Australian Monthly Climate Summary: January 2007
Tuesday 6th February, 2007
January 2007 saw a return to above-normal rainfall over large parts of Australia, although it remained dry over eastern parts of the country. It was particularly wet over much of South Australia, and the Northern Territory away from the Top End. Averaged over Australia rainfall was 20% above normal, and it was above normal in all states except New South Wales (38% below). Area-averaged temperatures were near normal (anomaly +0.01°C) with above-normal minima (+0.33) offsetting below-normal maxima (−0.32).
Maximum temperatures were well above normal over the New South Wales ranges (extending into southern Queensland) and in eastern and central Victoria. Anomalies were in the +2 to +4°C range over this region, and reached record levels locally around Goulburn. It was also warmer than normal in most of Tasmania, the remainder of Victoria and NSW, the southern parts of South Australia, south-eastern Queensland, Cape York Peninsula and the Top End.
It was a very cool month over the southern and central Northern Territory and adjacent far western Queensland. Anomalies reached −3°C near the NT/Queensland border, around Jervois and Urandangi, and were below −2°C over large parts of the southern Northern Territory. The NT as a whole had its sixth-lowest mean January maximum on record (anomaly −1.53°C). The other substantial cool region was over central Western Australia. Anomalies were below −1°C over a region extending well inland from the coastline between Carnarvon and Perth, reaching −3°C around Geraldton.
Overnight minima were above normal over most of the eastern two-thirds of the country, but anomalies were generally less than +2°C. The largest anomalies were over south-western Victoria and far south-eastern South Australia, reaching +2 to +3°C, which placed them in the highest decile. In contrast, most of Western Australia and the western Northern Territory were rather cool. Anomalies were in the −1 to −2°C range over a large part of central Australia bounded by Perth, Wiluna and Onslow, with a few records being set locally inland from Carnarvon.
* Anomaly is the difference from the long-term average
The heaviest rain fell during mid-month as a result of a major southward penetration of tropical moisture shortly after the development of the monsoon. Heavy rains initially affected the southern half of the Northern Territory, then spread to far western Queensland, much of South Australia, and western Victoria over the period 18−21 January, before easing. Most of this area had monthly rainfall in the highest decile, although records were only set at a few locations. A number of stations had more rain during this event than they received in all of 2006, most notably Bedourie (far western Queensland), which received 169 mm on 21 January after recording only 68 mm in all of 2006. A related system also produced heavy rain in southern Tasmania, giving them a month in the highest decile, the first wet month in the region since late 2005. South Australia had its ninth-wettest January on record (73% above normal).
The other major rain event occurred in the first week of the month in Western Australia, as moisture from tropical cyclone Isobel interacted with a mid-latitude system to produce heavy rain and high winds in the southern part of the state. The heaviest rain was centred on the Esperance area, with several stations receiving daily falls in excess of 150 mm on 5 January, causing severe flooding. Record monthly falls occurred around Esperance with decile 10 falls extending north into the southern Goldfields region.
It was a rather dry month over the easternmost part of Australia south of the Tropic of Capricorn, notably in eastern Victoria, New South Wales on and east of the ranges, and coastal Queensland south of Rockhampton. Patches of decile 1 falls were scattered through this area, particularly between Brisbane and Rockhampton. It was also rather dry on Cape York Peninsula, in the Top End of the Northern Territory, and in the western Pilbara around Exmouth, where no rain fell.