some areas. Strahan had the warmest night, not falling below 20.7 C on the 8th, the warmest night there since 1983. Launceston had 2 nights over 17 C and Hobart had 4 nights over 15 C.

From the 11th, the easterly pattern was replaced by westerlies with several cold fronts crossing the state. Northerly winds on the 15th kept overnight temperatures warm, but otherwise nights were generally cool, particularly on the 13th, 16th, 22nd, 24th and 27-28th. Mount Wellington fell to -3.3 C on the 27th as snow fell on the mountain. On the same morning Cape Grim had its lowest December temperature on record, falling to 6.9 C.

Averaged over the month, minimum temperatures were generally slightly warmer than usual in the west and slightly cooler than usual elsewhere. 

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Extremes in December 2010
Hottest day 29.4 C at St Helens Aerodrome on the 4th
Warmest days on average 21.4 C at Ouse Fire Station
Coolest days on average10.2 C at Mount Wellington
Coldest day 2.9 C at Mount Wellington on the 21st
Coldest night -3.3 C at Mount Wellington on the 27th
Coolest nights on average 2.1 C at Mount Wellington
Warmest nights on average 12.9 C at Hogan Island
Warmest night 20.7 C at Strahan Aerodrome on the 8th
Warmest on average overall 16.4 C at Flinders Island Airport
Coolest on average overall 6.1 C at Mount Wellington
Wettest overall 294.2 mm at Mount Read
Driest overall 21.6 mm at Hermitage (Shannon River)
Wettest day 86.2 mm at Erriba (Jubb Road) on the 8th
Highest wind gust 157 km/h at Maatsuyker Island Lighthouse on the 10th

Maps
ObservedAnomalyDecile rank
Total
rainfall
Map of Rainfall totals Map of Percentage of normal rainfall Map of Rainfall deciles
Mean
daily
maximum
temperatures
Map of Mean maximum temperature Map of Anomaly in mean maximum temperature Map of Decile rank of mean maximum temperature
Mean
daily
minimum
temperatures
Map of Mean minimum temperature Map of Anomaly in mean minimum temperature Map of Decile rank of mean minimum temperature

Click on a map to show it full size in a pop-up window


Record highest total December rainfall
Total rainfall
for December 2010 (mm)
Previous wettest
for December
Years of
record
Average for
December
Macquarie Island 142.2 123.1 in 1951 63 78.3
Barrington Post Office 177.2 169.4 in 1993 44 72.3

Highest total December rainfall for at least 20 years
Total rainfall
for December 2010 (mm)
Most recent December
at least this wet
Years since
wetter
Average for
December
Lorinna 173.4 319.9 in 1916 53 84.7
Mole Creek 173.0 173.9 in 1973 37 68.5
Launceston (Ti Tree Bend) 91.4 145.1 in 1985 25 47.0



Record lowest December temperature
Lowest temperature
in December 2010 (C)
Previous coolest
for December
Years of
record
Average for
December
Cape Grim BAPS (Comparison) 6.9 on the 27th 7.0 on the 6th in 2002 20 11.8




