Monday, 3 August 2009 - Monthly Climate Summary for Tasmania - Product code IDCKGC27R0

Tasmania in July 2009: Consistent rain in the north, west and southeast

Rainfall for July was above average in western, northern and far southeastern Tasmania after cold fronts repeatedly brought moderate rainfalls to these areas and a particularly active front on the 11th and 12th delivered over 100 mm to some parts of the north. Totals were mostly near average for the remainder, but it was drier than usual in the central east and parts of the southern Midlands and Upper Derwent Valley. Minimum temperatures ranged from very cold to very warm but maximum temperatures were less variable.

An archive of previous monthly summaries for Tasmania is also available, as are summaries for other states and many other climate summaries and diagnostics. The next routine Climate Summaries for Tasmania, covering August and winter, are expected to be published on Tuesday 1 September 2009.

Details

Fronts bring rain to the west, north and far southeast: Numerous fronts crossed the state during July repeatedly bringing moderate rainfall totals to the west, north and far southeast. The highest totals fell in northern areas on the 11th and 12th when a complex front crossed the state and an associated low passed near the west and south. Over 100 mm fell at several sites in the north in the 24 hours to 9 am on the 12th, and Mole Creek, Yolla, Barrington and Gowrie Park all had their wettest July day on record. This widespread heavy rain on already moist soils caused minor to moderate flooding of several rivers in the central north and northeast. The consistency of the rain in the west and north was also notable. At Strahan, for example, there were nine days when rainfall totals exceeded 15 mm; in a typical July this occurs only around three times. These two factors combined to give above average July rainfall to the west, north and far southeast, and some sites had their highest total July rainfall since 1975. Because the airflow was predominately westerly, it was drier than usual in the central east and parts of the southern Midlands and Upper Derwent Valley (this was in marked contrast to the wet June seen in the east). Elsewhere, rainfall was near normal.

Very warm and very cold nights: Very warm and very cold nights alternated during July, but over the whole month mean minima at most sites were near average or slightly warmer than normal. Hobart Airport did have its highest July mean minimum temperature since 1988, while Fingal and Orford were their warmest in July since 2001 and most other sites were their warmest for three or four years. On the 20th, many locations had their warmest July night in 10 or 15 years, including Devonport and Launceston which were their warmest since 1994. The 1st, 12th and 29th and 30th were also much warmer than usual. In contrast, some sites had their coldest July night in 10 or 15 years on the 24th. One such site was Friendly Beaches, which fell to −0.9°C and hasn't recorded a July temperature this cold since it opened in 1997. Other very cold nights were the 7th to the 10th, 17th and 18th. Liawenee fell below −7°C four times; something that would usually be expected only twice in July.

Mostly near average days: Daytime temperatures in July were not as extreme as overnight temperatures and on most days maxima were not too far from average. The coldest days were around the 6th and 16th as a southerly airstream suppressed temperatures, but most sites still managed to reach at least nine or ten degrees. It was also very cold in the Derwent Valley on the 8th and 10th when fog that formed overnight failed to clear during the day. Bushy Park only managed to reach 2.7°C on the 8th. The 20th and 21st were much warmer, and most maxima reached the mid to high teens on these days. On the 20th Friendly Beaches had the warmest temperature for the month (19.7°C), and Bicheno (18.6°C) had its warmest July day since 1994. Mean maxima across the state were mostly within half a degree of normal, generally cooler than normal except for parts of the north and east. Many sites in the north and east had their warmest July for three or four years. 

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

Extremes

Hottest day
Highest temperature
19.7°C at Friendly Beaches on the 20th
Warmest days on average
Highest mean daily maximum temperature
14.4°C at Bicheno (Council Depot)
Coolest days on average
Lowest mean daily maximum temperature
2.1°C at Mount Wellington
Coldest day
Lowest daily maximum temperature
−2.3°C at Mount Wellington on the 6th
Coldest night
Lowest temperature
−8.6°C at Liawenee on the 17th
Coolest nights on average
Lowest mean daily minimum temperature
−1.8°C at Mount Wellington
Warmest nights on average
Highest mean daily minimum temperature
9.1°C at Hogan Island
Warmest night
Highest daily minimum temperature
12.8°C at Low Head on the 20th
Wettest overall
Highest total rainfall
585.8 mm at Mount Read
Driest overall
Lowest total rainfall
14.8 mm at Friendly Beaches
Wettest day
Highest daily rainfall
123.6 mm at Mole Creek on the 12th
Highest wind gust
137 km/h at Maatsuyker Island Lighthouse
and Scotts Peak Dam on the 20th

