Southeast Australia Struck by Anomalous Heat Wave
Southern Australia has endured an anomalous ‘Summer in March’ heat wave the first two weeks of this month akin to what the eastern two-thirds of the U.S. experienced in March 2012. Temperatures have averaged as much as 10°C (18°F) above normal.
The Australian Bureau of Meteorology released a special statement concerning this unusual heat event. The one statistic that seemed the most remarkable was that Melbourne, Victoria recorded 9 consecutive days (from March 4 to 12) when temperatures peaked at 30°C (86°F) or warmer (in fact all 9 days exceeded 32°C/89.6°F). This was the longest string of 30°C+ temperatures ever measured in the city for any month of the year since records began in 1855 (the previous record was 8 days on January 24-31, 1974). The nights were mild as well with 7 consecutive days (March 7-13) recording minimum temperatures of 20°C (68°F) or warmer, also an all-time record for such for any month. On the night of March 13th the minimum fell to only 26.5°C (79.7°F), the city’s warmest March night on record. Adelaide, South Australia experienced 10 consecutive days with highs above 32°C (89.6°F) from March 3 to March 12, the 2nd longest such streak in March on record (the longest was 15 days on March 3-17, 2008).Departure from normal maximum temperature (top map) and minimum temperature (bottom map) for the period of March 1-12, 2013.
Maps courtesy of the Australian Bureau of Meteorology.
The unusual heat was confined to the southern portions of Victoria, South Australia, and Tasmania. In spite of the long duration of the event few monthly record maximum temperatures were set although Bushy Park, Tasmania hit 37.4°C (99.3°F) on March 12th, just 0.6°C (1.1°F) short of the Tasmanian state monthly heat record of 38.0°C (100.4°F) set at Campania (Kincora) on March 14, 2008. Hobart hit 36.6°C (97.9°F), just shy of its March record of 37.3°C (99.1°F) set on March 13, 1940. The warmest temperature measured in Victoria was 40.4°C (104.7°F) at Mortlake Rececourse on March 11th and in South Australia 41.2°C (106.2°F) at Tarcoola Aero on March 12th. Both these figures are well short of March state monthly records.
The warmth can, in some way, be attributed to record high sea-surface temperatures (+0.5°C above normal), which have been observed all summer in the Australia region. Since February the sea-surface temperatures have become even more anomalous off the southern coast of Australia where they now stand some +3.0°C (5.4°F°) above normal. A strong and persistent high-pressure ridge has dominated the mid-latitudes of the southern hemisphere between Australia and New Zealand for the past several months contributing to the warm and dry weather. The North Island of New Zealand is currently experiencing an extreme drought.
Christopher C. Burt