Evaluation: August- December 2012 Predictions

Mid to late December:

While the predicted timings lined up very well, the “heavy rain” I expected did not eventuate in southern Queensland, but did fall at the right times on the Central Coast of North Queensland.  Rockhampton got a little of this on January 1.  Fronts did come through and there were widespread storms, but not heavy or general enough for me.

Starting from 1 August, I announced I would try to predict weather enhancements up to 5 months ahead.  By “enhancement”  I meant “an upper level disturbance or upper trough, which can lead to anything from extra clouds, isolated showers and storms, through to widespread heavy rain”. (I would now include a heatwave or bushfire conditions, followed by a change.)  My initial forecast was for enhancements in “early to mid-August (which may last a week or two), another late September to mid-October, and maybe late October to early November. Indications are that there will be heavier rain events starting in the period early to mid-November and early to mid-December” including specifically “a small rain event around 5-8 August and another probably larger one in the period 15-25 August, (I’m tipping close to 18-20 August).”

Over time I improved my methods, to the point I am confident in predicting specific dates +/-  5 days, and made more precise predictions.

What have I learnt?

That this method doesn’t necessarily predict rain (I admit I got carried away thinking it could) and I will leave predictions of amount of rain to the experts- the Bureau.

That I can accurately predict a change in the weather (indicated by a temperature change or rain) up to 160 days ahead.

That there are regularly repeating cycles of weather.

That this method may be used in southern parts of Australia as well.

Here is a plot showing predicted weather enhancements vs rainfall events (the average of 3 day sums as a percentage of the median across 10 locations) vs minimum temperature (the average of 3 day means of percentage anomalies from the long term mean in Kelvin).  The observed changes are colour coded according to the date that I made the predictions.Pred v actual 2012

16 out of 17 rain events are in the predicted time range.  (The one I missed –October 11-13- was my own stupid fault for not believing what the method indicated, because I had only just realised that a 3 day average of temperatures gave a far more accurate prediction than a 30 day average!)  That’s 94%.

Another 2 changes I did predict did not bring rain, and there were 2 changes that I didn’t predict because I was focussed on rain rather than weather change.

Therefore, I make the claim: I can predict when there will be a weather enhancement or change, indicated by a change in minimum temperature and/or a rainfall event, 160 days in advance, with an accuracy of +/- 5 days.  This can be refined 40 days out by analysing actual rainfall.  The weather change will affect sub-tropical Queensland, but also can include Central Coastal Queensland (Bowen to St Lawrence) and Northern New South Wales.

I again mention that rainfall is measured at 9.00 a.m. on the day after it falls.  As well, my method captures the average of 3 day rainfall and temperature  anomalies across 10 sites in subtropical Queensland.  I do not predict rain for specific locations.

Outlook for 2013 in sub-tropical Queensland

An enhancement (weather change, temperature change, or rain) on these dates +/- 5 days:

January:  3, possibly 8, 14, 18, possibly 21, 25, 30-31.

February:  Possibly 4, 7, 14, 20, and 26.

March:  2, possibly 5, 7-9, maybe 13, 17, 20, 31.

April:  7, 9, 11, 13, 15, 19, 27.

May: 4, 9, 13, 19, 29.

June: 6 (so far).

SOI 30 day mean (to 31 December) is -7.9 (neutral, but borderline El Nino if it stays below -80).

Weekly NINO 3.4 Index (to 30 December) was + 0.05 (neutral).

The Indian Ocean Dipole is currently +0.38 (neutral).

2 Responses to “Evaluation: August- December 2012 Predictions”

  1. Nicole K Says:

    Your dates seem to line up accurately in regard to changes in the weather, hopefully we will get some decent rainfall soon, all the dams are evaporating faster than the cattle can drink the water. Already on our 3rd truck load of water…Thanks Ken, good work.

  2. Ken Stewart Says:

    Thanks Nicole
    I’m looking at another metric for my predictions and hope to have another post up in the next couple of days.
    Ken

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