Monday, 1 October 2012 - Monthly Climate Summary for Tasmania - Product code IDCKGC27R0

Tasmania in September 2012: Spring arrives

A cold burst at the end, several warm days but a few cold nights, rain and showers, and destructive winds: in many ways September 2012 was a classic Tasmanian spring month. Overall it was warmer than usual, with rain above average in most areas.

• Warm days and nights overall
• Very windy between the 6th and 9th
• Warm on the 27th
• Devonport's coldest September night in 17 years

Extremes Maps Records Summaries Important notes the top

A few wet bursts

September rainfall was above average across most of Tasmania, with some areas well above average. At most sites it was wetter than in 2011 but there have been wetter Septembers sometime in the last few years.

The wettest September days were from the 5th to 9th, the 21st to 23rd, and the 28th to 30th. A cold front produced daily rainfall totals of up to 50 mm in the north, west and central areas on the 5th, though totals were generally less than 10 mm in the southeast. Similar daily rainfall totals were observed in the west and in central areas through to the 8th as several cold fronts crossed Tasmania. Mount Read recorded 50.8 mm in the 24 hours to 9am on the 7th, the wettest day of the month.

A trough of low pressure crossed Tasmania overnight on the 20th and into the 21st as a low pressure system moved through Bass Strait. Rainfall totals of up to 40 mm were recorded in the north and west in the 24 hours to 9am on the 21st, while falls of around 10 to 20 mm were observed elsewhere. Heavier rain developed in the southeast on the 21st as the low moved into the Tasman Sea, with totals of up to 40 mm recorded in the 24 hours to 9am on the 22nd. Tea Tree, just north of Hobart, recorded its wettest September day on record with 36.8 mm to 9 am on the 22nd. A cold front followed on the 23rd producing falls of up to 20 mm in most areas, and up to 40 mm in the west. A cold outbreak at the end of the month brought rain across the state, with some thunderstorms and hail, and snow down to around 400 m.

Mount Read was the wettest location, recording at least 431 mm (the actual total is probably higher as some snow was not properly captured), followed by Strathgordon Village with 372 mm. Maria Island (Point Lesueur) was the driest location with only 28 mm.

Warm days overall

There were many cool days throughout September, but there were also some very warm ones; overall days were warmer than usual.

The 27th was the warmest day of the month, with maximum temperatures generally 3 to 8 degrees above average, and as much as 10 degrees above average in eastern districts where temperatures peaked in the mid twenties. Friendly Beaches recorded the highest temperature with 26.6 °C, the warmest day of the month.

The 4th and 5th were warm days for so early in Spring, with maximum temperatures up to 7 degrees above average due to warm northerly winds ahead of a cold front, reaching into the low twenties along the east coast and into the high teens elsewhere. Days were also warm around the 12th and the 22nd.

The coldest days were around the 7th, 17th, 24th and 29th. Cold southwesterly winds and rain kept temperatures below 15 °C on the 7th, and below 5 °C in central areas. On Mount Wellington the temperature only reached a maximum of -1.8 °C on the 29th, the coldest day of September.

Maximum temperatures were up to one degree warmer than average overall, but were not as warm as in September last year. The warmest days were at Friendly Beaches where the maximum temperature averaged at 16.7 °C for the month, whilst the coolest days on average were at Mount Wellington with 5.9 °C.

Some very cold nights, some very mild nights

There were several very cold nights in September, but some very warm ones too; overall nights were warmer than usual.

Nights were especially cold over the first few days of the month. Temperatures dropped below zero in the northwest and approached -5 °C in central areas. Liawenee recorded the coldest nights of the month during this period, with -7.0 °C on the 1st and -6.2 °C on the 4th. In Devonport the temperature dropped to -0.3 °C on the morning of the 1st, its coldest September temperature in 17 years (since -2.0 °C was recorded on 8 September 1995). It was also quite cold on the 15th when sub-zero temperatures were recorded in central and northern parts, and around the 24th to 25th. There were some reports of frost on the morning of the 26th.

There were also several mild nights throughout September, but the warmest tended to be in the second half of the month. A moist and warm northerly flow kept minimum temperatures 2 to 6 degrees above average between the 19th and 23rd, and on the 27th and 28th. Flinders Island Airport recorded the warmest night of the month on the 27th, when the temperature only fell to a minimum of 14.0 °C, its warmest September night in 10 years (since a minimum of 15.7 °C was recorded on 16 September 2002).

Overall, minimum temperatures were up to one degree warmer than average across Tasmania. The coolest nights on average were -0.5 °C at Mount Wellington, whilst the warmest nights on average were at Swan Island with 9.3 °C.

Strong winds, hail and snow

Strong and gusty winds affected Tasmania between the 6th and 9th as a series of vigorous cold fronts crossed the state. Wind gusts in excess of 100 km/h were recorded in coastal areas on these days, with associated power outages affecting several thousand premises. Conditions were wet and windy across much of the state as a cold front crossed Tasmania on the 7th, with thunderstorms and hail in the south and west and snow down to 300 m. Wind gusts reached 137 km/h at Scotts Peak and 106 km/h at Wynyard, where an uprooted tree landed on a car. The strongest wind gust of 159 km/h was recorded at Hogan Island.

On the 8th, an intense low pressure system to the southwest of New Zealand and a high over the western Great Australian Bight directed a strong west to southwest flow over Tasmania, with snow down to 400 m. Wind gusts exceeded 100 km/h in the northwest, southeast and central areas, peaking at 130 km/h on Mount Wellington and 107 km/h in Hobart and Liawenee. The strong winds caused roof damage in many areas north of the central plateau and around Hobart and Geeveston. More trees were felled in Wynyard, and in Hobart a large branch was brought down in Salamanca Place. Windy conditions continued across most of Tasmania on the 9th (Mount Wellington recorded a maximum wind gust of 156 km/h and Bruny Island a wind gust of 113 km/h), though no damage was reported.

The 29th saw another cold outbreak bring showers, thunderstorms, hail and gusty winds to much of the state. Showers fell as snow to around 400 m, and wind gusts over 100 km/h were reported from several exposed sites.

A warm start to Spring in Hobart

Despite a cold end to September, both maximum and minimum temperatures were warmer than average in Hobart for the month overall. The mean maximum temperature of 15.9 °C was 0.8 °C above the long-term average, whilst the mean minimum temperature of 7.3 °C, was 0.9 °C above average. The warmest day was on the 27th, when the temperature reached a balmy 25.0 °C. Other warm days up around 20 °C were on the 4th, 5th, and 12th. There was a lack of especially cold days: the temperature stayed below 12 °C on only 3 days (the 10th, 18th and 29th), compared to an average of 5 days for September.

Hobart had many mild nights: the temperature remained above 10 °C on 8 mornings, more than double the September average of 3. The warmest minimum temperature was on the morning of the 23rd, when the temperature only fell to 12.2 °C. There were a few cold nights, the temperature dropping below 5 °C on 8 mornings which is close to the average of 9. The coldest morning was on the 1st, when the temperature fell to 2.8 °C.

Hobart's September rainfall total of 68 mm was almost 15 mm above average. The wettest days were on the 7th and 21st, when daily totals of close to 15 mm were recorded in the 24 hours to 9 am on the 8th and 22nd respectively.

* The true total at Mount Read is probably higher, as it is likely some snow was lost.

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

* The true total at Mount Read is probably higher, as it is likely some snow was lost.

Extremes Maps Records Summaries Important notes the top