Records

Record highest July daily rainfall
Highest daily rainfall
in July 2009 (mm)
Previous highest
for July
Years of
record
Yolla (Sea View) 119.4 on the 12th 97.3 on the 5th in 1963 103
Mole Creek 123.6 on the 12th 79.5 on the 15th in 1951 93
Barrington Post Office 99.0 on the 12th 75.8 on the 21st in 2000 43
Gowrie Park 84.0 on the 12th 61.0 on the 21st in 2000 34



Highest total July rainfall for at least 20 years
Total rainfall
for July 2009 (mm)
Most recent higher
for July
Years since
higher
Average for
July
Savage River Mine  348.0 376.4 in 1972 36 236.5
King Island Airport 166.8 214.8 in 1975 34 113.9
Marrawah 230.4 242.4 in 1975 34 140.0
Yolla (Sea View) 275.4 382.4 in 1975 34 192.8
Mole Creek 241.4 330.6 in 1975 33 148.1
Naracoopa 197.8 218.8 in 1975 33 127.1
Yambacoona 162.2 233.2 in 1975 30 115.7



Highest July mean daily minimum temperature for at least 20 years
Mean daily minimum
temperature
for July 2009 (°C)
Most recent higher
for July
Years since
higher
Average for
July
Hobart Airport 5.2 5.3 in 1988 21 4.1



Summaries

In this table, key sites have been highlighted to make them easier to find. This table is very wide and may not fit if printed.


