Unprecedented heatwave makes lap of the continent
Sat 8 Dec 2018

A heatwave that has set record high temperatures at many places with long weather histories has been lapping the continent over the past two weeks. Beginning along the QLD coast during the last week of November, the area of extreme heat moved west to reach the WA Kimberley last Thursday 6^th before some was carried SE in a northwesterly stream to give record warm nights in parts of SA, VIC and TAS on Friday 7^th and Saturday 8^th.

In QLD, extreme heatwave conditions occurred along the coast from Rockhampton almost to the tip of the Cape York Peninsula between 24 and 29 November with many locations with long histories of weather observation recording their November and, in some cases, their all-time highest temperatures. In a media release on 30 November, Bureau of Meteorology State Manager for Queensland, Bruce Gunn, said "The severity of conditions is reflected both in the number of records broken and number of fires, many of which [were then] still burning." The QLD bushfires were covered briefly in an earlier story; this article deals with the exceptional number of records set.

• Weather records at Cairns Airport go back to 1942 and before that observations were made at the Post Office back to 1889. At both locations, the previous highest November temperature was 37.2° in 1971 and 1900 respectively. While temperatures at different locations can't strictly be compared, Cairns Airport had five consecutive days that broke the old November record (26 to 30 November). Three of them, 42.6, 42.1 and 40.5° on 26, 27 and 28 November, broke or equalled the previous all-time record of 40.5 at the Airport, but not the 43.2 figure from 1923 at the old PO site. However, the Cairns Racecourse maximum of 43.6° on 26 November, repeated the next day for good measure, was the highest temperature ever recorded in the city area.
• Mackay is in a similar situation with weather observations made at the Post Office from 1908 and the Airport from 1950. Every day from 24 to 28 November had a higher maximum temperature than the previous November record of 36.6° at the Airport in 2008 with the hottest day, 39.7 on the 26^th beating the previous all-time record of 38.5 set in 1955, also at the Airport.
• Other stations with at least a half-century of observations to set all-time high maximum temperature records were Low Isles Lighthouse 38.9 (previous all-time record 38.8) and Innisfail 41.0 (40.3), while South Johnstone Experimental Farm with 51 years of observations had the distinction of breaking its all-time record twice, finally arriving at 42.2 (40.4).
• Stations with at least a half-century of observations to set November high maximum records were Ingham 43.1 (42.0, broke record twice), Ayr DPI Research Station 41.9 (41.0), Lady Elliot Island 31.3 (31.0), Cardwell 40.0 (37.7, broke record twice), Townsville Airport 41.7 (41.0) and Collinsville Post Office 41.9 (41.6)
• As the heat built up, so the nights became warmer with many places recording their hottest November night on record at between 27 and 30°.
• The lengthy lists of high maximum and minimum temperatures are given in each day's Daily Weather Summary for Saturday 24, Sunday 25, Monday 26, Tuesday 27, Wednesday 28 and Thursday 29 November.
• Combinations of temperature, humidity and wind that lead to catastrophic fire danger have been observed only once before since the new Fire Danger Rating System (FDRS) was introduced in 2010. That was very briefly, only an hour or so, in the Birdsville area. On Wednesday 28 November, Rockhampton Airport recorded Catastrophic conditions for approximately three-and-a-half hours during the afternoon. It was the first time this area has recorded Catastrophic conditions and the most prolonged event in Queensland since the implementation of the current FDRS.

Bob Henson gives a detailed account of the QLD heat and bushfires in his Weather Underground blog. The Guardian expresses concern over the heatwave's impact on the Great Barrier Reef, Professor Terry Hughes tweeting "This is terrifying. An early summer heatwave breaks all records, lifting the chances of another episode of coral mortality on the #greatBarrierReef next Feb/March."

In the NT, heatwave conditions were reflected in all-time maximum temperature records of 38.7° at Gove Airport on 4 December (previous 38.0 in 40 years), Borroloola Airport 44.6 on 5 December (44.2, 25 years), and Groote Eylandt Airport 40.7 on 6 December (39.9, 20 years). A number of November and high minimum temperature records were also broken.

In WA, where high temperatures are a fact of life until The Wet arrives, only one high maximum temperature all-time record fell, but for emphasis it fell twice. Fitzroy Crossing's previous all-time record was 45.7° in 2009 in 23 years of observations. New maxima of 46.4 on the 7^th then 46.5 on the 8^th have reset it nearly a degree higher. Again, a number of November and high minimum temperature records were also broken.

In SE Australia, heat began streaming in from the NW on Friday 7 December, first reflected in some overnight November record high minima in SA, VIC and TAS. This continued on Saturday 8^th with November records for high minima broken in eastern VIC and TAS. The most noteworthy was at East Sale Airport where the minimum of 22.6° was a full 1.2° above the previous highest November minimum in 74 years of observations.

And an honourable mention goes to Macquarie Island, 1500km SE of Hobart, which had its hottest November day in 71 years when the mercury soared to 11.1° on 28 November. Two mornings later, the island had its warmest November night on record, 7.2°.