Hottest May day prediction for Sydney crashed in a heap – while warmest May on record looks restricted to centre of Sydney

The media have been hyperventilating over the Indian Summer in Sydney – but this story took the cake – Sydney to register hottest May day in 95 years with temps tipped to hit 28C as May ‘heatwave’ lingers
In fact Wednesday the 27th saw Sydney reach 24°C – a 4 degree fail for the BoM.
OK forecasting is fraught.
SYDNEY (OBSERVATORY HILL) (066062) looks headed for an all time record warm May – the previous record was 1958 – but how widespread is this record warmth.
This table shows that this month Sydney Airport is about equal with May 1958 but at Richmond RAAF this month is well down on May 1958.

Can anybody find another Sydney site which has this month warmer than May 1958? Two sites to check – BoMAWN

6 comments to Hottest May day prediction for Sydney crashed in a heap – while warmest May on record looks restricted to centre of Sydney

  • Ian George

    Can’t find one as most Sydney w/s don’t go back that far. Two things are interesting though.
    * The mean temp for Sydney Obs for May so far is below that of 1958.
    * May’s average temp for Sydney Obs is lower than all of the w/s in Sydney but looks as if it will have a higher May temp than all Sydney stations. Surely an ‘outlier’ that will be corrected through the homogenised ACORN record ASAP.

  • Ian George

    Too late, Warwick. The ACORN data homogenisers have already been busy. Here is Sydney Obs May, 1958 raw data v ACORN data.
    1958 is now 0.2C cooler.

    Raw ACORN
    26.3 25.8
    27.1 26.6
    27.6 27.1
    23.2 23.1
    24.0 23.4
    22.4 22.4
    24.0 23.4
    25.2 24.7
    18.3 18.3
    18.8 18.8
    22.5 22.5
    22.5 22.5
    21.7 21.8
    22.2 22.1
    25.9 25.4
    22.2 22.1
    21.6 21.6
    23.6 23.6
    20.7 20.6
    23.2 23.1
    19.9 19.8
    22.9 22.9
    22.4 22.4
    26.8 26.3
    25.2 24.7
    19.2 19.1
    20.9 21.0
    20.9 21.0
    21.1 21.1
    19.5 19.4
    20.7 20.6

    22.7 22.5 (monthly average)

    It will be interesting if they still regard this May average as a record when other Sydney w/s don’t show temps as high as the Obs.

  • weathercycles

    Also plenty of room to fiddle the books here. The Sydney observatory data has” not been checked” and verified and so is subject to change in the future.

    picasaweb.google.com/110600540172511797362/BOMWeatherObs#6018393242775646194

    wonder how long it will take to go through ‘quality control’?

    only one day below the mean in May 2014
    The monthly mean could be broken here ( 22.7 degc)
    Certainly a warm month in Sydney.
    Meanwhile NZ has been very cold and the low pressure belt bubbles have been popping up over the s/west of WA currently

  • In ACORN – 1923 has the warmest May for Sydney at 22.7 – which has been pumped up a whole degree from the CDO number.

  • Ian George

    Good find, wazsah.
    Thought I would run the data comparisons between CDO and ACORN for May 1923 – just shake my head.
    CDO ACORN
    23.3 25.0
    22.8 24.6
    21.1 21.9
    20.8 21.7
    21.2 22.1
    20.9 21.8
    22.9 24.6
    22.9 24.6
    22.1 22.8
    20.9 21.8
    19.1 19.9
    23.4 25.1
    23.3 25.0
    23.4 25.1
    25.1 26.3
    19.0 19.7
    20.8 21.7
    20.7 21.6
    24.1 25.2
    29.4 30.6
    23.7 25.5
    20.0 20.6
    21.9 22.7
    19.8 20.5
    18.3 19.1
    15.1 15.6
    13.8 14.3
    21.4 22.2
    24.4 25.5
    24.6 25.8
    21.4 22.2

    21.7 22.7 (Av max mean)
    So 1958 is adjusted down, yet 1923 is adjusted up so much it now bypasses 1958 for a record. To show the disparity, check the 15th May between CDO and ACORN. CDO shows 1958 0.8C higher than 1923 – but after adjustments 1923 is now 0.9C higher.
    CDO (58) ACORN(58) CDO(23) ACORN(23)
    15th May 25.9 25.4 25.1 26.3

    I’ve also seen this before with a comparison between Bourke and Cobar for Jan, 1939 where Bourke was hotter than Cobar (CDO) and then, after ACORN adjustments, Cobar was hotter than Bourke (even though Bourke has a higher Jan average mean!).

    Surely the BoM can’t justify these types of adjustment. ACORN is being used as the ‘Rolls Royce’ of Aust temp data, has been explained and defended by the BoM, and is being used as the comparative evidence to prove all those heat records in the past few years i.e. hottest day, month, season, year.

  • Here are your CDO and ACORN columns with AC minus CDO diffs and sorted by CDO. So ACORN adjustments peak in the CDO range 22.8 to 23.7 –

    Makes sense to me.
    I should warn – just now we are flooded with spam comments that get caught in a spam list in the blog innards. I have not got time to check the list for real comments – so if you leave a long comment – or a comment with more than 2 links – it will likely vanish – sorry. If you have a long complex comment just email it.

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