Massive failure in BoM forecast temperatures Sydney and SE regions

Friday night I started thinking the forecasts for Saturday max’s looked a trifle optimistic – so Saturday morning I kept a screen dump of Sydney region forecast max. I have just added what look to be the max’s from this BoM page. The BoM has access to more detailed data so numbers will change slightly.

Results from the regions seem similarly skewed too hot, forecast number from Canberra Times first then reality.
Canberra 33 — 30
Goulburn 35 — 29.1 Airport
Cooma 30 — 27 Airport
Wagga 34 — 28.5
Hay 34 — 32.5 Airport
BrokenHill 32 — 30.3 Airport
Dubbo 41 — 39
Bourke 43 — 41.8
Readers might have some other examples.
But of course all the TV News weather people quote the original forecast numbers as though they actually happened.
Added Sunday early am: Friday results were pretty poor too.
Goulburn 36 — 33.6 Airport
Cooma 33 — 28.2 Airport
Wagga 39 — 35
Albury 39 — 34
Hay 40 — 36.7 Airport
BrokenHill 40 — 36.2 Airport
Mildura 34 — 31.5
SwanHill 35 — 33

5 comments to Massive failure in BoM forecast temperatures Sydney and SE regions

  • Dave N

    Meanwhile, Queensland has one day above 30 and they’re calling it a “heatwave”:

    www.abc.net.au/news/2012-12-04/electricity-demands-extreme-amid-qlds-scorcher-day/4407172

  • WSH

    I am watching todays result in sth Qld Dave. For the last few days the BoM forecasts have mostly been too high.
    Today has been similar – most places have not reached BoM forecast numbers.
    Forecast vs Actual
    Brisbane 39 — 37.5
    Ipswich 41 —-37.5 (Amberley)
    Normanton 40 —-37.1
    Roma 38 —34.7
    Charleville 37—35
    Longreach 41 —37.7
    Townsville 34—-31.5
    There is a few. This follows on from days of over-egging forecasts for southern Qld.
    Will have another look in the morning

  • This is a very interesting analysis. I had sensed that forecasts were generally positively stretched and ambitious but had not realized how systematic and widespread the propaganda effort was. It is certainly true that people judge weather by forecasts as much as in actual experience. As usual they are not interested in facts or science but only in politics.

  • Graeme Inkster

    The B.O.M. appears to have trouble when there is a noticeable change in temperature.

    It seems to take about 2-3 days before their forecasts start to narrow in on the actual range.

    Thus the last 4 days have seen a drop in overnight temperatures.
    Forecast amended forecast measured
    (original) (next night) (unofficial)
    13 12 12.1
    10 8 7.3
    11 7 5.5
    9 9 9.1

  • Mike Borgelt

    When I was a forecaster nearly 40 years ago 3 deg C was a major error. Of course they have trouble when the weather changes. Persistence is the best forecasting technique. Tomorrow will be like today works well except when the weather changes.