In this post I demonstrate a simple way of comparing current temperatures for a particular location with those previously recorded. In this way it is possible to show the climatic context.
Using data from Climate Data Online, I plot maximum temperature for each day of the year, and then for a particular short period: in this case the last week of November and the first week of December, which coincides with the recent very warm spell here in Queensland. To account for leap and ordinary years this period is 15 days. In ordinary years 24th November is Day 328 and 7th December is Day 341, while in leap years this same calendar period is Day 329 to 342. I also calculate the running 7 day mean TMax for this period, and the number of consecutive days above 35C.
To put the recent heatwave in context, I have chosen six locations from Central and Southern Queensland which regularly feature on ABC-TV weather: Birdsville, Charleville, Roma, Longreach, Ipswich (Amberley RAAF), and Rockhampton.
The Police Station data are from 1954 to 2005, and the Airport from 2000. This shows the range of temperatures throughout the year. The red arrow indicates the current period. The next plot shows data only for the period in question.
Fig. 2: 24 November- 7 December: Airport data
Note there were three days where the temperature this year was the highest for those days since 2000, but didn’t exceed the highest in this time period, which was in November. The other days were well within the historic range.
For interest, let’s now see how this year compares with the Police Station record. (The average difference in TMax during the overlap period was 0.0 to 0.3C.)
Fig. 3: 24 November- 7 December: Police Station data
In a similar range.
This heatwave was the third hottest since 2000 and fifth overall.
Five previous periods had more consecutive days above 35C. 2006 had 22.
Fig. 6: Charleville Aero since 1942
Temperatures in this period reached the extremes of the range on three days.
(Although the Post Office record begins in 1889, there are too many errors in the overlap period so the two records can’t be compared.)
A new record for early December was set, but note this was the same temperature as 29th November 2006.
Definitely the hottest for this period since 1942.
Note this was not the longest warm spell by a mile: there were many previous periods with up to 26 consecutive days above 35C.
Although there is not one day of overlap so the two records can’t be compared, you can see that Airport (from 1992) and Post Office records are similar.
A new record for this time of year was set: 44.4C, and six days in a row above 40C. Pretty hot….
…but there were longer hot periods in the past (since 1992).
Fig. 13: Longreach Aero since 1966.
Hot, but no record.
Although there is good overlap with the Post Office, temperatures for this period differ too much: from -1 to +0.7C.
Fifth hottest period since 1966.
And in the past there have been up to 47 consecutive days above 35C at this time of year.
Ipswich (Amberley RAAF):
Not unusually hot for this time of year.
Ninth hottest since 1941.
Hotter for longer in the past.
Very hot, but no records. (The heat lasted another two days, with 36.6 and 37.3 on 8th and 9th.)
Fourth hottest 7 day average on record (since 1939).
Again, a number of hot days, but there were as many and more in the past.
To conclude: the recent heatwave was very hot certainly, and was extreme in southern inland Queensland. While Charleville had the highest seven day mean temperature on record, NO location had as many consecutive hot days (above 35C) as in the past.
This is a handy method for showing daily data in context. It can used for any period of the year, can be tuned to suit (I chose TMax above 35C, but temperatures below a set figure could be found), and can be used for any daily data.
If you would like a comparison done for a location that interests you, let me know in comments including time period and parameters of interest (e.g. Sydney, first 2 weeks of December, TMax above 30C say, or Wangaratta, September, daily rainfall over 10mm say.)