Wednesday, 5 January 2011 - Monthly Climate Summary for Tasmania - Product code IDCKGC17R0

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

Extremes Maps Records Summaries Important notes the top

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. 

Extremes Maps Records Summaries Important notes the top

Maps
	Observed	Anomaly	Decile rank
Total rainfall
Mean daily maximum temperatures
Mean daily minimum temperatures

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

Extremes Maps Records Summaries Important notes the top

Extremes Maps Records Summaries Important notes the top