WA, SA, TAS record their hottest February on record

Maximum temperatures were in the top 10% of hot Februaries across two-thirds of the nation...

...and minimum temperatures weren't too far behind.

WA bore the brunt of the heat, with maximum temperatures over much of the inland averaging 4C to over 6C above average for the month.

While the minimum temperature anomalies weren't as great, most of WA, SA, NSW, VIC and TAS recorded average minima for the month between 2 and 4C above the norm.

The rare phenomenon, for recent times, of average rainfall across most of the east and south masked a generally dry February nationwide. Across much of northern WA and the NT, the monsoon was a non-event, and there was a notable lack of cyclone activity. Lack of moisture and lack of cloud allowed in abundant solar radiation.

A lack of rainfall and tropical cyclones, a poor monsoon and the onward march of global warming conspired to make February an unusually warm one across most of the continent, with exceptionally high daily and monthly temperatures in the west and south.

A Special Climate Statement produced by Glenn Cook of the WA Climate Services Centre and Dr Blair Trewin of the National Climate Centre reports that WA, SA and TAS all recorded their hottest February on record averaged spatially across each state.  "To emphasize the extreme maximum temperatures in many regions, Marble Bar in the WA Pilbara recorded a mean maximum temperature of 44.9C.  This is the highest mean monthly maximum temperature recorded in Australia for any month", says the report.

Western Australia

Maps and show that much of inland WA recorded both its highest maximum and minimum average temperatures for February since comparable records began in 1950. Only a narrow stip along the west coast escaped the heat. Large areas were 5 or 6C above the standard 1961-1990 mean for maximum temperatures (see ) and 3 to 5 above for minimum temperatures (). The average mean maximum across the state of WA for February was 37.8C, 3.1C above the 1961-1990 mean. This exceeded the previous record February (1998, anomaly 2.6C), and was just below the record for any month of 37.9C in December 1972. Taking the high minimum temperatures into account, February 2007 was the hottest month on record for WA.

Marble Bar's average monthly maximum of 44.9C was its hottest in 107 years, coming in at 0.3C hotter than its previous monthly record set in January 2005. It was also 0.1C higher than the highest monthly average ever recorded in Australia, at Emu Creek Station in the Pilbara in January 2005 and February 1998.

Records for the number of consecutive days of extreme heat also fell. There were 43 days over 42C at Marble Bar from 16 January to 27 February, while Newman and Wiluna recorded 29 and 21 consecutive days respectively over 40C.

The report describes the heat of the first week of February as exceptional, "particularly in the southern inland. Hyden reached 48.6C on 3 February, the highest temperature ever recorded so far south in WA, and all-time site records were set at many other locations, including Northam (48.1), Cunderdin (48.0), Narrogin (44.7) and Lake Grace (46.1).  Meekatharra, which had only previously had five days over 45C in 57 years of observations, had five in the first week of February 2007, including a record 45.5C on 2 and 4 February."

Elsewhere

In the southeastern states, SA and the far south of the NT, the month was notable for persistent heat rather than individual heatwaves. Nights were particularly warm. Sydney set a February record of 22 nights above 20C, while Melbourne had an unprecedented 24 consecutive nights above 15C from 10 February to 5 March. Alice Springs reached 35C every day of February for the first time while in TAS, Bushy Park, Ouse and Cressy all exceeded 22C every day, a first for the state. In SA, Adelaide's mean maximum temperature of 32.9 was the highest for February since 1906.

Looking at mean temperatures averaged over whole states, SA recorded its hottest set of maximum and TAS its hottest set of minimum temperatures for the month of February.

Causes

Lack of rain (see ), and therefore cloud and cooler conditions, was a major contributor, particularly in WA which experienced its fourth driest February on record, some 76% below the 1961-1990 average. There was a virtual failure of the monsoon across the state, and across large tracts of the NT. There was also a lack of tropical cyclones. Only one tropical cyclone had occurred in the Australian region to the end of February, something that hasn't happened since reliable records began in the mid 1950s. There were no cyclones at all in the WA region to the end of February (TC Isobel at New Year was found not to have reached cyclone strength when later reanalysed), which hasn't occurred since the 1978-79 season.

The Special Climate Statement concludes that global warming is at least partly responsible for this widespread temperature aberration. "Extreme heat is becoming an increasingly common occurrence over Australia in line with global warming" it says. "This means that months like February 2007 have an increased chance of occurrence and that these high temperatures cannot be attributed to natural climate variability alone."