Summary statistics for July 2009
Maximum temperatures
for July
(°C)
Minimum temperatures
for July
(°C)
Rainfall
for July
(millimetres)
Mean for
July
2009
Diff
from
average
Highest for
July
2009
Mean for
July
2009
Diff
from
average
Lowest for
July
2009
Total for
July
2009
Average
for
July
Rank of
July
2009
Fraction of
July
average
Northern (district 91)
Bridport 13.2 0.0 15.5 20th 5.4 −0.1 1.2 7th 112.6 76.8 very high 147%
Burnie 13.1 +0.4 14.6 19th 6.4 +0.5 2.0 7th 115.2 124.6 average 92%
Cape Grim BAPS 12.6 +0.1 14.5 19th 8.2 0.0 3.4 7th 150.2 103.3 very high 145%
Cressy Research Station 11.6 −0.2 15.3 30th 1.2 −0.3 −4.6 17th 73.6 61.9 average 119%
Devonport Airport 13.0 +0.3 15.6 4th 5.1 +0.5 −0.5 7th 82.2 96.5 average 85%
Launceston 13.0 +0.4 15.1 29th 2.6 +0.4 −2.3 17th 92.2 76.6 high 120%
Launceston Airport 11.8   14.6 30th 2.2   −3.5 17th 78.8
Low Head 12.9 +0.2 14.6 20th 7.2 +0.3 1.2 7th 82.0 70.9 average 116%
Luncheon Hill 10.2 −0.4 13.1 9th 4.9 0.0 1.1 7th 253.6 187.9 high 135%
Marrawah 12.3 +0.1 15.0 19th 7.0 +0.4 2.0 7th 230.4 140.0 very high 165%
Scottsdale 11.8 −0.1 14.3 20th 3.8 +0.1 −0.8 31st 141.2 119.5 average 118%
Sheffield School Farm 10.9 +0.1 14.1 19th 3.0 −0.3 −2.5 17th 210.4 121.5 very high 173%
Smithton Aerodrome 12.8 −0.3 15.8 19th 4.6 0.0 −2.4 7th 129.0 115.6 average 112%
Wynyard Airport 13.0 +0.4 15.3 19th 3.3 −0.1 −2.4 7th 136.6 132.9 average 103%
East Coast (district 92)
Bicheno 14.4 +0.4 18.6 20th 6.1 0.0 1.2 24th 30.0 52.9 low 57%
Eddystone Point 13.7 +0.7 16.1 10th 7.1 +0.1 2.7 7th 75.8 76.5 average 99%
Fingal 12.3 +0.2 16.2 30th 1.5 +1.0 −4.2 24th 29.8 55.7 low 54%
Friendly Beaches 13.6 −0.1 19.7 20th 5.6 −0.1 −0.9 24th 14.8 45.7 low 32%
Lake Leake 8.3 −0.1 12.2 20th 0.5 +0.3 −5.7 24th 69.2 78.1 average 89%
Maria Island 12.4   16.2 30th 7.4   4.3 24th 47.4
Orford 12.7 −0.3 16.8 20th 4.3 +0.8 −1.0 8th 51.2 58.6 average 87%
Scamander 14.1 +0.3 17.5 30th 4.8 +0.3 0.5 18th 38.6 55.7 average 69%
St Helens Aerodrome 13.4   16.2 20th 4.8   −0.4 18th 64.8
Swan Island 13.3   15.5 10th 8.4   4.1 7th 70.8
Swansea Post Office 13.6 +0.3 17.9 20th 3.9 +0.3 −1.8 24th 20.6 47.8 low 43%
Midlands (district 93)
Ross 11.3 +0.1 14.7 30th 2.0 +0.5 −3.8 24th 44.6 41.1 average 109%
Southeast (district 94)
Campania 12.7   17.4 20th 3.8   −0.9 8th 29.2 36.1 average 81%
Cape Bruny 11.6 −0.4 15.8 20th 6.5 −0.2 2.6 8th 103.8 74.9 high 139%
Cape Bruny Lighthouse 11.3 +0.1 15.5 20th 6.4 +0.3 3.0 8th 139.4 95.7 high 146%
Dover 11.8 −0.5 15.4 30th 3.7 +0.1 −1.9 8th 85.6 85.9 average 100%
Geeveston 11.8 −0.2 15.3 19th 2.6 +0.4 −2.6 18th 93.8 91.0 average 103%
Grove 12.0   16.1 20th 2.3   −3.5 18th 66.4
Hobart 12.5 +0.8 17.2 20th 5.3 +0.8 0.5 8th 39.0 52.4 average 74%
Hobart Airport 12.4 0.0 17.2 20th 5.2 +1.2 1.3 8th 43.2 43.9 average 98%
Maatsuyker Island Lighthouse 10.8 −0.2 14.3 12th 7.0 +0.4 4.7 7th 188.2 129.3 high 146%
Melton Mowbray 10.9 −0.4 15.7 20th 2.7 +0.6 −3.3 8th 24.0 31.0 average 77%
Mount Wellington 2.1 −0.2 6.6 8th −1.8 −0.1 −5.4 24th 81.6 73.8 average 111%
Tasman Island 10.7   16.0 20th 6.4   3.5 7th 87.2
Tunnack Fire Station 9.0 −0.5 12.9 19th 1.8 0.0 −3.3 24th 34.2 45.1 low 76%
Derwent Valley (district 95)
Bushy Park 11.6 +0.5 16.3 20th 1.3 −0.2 −3.8 24th 39.6 49.4 average 80%
Maydena Post Office 9.9 −0.8 14.9 20th 2.6 +0.4 −1.3 9th 123.9 107.6 average 115%
Ouse Fire Station 11.4 −0.3 15.4 20th 1.3 +0.2 −4.6 17th 31.2 48.4 low 64%
Tarraleah Village 8.1 −0.2 11.0 19th 1.2 +0.9 −3.0 17th 108.0 116.9 average 92%
Central Plateau (district 96)
Butlers Gorge 7.5 +0.6 10.1 19th 0.6 +1.1 −6.6 8th 192.2 175.8 average 109%
Lake St Clair National Park 6.9 −0.4 9.5 20th 0.1 +0.2 −5.5 8th 272.7 203.3 high 134%
Liawenee 5.3   9.1 30th −1.5   −8.6 17th 170.0
West Coast (district 97)
Hartz Mountain 5.1 −1.0 8.6 8th 1.1 −0.3 −1.0 17th 127.6 96.0 very high 133%
Mount Read 3.3 −0.3 5.7 15th −0.2 −0.2 −3.1 7th 585.8 394.7 high 148%
Scotts Peak Dam 8.5   12.2 14th 3.3   −0.9 10th 296.2 192.5 very high 154%
Strahan Aerodrome 12.1 −0.1 14.8 10th 5.4 +0.4 −1.6 16th 309.8 162.9 very high 190%
Strathgordon Village 9.0 +0.1 12.2 20th 3.5 +0.6 −1.2 8th 378.5 271.0 high 140%
Warra 8.1   11.5 19th 2.7   −2.7 8th
King Island (district 98)
King Island Airport 13.4 +0.2 15.9 19th 7.7 +0.3 2.1 17th 166.8 113.9 very high 146%
Flinders Island (district 99)
Flinders Island Airport 13.8 +0.6 18.2 21st 7.4 +1.1 −1.4 7th 58.0 84.4 low 69%
Hogan Island 12.9   17.6 21st 9.1   6.8 2nd 125.0
Antarctica and Macquarie Island (district 300)
Macquarie Island 4.2 −0.7 6.7 1st 1.0 −0.6 −6.0 18th 58.6 71.5 average 82%


Notes

This statement has been prepared based on information available at 10 am Monday 3 August 2009. 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

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