Australian Seasonal Climate Summary: Summer 2008/09 (December-February)
Monday 2 March, 2009
The summer of 2008−09 saw very wet conditions through large parts of the northern tropics, while being slightly drier than normal in most of the southern half of the continent. Temperatures also matched this pattern. They were generally cool (especially daytime maxima) in northern Australia, and warmer than normal in much of the south, largely as a result of an exceptional heatwave which affected south-eastern Australia in late January and early February.
National maximum temperatures (0.03°C below normal) were very close to normal. The north was cool and the south warm, with the dividing line running approximately Broome-Alice Springs-Rockhampton. The cool anomalies in the north were the more pronounced; despite a hot December, maximum temperatures were well below normal in inland northern Queensland, with anomalies as large as −3 to −4°C in a belt extending from Richmond to Camooweal and into the Northern Territory around Brunette Downs. They were at least 1°C below normal in much of northern Queensland and the northern half of the Northern Territory, as well as in the Kimberley.
The south was warmer than normal but anomalies were mostly fairly weak, reaching +1°C only in northern Victoria and adjacent southern inland New South Wales, patches in southern Queensland, parts of central South Australia and much of the Western Australian interior. In the south-east, the first half of the summer was cool, but an intense heatwave in late January and early February (described more fully in a Special Climate Statement) lifted seasonal means above normal.
Minimum temperatures were above normal over most of the continent, with the major exceptions being parts of the tropics, the west coast of Western Australia south of Geraldton, and much of Victoria and Tasmania; even there, anomalies were rarely below −1°C. Large positive anomalies were also rare, with the warmest areas (1−2°C above normal) being northern South Australia and the southern interior of Western Australia. The national average of 0.46°C above normal was the 13th highest on record.
* Anomaly is the difference from the long-term average
Nationally-averaged rainfall was 33% above normal, making it the tenth-wettest summer on record, with all three months being wetter than average (although only slightly so in February). Rainfall was consistently high in the tropics, especially in Queensland which had its sixth-wettest summer on record (49% above normal). Falls were in the highest decile in most of Queensland north of a Mackay-Longreach line, except on Cape York Peninsula north of Cooktown, and records were set around Townsville on the coast, and Urandangie in the far west. January and February were especially wet in northern Queensland, with significant flooding both in coastal streams and in the north-west, with the region as a whole experiencing its wettest January-February since 1991; district averages ranged from the third to the fifth-highest on record.
The wet tropical conditions also extended across the Northern Territory and Western Australia. Whilst rainfall in the NT Top End was fairly close to normal, further south in the Territory a belt of highest-decile totals extended across the region from the Queensland border to Katherine and the Victoria River district, with some records set in the latter. The north-east of Arnhem Land was also very wet. Most of the Kimberley region of Western Australia was also in the highest decile, with some records set in the east, although unlike the other regions, December was the wettest of the three months there.
Widespread above-normal rainfalls in December were enough to push seasonal totals near (or even above) normal in much of South Australia and Victoria, despite a very dry January-February (the January-February period was the second-driest on record for Victoria, and site records were set throughout western and central Victoria, including Melbourne, and south-eastern South Australia). They were also above normal in much of Western Australia, although only in the Pilbara and around Esperance did they reach the highest decile, while parts of coastal and northern inland New South Wales were also wetter than normal after heavy February rains. The only region with rainfall in the lowest decile was an area to the east of Melbourne.