Summary statistics for December 2010
Maximum temperatures
for December
(C)
Minimum temperatures
for December
(C)
Rainfall
for December
(millimetres)
Mean for
December
2010
Diff
from
average
Highest for
December
2010
Mean for
December
2010
Diff
from
average
Lowest for
December
2010
Total for
December
2010
Average
for
December
Rank of
December
2010
Fraction of
December
average
Northern (district 91)
Bridport (Sea View Villas) 19.3 -0.8 24.2 4th 10.7 -0.4 4.5 28th 62.5 44.4 average 141%
Burnie (Round Hill) 18.7 -0.7 22.6 30th 10.9 -0.2 6.0 27th 125.2 63.8 v high 196%
Cape Grim BAPS (Comparison) 17.0 -0.2 21.2 3rd 11.5 -0.3 6.9 27th 60.2 46.3 high 130%
Cressy Research Station 20.4 -2.4 29.2 4th 8.2 -0.2 -0.5 28th 91.4 46.8 high 195%
Devonport Airport 19.0 -0.5 22.6 29th 10.4 -0.1 3.9 28th 94.4 53.7 high 176%
Launceston (Ti Tree Bend) 21.2 -1.2 27.3 4th 10.7 +0.1 3.7 28th 91.4 47.0 v high 194%
Launceston Airport 20.7   27.5 4th 8.5   1.3 28th 58.0
Low Head 18.2 -0.6 21.6 1st 12.6 -0.1 6.5 28th 61.2 44.5 high 138%
Luncheon Hill (Forestry) 17.3 -1.2 26.2 4th 8.7 +0.2 2.8 27th 126.4 95.6 high 132%
Marrawah 17.8 -0.5 22.8 4th 10.7 +0.1 6.0 27th 84.4 64.7 high 130%
Scottsdale (West Minstone Road) 19.5 -1.3 27.0 4th 8.7 -0.5 2.8 28th 82.6 67.6 high 122%
Sheffield School Farm 18.2 -1.3 26.0 4th 8.0 -0.9 2.8 27th 193.0 69.9 v high 276%
Smithton Aerodrome 18.9 -0.5 26.7 4th 9.6 0.0 3.2 30th 69.6 61.5 average 113%
Wynyard Airport 19.1 -0.4 28.8 4th 9.3 -0.2 3.9 28th 138.4 65.2 v high 212%
East Coast (district 92)
Bicheno (Council Depot) 19.1 -0.9 25.1 29th 11.6 +0.1 5.5 28th 60.1 68.5 average 88%
Eddystone Point 20.4 +1.0 27.3 4th 11.6 -0.6 7.1 22nd 66.8 59.9 average 112%
Fingal (Legge Street) 19.3 -2.2 27.0 4th 8.2 -0.4 0.3 28th 92.6 50.0 high 185%
Friendly Beaches 19.7 -2.1 26.1 29th 11.2 -0.5 6.0 27th 64.2 40.1 high 160%
Lake Leake (Elizabeth River) 16.3 -1.3 23.2 31st 6.7 -0.2 0.3 28th 89.0 73.1 high 122%
Maria Island (Point Lesueur) 18.5   24.3 4th 11.6   7.2 27th 59.4
Orford (Aubin Court) 19.3 -1.1 26.2 4th 10.6 +0.1 5.3 27th 58.8 64.0 average 92%
Scamander 19.5 -0.8 26.0 29th 11.5 +0.2 5.3 27th 65.8 62.2 average 106%
St Helens Aerodrome 20.2   29.4 4th 11.3   5.3 28th 64.0 49.8 high 129%
Swan Island 18.8   24.2 15th 12.7   8.6 28th 69.2
Swansea Post Office 19.8 -0.9 26.0 29th 10.1 -0.4 2.0 28th 59.4 59.9 average 99%
Midlands (district 93)
Ross (The Boulevards) 20.8 -1.8 27.2 4th 8.4 -0.1 0.0 28th 77.4 40.4 high 192%
Southeast (district 94)
Campania (Kincora) 21.1 -1.8 28.8 31st 9.1 -0.8 3.4 13th 24.8 35.5 low 70%
Cape Bruny (Cape Bruny) 18.2 0.0 25.2 8th 10.4 -0.2 5.0 27th 64.4 59.7 average 108%
Cape Bruny Lighthouse 17.4 +0.4 24.5 8th 10.6 +0.3 5.0 22nd 83.4 76.7 average 109%
Geeveston (Cemetery Road) 19.3 -0.6 27.4 8th 8.9 +0.3 3.4 27th 60.2 71.4 average 84%
Grove (Research Station) 19.5   26.3 8th 8.3   2.9 28th 62.2
Hobart (Ellerslie Road) 20.3 0.0 26.2 8th 11.2 +0.4 6.4 27th 31.0 56.7 low 55%
Hobart Airport 20.5 -0.1 26.7 8th 10.7 0.0 5.8 27th 30.6 53.3 average 57%
Maatsuyker Island Lighthouse 15.9 +0.2 26.6 8th 9.8 +0.2 5.5 27th 112.2 90.5 high 124%
Melton Mowbray (North Stockman) 19.9 -1.9 28.7 31st 8.7 -0.2 3.6 27th 27.8 37.2 average 75%
Mount Wellington 10.2 -0.8 16.7 31st 2.1 -0.7 -3.3 27th 80.2 87.4 average 92%
Tasman Island 15.5   20.3 4th 9.5   4.5 27th 61.2
Tunnack Fire Station 17.6 -2.0 23.4 8th 7.1 -0.3 1.6 27th 90.8 53.8 v high 169%
Derwent Valley (district 95)
Bushy Park (Bushy Park Estates) 21.2 -0.8 27.5 31st 8.9 -0.2 3.0 16th 40.2 50.6 average 79%
Maydena Post Office 18.3 -1.4 25.6 31st 8.1 +0.7 2.5 27th 106.9 89.6 high 119%
Ouse Fire Station 21.4 -1.6 28.4 31st 8.6 0.0 2.5 27th 29.0 35.1 average 83%
Tarraleah Village 17.0 -0.8 25.4 31st     5.5 1st 94.9 91.4 average 104%
Central Plateau (district 96)
Butlers Gorge 15.4 -1.2 25.9 31st 5.6 +0.1 0.2 31st 120.6 126.9 average 95%
Lake St Clair National Park 16.2 -1.0 26.0 31st 5.5 +0.5 -0.2 31st 143.6 134.1 average 107%
Liawenee 14.8   21.9 31st 3.7   -1.7 27th 121.2 70.4 high 172%
West Coast (district 97)
Hartz Mountain (Keoghs Pimple) 13.4 -1.4 20.8 31st 4.3 -0.8 -1.1 27th 68.0 80.1 low 85%
Mount Read 10.7 -0.9 19.6 31st 3.7 -0.1 -2.3 27th 294.2 304.5 average 97%
Scotts Peak Dam 18.1 -0.2 28.0 2nd 7.5 -0.4 1.5 27th 171.8 155.5 high 110%
Strahan Aerodrome 18.8 -0.9 26.5 3rd 10.0 +0.4 5.1 27th 99.2 88.1 average 113%
Strathgordon Village 17.1 -0.1 24.5 8th 8.1 -0.1 2.5 27th 200.8 202.3 average 99%
Warra 16.2   23.3 8th 6.3   0.5 27th 160.2
King Island (district 98)
King Island Airport 18.8 +0.2 27.6 31st 11.3 +0.4 5.8 30th 57.0 50.9 average 112%
Flinders Island (district 99)
Flinders Island Airport 20.3 +0.2 28.6 31st 12.6 +0.8 4.5 31st 68.4 58.3 high 117%
Hogan Island 19.2   27.1 31st 12.9   8.3 27th 78.8
Antarctica and Macquarie Island (district 300)
Macquarie Island 8.3 +0.4 11.5 20th 4.6 +0.3 1.4 6th 142.2 78.3 highest 182%

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 Wednesday 5 January 2011. 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